Whey as a screening and fermentation medium for protease-producing Bacillus strains
DOI:
https://doi.org/10.31989/ffs.v5i11.1797Abstract
Background: Microbial proteases provide sustainable alternatives to chemical processes and have wide applications in food and biotechnology. Among various microbial sources, Bacillus species are particularly recognized for their ability to produce extracellular proteases with high stability and broad substrate specificity.
Objective: In this study, two protease-producing strains, Bacillus amyloliquefaciens LK1 (LK1) and Bacillus subtilis LK2 (LK2), were isolated from soil and cultivated in whey, an abundant and cost-effective dairy by-product. Both strains secreted extracellular serine proteases with molecular weights of about 30 kDa and isoelectric points around 8.5.
Methods: Whey was used as a screening and cultivation medium for protease-producing Bacillus strains. Strains were selected based on the size of clear zones. Proteases were purified by batch-column cation-exchange chromatography.
Results: The enzymes were active over a broad pH range (6–10), showing maximal activity at pH 8–9 and at temperatures between 60 and 65°C. The proteases remained stable at 55°C for several hours but were strongly inhibited by PMSF and partially by EDTA/EGTA, confirming their classification as serine proteases. Among the two proteases, LK1 exhibited superior tolerance to salts and detergents and efficiently hydrolyzed whey proteins into peptides and free amino acids. These hydrolysates were enriched in bioactive compounds, potentially exhibiting antioxidant, antimicrobial, and immunomodulatory activities.
Conclusion: The results highlight the suitability of whey-based fermentation for producing functional peptides and demonstrate the potential of LK1 protease to enhance protein digestibility, nutritional quality, and clean-label food processing. These findings underscore the enzyme’s applicability in dairy science and its promise for developing functional food ingredients derived from whey proteins.
Keywords: Microbial proteases, Bacillus amyloliquefaciens LK1, Bacillus subtilis LK2, Fermentation optimization, Whey protein hydrolysis, Enzyme characterization, Functional foods
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Copyright (c) 2025 Anna Mkhitaryan, Ani Paloyan, Lev Khoyetsyan, Karine Dukova, Mareta Izmailyan, Marina Kinosyan, Tamara Davidyan, Garegin Haxoyan, Artur Hambardzumyan
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