Evaluation of Semi-Solid-State Fermentation of Elaeocarpus serratus L. Leaves and Black Soymilk by Lactobacillus plantarum on Bioactive Compounds and Antioxidant Capacity

Elaeocarpus serratus L. leaves (EL) containing phenolic compounds and flavonoids, including myricitrin with pharmacological properties, could be valorized as nutritional additive in foods. In this study, the semi-solid-state fermentation of EL and black soymilk (BS) by Lactobacillus plantarum BCRC 10357 was investigated. Without adding EL in MRS medium, the beta-glucosidase activity of L. plantarum quickly reduced to 2.33 +/- 0.15 U/mL in 36 h of fermentation; by using 3% EL, the stability period of beta-glucosidase activity was prolonged as 12.94 +/- 0.69 U/mL in 12 h to 13.71 +/- 0.94 in 36 h, showing positive response of the bacteria encountering EL. Using L. plantarum to ferment BS with 3% EL, the beta-glucosidase activity increased to 23.78 +/- 1.34 U/mL in 24 h, and in the fermented product extract (FPE), the content of myricitrin (2297.06 mu g/g-FPE) and isoflavone aglycones (daidzein and genistein, 474.47 mu g/g-FPE) at 48 h of fermentation were 1.61-fold and 1.95-fold of that before fermentation (at 0 h), respectively. Total flavonoid content, myricitrin, and ferric reducing antioxidant power in FPE using BS and EL were higher than that using EL alone. This study developed the potential fermented product of black soymilk using EL as a nutritional supplement with probiotics.

Automated summary

This study demonstrated that fermentation using EL and black soymilk increased beta-glucosidase activity, leading to higher levels of myricitrin and isoflavone aglycones. The potential fermented product developed using EL as a nutritional supplement with probiotics showed enhanced total flavonoid content and antioxidant power.