Involved Microorganisms in the Production of Indigenous Fermented Food from West Africa: Technological Characteristics and Probiotic Power

Abstract

Fermented cereal products, such as corn, millet, rice, and wheat, are popular in West Africa due to their affordability and health benefits. These grains undergo nutritional and biochemical changes, enriched by microorganisms like lactic acid bacteria (LAB) group, yeasts, and probiotic strains which are essential for maintaining gut microbiota and immune system balance. Dairy products, particularly cow’s milk, are providing protein, vitamins, and calcium. West African indigenous fermented foods are produced with kpété-kpété, Kudemé, and rabilé as starter cultures. Consuming cereal-based fermented foods enriches the intestinal microbiome with gram-positive bacteria, yeast, and fungi species, providing health benefits. Probiotic bacteria have potential applications in managing insulin-independent diabetes and obesity, and their consumption may exert antidiabetic and antioxidant properties. Yeasts play a crucial role in the quality, taste, texture, and flavor of fermented food products, contributing to flavor formation and improving nutritional value. Traditional fermented foods in Africa are produced through fermentation with lactic acid (LAB) or yeasts, or mixtures of both. However, food safety concerns arise due to raw materials, packaging, and unhygienic conditions. Therefore, it is essential to have a standardized starter cultures.

1. Introduction

The people of Western Africa make a wide range of traditional fermented foods, made mostly from cereals, roots, non-timber forest products, milk, and fish, such as Tchoukoutou, Tchakpalo, Gowè, Agbelima, Mawè, Ogi, kunu, Lafoun, Afitin, soumbala, Iru, Sonru, Lanhouin, Gari, Attiéké, Konkonté, fufu, and Dèguè. These foods are obtained by homemade technology, especially by uncontrolled or traditional fermentation. Traditional fermentation is an indigenous, spontaneous process involving the growth of microorganisms, primarily lactic acid bacteria and yeasts [1]. Indeed, raw food materials undergo three types of fermentation: lactic acid, alcoholic, and acetic acid fermentations. These are categorized into aerobic and anaerobic fermentations. Aerobic fermentation includes alkaline and fungal organisms, while anaerobic fermentation includes lactic and alcoholic products. Alcoholic fermentation primarily involves wines and beers, and lactic acid fermentation occurs in cereals, milk, and tubers [2]. These microorganisms convert perishable foods into safe, edible, and shelf-stable forms, enhancing food digestibility and palatability by producing a variety of metabolites like organic acids, alcohols, carbon dioxide, and bacteriocins [1, 3]. Fermented foods are safe and health-promoting due to their pH level of 4.0 or lower, lactic acid production, and the role of lactic acid bacteria (LAB) and yeasts in food fermentation. However, improper production is common in developing African countries, especially in West African countries. Food safety concerns are paramount, and basic practices like hand washing and proper cleaning are essential. Adherence to Good Manufacturing Practices and Good Hygiene Practices can improve product safety. Quick response from producers, handlers, and consumers can potentially eradicate foodborne illnesses [4].

It would be very important to use standardized starters that also possess probiotic properties in order to solve the conformity, stability, and reproducibility of the production diagrams of the various traditional West African foods. The objectives of this literary review study were to provide new insights into microorganisms involved in the manufacture of traditional West African foods and their potential use as a probiotic.

2. Methodology

The data published on West African indigenous fermented foods between 2015 and 2024 was collected from different sources using appropriate databases: Google Scholar, Scopus, ScienceDirect, Hinari, and AGORA. The information collected mainly focused on: fermented foods, Lactic Acid Bacteria, Yeast, Molds, Bacillus, Enterobacteria, cereal-based foods, root-based fermented foods, and probiotics. Owing to the paucity of study on this subject, we also found significant review publications and examined their citations and reference lists [5].

3. Results and discussion

3.1 Indigenous fermented food safety

In 2021, 29.3% of the global population was moderately or severely food-insecure, with foodborne pathogens being the primary cause. Indigenous fermented foods use artisanal methods, but spoilage or pathogenic microorganisms can occur due to hygienic conditions, substrates, ingredients, and environmental conditions according to Ramos et al. [6].

Fermentation is a traditional food preservation method that has been used for 5000 years, particularly in roots and tuber crops for their long shelf life, safety, and health benefits. It has been primarily used since the Neolithic revolution, with cheese-making being developed in Iraq. The global fermented food and ingredients market is projected to reach $59 billion by 2026, with over 5000 varieties produced and consumed globally. The occurrence of different fermented foods in specific regions and countries is influenced by dietary habits, cultures, availability, accessibility, cultural and socioeconomic factors, ethnicity, religion, and race. Lactic acid food fermentation is a process where microorganisms convert fermentable sugars into lactic acid and other limited products. Fermented foods are popular in Africa, including fermented milk, sour porridge, and alcoholic and non-alcoholic beverages. Cereals can be processed through fermentation to modify taste, flavor, acidity, and food digestibility. Fermented meats and fish can also be adequate purveyors of probiotic bacteria if properly applied. However, there is a lack of knowledge about the specific health benefits (probiotic properties) and characteristics of bacterial strains (starters strains) used for their production [7, 8, 9].

3.2 Typology of West African traditional fermented foods and beverages

Fermented foods and beverages are traditionally processed from various agricultural raw materials, including cereals like maize, sorghum, millet, non-timbers like Parkia biglobosa, Roselle, tubers, fish, palm wine, and milk in West African countries.

