Carboxymethyl Cellulase (CMCase) from UV-irradiation Mutated Bacillus cereus FOA-2 cultivated on Plantain (Musa parasidiaca) Stalk-based Medium: Production, Purification and Characterization

Abstract

Strain improvement has become an important strategy in large scale microbial fermentation processes to increase the production yield of enzymes at minimal cost. Here, ultraviolet (UV) irradiation-induced mutant strain of Bacillus cereus, identified using 16S rRNA molecular gene sequencing was subjected to cellulolytic potential screening before cultivating it for carboxymethyl cellulase (CMCase) production under submerged fermentation using a cost-effective plantain stalk–based medium. The enzyme was homogenously purified by a combination of ammonium sulphate precipitation and chromatographic techniques on both DEAE Sephadex A-50 anion-exchange and Sephadex G-100 size-exclusion columns. Sodium dodecyl sulphate polyacrylamide gel electrophoresis was used to determine the molecular weight. Remarkably, this 56 kDa purified cellulase was most active at 70°C and pH 6.0. The CMCase retained over 60% of initial activity after pre-incubation at 60°C for 3 h and was also very stable in both acidic and mild basic medium (pH 3.0-9.0). Cellulase activity was enhanced by Mn2+, Na+, Mg2+ and K+ but inhibited by Pb2+, Hg2+ and Cu2+ at 5 mM. The Km and Vmax of the enzyme with carboxymethyl cellulose are respectively, 3.25 mg/mL and 29.76 U/min/mg. The purified cellulase from B. cereus FOA-2 possesses remarkable properties for suitable application in biotechnological industries.

Keywords

• Cellulase
• Bacillus
• Purification
• UV-irradiation
• Mutant strain
• Biotechnology