Effect of indigenous lactic acid bacteria fermentation on enrichment of isoflavone and antioxidant properties of kerandang (Canavalia virosa) extract

Five strains indigenous lactic acid bacteria i.e. Lactobacillus plantarum-pentosus T14, Lactobacillus plantarum-pentosus T20, L. plantarum T32, L. plantarum T33 and L. plantarum-pentosus T35 were tested for their capabilities to transform isoflavone glucosides to aglycones in the kerandang crude extract. Changes in growth, pH, titratable acidity (TA), β-glucosidase activity was investigated during fermentation at 37°C for 24 h. Isoflavone transformation was analyzed using UPLC (Ultra Performance Liquid Chromatography). The antioxidant properties were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferrous ion-chelating ability method. The result showed that initial cell population of 10^6 - 10^7 CFU/ml rapidly increased and reached 10^9 CFU/ml in MRS-kerandang extract after 9 to 12 h of fermentation and constant to 24 h fermentation. All five strains produced lactic acid followed by the decreasing of pH. Lactobacillus plantarum-pentosus T14 showed the highest β-glucosidase activity is 558 ± 9.8 mU/ml culture at 12 h fermentation. All five strains were able to transform isoflavone glucoside to aglycone. L. plantarum-pentosus T14 have a better ability to transform, followed by L. plantarum-pentosus T20, L. plantarum T32, L. plantarum T33 and L. plantarum-pentosus T35.