PRODUCTION AND PHYSICOCHEMICAL PROPERTIES OF THERMOSTABLE, CRUDE CELLULASE FROM ENTEROBACTER CLOACAE IP8 ISOLATED FROM PLANT LEAF LITTERS OF LAGERSTROEMIA INDICA Linn.

Abstract

Cellulases have wide applications and biotechnological potentials for various industries. A bacterium producing an extracellular, thermostable cellulase was isolated from plant leaf litters of Lagerstroemia indica Linn, inside a botanical garden. According to morphological, biochemical and physiological characterization, it was tentatively identified as Enterobacter sp. Molecular characterization, using the 16S rRNA gene sequencing was used to confirm the identity of the bacterium as Enterobacter cloacae IP8. Effects of some cultural factors such as carbon and nitrogen sources, pH and temperature, on cellulase production from the bacterium, were investigated. Some physicochemical properties of the crude cellulase from E. cloacae IP8 were determined to evaluate its potentials for industrial applications. The maximum yield of cellulase (10.78 U/mL) was at 28 h of incubation using carboxymethyl cellulose (CMC) (1.5%, w/v), peptone (2.0%, w/v), inoculum size (1.0%, v/v), pH and temperature of 7.0 and 45 oC, respectively, and agitation speed 150 rpm. The crude cellulase exhibited optimum activity at 60 oC, retaining 75.0% of its maximal activity at 70 oC. It had optimum pH of 7.0, retaining 58.0% of its original activity at acidic pH 5.0. Metal ions Na+, Ca2+ and Mg2+ remarkably enhanced activity of the cellulase while K+ and EDTA inhibited activity of the cellulase from E. cloacae IP8. The characteristics of the cellulase from E. cloacae IP8 revealed the enzyme as being thermostable and an acidic to neutral metalloenzyme. Therefore, the enzyme from this strain could be applied in industrial applications such as lignocellulosic biomass conversion into fuel and other value added products.