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Proteolytic enzymes from Bacillus subtilis AB2 as antibiofilm adjuvants: Bioprocess optimization, mechanistic insights, and synergy with antibiotics
Afra M. Baghdadi
J. Microbiol. 2025;63(12):e2509019.   Published online December 31, 2025
DOI: https://doi.org/10.71150/jm.2509019
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AbstractAbstract PDFSupplementary Material

Collagenase and keratinase are two important proteolytic enzymes with recognized applications in biotechnology and medicine, particularly in the enzymatic removal of necrotic tissue and the control of infection. In the present work, a soil isolate of Bacillus subtilis strain AB2 (PX453297.1) was optimized for enzyme production under different nutritional and physicochemical conditions. The enzymes were recovered by ammonium sulphate precipitation and dialysis, examined by SDS-PAGE and zymography, and further assessed for pH and temperature optima, stability, the influence of metal ions, and kinetic parameters. Maximum collagenase activity (4.41 ± 0.22 U/ml) was observed at 37°C and pH 7.5 in a glucose–peptone medium, whereas keratinase production was enhanced between 37 and 40°C at pH 7.5 in lactose–peptone medium. Protein bands of approximately 55 and 33 kDa were detected, representing 6.2- and 5.5-fold purification. Collagenase showed an alkaline optimum (pH 10.0, 37–45°C) with Km 0.31% and Vmax 1.92 U/ml, while keratinase exhibited dual optima (pH 3.0 and ~7.0) with Km 0.27% and Vmax 0.84 U/ml. Biofilm assays revealed that collagenase reduced pre-formed biomass by 62–68% and viable counts by 1.1–1.7 log10, clearly outperforming keratinase (41–57%, 0.7–1.2 log10). When combined with conventional antibiotics, both enzymes potentiated activity, with notable synergy between collagenase and oxacillin against Staphylococcus aureus (FICI 0.31–0.37), ciprofloxacin against Pseudomonas aeruginosa (FICI 0.37–0.50), and meropenem against Klebsiella pneumoniae (FICI 0.28–0.44). These results indicate that B. subtilis AB2 produces collagenase and keratinase with distinct biochemical characteristics and strong antibiofilm properties, underscoring their promise as adjuncts in chronic wound care as well as in industrial applications.

Journal Article
iTRAQ-facilitated proteomic analysis of Bacillus cereus via degradation of malachite green
Bobo Wang , Jing Lu , Junfang Zheng , Zhisheng Yu
J. Microbiol. 2021;59(2):142-150.   Published online February 1, 2021
DOI: https://doi.org/10.1007/s12275-021-0441-0
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AbstractAbstract PDF
The wide use of malachite green (MG) as a dye has caused substantial concern owing to its toxicity. Bacillus cereus can against the toxic effect of MG and efficiently decolourise it. However, detailed information regarding its underlying adaptation and degradation mechanisms based on proteomic data is scarce. In this study, the isobaric tags for relative and absolute quantitation (iTRAQ)-facilitated quantitative method was applied to analyse the molecular mechanisms by which B. cereus degrades MG. Based on this analysis, 209 upregulated proteins and 198 downregulated proteins were identified with a false discovery rate of 1% or less during MG biodegradation. Gene ontology and KEGG analysis determined that the differentially expressed proteins were enriched in metabolic processes, catalytic activity, antioxidant activity, and responses to stimuli. Furthermore, real-time qPCR was utilised to further confirm the regulated proteins involved in benzoate degradation. The proteins BCE_4076 (Acetyl-CoA acetyltransferase), BCE_5143 (Acetyl-CoA acetyltransferase), BCE_5144 (3-hydroxyacyl-CoA dehydrogenase), BCE_4651 (Enoyl-CoA hydratase), and BCE_5474 (3-hydroxyacyl-CoA dehydrogenase) involved in the benzoate degradation pathway may play an important role in the biodegradation of MG by B. cereus. The results of this study not only provide a comprehensive view of proteomic changes in B. cereus upon MG loading but also shed light on the mechanism underlying MG biodegradation by B. cereus.

Citations

Citations to this article as recorded by  
  • Engineering globins for efficient biodegradation of malachite green: two case studies of myoglobin and neuroglobin
    Jiao Liu, Jia-Kun Xu, Hong Yuan, Xiao-Juan Wang, Shu-Qin Gao, Ge-Bo Wen, Xiang-Shi Tan, Ying-Wu Lin
    RSC Advances.2022; 12(29): 18654.     CrossRef

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