Hydrolytic enzymes production by thermotolerant Bacillus altitudinis IARI-MB-9 and Gulbenkiania mobilis IARI-MB-18 isolated from Manikaran hot springs

Abstract

Thermostable bacterial enzymes play a major role in hydrolysis of lignocellulosic compounds to fermentable sugars at high temperatures. A total 154 bacteria were isolated from Manikaran hot springs using standard serial dilution method. Among 154, 27 bacterial strains could grow at temperatures >70 °C. The thermotolerant bacteria were screened for hydrolytic enzyme activities at high temperatures (50-70 °C). On the basis of stability and efficient activity of hydrolytic enzymes, two bacterial strains IARI-MB-9 and IARI-MB-18 were selected for present study. Production of hydrolytic enzymes under submerged and solid state fermentation condition was done using paddy straw as sole carbon source. 16S rRNA gene sequencing and phylogenetic analysis revealed that these bacterial strains were belonged to Firmicutes and Proteobacteria. The closest phylogenetic neighbours according to the 16S rRNA gene sequence data for the two isolates IARI-MB-9 and IARI-MB-18 were Bacillus altitudinis and Gulbenkiania mobilis respectively. Bacillus altitudinis (IARI-MB-9) and Gulbenkiania mobilis (IARI-MB-18) were found to be the efficient cellulase producers 32.8 and 37.0 IU ml-1g-1 under submerged and 32.5 and 35.5 IU ml-1g-1 under solid state fermentation condition at 60 ºC respectively. To our knowledge, this is the first report for the presence of Bacillus altitudinis and Gulbenkiania mobilis in thermal spring with multifarious hydrolytic enzymes production. Such thermotolerant bacterial strains have potential to be used to develop as consortia for bioconversion of lignocellulosic residue to fermentable sugars preferably at high temperature.