Enhancing Nutritional and Health Benefits of Wheat Bran Through Bifunctional LAB Screening and BCAA-Enriched Fermentation

초록

Lactic acid bacteria (LAB)-mediated fermentation has been widely explored as a strategy to enhance the nutritional functionality of cereal processing by-products. In this study, 50 LAB strains previously isolated from Korean traditional fermented foods and obtained from the National Agrobiodiversity Center (KACC, Jeonju-si, Republic of Korea) were systematically screened for bifunctional carbohydrate and protein degradation capacities, and their potential to improve the nutritional functionality of wheat bran was evaluated. Paper disc assays revealed substantial inter-strain variability, with clear zone diameters ranging from 12.35 to 29.52 mm for carbohydrate degradation and 11.61 to 25.45 mm for protein degradation. Ten strains exceeding both upper-quartile enzymatic degradation cutoff thresholds (>= 25.25 mm for carbohydrate degradation and >= 17.98 mm for protein degradation, respectively) were putatively identified as Lactiplantibacillus plantarum and Lacticaseibacillus paracasei based on 16S rRNA gene sequencing (99.73-100% similarity). Substrate-specific fermentation using L. paracasei KS 595 across four substrates (brewed soy sauce soybean meal, pea, floury rice, and wheat bran) demonstrated substrate-dependent differences in growth and branched-chain amino acid (BCAA) accumulation, with the highest increase observed in pea fermentation. Strain-specific evaluation during wheat bran fermentation revealed distinct differences in growth kinetics, pH reduction, and BCAA production driven by cell-envelope proteinases and intracellular peptidases, with viable cell counts reaching 9-10 log CFU/mL after 48 h. Biogenic amine analysis indicated that histamine levels remained below commonly accepted safety limits in all strains, while L. paracasei KS 543 showed no detectable tyramine or histamine. Although the potential improvement in plant protein bioavailability was indirectly inferred through the free BCAA enrichment rather than directly measured in vivo, these results support a systematic screening approach for selecting LAB strains capable of producing BCAA-enriched fermented wheat bran, with potential implications for improving plant protein bioavailability and addressing nutritional needs in aging and active populations.

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