The objective of this study was to evaluate the fermentative characteristics of lactic acid bacteria isolated from local fermented foods and consume raffinose and stachyose during fermentation soymilk. Lactobacillus plantarum pentosus SMN, 01, Lactobacillus casei subsp rhamnosus FNCC, 098, Lactobacillus casei subsp rhamnosus FNCC, 099, Streptococcus thermofilus, 001, Lactobacillus delbrueckii subsp. bulgaricus FNCC, 0045, Lactobacillus plantarum SMN, 25, and Lactobacillus plantarum pentosus FNCC, 235 exhibited variable α-galactosidase activity with Lactobacillus plantarum SMN, 25, showing the highest activity in MRS supplemented media. However, all organisms reached the desired therapeutic level (10 8 cfu/mL) likely due to their ability to metabolize oligosaccharides during fermentation in soymilk at 41 °C. The oligosaccharide metabolism depended on α-galactosidase activity.

This study investigated the possible application of β-glucosidase producing lactic acid bacteria isolated from local fermented foods as a functional starter culture to obtain the bioactive isoflavones, genistein and daidzein, in fermented soymilk. Seven strains of bacteria, Lactobacillus plantarum pentosus SMN 001, Lactobacillus casei subsp rhamnosus FNCC 098, Lactobacillus casei subsp rhamnosus FNCC 099, Lactobacillus casei subsp rhamnosus FNCC 113, Lactobacillus delbrueckii subsp. delbrueckii FNCC 045, Lactobacillus plantarum SMN 025 and Lactobacillus plantarum pentosus FNCC 235 exhibited variable β-glucosidase activity. L. plantarum SMN 025 and L. casei subsp rhamnosus FNCC 098 exhibited the highest β-glucosidase activity of 0.653 and 0.643 U/mL respectively. Acid development, viable populations, β-glucosidase activity and quantification of isoflavone using HPLC were performed at 0, 6, 12, 18, 24 and 30 h of incubation at 41 °C. Seven β-glucosidase-producing strains are able to increase aglycones in fermented soymilk, however, each of the strain produces significantly different bioconversion (p<0.05) of the glucoside isoflavones into their bioactive aglycones. During this fermentation period, with L. plantarum SMN 025, and L. casei subsp rhamnosus FNCC 098, the high level reduced from 150.62 μg/mL (at 24 h) to 142.58 μg/mL and from 150.62 μg/mL (at 24 h) to 144.71 μg/mL, respectively. The indicate that two β-glucosidase producing lactic acid bacteria have great potential for enrichment of bioactive isoflavones in soymilk fermentation.