Abstract:
Cellulolytic bacteria have gained worldwide interest due to their ability to secrete
thermostable enzymes with multiple uses. In this study, cellulolytic bacteria were
isolated from local hot springs on carboxymethyl cellulose (CMC) agar and screened
using 0.1% Congo red. Strains LB-4, LB-6 and LB-8 were found to have high
cellulolytic indices of 1.8, 2.0 and 1.5, respectively. These strains were preliminarily
identified based on morphology, gram’s reaction, and biochemical characteristics.
They were rod-shaped, stained blue and possibly belong to a genus of motile
Bacillus. The isolates were further subjected to homology analysis of the 16S rRNA
gene. BLAST search showed strains LB-4, LB-6 and LB-8 to be 99.13%, 98.26%
and 98.91% identical to Bacillus subtilis, Bacillus sp., and Bacillus licheniformis in
the NCBI GenBank, respectively. The cellulolytic activity of each strain was
evaluated using submerged fermentation that was terminated by the dinitrosalicylic
acid (DNS) method. The optimum cellulase activity of the bacteria strains were
observed after 24 hr at pH 7 and 40ºC while utilizing 1% CMC as a carbon source
and 1% yeast extract as a nitrogen source. It can be concluded that cellulolytic
bacteria were screened and identified from Lubimbi hot springs and the cellulase
activity of each strain was optimized for different fermentation conditions. These
strains have potential use in the pre-treatment of crop residues for biogas production