Every village/city/town/region of West Africa has its own typical fermented foods that play a major role in socioeconomic progress, depending on the kind of raw food that is present there [10, 11]. Foods that are fermented locally (see some example on Figure 1) can be categorized based on their raw materials (fish, dairy, legumes, grains, potatoes, root, and tree sap) or food type (beverages, spices, or staples). These meals are usually made at home by inoculating microorganisms linked to raw foods and processing conditions on their own [13]. Due to biochemical and microbial activity, each regionally fermented meal has unique microbiological and organoleptic characteristics [14].

Figure 1.

Popular fermented foods of West African origin. A: garri, B: agbelima, C: abacha, D: amala, E: adjuevan, F: guedj, G: azu-okpo, H: momone, I: ogiri, J: okpeyi, K: ugba, L: dawadawa/iru/soumbala/netetu, A1: tej, B1: pito, C1: mmaya ngwo/emu, D1: thobwa, E1: kunu-zaki, F1: nunu/nono/fene, G1: wara, H1: domiati, I1: fura, J1: kenkey, K1: agadi/eko, L1: akamu/ogi [12].

3.3 Type of indigenous starter cultures

Preparation of live microorganisms specifically employed to aid in the onset of fermentation and induce certain alterations in the substrate’s chemical composition and sensory qualities in order to produce a more uniform result is known as a starter culture [15].

In commercially fermented foods, starter cultures are essential for introducing microorganisms to improve preservation, nutritional content, sensory appeal, and economic worth. Traditional methods like backslopping, using natural microorganisms are prone to slow or failed fermentations, contamination, and inconsistent quality, while starter cultures allow for the development of individual fermented food varieties. The modern industrial production of fermented foods and beverages requires consistent quality, predictable production schedules, and strict quality control. Pure culture techniques were developed in the 1860s, with starter strains prepared in heat-sterilized milk, with calcium carbonate added as a buffer to maintain a neutral pH. Later, crude dry culture preparations and freeze-dried cultures became available. Frozen cultures, now the most common form, were introduced in the 1960s due to advancements in freezing and freeze-drying technologies. The modern starter culture industry provides cultures for almost all types of fermented foods and beverages, and most growers also produce and sell starter culture propagation media, milk coagulation enzymes for cheese-making, and other ancillary products. The industry is dominated by a small number of large companies [16].

The type of starter culture or strains found in West African indigenous fermented foods are composed of lactic acid bacteria, yeast, molds, and Bacillus strains. For example Three Weissella isolates Wc 69, Wc 21, and Wc 114 significantly decreased the initial pH of De Man, Rogosa et Sharpe (MRS) broth in less than 42 hours, demonstrating their osmotolerant, alpha amylase, thermotolerant, and pectinase properties, making them suitable for improving attieké quality [17].

The most popular starter used in West Africa are kpété-kpété, Kudemé, rabilé, …

3.3.1 Kudeme

Agbelima, or fermented cassava dough, is a traditional Ghanaian dish made from fermented cassava and is made using the traditional inoculant known as kudeme. It aids in enhancing the agbelima’s flavor, color, and texture [18, 19].

Bacillus sp. and lactic acid bacteria dominate microflora of kudeme [20].

3.3.2 Kpété-kpété

Producers frequently employed the traditional starter, known in the local language of Bariba (people of the Republic of Benin) as kpètè-kpètè, throughout the fermentation process [21]. It is known that yeasts and lactic acid bacteria are present in the tchoukoutou starter [22]. Since several of the bacteria isolated from this starter have been shown to be effective in treating opportunistic infections, they may have probiotic properties [23].

According to earlier research [23], this residue (kpètè-kpètè) from tchoukoutou has a lot of potential in the functional microflora, which includes lactic acid bacteria and yeasts.

3.3.3 Rabilé

“Rabilé” is a dry yeast obtained from sorghum beer (commonly called “Dolo” in Burkina Faso), which is used as a traditional yeast, but primarily as an ingredient in sauces and dishes from Burkina Faso [24]. Railé is harvested at the end of dolo fermentation process. Rabilé is a mix of Saccharomyces cerevisiae, Rhodotorula mucilaginosa, Pichia kudriavzevii, Candida pseudorhangii, Candida heliconiae, Candida utilis, Shizosaccharomyces pombe and Sporobolomyces odoratus [24, 25, 26]. Mogmenga [25] identified 17 yeast strains from traditional Rabilé beer in Burkina Faso, including S. cerevisiae, P. kudriavzevii, and R. mucilaginosa. These strains showed strong antibacterial, antioxidant, hydrophobic, auto-aggregation, and co-aggregation abilities. They were safe and could be used as probiotic supplements. They conclude that these yeast strains could also be used in developing functional foods with health benefits.

3.4 Microbes associated with West African traditional fermented foods and their probiotic properties

Probiotics are live microorganisms that provide health benefits to the host when ingested [27]. These live microorganisms could be LAB, yeasts, molds, Bacillus, etc.… (Table 1).

