Proteolytic Bacillus sp. Isolation and Identification from Tannery Alkaline Baths

Lageiro, Manuela; Simões, Fernanda; Alvarenga, Nuno; Reis, Alberto

http://hdl.handle.net/10362/190068

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The application of microbial alkaline proteases holds significant potential for eco-sustainable industrial processes by reducing chemical usage and lowering the costs of effluent treatment. In the search for novel proteases with industrial relevance, several microbial strains were isolated from alkaline baths of the Portuguese tannery agroindustry. The most promising protease-producing strains were selected for identification and further study. Two isolates demonstrated the highest proteolytic activity, reaching 0.51 ± 0.01 U mL−1 and 0.70 ± 0.01 U mL−1 after 7.5 h of submerged cultivation in nutrient broth. Based on API biochemical tests, molecular biology techniques, and GC-FAME analysis of membrane lipids, the isolates were identified as Bacillus subtilis and incorporated into INIAV’s collection of industrial microbial cultures as B. subtilis CCMI 1253 (BMR2) and B. subtilis CCMI 1254 (BMR1). The most promising protease producer, B. subtilis CCMI 1253 (BMR2), exhibited a maximum specific growth rate of 0.88 ± 0.10 h−1. The proteases produced exhibited good extracellular proteolytic activity, with adaptability to industrial conditions, indicating their suitability for agroindustry applications such as leather making, detergent formulations and the treatment of effluents and protein residues. The results support the potential of microbial proteases as valuable tools in the bioeconomy and green chemistry.

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Funding Information: This research was funded by the Foundation for Science and Technology (FCT) under the grant UIDB/04035/2020 (doi:10.54499/UIDB/04035/2020) to GEOBIOTEC (GeoBioSciences GeoTech-nologies and GeoEngineering) Research Unit. Publisher Copyright: © 2025 by the authors.

Palavras-chave

Bacillus subtilis Bio-economy Detergent Enzymatic activity Leather Proteases Stain removal Analytical Chemistry Chemistry (miscellaneous) Molecular Medicine Pharmaceutical Science Drug Discovery Physical and Theoretical Chemistry Organic Chemistry