Seventeen strains of cellulase producing bacteria were isolated from soil samples collected in Nan province, Thailand. They exhibited cellulase activity as a clear zone surrounded their colonies grown on carboxymethyl cellulose (CMC) agar medium ranged from 0.63 to 2.95 cm in diameter. Their hydrolysis capacity values
were 1.65 - 7.55. The bacteria isolated were divided into 2 groups and belonged to genus Bacillus and Paenibacillus based on their phenotypic characteristics and chemotaxonomic characteristics such as meso-diaminopimelic in cell wall peptidoglycan and menaquinones of MK-7. Bacillus strains, P3-1 and P4-6 in Group I, produced maximum cellulase at 0.015 U ml-1. Their optimal pH and temperature for enzyme production and enzyme activity were 7.0 and 50 oC, respectively. The strains P3-1 and P4-6 were closely related to Bacillus velesensis LMG 22478T (100% similarity) whereas representative strain, S10-4, in Group II, was closely related to P. cellulositrophicus KCTC 13135T (98.7% similarity) based on 16S rRNA gene sequence. On the basis of their phenotypic, chemotaxonomic characteristics and phylogenetic analysis of 16S rRNA gene sequence, the strains P3-1 and P4-6 were identified as B. velesensis and the strain S10-4 was a novel species in the genus Paenibacillus.
Key words: Cellulase, Bacillus, Paenibacillus, 16S rRNA gene sequence, Thai soil
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