3.3. Proteomic analysis of the crude cell wall degrading multi-enzyme
The protein profile of the crude multi-enzyme extract of A. aculeatus from solid-state fermentation is shown in Fig. 1. Proteomic profiling of the multi-enzyme by LC–MS/MS yielded several matches to proteins of Aspergillus sp. origin classified as enzymes in various glycosyl hydrolase families with known functions in plant cell wall degradation (Table 3). Other enzymes were identified as starch-degrading amylolytic enzymes and proteolytic enzymes which could attack the non-cellulosic components in the substrates. Several pectinolytic enzymes were also identified,including endo-polygalacturonase, pectin esterase, and rhamnosidase. A variety of hemicellulases were found, including a number ofendo- and exo-acting hemicellulases, i.e., endo--1,4-mannanase,-xylosidase, -1,4-mannosidase, and -galactosidase. A complete cellulolytic enzyme system was also identified in the enzyme extract, comprising endo-glucanase, cellobiohydrolase, and -glucosidase. In addition, other hydrolases were also present in the secretome, including different enzymes attacking starch and othernon-cellulosic polysaccharides. The variety of possible enzymatic activities among the proteins identified suggested that A. aculeatus possesses a complex enzyme system for decomposition of starch and lignocellulosic polysaccharides in plant cells. In particular, the variety of glycosyl hydrolases could act cooperatively to dissociate plant cell wall efficiently, and thus be useful for reducing viscosity of cassava substrates.