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Background: Folate (vitamin B9) occurs naturally mainly as tetrahydrofolate (THF), methyl-tetrahydrofolate (M-THF), and formyl-tetrahydrofolate (F-THF), and as dietary synthetic form (folic acid). While folate auxotrophy and prototrophy are known for several gut microbes, the specific folate forms produced by gut prototrophs and their impact on gut auxotrophs and microbiota remain unexplored., Methods: Here, we quantified by UHPLC-FL/UV folate produced by six predicted gut prototrophs (Marvinbryantia formatexigens DSM 14469, Blautia hydrogenotrophica 10507  T , Blautia producta DSM 14466, Bacteroides caccae DSM 19024, Bacteroides ovatus DSM 1896, and Bacteroides thetaiotaomicron DSM 2079  T ) and investigated the impact of different folate forms and doses (50 and 200 µg/l) on the growth and metabolism of the gut auxotroph Roseburia intestinalis in pure cultures and during fecal anaerobic batch fermentations (48 h, 37 °C) of five healthy adults., Results: Our results confirmed the production of folate by all six gut strains, in the range from 15.3 ng/ml to 205.4 ng/ml. Different folate forms were detected, with THF ranging from 12.8 to 41.4 ng/ml and 5-MTHF ranging from 0.2 to 113.3 ng/ml, and being detected in all strains. Natural folate forms, in contrast to folic acid, promoted the growth and metabolism of the auxotroph R. intestinalis L1-82, with dose-dependent effects. During fecal batch fermentations, folate forms at both levels had no detectable effect on total bacteria concentration, on gut community composition and metabolic activity and on Roseburia spp. abundance, compared to the control without folate addition., Conclusions: Our study demonstrates for the first time in vitro the production of different natural folate forms by predicted gut prototrophs and the stimulation on the growth of the folate auxotrophic butyrate-producing R. intestinalis L1-82. Surprisingly, folate did not impact fecal fermentations. Our data suggest that the dietary folate forms at the tested levels may only have limited effects, if any, on the human gut microbiota in vivo., (© 2024. The Author(s).)

With the aim of selecting starter cultures with interesting probiotic potential and with the ability to produce folate in a food matrix, yeast strains isolated from fermented cereal-based African foods were investigated. A total of 93 yeast strains were screened for their tolerance to pH 2 and 0.3% of bile salts. Pichia kudriavzevii isolates gave the best results. Selected P. kudriavzevii strains were tested for survival to the simulated human digestion and for adhesion to Caco-2 cells. Moreover, presence of folate biosynthesis genes was verified and production of extra and intra-cellular folate determined during growth in culture medium. 31% of yeast strains could tolerate pH 2, while 99% bile salts. Survival rate after simulated digestion ranged between 11 and 45%, while adhesion rate between 12 and 40%. Folate production was mainly intracellular, maximum after 24 h of growth. To be closer to traditional cereal-based fermentations, a P. kudriavzevii strain with good probiotic potential was co-inoculated with Lactobacillus fermentum strains in a pearl millet gruel. This resulted in in situ folate production that peaked after 4 h. The use of strains with both probiotic and nutritional enrichment properties may have a greater impact for the consumers., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Micronutrient deficiency is a form of malnutrition responsible for different metabolic diseases, widely shared among developing low-and middle-income African countries. While deficiencies of calcium, iron, vitamin A, zinc, and selenium have been counteracted mainly by implementing mandatory food fortification programs, little attention was given so far on strategies to decrease inadequate intake of water-soluble B-group vitamins. In this review, we summarize the physiological role of B-group vitamins, and discuss the approaches commonly used to tackle their deficiencies in Africa, namely (i) dietary diversification, (ii) supplementation, and (iii) fortification, with the main focus being here the microbial-based biofortification of food. We report the increasing evidence of plant-based African fermented foods as important sources of these vitamins and how microbial-based biofortification strategies may enhance their content and bioavailability during plant-based fermentation, especially seen for folate (vitamin B9), riboflavin (vitamin B2), and cobalamin (vitamin B12). The selection of pro-technological functional microbial strains from spontaneous fermentation and/or unconventional food matrices, the employment of vitamin overproducing lactic acid bacteria, as well as the implementation of adequate food processes are promising tools that could be implemented in the production of staple home-made fermented foods to counteract B-group vitamins deficiencies. Further research is needed to explore the biotechnological potential of underexploited indigenous microbial strains and the impact of fortified foods on gut host health. [ABSTRACT FROM AUTHOR]