Characterization of a versatile glycoside hydrolase Cel5M from Pectobacterium carotovorum HG-49 for ramie degumming

Abstract

A novel versatile glycoside hydrolase Cel5M was identified from Pectobacterium carotovorum and used in ramie degumming. The full-length Cel5M (GenBank: MH544226) containing the catalytic domain Cel5MD and its carbohydrate-binding module (CBM3) were expressed in E. coli. Both Cel5M and Cel5MD showed a broad substrate spectrum cleaving konjac glucomannan (KGM), carboxymethylcellulose (CMC) and oat spelt xylan. The optimal temperature of Cel5MD was 55oC with CMC and KGM, whereas the optimum temperature of Cel5M was 65oC with KGM and 60oC with CMC. The improved thermal activity with KGM was probably reflected also in the much lower K m with KGM than with CMC, indicating stronger binding of the full-length enzyme with KGM. Both enzymes were highly stable over a broad pH range from pH 5.0 to 9.0 with KGM. The use of the Cel5M enzyme together with the wild-type P. carotovorum HG-49 strain showed significant improvement when compared to using the mere strain HG-49 for application in ramie degumming. Moreover, the whole P. carotovorum Cel5M gene was over-expressed in P. carotovorum HG-49 itself to improve the ramie-degumming capacity. Altogether, this study indicates that in situ production of processing enzymes could be utilized in the textile industry.