Fermented foods	Source	Origin	Associated potential probiotics	References
Akamu and ogi	Maize	Nigeria	Lactobacillus spp., Saccharomyces, Candida spp.	[28]
Pito, asana and Burukutu	Sorghum or Millet	Nigeria Ghana	Lactobacillus plantarium, Lb. brevis, Lb. acidophilus, Saccharomyces, Pediococcus halophilus, Candida tropicalis	[10]
Ogiri and okpei	Castor or melon seeds	Nigeria	Bacillus spp., Pedicoccus, Proteus, Micrococcus, Lactobacillus, Streptococcus	[29, 30]
Nono, nyamie and fene	Cow or goat milk	Nigeria Ghana Mali	Lactobacillus lactis, Lb. acidophilus, Streptococcus lactis	[31, 32, 33, 34]
Momoni and Lanhouin	Fish	West Africa	Micrococcus, Streptococcus, Pediococcus, Bacillus, Staphylococci, Streptococci, Corynebacterium	[35]
Dawadawa and iru	African locust bean	Ghana, Nigeria	Bacillus subtilis, B. licheniformis, B megaterium, B. coagulans, B. circulans and Staphylococcus sp.	[36]
Ugba and ukpaka	African oil bean	Nigeria	Bacillus sp., Micrococcus sp.	[29]
Fufu	Cassava	Nigeria	L. fermentum, Pediococcus pentosaceus, Candida tropicalis, Lactobacillus plantarium, Leuconostoc mesenteroides, Lactobacillus cellobiosus, Bacillus subtilis	[30]
Mmaya ngwo, nkwu enu, Bandji	Palm sap	Nigeria Ghana Ivory-Coast; Mali	Lactobacillus brevis, Pediococcus, Leuconostoc, Zygosaccharomyces baili, Brevibacterium, Bacillus, Saccharomyces cerevisiae, Zygosaccharomyces baili, Pichia, Candida tropicalis, Lactobacillus	[37]
Gari	Cassava	West Africa	Bacillus spp., Streptococcus spp., Leuconostoc, Candida sp., Lactobacillus coryniformis, L. fermentum, L. plantarum, S. cerevisiae	[38]
Kunu-zaki	Millet or sorghum	Nigeria	Lactobacillus plantarum, L. pentosus, L. celbiosus, L. mesenteroides, Saccharomyces cerevisiae	[39]
Fura	Millet/milk	Ghana	Candida krusei, Kluyveromyces marxianus, Candida tropicalis, Candida rugosa, Candida fabianii, Candida norvegensis and Trichosporon asahii	[40]
Ogi-baba	Sorghum bicolor	Nigeria	Lactobacillus plantarum strain OB6	[41]
Pito	Sorghum bicolor	Nigeria	Pediococcus pentosaceus strain PB2	[41]
Tchoukoutou	Sorghum bicolor	Benin	Kpété-kpété (Enterococcus faecium, Lactobacillus fermentum, Lactobacillus caseï, Leuconostoc mesenteroides, Streptococcus thermophilus)	[42]
Dolo	Sorghum or millet	Burkina Faso	Rabilé (S. cerevisiae, P. kudriavzevii, and R. mucilaginosa)	[25]

Table 1.

Probiotic profile of some indigenous West African fermented foods.

3.4.1 Characteristics of probiotic strains

Microbes to be used in native fermented foods of West Africa must have the following characteristics:

• Safety: Species of lactic acid bacteria and yeasts for cereal (for example) bioprocessing should be Generally Recognized as Safe (GRAS) and Presumed to be Safe presumption of safety (QPS) based on Food and Drug Administration (FDA) and European Food Safety Authority (EFSA) evaluations. To demonstrate safety, identify potential starter cultures using appropriate taxonomical tools. A polyphasic approach, analyzing genotypic and phenotypic data, is more reliable for identifying starter strains from cereal or root substrates [43, 44, 45].

• Fermentative activity: To gain a competitive edge, potential starter strains of LAB and yeasts need to be able to metabolize a variety of carbohydrates found in cereals and roots, withstand stressful fermentation conditions, and release inhibitory metabolites. These attributes provide process control and product predictability and are essential to the initiator’s competitive advantage [46, 47]. For example according to the finding of Perricone team and Owusu-Kwateng team [44, 48], the performance of LAB and yeast to serve as starter cultures depends on the acid and CO₂ production rates, respectively because the acids inhibit unwanted microbiota and improve the activity of the body’s own enzymes.

• Organoleptic properties: The key factor influencing a consumer’s meal decision is their sensory perception. LAB and yeasts through their metabolism of organic molecules in grain substrates produce unique flavor-active non-volatile and volatile chemicals [49, 50]. Esters, carbonyls, and organic acids are important molecules that contribute to fragrance and flavor [50].

• Antagonistic properties (bioprotective microbes): Antibacterial fermentative microbes and secondary metabolites have been suggested as potential substitutes for synthetic compounds in cereal-fermented products. However, fungal contamination remains a significant public health concern. Antifungal LAB genera include Lactobacillus, Leuconostoc, and Pediococcus [51, 52, 53]. It is hypothesized that the synergistic interplay of metabolites, such as fatty acids, organic acids, and cyclic dipeptides, is what gives these strains their antifungal impact [54]. For instance, in Kunu-zaki, Lactobacillus fermentum 5KJEU5 stopped Aspergillus flavus F008BA and Penicillium citrinum 3AS1 from growing for more than 8 days at room temperature (25°C) [55].

