Enhanced growth of lactobacilli and bioconversion of isoflavones in biotin-supplemented soymilk by electroporation

Abstract

This study aimed at utilizing electroporation to further enhance the growth of lactobacilli and their isoflavone bioconversion activities in biotin-supplemented soymilk. Strains of lactobacilli were treated with different pulsed electric field strength (2.5, 5.0 and 7.5 kV/cm) for 3, 3.5 and 4 ms prior to inoculation and fermentation in biotin–soymilk at 37°C for 24 h. Electroporation triggered structural changes within the cellular membrane of lactobacilli that caused lipid peroxidation (p < 0.05) and alteration of membrane fluidity (p < 0.05). This was due to the application of electric potential difference across membrane that induced pores formation and subsequently increased membrane permeability. Reversible permeabilized cells resumed growth to >9 log CFU/ml after fermentation in biotin–soymilk (p < 0.05). Lactobacilli cells treated at electric field strength of 7.5 kV/cm for 3.5 ms also showed enhanced β-glucosidase activity (p < 0.05) compared to lower doses and control, leading to increased bioconversion of isoflavones glucosides to aglycones in biotin–soymilk (p < 0.05). Results from this study show that electroporation could be used to produce biotin–soymilk with increased bioactive aglycones.

Keywords::

• electroporation
• Lactobacillus
• soymilk
• isoflavones
• cellular membrane

Declaration of interest: The authors would like to acknowledge the financial assistance provided by Universiti Sains Malaysia via the USM RU Grant (1001/ PTEKIND/ 815056), USM IPS Research Fund Grant and the Universiti Sains Malaysia Fellowship. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.