The bioconversion of lignocellulose has attracted global attention,due to the significant potential of agricultural and forestry wastes as renewable zero-carbon resources and the urgent need for substituting fossil ca...The bioconversion of lignocellulose has attracted global attention,due to the significant potential of agricultural and forestry wastes as renewable zero-carbon resources and the urgent need for substituting fossil carbon.The cellulosome system is a multi-enzyme complex produced by anaerobic bacteria,which comprises cellulases,hemicellulases,and associated enzymatic and non-enzymatic components that promote biomass conversion.To enhance their efficiency in degrading recalcitrant lignocellulosic matrices,cellulosomes have been employed to construct biocatalysts for lignocellulose bioconversion,such as consolidated bioprocessing and consolidated bio-saccharification.Hemicelluloses,the second most abundant polysaccharides in plant cell walls,hold valuable application potential but can also induce inhibitory effects on cellulose hydrolysis,thus highlighting the indispensable roles of hemicellulases within the cellulosome complex.This review evaluated current research on cellulosomal hemicellulases,comparing their types,abundance,and regulation,primarily focusing on eight known cellulosome-producing species of different origins.We also reviewed their growth conditions,their hemicellulose-degrading capabilities,and the inhibitory effects of hemicellulose on cellulosome-based lignocellulose saccharification.Finally,we proposed strategies for targeted enhancement of hemicellulase in cellulosomes to improve lignocellulose bioconversion in future studies.展开更多
Production of economically viable bioethanol is potentially an environmentally and financially worthwhile endeavor.One major source for fermentable sugars is lignocellulose.However,lignocellulosic biomass is difficult...Production of economically viable bioethanol is potentially an environmentally and financially worthwhile endeavor.One major source for fermentable sugars is lignocellulose.However,lignocellulosic biomass is difficult to degrade,owing to its inherent structural recalcitrance.Cellulosomes are complexes of cellulases and associated polysaccharide-degrading enzymes bound to a protein scaffold that can efficiently degrade lignocellulose.Integration of the enzyme subunits into the complex depends on intermodular cohesin-dockerin interactions,which are robust but nonetheless non-covalent.The modular architecture of these complexes can be used to assemble artificial designer cellulosomes for advanced nanotechnological applications.Pretreatments that promote lignocellulose degradation involve high temperatures and acidic or alkaline conditions that could dismember designer cellulosomes,thus requiring separation of reaction steps,thereby increasing overall process cost.To overcome these challenges,we developed a means of covalently locking cohesin-dockerin interactions by integrating the chemistry of SpyCatcher-SpyTag approach to target and secure the interaction.The resultant cohesin-conjugated dockerin complex was resistant to high temperatures,SDS,and urea while high affinity and specificity of the interacting modular components were maintained.Using this approach,a covalently locked,bivalent designer cellulosome complex was produced and demonstrated to be enzymatically active on cellulosic substrates.The combination of affinity systems with SpyCatcher-SpyTag chemistry may prove of general use for improving other types of protein ligation systems and creating unconventional,biologically active,covalently locked,affinity-based molecular architectures.展开更多
基金supported by the National Natural Science Foundation of China[32070028 and 32370035 to Y.-J.L.,32070125 to Y.F.,and 32170051 to Q.C.]the National Key Research and Development Program of China[2021YFC2103600 to Y.-J.L.and 2023YFC3402304 to Y.F.]+2 种基金the International Partnership Program of Chinese Academy of Sciences[323GJHZ2022004MI to Y.-J.L.and A.K.]Shandong Energy Institute[SEI I202142 to Y.-J.L.,SEI S202106 to Q.C.,SEI I202106 to Y.F.]QIBEBT[Grant No.QIBEBT ICP2023046 to Y.F.].E.A.B.is the incumbent of The Maynard I.and Elaine Wishner Chair of Bio-organic Chemistry.
文摘The bioconversion of lignocellulose has attracted global attention,due to the significant potential of agricultural and forestry wastes as renewable zero-carbon resources and the urgent need for substituting fossil carbon.The cellulosome system is a multi-enzyme complex produced by anaerobic bacteria,which comprises cellulases,hemicellulases,and associated enzymatic and non-enzymatic components that promote biomass conversion.To enhance their efficiency in degrading recalcitrant lignocellulosic matrices,cellulosomes have been employed to construct biocatalysts for lignocellulose bioconversion,such as consolidated bioprocessing and consolidated bio-saccharification.Hemicelluloses,the second most abundant polysaccharides in plant cell walls,hold valuable application potential but can also induce inhibitory effects on cellulose hydrolysis,thus highlighting the indispensable roles of hemicellulases within the cellulosome complex.This review evaluated current research on cellulosomal hemicellulases,comparing their types,abundance,and regulation,primarily focusing on eight known cellulosome-producing species of different origins.We also reviewed their growth conditions,their hemicellulose-degrading capabilities,and the inhibitory effects of hemicellulose on cellulosome-based lignocellulose saccharification.Finally,we proposed strategies for targeted enhancement of hemicellulase in cellulosomes to improve lignocellulose bioconversion in future studies.
文摘Production of economically viable bioethanol is potentially an environmentally and financially worthwhile endeavor.One major source for fermentable sugars is lignocellulose.However,lignocellulosic biomass is difficult to degrade,owing to its inherent structural recalcitrance.Cellulosomes are complexes of cellulases and associated polysaccharide-degrading enzymes bound to a protein scaffold that can efficiently degrade lignocellulose.Integration of the enzyme subunits into the complex depends on intermodular cohesin-dockerin interactions,which are robust but nonetheless non-covalent.The modular architecture of these complexes can be used to assemble artificial designer cellulosomes for advanced nanotechnological applications.Pretreatments that promote lignocellulose degradation involve high temperatures and acidic or alkaline conditions that could dismember designer cellulosomes,thus requiring separation of reaction steps,thereby increasing overall process cost.To overcome these challenges,we developed a means of covalently locking cohesin-dockerin interactions by integrating the chemistry of SpyCatcher-SpyTag approach to target and secure the interaction.The resultant cohesin-conjugated dockerin complex was resistant to high temperatures,SDS,and urea while high affinity and specificity of the interacting modular components were maintained.Using this approach,a covalently locked,bivalent designer cellulosome complex was produced and demonstrated to be enzymatically active on cellulosic substrates.The combination of affinity systems with SpyCatcher-SpyTag chemistry may prove of general use for improving other types of protein ligation systems and creating unconventional,biologically active,covalently locked,affinity-based molecular architectures.