• Nutritional properties: Bio-enrichment and reduction of antinutritional compounds by selected microbial strains can improve the nutritional value of cereal substrates. Some lactic acid bacteria and yeast strains can overproduce and release essential nutrients during fermentation. For example, LeBlanc et al. [56] have studied the synthesis of B-group vitamins by lactic acid bacteria, including riboflavin, folate, and cobalamin. Phytate, an important anti-nutritional compound in cereals, can be reduced by endogenous or exogenous phytases. Phytase activity is expressed at species and strain-specific levels in LAB and yeasts involved in cereal fermentation. Selecting suitable phytase-active strains can improve the bioavailability of phosphorus, iron, and zinc, which are important micronutrients in diets [55].

• Production of bioactive compounds: Starter cultures can release non-nutritive compounds into fermented foods, improving consumer health and well-being. These bioactive compounds can be components of microbial cells, metabolites, or modified cereal components. They offer antimutagenic, anticarcinogenic, antipathogenic, antiobesitic, antidiabetic, antioxidant, and hypoglycemic properties. High GABA (γ-aminobutyric acid)-producing LAB strains can accumulate GABA in fermented cereal products, improving cardiovascular functions. Bioactive fatty acids like Conjugated Linoleic Acid (CLA) and Conjugated Linolenic Acid (CLNA) are being explored in LAB strains for functional cereal products. Yeast components and metabolites have antioxidant functions [55, 57, 58, 59].

3.4.2 Selection criteria of probiotic strains

These bacteria were chosen using a number of criteria, including:

• Technological characteristics: stability, viability, and growth in raw materials;

• Perceived sensory qualities in acceptable environments;

• Post-consumption survival in the gastro-intestinal tract; and

• Functional characteristics: adhesion, antigenotoxicity, antimicrobial production, immune stimulation, safety, and pathogen prevention [60].

3.4.3 West African indigenous fermented foods as probiotic foods

Live LAB from fermented foods have been documented for their health effects and probiotic potentials [61, 62, 63].

Some of the documented roles of probiotics in food manufacturing are below:

• Some LAB produce technologically important substances like Exopolysaccharides (EPS), which improve the rheological and functional properties of foods and enhance the technological properties of sourdough, fermented milk, and beverages [64, 65]. These EPS also play a significant role as prebiotics and are valuable in food industries and pharmaceutical (used as a substitute for antitumor, immunostimulatory, immunomodulatory, and antioxidant agents) industries [66, 67].

• By maintaining the balance of the gut microbiota to fight viral infections, secondary bacterial infections, and microbial dysbiosis, probiotics are essential for modulating both the innate and adaptive immune systems. Fermented foods from Africa are rich in potential probiotic microorganisms, including Saccharomyces, Bacillus, and lactic acid bacteria (LAB). Furthermore, food-derived fermented bioactive peptides are crucial in preventing diabetes, hypertension, lung damage, cardiovascular disease, and other COVID-19 comorbidities. Potential probiotics and bioactive peptides should be regularly included in the diet to support the body’s systems and perhaps improve prognosis [12].

• Probiotic bacteria can be given to human and animal hosts through fermented meals [68]. They are regarded as historic foods worldwide and are distinguished by their sensory qualities [69]. According to Narzary [70], these foods are a staple of the traditional diets in the majority of underdeveloped nations across several continents, including Africa. The microbiological composition, flavor, texture, and nutritional content of fermented foods vary [71]. According to Achi [28], fermentation is the process of transforming and preserving food via the employment of microbes. The procedure is low-cost, simple to use, and does not require much technical expertise. Food that has undergone fermentation has improved organoleptic qualities, increased shelf life, and is easier to access and digest [28, 29, 72].

• Common regional spices found throughout East, Central, and West Africa are fermented legumes with African origins [73, 74]. They have a high protein content and are produced by uncontrolled and spontaneous alkaline fermentation [75]. Ugba/Ukpaka (Nigeria), brewed from African bean seeds (Pentaclethra macrophylla) [76]; Ogiri (Nigeria), brewed from castor beans (Ricinus communis), fluted pumpkin seeds (Telfairia occidentalis), or melon seeds (Citrullus vulgaris) [36, 77] are common derivatives of legume-based fermentation. Furthermore, the African carob tree (Parkia biglobosa) is the source of Dawadawa/iru (Nigeria), Soumbala (Burkina Faso), Netetu (Senegal), Kinda (Sierra Leone), and Kpalugu (Ghana) by the fermentation of its seeds [29, 78, 79]. In low-income homes, these ingredients are frequently utilized as inexpensive meat alternatives and sauces in most local meals [11]. The Bacillus group (Bacillus subtilis, B. licheniformis, B. megaterium, B. coagulans, and B. circulans) [29, 80], Micrococcus, Corynebacterium, and Enterococcus faecium [81] are the most often associated bacteria. Saccharomyces cerevisiae, Yarrowia lipolytica, Rhodotorula gluti, and Streptococcus natalensis have all been mentioned by certain writers [82]. Similar microbes, especially those belonging to the Saccharomyces, Enterobacter, and Bacillus genera, have been linked to the fermentation of legumes in Asia, and many of them have probiotic qualities [75, 83].

