초록
<P><B>Abstract</B></P> <P> <I>Bacillus amyloliquefaciens</I> SS35 was subjected to ultraviolet irradiation to improve the enzymatic hydrolysis of lignocellulosic biomass. The resulting mutant, UV2, produced endoglucanase, carboxymethyl cellulase, CMCase-UV2 with 1.6–4.1-fold higher activity against cellulosic substrates than the wild type, CMCase-WT. CMCase-UV2 exhibited wider pH stability in the acidic range than CMCase-WT. The TLC analysis showed that the hydrolysis of CMC-Na and β-glucan by CMCase-UV2 produced glucose along with cello-oligosaccharides and cellobiose in 45 min, whereas, CMCase-WT produced, only cello-oligosaccharides and cellobiose in 120 min by endolytic mode of action. The hydrolysis of pretreated <I>Pennisetum purpureum</I> by CMCase-UV2 gave total reducing sugar yield 154.2 mg/g pretreated biomass in 48 h, which was 1.8-fold higher than CMCase-WT. CMCase-UV2 was the promising endoglucanase which improves the saccharification of lignocellulosic biomass therefore, it will improve the efficiency of the process, lignocellulose-based biorefineries for bioethanol production. The gene encoding cellulase was amplified from wild-type and UV2 strains using degenerate primers designed from phylogenetically related spp. <I>Bacillus amyloliquefaciens</I> KHG19 for family 5 glycoside hydrolase. Sequences analysis of genes from wild-type and UV2 strains showed the mutation, D233G. These results will provide information for protein engineering in designing mutant of endoglucanase for improved catalytic efficiency and pH stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mutant of <I>Bacillus amyloliquefaciens</I> SS35 was developed by UV irradiation. </LI> <LI> Mutant CMCase-UV2 gave enhanced pH stability in the acidic range. </LI> <LI> <I>V</I> <SUB> <I>max</I> </SUB> of CMCase-UV2 was increased by 2-fold against carboxymethyl cellulose sodium salt. </LI> <LI> Aspartate 233 was substituted by glycine in CMCase-UV2. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>