ABSTRACT

Cellulases are a group of hydrolytic enzymes and are capable of degrading lignocellulosic materials. Cellulases have wide range of applications. This work was focused on factors relevant for improvement of enzymatic hydrolysis of sawdust by using Aspergillus niger. The main purpose of this study was to reduce the production cost of cellulase by optimizing the production medium with alternative carbon source such as timber sawdust. The varied cultural parameters include carbon and nitrogen sources and their concentrations, pH (3-10), incubation temperature (30-90°C), incubation time (1-8days) and effect of agitation. Production of cellulase.was analysed by Anthrone colorimetric method. Timber sawdust (1.0% (w/v)) and (NH4)2SO4(1.0% (w/v)) were found to be the best combination of carbon and nitrogen sources for the production of cellulase by A. niger. Maximum enzyme production was achieved at pH 4.0 of Mendels media and at incubation temperature of 40°C Enzyme production increased with increase in the fermentation period up to the 96h and then declined thereafter. Submerged fermentation at 200rpm at 40°C gave higher yield of cellulase compared to static condition. Characterization of the crude enzyme showed that the enzyme was maximally active at 50°C and retained over 99% of its maximum activity at 50°C for 3brs. However, the enzyme was stable within 50°C to 70°C. Optimum pH for activity was found to be pH 5.0 while maximum stability was obtained at pH 6.0. The cellulase activity was stimulated by the Zn2 , Ba2 , Cu2 , Mg2 , Ca2ions, however, EDTA inhibited the enzyme activity. Cellulase producti9n from A. niger can be an advantage as the enzyme production rate is normally higher as compared to other fungi.