Isolation and screening of cellulase producing bacteria
The cow dung samples were collected from the village of Burd-wan district, West Bengal, India, in plastic bags by sterilized spatula and stored in an ice box for approximately 12 h. It
was brought to the laboratory for isolation of cellulolytic bacte-ria. One gram of cow dung sample was suspended with 100 ml of distilled water and was homogenized by constant shaking using an orbital shaker for 2 h at 180 rpm. Serial dilutions from 10_6 to 10_7 were prepared using sterilized distilled water. An aliquot of 100 lL of each dilution was spread plated onto Omeliansky’s agar medium (Omeliansky, 1902) [g/L (W/V), (NH4)2SO4 1; K2HPO4 1; MgSO4.7H2O 0.5; NaCl traces; carboxymethyl cellulose (CMC) 1%, pH 7] and incubated at 37 LC. Morpholog-ically dissimilar and discrete colonies were picked from different dilution plates and streaked on separate Omeliansky’s agar medium and incubated at 37 LC for 96 h. The replica plates were also prepared separately for staining. Cellulase producing bacte-ria were screened by congo red staining (Teather and Wood, 1982) and C1 strain was selected as potent cellulolytic bacteria (colony showing largest zone of decolorization).