Exploring the use of Safety-Assessed Bacteriocin-Producing Enterococci as Starters for Production of Soy Yoghurt Analogues

Plant-based yoghurt analogs have gained significant popularity recently. Key driving factors are lactose intolerance and the perception that plant-based foods are more sustainable than dairy alternatives. When preparing plant-based yoghurt analogs, often conventional yoghurt cultures are used, despite the fact that plant-based substrates differ significantly from milk. Enterococci are known for their broad carbohydrate utilization repertoire, and many strains are considered safe and are used as probiotics. In this study, we explored the potential of enterococci for fermenting soymilk. Out of four strains tested, Enterococcus faecium BT0194, Enterococcus lactis B0167_2, E. lactis BT0173_2, and E. lactis CS4674, three strains acidified plain soymilk to a pH below 4.7 using an initial inoculum of 10⁶ cells/ml (standard inoculum when preparing yoghurt). Enterococcus is renowned for producing bacteriocins; all strains harbored multiple bacteriocin genes. Thus, we investigated whether the four strains could confer a bioprotective effect, and indeed, a strong antimicrobial effect was observed against the tested pathogens. Three strains demonstrated α-galactosidase activity, which is necessary for degrading the indigestible and flatulence-inducing α-galactosides raffinose, stachyose, and verbascose, which are undesirable in soymilk. Additionally, all tested strains had the ability to degrade phytic acid, an unwanted antinutrient found in many plant-based foods, including soymilk. In conclusion, our results demonstrate that the Enterococcus strains tested exhibit considerable potential for use in plant-based fermentations, due to efficient acidification capacity and a capacity to degrade phytic acid in soymilk.