Sorghum Malt Extract as a Growth Medium for Lactic Acid Bacteria Cultures: A Case of Lactobacillus plantarum MNC 21

Co-fermentation of non-Saccharomyces yeasts with Lactiplantibacillus plantarum FST 1.7 for the production of non-alcoholic beer

The non-alcoholic beer (NAB) sector has experienced steady growth in recent years, with breweries continuously seeking new ways to fulfil consumer demands. NAB can be produced by limited fermentation of non-Saccharomyces yeasts; however, beer produced in this manner is often critiqued for its sweet taste and wort-like off-flavours due to high levels of residual sugars and lack of flavour metabolites. The use of Lactobacillus in limited co-fermentation with non-Saccharomyces yeasts is a novel approach to produce NABs with varying flavour and aroma characteristics. In this study, lab-scale fermentations of Lachancea fermentati KBI 12.1 and Cyberlindnera subsufficiens C6.1 with Lactiplantibacillus plantarum FST 1.7 were performed and compared to a brewer's yeast, Saccharomyces cerevisiae WLP001. Fermentations were monitored for pH, TTA, extract reduction, alcohol production, and microbial cell count. The final beers were analysed for sugar and organic acid concentration, free amino nitrogen content (FAN), glycerol, and levels of volatile metabolites. The inability of the non-Saccharomyces yeasts to utilise maltotriose as an energy source resulted in extended fermentation times compared to S. cerevisiae WLP001. Co-fermentation of yeasts with lactic acid bacteria (LAB) resulted in a decreased pH, higher TTA and increased levels of lactic acid in the final beers. The overall acceptability of the NABs produced by co-fermentation was higher than or similar to that of the beers fermented with the yeasts alone, indicating that LAB fermentation did not negatively impact the sensory attributes of the beer. C. subsufficiens C6.1 and L. plantarum FST 1.7 NAB was characterised as fruity tasting with the significantly higher ester concentrations masking the wort-like flavours resulting from limited fermentation. NAB produced with L. fermentati KBI12.1 and L. plantarum FST1.7 had decreased levels of the undesirable volatile compound diacetyl and was described as 'fruity' and 'acidic', with the increased sourness masking the sweet, wort-like characteristics of the NAB. Moreover, this NAB was ranked as the most highly acceptable in the sensory evaluation. In conclusion, the limited co-fermentation of non-Saccharomyces yeasts with LAB is a promising strategy for the production of NAB.

Structure Characterization of Polysaccharide from Chinese Yam (Dioscorea opposite Thunb.) and Its Growth-Promoting Effects on Streptococcus thermophilus

To clarify the mechanisms underlying the growth-promoting effects of yam polysaccharide on Streptococcus thermophilus (S. thermophilus), the yam polysaccharide was extracted using a deep eutectic solvents (DESs) method and separated into four fractions by DEAE-cellulose 52. These fractions were used as the alternative carbon source to substitute lactose to compare their growth-promoting effects on S. thermophilus. Furthermore, their molecular weight, monosaccharide and functional groups' composition, microscopic forms and other basic structure characterizations were analyzed. The results showed that all the fractions could significantly promote S. thermophilus growth, and fractions exhibited significantly different growth-promoting effects, whose viable count increased by 6.14, 6.03, 11.48 and 11.29%, respectively, relative to those in the M17 broth medium. Structure-activity relationship analysis revealed that the high growth-promoting activity of yam polysaccharide might be more dependent on the higher molecular weight, the higher galacturonic acid content and its complex spatial configuration, and the existence of β-glycosides would make the yam polysaccharide have a better growth-promoting effect on S. thermophilus.