Implications of cellobiohydrolase glycosylation for use in biomass conversion

Tina Jeoh¹ , William Michener² , Michael E Himmel³ , Stephen R Decker³ and William S Adney³

¹Biological and Agricultural Engineering Department, University of California at Davis, Davis, California, USA

²National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA

³Chemical and Biosciences Center, National Renewable Energy Laboratory 1617 Cole Blvd., Golden, CO 80401, USA

author email corresponding author email

Biotechnology for Biofuels 2008, 1:10doi:10.1186/1754-6834-1-10


Published:	1 May 2008

Abstract

The cellulase producing ascomycete, Trichoderma reesei (Hypocrea jecorina), is known to secrete a range of enzymes important for ethanol production from lignocellulosic biomass. It is also widely used for the commercial scale production of industrial enzymes because of its ability to produce high titers of heterologous proteins. During the secretion process, a number of post-translational events can occur, however, that impact protein function and stability. Another ascomycete, Aspergillus niger var. awamori, is also known to produce large quantities of heterologous proteins for industry. In this study, T. reesei Cel7A, a cellobiohydrolase, was expressed in A. niger var. awamori and subjected to detailed biophysical characterization. The purified recombinant enzyme contains six times the amount of N-linked glycan than the enzyme purified from a commercial T. reesei enzyme preparation. The activities of the two enzyme forms were compared using bacterial (microcrystalline) and phosphoric acid swollen (amorphous) cellulose as substrates. This comparison suggested that the increased level of N-glycosylation of the recombinant Cel7A (rCel7A) resulted in reduced activity and increased non-productive binding on cellulose. When treated with the N-glycosidase PNGaseF, the molecular weight of the recombinant enzyme approached that of the commercial enzyme and the activity on cellulose was improved.