Mung beans processed by solid-state bioconversion improves phenolic content and functionality relevant for diabetes and ulcer management

Abstract

Abstract Mung bean substrate was enriched with phenolic antioxidants and levo-dihydroxy phenylalanine ( l -DOPA) through solid-state bioconversion (SSB) by Rhizopus oligosporus, with the goal to enhance health-linked functionality. The alpha-amylase inhibition linked to diabetes management and Helicobacter pylori inhibition linked to peptic ulcer management were investigated in bioprocessed extracts. The protein content and β-glucosidase activity of the substrate which are indicators of effective fungal colonization, increased with growth. The phenolic content increase with growth was linked to fungal β-glucosidase activity, indicating phenolic mobilization. The antioxidant activity as measured by DPPH (1,1-diphenyl-2-picrylhydrazyl) inhibition method were high (65%) initially and increased to 90% on day 12, than maintained higher levels during the rest of growth. The antioxidant activity measured by β-carotene assay was high between days 4–8 when phenolic levels increased. Fungal-linked superoxide dismutase (SOD) activity was high in late stages indicating quenching of reactive oxygen species. The l -DOPA content was low during early growth stage (0.6–0.7 mg/g DW) and gradually doubled to 1.2 mg/g DW in late stages. The α-amylase inhibition potential was moderately high during early stages (days 0–2) followed by higher inhibition during days 4–10 which correlate to higher phenolic content. The change in the antimicrobial activities of the extracts against H. pylori was high on day 4 and was associated with high antioxidant activity but not high phenolic content. Elevated inhibition on day 8 directly correlated with high total phenolics content suggesting the role of phenolic mobilization. The major implication from this research is that SSB is a good strategy to improve the phenolic content of mung beans for enhanced functionality with improved antioxidant activity that contributes to α-amylase inhibition relevant to potential diabetes management and H. pylori inhibition linked to peptic ulcer management. Industrial relevance Solid State Bioconversion (SSB) of mung bean by R. oligosporus is a good strategy to enhance ingredient functionality due to mobilization of phenolic antioxidants. Such enhanced phenolic antioxidant activity potentially contributes to health-relevant functionality such as amylase inhibition for diabetes management and H. pylori inhibition for peptic ulcer management. Optimization of such SSB systems at industrial scale can help large-scale low cost production of such health-relevant ingredients.