GH10 XynF1 and Xyn11A: the predominant xylanase identified in the profiling of extracellular proteome of Aspergillus oryzae LC1

Abstract

Advanced techniques of enzyme production and purification have become prerequisite due to their diverse industrial applications. There is an utmost requirement for screening of new strains capable of synthesising industrially useful enzymes. The present study reports the production and profiling of extracellular proteins expressed by the newly isolated strain of a filamentous fungus, Aspergillus oryzae LC1. The extracellular enzyme production was done by submerged fermentation using Mendel’s and Sternberg’s medium (MSM), and its optimisation was done using one factor at a time (OFAT). The presence of xylanase was confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and zymography. In addition, the profiling of extracellular proteome of Aspergillus oryzae LC1 was carried out by liquid chromatography coupled tandem mass spectrometry (LC-MS/MS). In this study, media optimisation showed 5.7-fold increase in xylanase activity. The multiple bands observed in zymography revealed the presence of various forms of xylanase. A total of 73 proteins were identified in LC-MS/MS analysis. Functional classification showed that the hydrolytic enzymes consisted of 48% glycoside hydrolase, 11% proteases, 1% polysaccharide lyase and esterase’s, 9% oxidoreductases and 30% other proteins. A total of 26 families of glycosidic hydrolase were detected with other protein families such as serine peptidase, S, LysM, G-D-S-L, M35, carboxyl esterase (CE1), pectate lyase (PL) and oxidoreductases. Among the huge diversity of synergistically acting biomass cleaving enzymes, endo-1, 4-β xylanase with isoforms: xyn F1, xyn B, β xylanase and xyn 11A belonging to GH10 family covered the major portion of the total percentage of identified proteins. As per our knowledge, this is the first report of extracellular proteome analysis of Aspergillus oryzae LC1 suggesting its capability for recombinant expression and evaluation in hemicellulose deconstruction applications.