Identification of endoglucanases, xylanases, pectinases and mannanases in the multi-enzyme complex of Bacillus licheniformis SVD1

摘要

Micro-organisms that degrade plant biomass require a range of enzymes to effectively degrade such substrates into sugar monomers. Some organisms secrete a host of free, extracellular enzymes while others produce a multi-enzyme complex (MEC) consisting of a variety of these enzymes. This study examined the cellulolytic and hemi-cellulolytic system of Bacillus licheniformis SVD1 with respect to the presence of key enzymes within the MEC found in this organism. When cultured on birchwood xylan, the MEC in B. licheniformis SVD1 was found to contain two endoglucanases (at 25-27 kDa, 30-32 kDa), seven xylanases (at 20 kDa, 38 kDa, 42 kDa, 45 kDa, 48 kDa, 54 kDa and 70 kDa), two mannanases (25 kDa, 40-42 kDa) and one pectinase (a pectate lyase at 70-72 kDa). Identification of enzymes was based on zymogram analysis. The MEC contained 17 different protein species based on SDS-PAGE analysis and 9 of these proteins could be identified through zymograms. Further work will be conducted to confirm the identity of other proteins in the MEC. The crude extract contained a further endoglucanase of 55 kDa, a mannanase of 53 kDa and a pectin methyl esterase of 38 kDa, indicating that not all enzymes are incorporated into the MEC. Understanding the composition of a hemi-cellulolytic system when cultured on a substrate may assist in utilising such a system for the synergistic degradation of complex lignocellulose substrates.