title: Characterization of a Cellulomonas fimi exoglucanase/xylanase-endoglucanase gene fusion which improves microbial degradation of cellulosic biomass.
abstract: Effective degradation of cellulose requires multiple classes of enzyme working together. However, naturally occurring cellulases with multiple catalytic domains seem to be rather rare in known cellulose-degrading organisms. A fusion protein made from Cellulomonas fimi exo- and endo- glucanases, Cex and CenA which improves breakdown of cellulose is described. A homologous carbohydrate binding module (CBM-2) present in both glucanases was fused to give a fusion protein CxnA. CxnA or unfused constructs (Cex+CenA, Cex, or CenA) were expressed in Escherichia coli and Citrobacter freundii. The latter recombinant strains were cultured at the expense of cellulose filter paper. The expressed CxnA had both exo- and endo- glucanase activities. It was also exported to the supernatant as were the non-fused proteins. In addition, the hybrid CBM from the fusion could bind to microcrystalline cellulose. Growth of C. freundii expressing CxnA was superior to that of cells expressing the unfused proteins. Physical degradation of filter paper was also faster with the cells expressing fusion protein than the other constructs. Our results show that fusion proteins with multiple catalytic domains can improve the efficiency of cellulose degradation. Such fusion proteins could potentially substitute cloning of multiple enzymes as well as improving product yields.
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, UK; Department of Biomedical Sciences, School of Basic & Biomedical Sciences, University of Health & Allied Sciences, Ho, Ghana. Electronic address: koduedu@gmail.com.
authors.forename: Kwabena O
authors.initials: KO
authors.lastname: Duedu
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, UK. Electronic address: c.french@ed.ac.uk.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: French
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018533:Biomass; D002480:Cellulase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D040143:Cellulomonas / Q000201:enzymology* / Q000235:genetics*; D002482:Cellulose / Q000378:metabolism*; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016971:Citrobacter freundii / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D050939:Gene Fusion; D005798:Genes, Bacterial; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; D002482:Cellulose; D002480:Cellulase; D043364:Endo-1,4-beta Xylanases; D043366:Cellulose 1,4-beta-Cellobiosidase; C109691:microcrystalline cellulose
keywords: Biomass conversion; Cellulomonas fimi; Cellulose; Citrobacter freundii; Multicatalytic cellulases