Toward combined delignification and saccharification of wheat straw by a laccase-containing designer cellulosome.
Efficient breakdown of lignocellulose polymers into simple molecules is a key technological bottleneck limiting the production of plant-derived biofuels and chemicals. In nature, plant biomass degradation is achieved by the action of a wide range of microbial enzymes. In aerobic microorganisms, these enzymes are secreted as discrete elements in contrast to certain anaerobic bacteria, where they are assembled into large multienzyme complexes termed cellulosomes. These complexes allow for very efficient hydrolysis of cellulose and hemicellulose due to the spatial proximity of synergistically acting enzymes and to the limited diffusion of the enzymes and their products. Recently, designer cellulosomes have been developed to incorporate foreign enzymatic activities in cellulosomes so as to enhance lignocellulose hydrolysis further. In this study, we complemented a cellulosome active on cellulose and hemicellulose by addition of an enzyme active on lignin. To do so, we designed a dockerin-fused variant of a recently characterized laccase from the aerobic bacterium Thermobifida fusca The resultant chimera exhibited activity levels similar to the wild-type enzyme and properly integrated into the designer cellulosome. The resulting complex yielded a twofold increase in the amount of reducing sugars released from wheat straw compared with the same system lacking the laccase. The unorthodox use of aerobic enzymes in designer cellulosome machinery effects simultaneous degradation of the three major components of the plant cell wall (cellulose, hemicellulose, and lignin), paving the way for more efficient lignocellulose conversion into soluble sugars en route to alternative fuels production.
Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel;
Lital
L
Davidi
Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel;
Sarah
S
Moraïs
Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel;
Lior
L
Artzi
Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Doriv
D
Knop
Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Yitzhak
Y
Hadar
Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel;
Yonathan
Y
Arfi
Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel; ed.bayer@weizmann.ac.il.
Edward A
EA
Bayer
D050260:Carbohydrate Metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D044603:Cellulosomes / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D042845:Laccase / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014908:Triticum / Q000378:metabolism*; D000097722:Cohesins
D018797:Cell Cycle Proteins; D002482:Cellulose; D002868:Chromosomal Proteins, Non-Histone; D042845:Laccase; D008031:Lignin; D011994:Recombinant Proteins; D000097722:Cohesins
biomass conversion; catalysis; lignocellulose; multienzyme complex