Effect of Spices on the Microbial Diversity, Physicochemical Properties and Nutritional Properties of Fermented Millet (Pennisetum glaucum) Slurry

Fermentation improves taste, adds flavour and makes nutrients easily digestible. Millet porridge is produced from spontaneous fermentation of pearl millet grain with or without spices. A study was carried out to evaluate the proximate, nutritional, and bacterial diversity composition during fermentation of pearl millet slurry with and without spices. In this experimental study, some millet grains were fermented with selected spices, while others were fermented without spices. The pH, proximate and mineral analysis, and lactic acid production were determined in the fermented products. The 16S ribosomal RNA (16S rRNA) metagenomic method was used to identify the microbial diversity and abundance in the fermented millet slurry with and without spices. The slurry fermented with spices recorded 22.50 (mg/g) iron at 24 hours whilst without spices recorded a 10.10 (mg/g) iron content. Furthermore, zinc content at 24 hours for slurry with spices was 175.50 (µg/g) whilst without spices was 60.10 (µg/g). The lactic acid content for millet slurry without spices was between 7.16µg/mL and 9.22µg/mL whilst the lactic acid content for millet slurry with spices was between 6.55µg/mL and 9.88µg/mL produced after a 72-h fermentation period. Acetobacter was the most dominant genera in the fermented slurry (54.23%). The relative abundance of the genus Lacticaseibacillus (19.71% to 1.69%), Lactobacillus (0.49% to 5.25%), Limosilactobacillus (2.43% to 40.96%), Acetobacter (54.23% to 34.93%), Schleiferilactobacillus (16.29% to 0.84%) were present in the fermented slurry. The fermentation of pearl millet grains with spices improves the nutritional composition of pearl millet and provides a diversified fermenting bacteria community. The most dominant species in the slurry fermentation can be formulated into starter cultures to be used in controlled fermentation.