Effect of electroporation on viability and bioconversion of isoflavones in mannitol-soymilk fermented by lactobacilli and bifidobacteria

BACKGROUND: The aim of this study was to evaluate the effect of electroporation (2.5-7.5 kV cm(-1) for 3.0-4.0 ms) on the growth of lactobacilli and bifidobacteria, membrane properties and bioconversion of isoflavones inmannitol-soymilk. RESULTS: The viability of lactobacilli and bifidobacteria decreased immediately after electroporation. This was attributed to lipid peroxidation, which led to alterations in the membrane phospholipid bilayer, specifically at the polar head, interface and apolar tail regions. Such alterations also resulted in decreased membrane fluidity and increased membrane permeability upon electroporation (P < 0.05). However, the effect was reversible and treated cells showed better growth than the control upon fermentation for 24 h at 37 degrees C (P < 0.05). Additionally, electroporation increased the bioconversion of glucosides to bioactive aglycones inmannitol-soymilk, which was attributed to increased intracellular and extracellular beta-glucosidase activities of cells upon treatment (P < 0.05). CONCLUSION: Application of electroporation on lactobacilli and bifidobacteria could be beneficial for the development of fermented soymilk with enhanced bioactivity. Considering the enhanced bioactive aglycones, this soymilk could be useful for the prevention of hormone-dependent disorders. (C) 2012 Society of Chemical Industry