Genomics Review of Holocellulose Deconstruction by Aspergilli

Author(s)

Segato, Fernando ^[1] ; Damasio, Andre R. L. ^{[1, 2]} ; de Lucas, Rosymar C. ^[1] ; Squina, Fabio M. ^[2] ; Prade, Rolf A. ^{[1, 2]}

Affiliation

^[1] Oklahoma State Univ, Dept Microbiol & Mol Genet, Stillwater, OK 74078 - USA

^[2] Ctr Nacl Pesquisa Energia Mat, Lab Nacl Ciencia & Tecnol Bioetanol, Campinas, SP - Brazil

• Document type: Review article
• Source: MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS; v. 78, n. 4, p. 588-613, DEC 2014.
• Web of Science Citations: 33

Abstract

Biomass is constructed of dense recalcitrant polymeric materials: proteins, lignin, and holocellulose, a fraction constituting fibrous cellulose wrapped in hemicellulose-pectin. Bacteria and fungi are abundant in soil and forest floors, actively recycling biomass mainly by extracting sugars from holocellulose degradation. Here we review the genome-wide contents of seven Aspergillus species and unravel hundreds of gene models encoding holocellulose-degrading enzymes. Numerous apparent gene duplications followed functional evolution, grouping similar genes into smaller coherent functional families according to specialized structural features, domain organization, biochemical activity, and genus genome distribution. Aspergilli contain about 37 cellulase gene models, clustered in two mechanistic categories: 27 hydrolyze and 10 oxidize glycosidic bonds. Within the oxidative enzymes, we found two cellobiose dehydrogenases that produce oxygen radicals utilized by eight lytic polysaccharide monooxygenases that oxidize glycosidic linkages, breaking crystalline cellulose chains and making them accessible to hydrolytic enzymes. Among the hydrolases, six cellobiohydrolases with a tunnel-like structural fold embrace single crystalline cellulose chains and cooperate at nonreducing or reducing end termini, splitting off cellobiose. Five endoglucanases group into four structural families and interact randomly and internally with cellulose through an open cleft catalytic domain, and finally, seven extracellular beta-glucosidases cleave cellobiose and related oligomers into glucose. Aspergilli contain, on average, 30 hemicellulase and 7 accessory gene models, distributed among 9 distinct functional categories: the backbone-attacking enzymes xylanase, mannosidase, arabinase, and xyloglucanase, the short-side-chain-removing enzymes xylan alpha-1,2-glucuronidase, arabinofuranosidase, and xylosidase, and the accessory enzymes acetyl xylan and feruloyl esterases. (AU)

• FAPESP's process: 13/18910-3 - Secretion of heterologous glycoproteins in Aspergillus: effect of glycosylation pattern in functional parameters of glycosyl hydrolases
• Grantee: André Ricardo de Lima Damasio
• Support Opportunities: Scholarships in Brazil - BIOEN - Young Researchers
• FAPESP's process: 12/20549-4 - Secretion of heterologous glycoproteins in Aspergillus: effect of glycosylation pattern in functional parameters of glycosyl hydrolases
• Grantee: André Ricardo de Lima Damasio
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Young Investigators Grants
• FAPESP's process: 08/58037-9 - Library generation for biomass-conversion enzymes from soil metagenome
• Grantee: Fábio Márcio Squina
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Young Investigators Grants
• FAPESP's process: 10/18198-3 - Systems biology of sugarcane bagasse microbial decomposition interactions
• Grantee: Fábio Márcio Squina
• Support Opportunities: Research Grants - Visiting Researcher Grant - International