• Because they are inexpensive, essential to baby weaning diets, and useful as functional meals for kids and adults, fermented cereal products are widely consumed on a regular basis in West Africa [84]. Corn (Zea mays), millet (Panicum miliaceum), rice (Oryza sativa), and wheat (Triticum aestivum) are common grains of interest. To increase their nutritious content, these grains may occasionally be fermented alone or in combination. Grain-based fermented meals are thought to be health boosters because of their abundance of micronutrients and potential probiotic bacteria [85].

• Grain nutritional and biochemical changes occur during fermentation, enhancing texture and flavor. Nigerians eat a lot of akamu/ogi, a porridge prepared from fermented maize [38, 86, 87]. Kenkey and banku are popular in Ghana [88, 89]. Other variations that are indigenous to various parts of West Africa are Agidi/Eko, Tuwo, Kunu, Ogi-baba, and Fura. The LAB group (Leuconostoc sp., Lactiplantibacillus plantarum, Lactococcus lactis, and Pedicoccus sp.), as well as yeasts such Candida tropicalis, Geotrichum fermentum, and S. cerevisiae, are the microorganisms that are often related [38]. During fermentation, grains undergo nutritional and biochemical changes, improving taste and texture. Akamu/ogi, a porridge made from fermented maize, is widely consumed across Nigeria [38, 86, 87]. In Ghana, kenkey and banku are common [88, 89]. Other derivatives include Agidi/Eko, Tuwo, Kunu, Ogi-baba and Fura, which are native to several regions of West Africa. The commonly associated microorganisms are the LAB group (Leuconostoc sp., Lactiplantibacillus plantarum, Lactococcus lactis, and Pedicoccus sp.), yeasts such as Candida tropicalis, Geotrichum fermentum and S. cerevisiae [38]. The primary factors enhancing nutritional and organoleptic qualities are known to be produced by LAB, along with a broad spectrum of antibacterial agents and organic acids [10]. The probiotic qualities and activities of these LAB strains are maybe most significant. By producing enzymes like lipase, phytase, and esterase, which have specific roles during fermentation, yeasts contribute to improved flavor. According to Chinedu et al. [90], esterase affects taste and aroma, phytase lowers the amount of phytic acids, which can decrease protein digestibility, and lipolytic activity produces fatty acids, which are flavor precursors. Probiotic qualities are also exhibited by some of these yeast strains [91].

Example: Lb. plantarum has been isolated from fermented Nigerian cereals such as Ogi, Kunu-Zaki, Koko, Kenkey, and Ben-Saalga. It has probiotic functions, plantaricin production potential, and amylase enzyme expression, making it suitable for probiotics and industrial processing [45, 89, 92, 93, 94].

• Dairy products are widely consumed in various parts of Africa, with the greatest popularity in the pastoral areas (North Africa, Savanna, Sudan, and East African Highlands) [95]. Cow’s milk and other animal milk can be used. Typical examples include Wara and Nono (Nigeria); also known as Fene in Mali, Nyamie in Ghana, and Sour Milk in Ivory Coast [9]. Warakashi (Nigeria), obtained from milk, also called Wakashi in Ghana [96] or Wagashie/fromage peuhl in Togo; are value-added products of lactic fermentation [97]. During fermentation, most of the milk sugar (lactose) is converted into lactic acid through the action of LAB [11]. Fermented milk products have a high microbial diversity. The major microbes are lactobacilli (LAB), which are great providers of protein, vitamins, and calcium. Examples of these microorganisms include Lb. acidophilus, Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Ligilactobacillus salivarius, Limosilactobacillus fermentum and Lactiplantibacillus plantarum [31, 98]. More over Enterococcus faecium strains from Nigerian cow’s milk have shown good probiotic activity in vitro due to their low pH tolerance, bile salt-hydrolase (BSH) activity, safety and adhesion properties. Amylolytic lactic acid bacteria (ALAB) isolated from traditional Nigerian fermented foods are tolerant to pH 2 and bile salts [99].

• Fermented beverages: In Africa, there are various fermented drinks, including palm wine, traditional drinks like Pito/Asana, Burukutu, Mbonge Bigere/Tonto, and Tej, which contain probiotic microorganisms [77, 100]. Non-alcoholic African drinks include Kunu-Zaki, Togwa, Thobwa, and Mahewu, made from grains like sorghum, millet, corn, fruits, and honey [101]. Under a variety of names, including doka/nsafufuo/akpeteshi (Southern Ghana), sodabi (Togo, Benin), mmanya ngwo/nkwu ocha/emu (Nigeria), bandji (Ivory Coast, Mali, Burkina Faso), poyo (Sierra Leone), and singer (Gambia), palm juice and its derivatives are widely consumed throughout the West African region [101, 102]. Fermented grains, dairy products, and beverages also contain microorganisms with probiotic potential, such as LAB species (Lactobacillus, Pediococcus, Leuconostoc) and yeasts (S. cerevisiae, Zygosaccharomyces baili, Brevibacterium, Bacillus, Streptococcus, Candid spp., and Pichia) [102, 103]. These organisms may produce vitamins, digestive enzymes, and bioactive compounds that may help combat diseases. According to Ndukwe [104] drinking Kunu offers numerous health and nutritional benefits, including body tissue development, gallstone prevention, heart and breast cancer protection, bowl purging, relief of flatulent conditions, lactation enhancement in nursing mothers, and antioxidant properties. It also prevents heart attacks, thrombosis, cancer, and rheumatism symptoms. Kunu is rich in vitamins and minerals, with antioxidant, anti-inflammatory, and anti-fungal properties. It is beneficial for children, those with certain health conditions, and diabetics. It is a sustainable alternative with acceptable nutritional profile.

