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Title: Engineering of glycoside hydrolase family 7 cellobiohydrolases directed by natural diversity screening

Journal Article · · Journal of Biological Chemistry

Protein engineering and screening of processive fungal cellobiohydrolases (CBHs) remain challenging due to limited expression hosts, synergy-dependency, and recalcitrant substrates. In particular, GH7 CBHs are a family critically important for the bioeconomy as well as a methodology for improving these and other difficult to engineer enzymes. Here, we target the discovery of highly active natural GH7 CBHs and engineering of variants with improved activity. Using experimentally assayed activities of genome mined CBHs, we applied sequence and structural alignments to top performers to identify key point mutations linked to improved activity. From ~1500 known GH7 sequences, an evolutionarily diverse subset of 57 GH7 CBH genes was expressed in Trichoderma reesei and screened using a multiplexed activity screening assay. Ten catalytically enhanced natural variants were identified, produced, purified, and tested for efficacy using industrially-relevant conditions and substrates. Three key amino acids in CBHs with performance comparable or superior to Penicillium funiculosum Cel7A were identified and combinatorically engineered into P. funiculosum cel7a, expressed in T. reesei, and assayed on lignocellulosic biomass. The top performer generated using this combined approach of natural diversity genome mining, experimental assays, and computational modeling produced a 41% increase in conversion extent over native P. funiculosum Cel7A, a 55% increase over the current industrial standard T. reesei Cel7A, and 10% improvement over Aspergillus oryzae Cel7C, the best natural GH7 CBH previously identified in our laboratory.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Bioenergy Technologies Office (BETO)
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
2301755
Alternate ID(s):
OSTI ID: 2316135
Report Number(s):
NREL/JA-2800-87398; S002192582400125X; 105749; PII: S002192582400125X
Journal Information:
Journal of Biological Chemistry, Journal Name: Journal of Biological Chemistry Vol. 300 Journal Issue: 3; ISSN 0021-9258
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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