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A partial peptide sequence of β-glucosidase isoform (Bgl4) of Penicillium funiculosum NCL1 was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The cDNA (bgl4) encoding Bgl4 protein was cloned from P. funiculosum NCL1 RNA by consensus RT-PCR. The bgl4 gene encoded 857 amino acids that contained catalytic domains specific for glycoside hydrolase family 3. The cDNA was over-expressed in Pichia pastoris KM71H and the recombinant protein (rBgl4) was purified with the specific activity of 1,354.3 U/mg. The rBgl4 was a glycoprotein with the molecular weight of ~130 kDa and showed optimal activity at pH 5.0 and 60 °C. The enzyme was thermo-tolerant up to 60 °C for 60 min. The rBgl4 was highly active on aryl substrates with β-glucosidic, β-xylosidic linkages and moderately active on cellobiose and salicin. It showed remarkably high substrate conversion rate of 3,332 and 2,083 μmol/min/mg with the substrates p-nitrophenyl β-glucoside and cellobiose respectively. In addition, the rBgl4 showed tolerance to glucose concentration up to 400 mM. It exhibited twofold increase in glucose yield when supplemented with crude cellulase of Trichoderma reesei Rut-C30 in cellulose hydrolysis. These results suggested that rBgl4 is a thermo- and glucose-tolerant β-glucosidase and is a potential supplement for commercial cellulase in cellulose hydrolysis and thereby assures profitability in bioethanol production.

Aim: Lignocelluloytic enzymes are the largest class of hydrolase enzyme which utilizes the plant biomass to produce renewable sources. Hence practices for larger production of these enzymes at lower cost received much attention for industrial use. Hence this paper deals with expression and purification of cellobiohydrolase gene from Penicillium funiculosum NCL1. Methods & Results: A cellobiohydrolase gene, cbhII of Penicillium funiculosum NCL1 was cloned and expressed in Pichia pastoris X33. Two exons of the cbhII gene were amplified separately and fused by overlap extension PCR. The fused product was cloned in yeast expression vector pPICZαA and expressed in P. pastoris under the control of the AOX1 promoter. P. pastoris transformants expressing recombinant cellobiohydrolase were selected on CMC agar plate and their ability to produce the cellobiohydrolase was evaluated in flask cultures. P. pastoris X33 (pPICbh6) efficiently secreted the recombinant cellobiohydrolase into the medium and produced the cellobiohydrolase activity (5 U/ml) after 96 h of growth. The recombinant cellobiohydrolase produced by P. pastoris (pPICBH6) showed maximum activity at pH 4.0 and temperature 50˚C and higher specificity in hydrolysis of filter-paper.