Abstract
BackgroundAspergillus fumigatus Z5 has a strong ability to decompose lignocellulose biomass, and its extracellular protein secretion has been reported in earlier studies employing traditional techniques. However, a comprehensive analysis of its secretion in the presence of different carbon sources is still lacking. The goal of this work was to identify, quantify and compare the secretome of A. fumigatus Z5 in the presence of different carbon sources to understand in more details the mechanisms of lignocellulose decomposition by Aspergillus fumigatus Z5.ResultsCellulolytic A. fumigatus Z5 was grown in the presence of glucose (Gl), Avicel (Av) and rice straw (RS), and the activities of several lignocellulosic enzymes were determined with chromatometry method. The maximum activities of endoglucanase, exoglucanase, β-glucosidase, laminarinase, lichenase, xylanase and pectin lyase were 12.52, 0.59, 2.30, 2.37, 1.68, 15.02 and 11.40 U·ml-1, respectively. A total of 152, 125 and 61 different proteins were identified in the presence of RS, Av and Gl, respectively, and the proteins were functionally divided into glycoside hydrolases, lipases, peptidases, peroxidases, esterases, protein translocating transporters and hypothetical proteins. A total of 49 proteins were iTRAQ-quantified in all the treatments, and the quantification results indicated that most of the cellulases, hemicellulases and glycoside hydrolases were highly upregulated when rice straw and Avicel were used as carbon sources (compared with glucose).ConclusionsThe proteins secreted from A. fumigatus Z5 in the present of different carbon source conditions were identified by LC-MS/MS and quantified by iTRAQ-based quantitative proteomics. The results indicated that A. fumigatus Z5 could produce considerable cellulose-, hemicellulose-, pectin- and lignin-degrading enzymes that are valuable for the lignocellulosic bioenergy industry.
Highlights
Aspergillus fumigatus Z5 has a strong ability to decompose lignocellulose biomass, and its extracellular protein secretion has been reported in earlier studies employing traditional techniques
The results indicated that most of the proteins gathered in the acidic side ranging from pI 4–7, which suggested that the secretomes of A. fumigatus Z5 were mainly acidic enzyme
Several lignocellulases were detected when glucose, Avicel and rice straw were used as carbon sources, and the results indicated that rice straw was the optimal carbon source for the production of lignocellulases, whereas glucose significantly repressed the production of lignocellulases by A. fumigatus Z5
Summary
Aspergillus fumigatus Z5 has a strong ability to decompose lignocellulose biomass, and its extracellular protein secretion has been reported in earlier studies employing traditional techniques. The goal of this work was to identify, quantify and compare the secretome of A. fumigatus Z5 in the presence of different carbon sources to understand in more details the mechanisms of lignocellulose decomposition by Aspergillus fumigatus Z5. Lignocellulosic waste composed of cellulose, hemicelluloses, and lignin is one of the largest global carbon sources and is considered to be a potential feedstock for the production of biofuel [2]. Pectinase is commonly used in brewing, and pectic enzymes include pectolyase, pectozyme and polygalacturonase. These enzymes break down pectin, a polysaccharide substrate found in plant cell walls [9]. The efficient hydrolysis of lignocellulosic biomass involves the release of long chain polysaccharides and their breakdown into sugars, which requires relayed actions of these enzymes [2,10]
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