Addition of expansin to cellulase enhanced bioethanol production. Issue 12 (December 2016) - Kumar, Mohit
Graphical abstract: 3D computional model proposed to show the synergy between cellulase and expansin proteins. Residues depicted in this model are critical for their respective activies on cellulose microfibrils. Surface and interior cellulose carbons are colored in blue and green, respectively. Highlights: Purified recombinant cellulase exhibited highest activity towards CMC followed by Avicel PH101 and waste paper. Binding of expansin to waste paper was examined by UV fluorescence based detection and kinetic modeling. SEM analysis confirmed that bound expansin causes the amorphogenesis enhancing the cellulase activity. Production of bioethanol is enhanced by synergistic activity of cellulase and expansin. Abstract: A metagenomic clone (pUC-189) that exhibited clear zone on CMC agar plate showed homology with glycosyl hydrolase (GH) family 12 endoglucanase. Purified recombinant cellulase (C18) exhibited the highest activity towards CMC followed by Avicel PH101 and waste paper which was confirmed by chromatography. Role of expansin (E11CB) was investigated to address the poor activity of C18 towards waste paper. The Langmuir isotherm for binding of the purified E11CB to waste paper showed a good fit (R 2 = 0.97). Recombinant E11CB protein bound to waste paper was detected in situ by UV fluorescence of [Ln(DPA)3 ] 3− complex. Scanning electron microscopy confirmed that binding of E11CB transformed smooth microfibrils into rough and amorphic surface. Improvement in the enzymatic hydrolysis of pure cellulose and lignocelluloses was observed after treatment with purified E11CB at low cellulase loading. The enzymatic hydrolysate of waste cellulose paper was then used as the substrate for bioethanol production by Saccharomyces cerevisiae.