LAB strains with functional characteristics and enhanced technological and probiotic properties are suitable for improving the quality and production of indigenous fermented foods with health benefits.

3.5 Effect of consuming West African indigenous fermented foods on gastro-intestinal tract microbiota

Consuming fermented dairy products can protect against pathogenic bacterial strains like Bacteroides fragilis and Salmonella typhi by modulating gut microbiota or producing bioactive antimicrobial peptides. Enzymatic digestion of milk protein α-casein S1 produces peptides isracidin and casocidin, which inhibit the growth of Staphylococcus aureus, Listeria monocytogenes, Streptococcus pyogenes, Staphylococcus carnosus, and Escherichia coli. Whey protein also contains antimicrobial peptides [105, 106].

Consuming cereal-based fermented foods enriches the intestinal microbiome with gram-positive bacteria from the Firmicutes and Actinobacteria phyla, as well as yeast and fungi species. These products contain soluble fibers, resistant starch, phenolics, peptides, galacto- and fructo-oligosaccharides, making them potential prebiotic sources. Recent studies show that Bacteroidetes, a part of the human gut microbiota, utilize mixed-linkage β-(1,3)/β-(1,4)-glucans (MLGs) for gut microbial metabolism [107, 108, 109]. Dextrins from cereal products like maize starch stimulate Actinobacteria and Bacteroidetes growth, benefiting gut microbiota. Unabsorbed polyphenols reach the large intestine, where microbial degradation degrades them, modifying gut microbiota biodiversity and providing health benefits [110].

3.6 The technological aspect of microbes involved in the West African indigenous fermented foods

In food matrices, there is a mixture of fermenting microorganisms. This mix is made up of lactic bacteria, yeasts, molds, Bacillus,… In this section, we will discuss the role played by these microbes in obtaining various West African fermented foods.

3.6.1 Role of LAB in traditional fermented food and beverages

The role of LAB in traditional food and beverage fermentation is crucial for enhancing the quality and taste of these products. We distinguish:

• Lactic acid fermentation (LAB) is a safe process that converts fermentable sugars into lactic acid, producing metabolites and probiotic potentials. This process enhances food shelf-life and microbial safety, extends the nutritional quality of fermented foods and beverages (FFB), treats acute infantile diarrhea, and has antimicrobial properties. LAB also decreases antinutrient content in FFB, improving the bioavailability of essential dietary minerals. Its long history and positive health impacts make LAB a valuable tool in food production [4];

• Two Lactobacillus plantarum strains from Nigeria, kunu-zaki and ogi expressed the rhamnosidase gene, but only the amylase gene was expressed by Lb. plantarum ULAG11. Lb. plantarum ULAG24 showed resistance to acid, bile salt concentration, and anaerobic environments, and exhibited probiotic functions and plantaricin production potential. These diverse functional attributes suggest that these strains could be used for industrial processing of fermented cereals in West Africa [45];

• Lactic acid fermentation is a traditional African food fermentation process using lactic acid bacteria (LAB) as non-pathogenic microorganisms. These bacteria, mainly from the Lactobacillus, Lactococcus, Leuconostoc, Streptococcus, Weissella, and Enterococcus genera, produce lactic acid from carbohydrate metabolism using the glycolytic pathway or phosphoketolase metabolic pathway. The products impart desirable flavor, color, and sensory quality attributes to fermented foods. Common fermented foods from plant sources include dietary staples, porridges, alcoholic beverages, non-alcoholic beverages, and condiments [111];

• Prevention and treatment of dental caries: Probiotics, such as Lactobacillus and Bifidobacterium, have been found to have beneficial effects in the oral cavity by inhibiting cariogenic bacteria. Probiotics could also be used to prevent and treat dental caries, periodontal disease, and halitosis [9]. Using indigenous fermented food, which contains those microbes, could be benefit to the consumers;

• Prevention of Type II diabetes and obesity: Studies suggest that probiotic bacteria can help manage insulin-independent diabetes. Nutrients with prebiotic and probiotic properties have positive effects on host well-being, reducing obesity and diabetes. Probiotic bacteria induce beneficial changes in gut microbiota, reducing inflammation and reducing the systemic inflammatory response in type II diabetes. Consumption of yogurt rich in probiotic bacteria may exert antidiabetic and antioxidant properties, and probiotic soy milk could modulate blood lipoprotein levels, potentially managing diabetes complications and atherosclerotic risks [9].

• Lowering serum cholesterol levels: Cholesterol is crucial for human heart health, but dietary cholesterol is a leading cause of cardiovascular diseases like stroke and heart attack. Probiotic bacteria have been found to reduce serum cholesterol, with some studies suggesting that cholesterol precipitates out during in vitro studies and is excreted under in vivo conditions. However, more research is needed to determine if probiotics are purveyors of antibiotic resistance genes. Carnivores, such as Bifidobacterium longum SPM 1207 and Lactobacillus oris HMI68, have potential applications in controlling cholesterol levels in humans. Lactobacillus plantarum and L. brevis from pickle cabbage have shown potential to reduce cholesterol levels but increase high-density lipoprotein cholesterol levels in mice treated with probiotic bacteria. Probiotic consumption has been found to have a positive influence on metabolic disorders, counteracting obesity effects and regulating lipid metabolism [9].

