ORIGINAL ARTICLES   

Minerva Biotecnologica 2012 September;24(3):101-9

Copyright © 2012 EDIZIONI MINERVA MEDICA

lingua: Inglese

Isolation and characterization of cellulase producing Bacillus cereus MRLB1 from soil

Afzal I., Shah A. A., Makhdum Z., Hameed A., Hasan F.

Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan

Aim. The aim of the present study was to isolate the cellulolytic bacteria from soil.
Methods. The most efficient bacterium was found to produce 2.1 cm clear zone of hydrolysis on cellulose containing Congo red agar medium. The bacterium was identified through morphologic and microscopic examination and sugar fermentation tests based on API 50 CHB kit. The effect of time of incubation, pH, temperature, substrate concentration, size of inoculum, age of inoculum and organic nitrogen source on the production using carboxymethyl cellulose as substrate (CMC), was determined.
Results. The bacterium was closely related to Bacillus cereus, and was named as Bacillus cereus MRLB1. Result of incubation period revealed that maximum enzyme (45.42 U/mg) was produced around 72 hours of incubation. Most favorable temperature for enzyme production was 30 °C (51.87 U/mg) and higher temperatures adversely affected cellulase production. Maximum cellulase production was found at pH 6 (53.11 U/mg) and 3% (w/v) of substrate concentration (71.69 U/mg). Four percent (v/v) inoculum size appeared to be most effective for maximum cellulase production (62.1 U/mg). A 24 hours inoculum was the most favorable for maximal enzyme production (53.11 U/mg). Yeast extract was found to be the best organic nitrogen source for maximal cellulase production (123.89 U/mg) showing that the addition of an organic nitrogen source dramatically increased the bacterium’s ability to produce cellulase.
Conclusion. Bacillus cereus was found to produce the endoglucanase type cellulase. Since the enzyme is of industrial importance, the optimized culture conditions will be beneficial for its production on commercial scale.