초록
<P>Cellulolytic microorganisms such as fungi and bacteria are responsible for much of the cellulose degradation in soils. Despite the vast number of cellulase producers, there is a deficiency of microorganisms that can produce significant amount of the three components of a cellulase system. <I>i.e.</I> CMCases, exoglucanases and β-glucosidases to efficiently degrade cellulose to fermentable products.</P><P>Soil samples were collected from two sites of the Kenyan Rift valley; Hell’s gate National Park and a geothermal well in Eburru hill at depths of 155 m, 156 m and 157 m. Isolation of cellulolytic bacteria was carried out using minimal media supplemented with 1% CMC. Isolates obtained were characterized using both morphological and molecular methods. A quantitative cellulolytic test was carried out to select the isolate with the highest specific activity. Additionally the cell-free supernatant was used for functional studies to determine the isolate’s cellulase system components, optimum temperature, pH and time stability.</P><P>Phylogenetic analyses indicated that all isolates associated mainly with members of the <I>Bacillus licheniformis</I>. All isolates were capable of utilizing CMC, avicel and Cellobiose as their sole carbon sources. Isolate 3 from a depth of 156 m in the well was identified as <I>Bacillus licheniformis</I> strain vic and selected for further functional studies. This isolate was found to bear the three enzyme components of a cellulase system. A cell free extract was noted to hydrolysecellobiose, Avicel and CMC with enzyme specific activities of 0.46878 U/mg, 0.18784 U/mg and 0.13571 U/mg respectively. Optimum temperature for activity measured over 60 minutes was found to be 60<SUP>o</SUP>C with relatively high activity at both 70<SUP>o</SUP>C and 80<SUP>o</SUP>C. The optimum pH at the predetermined optimum temperature was found to be pH 5. The crude enzyme extract was stable for eight hours of incubation at 60<SUP>o</SUP>C and pH 5 retaining 92.2% of its activity. This makes <I>B.licheniformis</I> strain vic a quite attractive isolate for potential application in industries.</P>