• LAB as drug-delivery vehicles: LABs have potential as oral immunization vehicles due to their GRAS status, adjuvant profile, mucosal adhesion, and low intrinsic immunogenicity. Live bacterial vaccine vectors can be used for antigen delivery, but greater stability and low production costs are required to achieve maximum benefit. LABs are ideal candidates for drug-delivery, including oral and intranasal administration, and have the potential to treat asthma in humans. Intranasal vaccination with live bacterial vectors is more effective than vaccination against non-colonizing organisms, but live recombinant bacteria generally elicit a strong mucosal immune response. The safety profile and efficacy of LAB as expression vectors suggest a promising future for GRAS bacteria as expression vectors. Challenges include identifying, characterizing, and screening strains and understanding their mechanism of action in specific diseases [112, 113, 114]. These findings suggest that LAB isolated from various fermented indigenous foods from West Africa needs to be studied deeply in order to apply them in vaccinology sector.

• Antifungal agents and other antimicrobial agents from LAB: Antibiotic-resistant microbial species, including fungi, yeasts, and spoilage molds in food and feeds, are becoming more prevalent. These fungi and molds are also resistant to preservatives and chemical detergents. Lactobacillus reuteri produces antimicrobial compounds like lactic acid and propionic acid, which inhibit microorganisms [115, 116].

• Probiotic LAB strains as aflatoxin detoxifiers in Ogi: Lactiplantibacillus plantarum M26 and Limosilactobacillus fermentum W310 detoxified aflatoxins B1 and B2 [117].

• It has been discovered in Ghana that naturally fermented nunu cultures limit the growth of a number of human pathogens, including Bacillus cereus, Salmonella typhi, L. monocytogenes, Escherichia coli, and Staphylococcus aureus [118]. Furthermore, Burkina Faso’s yogurt-like products generated molecules that resembled bacteriocin and had antibacterial properties against Enterococcus faecalis 103907 CIP, B. cereus 13569 LMG, S. aureus ATCC 25293, and E. coli 105182 CIP [119].

3.6.2 Role of yeasts in traditional fermented foods and beverages

• Yeasts, a mixed population with LAB, significantly influence the quality, taste, texture, and flavor of fermented food products. They are essential functional microorganisms in indigenous food and beverage production, such as baker’s yeast for bread leavening and wine and beer fermentation. S. cerevisiae, the predominant yeast species in African indigenous fermented foods (IFF), has been designated “GRAS” status and used for recombinant food and feed additives. Yeasts have applications in ethanol production, single-cell protein production, feeds, industrial enzymes, and metabolites [4].

• Jespersen [120] states that Saccharomyces cerevisiae is primarily responsible for the production of aromatics and alcohols, but it also plays a role in lactic acid bacteria stimulation, nutritional value enhancement, probiotic effects, inhibition of unwanted microorganisms, and the synthesis of tissue-degrading enzymes.

• Macronutrient bioavailability: Cereals like maize have low protein content and bioavailability, leading to essential amino acid deficiency. Fermenting mawè with yeast cultures increased total free amino acids up to 30.4%. Protease, lipase, and esterase enzymes are secreted by these yeasts, which help release amino acids, taste, and aroma components during fermentation. β-Glucosidase, β-D-galactosidase, inulinase, and polygalacturonases are also produced when K. marxianus is used [121, 122, 123, 124].

• Micronutrient bioavailability: Cereals, contain high levels of antinutrient phytate, which is a strong chelating agent that limits the bioaccessibility and availability of micronutrients. Phytate is primarily present in the germ and is found in low quantities compared to other cereals, contributing to micronutrient deficiencies in communities where cereals are staple foods. Fermentation has been reported to improve the nutritional quality of fermented foods due to yeast growth and enzymatic activity of yeasts. One enzyme, phytase, hydrolyzes phytate to lower inositol phosphates. Phytase activity and genes encoding the enzyme have been identified in yeasts isolated from cereal fermentations. Phytase activity is dependent on pH and is affected by the concentration of external free inorganic phosphate [125, 126, 127, 128].

• Biosynthesis of folic acid: Folate, a water-soluble, fully oxidized monoglutamate form of vitamin B9, plays a critical role in cellular metabolism and plays a role in amino acid synthesis, nucleotide biosynthesis, and the oxidation and reduction of carbon units necessary for normal cell division and growth. In biological activity, folate derivatives including L-methylfolate, tetrahydrofolate (THF), and dihydrofolate are the primary actors. Developmental abnormalities and chronic illnesses are due to folate insufficiency. Fungi synthesize the vitamin de novo, while mammals consume folic acid through their diet. Folate derivatives are converted into one another by the uptake or release of C1 groups during folate biosynthesis. Based on the bioavailability of various forms of folate, the recommended daily allowance (RDA) for folate is determined in micrograms of dietary folate equivalents (DFE). Legumes contain the highest folate content, while fermented grains have a higher folate content. The fermentative yeast Saccharomyces cerevisiae is considered a producer of folic acid and its genetic composition favors its synthesis [128, 129, 130, 131, 132].

