Fermentative Bioconversion of β-Glucoside Like Isoflavones is a Better Indicator of β-Glucoside Hydrolysing Capability in Probiotic Lactic Acid Bacteria (LAB) Due to the Predominant Phosphoglucosidase Activity

ABSTRACT

Isoflavones provide multiple health benefits, such as the potential for prevention of cancer and osteoporosis. Isoflavones are naturally present as β-glucosides, rendering them unavailable for uptake in the human gut. In the present study, an attempt was made to understand the mechanism of β-glucoside hydrolysis by probiotic microbes. Six major probiotic-type strains were screened for β-glucosidase activity, and two annotated β-glucosidase genes were cloned and characterized from L. acidophilus. These proteins were more active on phosphorylated pNPG than on pNPG, indicating a Phosphoenolpyruvate (PEP)-dependent pathway involving phosphoglucosidase for the uptake and metabolism of β-glucosides such as isoflavones. The screening of these strains for the bioconversion of isoflavones showed above 90% isoflavone glucoside hydrolysis for four strains, with L. rhamnosus showing the highest hydrolysis. To the best of our knowledge, this is the first report comparing glucoside hydrolysis by whole bacterial cells with cell extracts and purified candidate proteins.

KEYWORDS:

• Isoflavones
• β-glucosidase
• soybean
• fermentation
• Lactobacillus
• probiotics

Acknowledgments

The authors acknowledge the funding received from the Council of Scientific and Industrial Research as a PhD fellowship. The authors are also grateful to ICAR-NAHEP-CAAST for the visiting fellowship. The authors also acknowledge the protein analysis’s help from Dr Gerhard Saalbach, John Innes Center and Dr Arjan Narbad, Quadram Institute Bioscience-Norwich, England.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08905436.2023.2236694

Additional information

Funding

This study was funded by the ICAR-IARI Institute fund.