Cereal-based fermented foods as microbiota-directed products for improved child nutrition and health in sub-Saharan Africa.

Several strategies, programs and policies have long been developed and implemented to alleviate child malnutrition in sub-Saharan African countries. However, stunting and wasting still persist at an alarming rate, suggesting that alternative strategies are needed to induce faster progress toward the 2030 SDGs targets of reducing malnutrition. Gut microbiota-directed intervention is now being recognized as an unconventional powerful approach to mitigate malnutrition and improve overall child health. In an African setting, manufactured probiotic and synbiotic foods or supplements may not be successful owing to the non-affordability and high attachment of African populations to their food tradition. This review analyses the potential of indigenous fermented cereal-based products including porridges, doughs, beverages, bread- and yoghurt-like products, to be used as microbiota-directed foods for over 6 months children. The discussion includes relevant strategies to effectively enhance the beneficial effects of these products on gut microbiota composition for improved child health and nutrition in sub-Saharan Africa. Characterization of probiotic features and general safety of food processing in sub-Saharan Africa as well as randomized clinical studies are still lacking to fully ascertain the health effects and suitability of these fermented foods in preventing and treating child malnutrition and diarrhea.

B-vitamins and heat processed fermented starchy and vegetable foods in sub-Saharan Africa: A review.

Micronutrient deficiency still occurs in sub-Saharan Africa (SSA) despite the availability of several food resources, particularly fermented foods and vegetables, with high nutritional potential. Fermentation enhances the quality of food in several aspects. Organoleptically, certain taste, aroma, and textures are developed. Health and safety are improved by inhibiting the growth of several foodborne pathogens and removing harmful toxic compounds. Furthermore, nutrition is enhanced by improving micronutrient contents and bioavailability from the food, especially vitamin B content. However, during processing and before final consumption, many fermented foods are heat treated (drying, pasteurization, cooking, etc.) to make the food digestible and safe for consumption. Heat treatment improves the bioavailability of B-vitamins in some foods. In other foods, heating decreases the nutritional value because some B-vitamins are degraded. In SSA, cooked starchy foods are often associated with vegetables in household meals. This paper reviews studies that have focused fermented starchy foods and vegetable foods in SSA with the potential to provide B-vitamins to consumers. The review also describes the process of the preparation of these foods for final consumption, and techniques that can prevent or lessen B-vitamin loss, or enrich B-vitamins prior to consumption.

Multifunctional properties and safety evaluation of lactic acid bacteria and yeasts associated with fermented cereal doughs.

Spontaneous cereal fermentations involve diverse lactic acid bacteria (LAB) and yeasts which may include multifunctional and safe or unsafe strains. This study assessed acidification ability, safety, antifungal activity and free amino acids release ability of LAB and yeasts previously isolated from spontaneously fermented cereal doughs in Benin. Fourteen LAB and thirteen yeast strains were studied in liquid media and/or in a model cereal dough prepared in laboratory conditions. Antifungal activity was assessed against Candida glabrata in liquid medium. Amino acids were determined by pre-column derivatization and separation with reversed-phase HPLC. Antimicrobial susceptibility was analysed by minimum inhibitory concentration determination. The acidification ability was higher for LAB compared to yeast strains. All LAB strains retarded the growth of C. glabrata Cg1 with the highest inhibition recorded for Weissella confusa Wc1 and Wc2. The highest free amino acid content was found in the doughs fermented with Pichia kudriavzevii Pk2 and Pk3. All the LAB strains were susceptible to ampicillin, chloramphenicol, erythromycin, but displayed phenotypic resistance to kanamycin, streptomycin and tetracycline. Positive PCR amplicon of resistance genes were detected in the following cases: 2 LAB strains were positive for kanamycin (aph(3)III), 5 strains were positive for streptomycin (aadA and/or strA and/or strB) and 3 strains were positive for tetracycline (tet (L) and/or tet (M)). For yeasts, most of the P. kudriavzevii strains were resistant to amphotericin B, fluconazole and itraconazole opposite to K. marxianus and Saccharomyces cerevisiae strains which were susceptible. The results obtained are valuable for selecting safe and multifunctional strains for cereal fermentation in West Africa.

Comparison of the microbial composition of African fermented foods using amplicon sequencing.

Fermented foods play a major role in the diet of people in Africa, where a wide variety of raw materials are fermented. Understanding the microbial populations of these products would help in the design of specific starter cultures to produce standardized and safer foods. In this study, the bacterial diversity of African fermented foods produced from several raw materials (cereals, milk, cassava, honey, palm sap, and locust beans) under different conditions (household, small commercial producers or laboratory) in 8 African countries was analysed by 16S rRNA gene amplicon sequencing during the Workshop "Analysis of the Microbiomes of Naturally Fermented Foods Training Course". Results show that lactobacilli were less abundant in fermentations performed under laboratory conditions compared to artisanal or commercial fermentations. Excluding the samples produced under laboratory conditions, lactobacilli is one of the dominant groups in all the remaining samples. Genera within the order Lactobacillales dominated dairy, cereal and cassava fermentations. Genera within the order Lactobacillales, and genera Zymomonas and Bacillus were predominant in alcoholic beverages, whereas Bacillus and Lactobacillus were the dominant genera in the locust bean sample. The genus Zymomonas was reported for the first time in dairy, cereal, cassava and locust bean fermentations.

