Technological and probiotic properties of lactic acid bacteria and yeasts isolated from Ghanaian spontaneously fermented pearl-millet porridge, Hausa koko

The spontaneous fermentation of cereals, such as for the production of Hausa koko from millet, could be improved by the use of starter cultures to enhance reproducibility and promote beneficial health effects. This study aimed to select bacteria and yeast which could be used to develop functional starter cultures for Hausa koko fermentation, by evaluating the functional properties of 70 lactic acid bacteria (LAB) and 53 yeast strains isolated during traditional processing of Hausa koko in Ghana. Initial screening of LAB genomes using the bacteriocin genome mining tool BAGEL4 and the Bacterial and Viral Bioinformatics Resource Centre identified 26 strains carrying genes potentially associated with folate, riboflavin, thiamin, nicotinate, nicotinamide, or bacteriocin production. These 26 LAB were further assessed for in vitro technological properties associated with successful fermentation, including acidification rate, exopolysaccharide production, amylase and proteolytic activity and antimicrobial properties. The tolerance to simulated gastrointestinal conditions, including low pH and bile salt, of selected LAB as well as 53 yeast strains was tested in vitro. In general, LAB exhibited good acidification properties with the greatest change in pH occurring within 4 to 8 h of fermentation, particularly in 3 strains. Five Limosilactobacillus pontis strains, 2 L. fermentum strains and one Pediococcus acidilactici strain showed exopolysaccharide production in vitro, while 17 strains demonstrated amylase activity under plate assay conditions, with 7 strains producing a clear zone of > 3.0 mm diameter on iodine-stained starch plates. Of the 26 LAB strains, 25 grew in 1% bile salt concentration, 15 grew at a pH of 2.5, and all 26 grew at a pH of 3.5 to 7, and at temperatures of 25 °C and 37 °C. Inhibitory activities against foodborne indicator pathogens were observed in vitro. All yeast strains showed similar good survival in gastrointestinal tract conditions and showed characteristics such as tolerance to various temperatures, low-to-neutral pH, and bile salt. The LAB strains L. reuteri LDOD-Sud, L. pontis LTAD-12g, and L. fermentum LMAN-Sdb, as well as the yeast strains Saccharomyces cerevisiae YSUN-Sud and Pichia kudriavzevii YTAD-12j displayed multiple in vitro traits consistent with desirable fermentative properties, suggesting potential as starter cultures for millet fermentation.