• Yeasts as important contributors to flavor formation: Native fermented foods and drinks from sub-Saharan Africa are renowned for having authentic flavors. During fermentation, S. cerevisiae and P. kudriavzevii create a variety of chemicals that give them their distinctive sensory qualities. The flavor they produced are alcohols, esters, organic acids, aldehydes, sulfur, carbonyls, esters, acids, furan, and phenolic (of which 51 were volatile) compounds. However, their importance in flavor formation has not been extensively investigated [133].

• Phytate complexes formed by chelation are insoluble at physiological pH, making it difficult for divalent ions to be absorbed in the human intestine. Phytase activity in yeasts, particularly P. kudriavzevii, is growth phase-dependent and found in solid foods, non/low-alcoholic beverages, and alcoholic beverages. Indigenous yeasts can improve the nutritional value of cereal-based products by producing folate through fermentation, which the human body cannot synthesize. Controlling processing conditions can increase folate contents in fermented food [133].

• Some strains, like C. rugosa, K. marxianus, P. kudriavzevii, and Trichosporon asahii, from cereal-based beverages burukutu, kunun-zaki, and ogi can increase intestinal epithelial electrical resistance. S. cerevisiae strains from fermented foods also showed potential probiotic properties, reducing IL-1a expression upon E. coli infection [133].

3.6.3 Synergistic interactions between LAB and yeast in a fermenting food matrix

• In Africa, traditional fermented foods (AFF) are made by fermentation using either lactic acid (LAB), yeasts, or a combination of the two. LAB plays an important role in converting substrates into lacto-fermented foods, working with beneficial yeasts and other microorganisms. The process involves complex microbial interactions, either symbiotic or synergistic, that cause a division of labor between microbes. Researchers have reported a coexistence and synergistic relationship between LAB and yeasts in traditional African fermentation products, particularly grain-based fermentations. The acidic environment created by LAB promotes yeast growth and provides growth factors such as vitamins and soluble nitrogen compounds. Key metabolic activities during grain-based fermentation include acidification, flavor formation, and yeast [4, 134].

• Yeasts and LAB have also been implicated in the fermentation of many other non-cereal products, such as fermented cassava tubers. The nutritional and functional qualities of food are influenced by the complementary metabolic activities of yeast and LAB, which makes it possible to choose strains with desired qualities for use as starting cultures in the creation of functional fermented meals [4, 134].

• In fermented foods, yeasts and lactic acid bacteria (LAB) interact through cross-feeding, metabolite exchange, and nutrient transport rates. LAB can be inhibited by yeast’s ethanol, while yeast cells release vitamins and biofactors that stimulate bacterial growth. Overgrowth of LAB and acetic acid bacteria increases lactic and acetic acid concentrations, inhibiting yeast growth. During fermentation, yeasts produce primary metabolites like ethanol, amino acid metabolites, and phenolic compounds. During spontaneous fermentations, changes in amino acid content, organic acid concentration, volatile aromatic compounds, and vitamin content can be detected [128].

• For example, in ogi, yeasts benefit from acidification facilitated by LAB, while LAB species provide growth factors, such as amino acids. Mutualistic interactions have also been reported between LAB species and yeasts from indigenous sub-Saharan African fermented milk products [133].

3.6.4 Bacillus species

• Bacillus spp. are the dominant bacteria in the fermentation of protein-rich legumes and seeds, particularly in the production of alkaline fermented condiments like iru, soumbala, and bikalga. The long cooking time of these fermented products allows them to select heat-resistant spore formers. The degradation of proteins by Bacillus spp., particularly B. subtilis, B. pumilus, and B. licheniformis, accumulates peptides and ammonia, increasing pH and promoting Bacillus spp. proliferation. Also, their ability to produce enzymes hydrolyzes cassava tissue is responsible for the textural changes during fermentation [134, 135, 136, 137, 138, 139].

• Fermentation technology, containing probiotics, offers health benefits and reduces stress, while inhibiting pathogenic and spoilage bacteria and fungi. However, food safety concerns arise due to raw materials, packaging, and unhygienic conditions. In West and Central Africa, fermented food condiments are primarily produced by Bacillus species, with manual operations and unhygienic conditions [111].

• Use of Bacillus species as probiotics: Bacillus species endospores have been proposed as heat-resistant alternatives, with clinical trials supporting their probiotic activity. Bacillus probiotics have been shown to reduce chronic gastro-intestinal symptoms and increase infection resistance. However, the presence of pathogenic strains and the dose required for probiotic effects in Bacillus-fermented foods remain unclear [140, 141, 142, 143, 144].

4. Conclusions

Fermented foods are safe and health-promoting due to their pH level, lactic acid production, and yeast involvement. They convert perishable foods into edible, shelf-stable forms, aiding in food digestibility and palatable food. However, improper production is prevalent in developing African countries, and adhering to Good Manufacturing Practice and Good Hygiene Practice can improve product safety. African fermented dairy products provide essential nutrients and extend shelf-life, with bioactive peptides playing a vital role in preventing diet-related diseases. Lactobacillus sp., common in Nigerian fermented foods like ogi and kunun-zaki, and other fermented found in West African countries; can colonize the vagina, kill viruses, and reduce the risk of infections. Consumption of these foods and beverages has been linked to improved brain health, cognitive function, and mental health disorders. Lactic fermentation positively impacts the nutritional value and digestibility of raw materials, increasing nutrient bioavailability, antioxidant activity, vitamin biosynthesis, and degradation of antinutritional ingredients.

Conflict of interest

The authors declare no conflict of interest.