A thermo-tolerant cellulase enzyme produced by Bacillus amyloliquefaciens M7, an insight into synthesis, optimization, characterization, and bio-polishing activity

Abstract In the current study, among 36 isolates, the bacterial strain M7 was selected as the highest cellulase producer and underwent traditional and molecular identification as Bacillus amyloliquefaciens M7. The productivity of the cellulase enzyme was optimized using the one-factor-at-a-time method. The optimization analysis showed that the best pH value for cellulase production was 7, in the presence of 1% bacterial inoculum size, 5 g·L −1 of carboxymethyl cellulose, 5 g·L −1 of peptone as nitrogen source, and incubation period of 24 h at a temperature of 35°C. The highest cellulase activity (64.98 U·mL −1 ) was obtained after optimizing conditions using BOX-Behnken Design. The maximum cellulase yield (75.53%) was obtained after precipitation by 60% ammonium sulfate, followed by purification by dialysis bag and Sephadex G-100 column chromatography. The purified cellulase enzyme was characterized by 6.38-fold enrichment, with specific activity (60.54 U·mg −1 ), and molecular weight of approximately 439.0 Da. The constituent of purified cellulase was 18 amino acids with high concentrations of 200 and 160 mg·L −1 for glycine and arginine, respectively. The purified cellulase enzyme was more stable and active at pH 8 and an incubation temperature of 50°C. The metal ions CaCl 2 , NaCl, and ZnO enhanced the activity of purified cellulase enzyme. Finally, the B. amyloliquefaciens M7-cellulase exhibits high bio-polishing activity of cotton fabrics with low weight loss (4.3%) which was attained at a maximum concentration (1%, v/v) for 90 min.