Isolation, identification and characterization of a cellulase-producing strain

Abstract:

[Objective] To obtain microorganism strains for comprehensive utilization of cellulose, an ambient temperature cellulase-producing strain was isolated and identified. The optimal culture conditions for enzyme production were determined. [Methods] Filter paper medium was used to enrich the microorganism cultures. CMC-Na medium was used to screen the cellulose-degrading strains initially under the condition of ambient temperature. A strain, KZ-2, was isolated and purified using LB medium, followed by identification utilizing morphological, physiological and biochemical properties, and 16S rRNA gene sequence profiles. Single factor test based on incubation time, culture temperate, initial pH and sodium chloride (NaCl) concentration was performed to optimize the conditions for cellulase production. [Results] Strain KZ-2, capable of producing extracellular cellulase under ambient temperature, was isolated from decomposing maize straw. It was identified as a strain of Enterobacter sp. and potentially to be a novel species. The optimized enzyme production could be obtained when the strain was cultivated for 120 hours at 25-35 °C with initial pH 4.5-5.5, NaCl concentration of 1.0%-2.0%. The maximum cellulase activity of 80.93 U/mL was achieved under the optimal conditions. Initial enzymatic property analyses of the cellulase produced demonstrated that the enzyme was most active at pH 7.0 with a temperature of 50 °C. [Conclusion] The cellulose-degrading strain KZ-2 is able to secrete cellulase under ambient temperature and is potentially a novel species. The strain is expected to be further studied and developed to explore its marketing values.