Effects of intrinsic microbial stress factors on viability and physiological condition of yeasts isolated from spontaneously fermented cereal doughs.

Fermented cereal doughs constitute a predominant part of West African diets. The environment of fermented doughs can be hostile for microbial survival due to high levels of microbial metabolites such as weak carboxylic organic acids and ethanol. In order to get a better understanding of the intrinsic factors affecting the microbial successions of yeasts during dough fermentation, survival and physiological responses of the yeasts associated with West African fermented cereal doughs were investigated at exposure to relevant concentrations of microbial inhibitory compounds. Three strains each of the predominant species, i.e. Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia kudriavzevii as well as the opportunistic pathogen Candida glabrata were studied. The strains were exposed to individual stress factors of cereal doughs, i.e. (i) pH 3.4, (ii) 3% (v/v) ethanol (EtOHpH3.4), (iii) 285 mM lactic acid (LApH3.4) and (iv) 150 mM acetic acid (AApH3.4) as well as to combinations of these stress factors, i.e. (v) (LA + AA)pH 3.4 and (vi) (LA + AA+EtOH)pH 3.4. Growth and single cell viability were studied by flow cytometry using combined SYTO 13 and propidium iodide (PI) staining. Intracellular pH (pHi), plasma membrane integrity and micro-colony development of stressed cells were studied by fluorescence microscopy using PI and carboxyfluorescein diacetate succinimidyl ester (CFDA-se). Viability of the yeast strains was not affected by pH 3.4 and 3% (v/v) ethanol (EtOHpH3.4). 285 mM lactic acid (LApH3.4) reduced the specific growth rate (µmax) from 0.27-0.41 h-1 to 0.11-0.26 h-1 and the viability from 100% to 2.6-41.7% at 72 h of exposure in most yeast strains, except for two strains of C. glabrata. 150 mM acetic acid (AApH3.4) as well as the combinations (LA + AA)pH 3.4 and (LA + AA+EtOH)pH 3.4 reduced µmax to 0.0 h-1 and induced significant cell death for all the yeast strains. Exposed to (LA + AA+EtOH)pH 3.4, the most resistant yeast strains belonged to S. cerevisiae followed by P. kudriavzevii, whereas C. glabrata and K. marxianus were more sensitive. Strain variations were observed within all four species. When transferred to non-stress conditions, i.e. MYGP, pH 5.6, after exposure to (LA + AA+EtOH)pH 3.4 for 6 h, 45% of the single cells of the most resistant S. cerevisiae strain kept their plasma membrane integrity, recovered their pHi to near physiological range (pHi = 6.1-7.4) and resumed proliferation after 3-24 h of lag phase. The results obtained are valuable in order to change processing conditions of the dough to favor the survival of preferable yeast species, i.e. S. cerevisiae and K. marxianus and inhibit opportunistic pathogen yeast species as C. glabrata.

Occurrence of lactic acid bacteria and yeasts at species and strain level during spontaneous fermentation of mawè, a cereal dough produced in West Africa.

Mawè is a West African spontaneous fermented cereal-based dough. Different types of mawè exist varying in type of cereal and/or production condition, with fermentations lasting 24-48 h. With the aim of obtaining a comprehensive understanding of the microbial ecology of mawè processing, a microbiological characterisation was performed for four mawè types, produced at eight sites in Benin. At the onset of the fermentations lactic acid bacteria (LAB) and yeast counts were on average 7.5 ±â€¯1.03 and 4.8 ±â€¯0.79 Log10 cfu/g, which increased to 9.2 ±â€¯0.38 and 7.4 ±â€¯0.42 Log10 cfu/g, respectively, at the end of the fermentations. LAB (n = 321) and yeasts (n = 298), isolated during the fermentations, were identified. The predominant LAB and yeast species were Lactobacillus fermentum and Pichia kudriavzevii, respectively, followed by Kluyveromyces marxianus, all present throughout the mawè fermentations. Further, microbial successions took place with Weissella confusa occurring mostly at the onset, while Pediococcus acidilactici and Saccharomyces cerevisiae were mainly associated with the end of the fermentations. Species diversity was influenced both by type of cereal and production condition. The dominating strain clusters of L. fermentum and P. kudriavzevii were ubiquitous and strain diversities were influenced by type of cereal and production site.