Quality characteristics and microbial community dynamics of soy whey fermented by Tibetan kefir grains

Abstract

The evolution of microbial flora was characterized during the soy whey fermentation process by Tibetan kefir grains by analyzing changes in bacterial and fungal community structures using amplicon sequencing. Moreover, changes in physicochemical indexes and active components were monitored. Acidity, pH, and oligosaccharides got a dramatic decline after 30 h of fermentation, while the aglycones isoflavones significantly increased which resulted in a noticeable increase of DPPH· scavenging ability from 53.0% to 70.2%, and many new aromatic volatile compounds were produced. Yeasts, lactic acid bacteria, and acetic acid bacteria grew to more than 7 log CFU/ml after fermentation. The relative abundance of Lactobacillus and Acetobacter changed dramatically in fermented soy whey, which can be ascribed to the increase in aglycone isoflavones levels, especially genistein. This research may deepen the understanding of the mechanism in the fermentation of soy whey by Tibetan kefir grains, and provide a scientific basis for the utilization of soy whey. Novelty impact statement The fermentation process of soy whey by Tibetan kefir grains was studied. Yeasts, lactic acid bacteria, and acetic acid bacteria grew to more than 7 log CFU/ml after fermentation, and Acetobacter became the dominant genus. Aglycone isoflavones and amino acid nitrogen significantly increased, and DPPH· scavenging ability increased to 70.2%. In addition, new aromatic volatile compounds were produced.