Cellotriose-hydrolyzing activity conferred by truncating the carbohydrate-binding modules of Cel5 from Hahella chejuensis

Abstract

Processivity is a typical characteristic of cellobiohydrolases (CBHs); it enables the enzyme to successively hydrolyze the ends of cellulose chains and to produce cellobiose as the major product. Some microbes, which do not have CBHs, utilize endoglucanases (EGs) that exhibit processivity, commonly referred to as processive EGs. A processive EG identified from Hahella chejuensis, HcCel5, has a catalytic domain (CD) belonging to the glycoside hydrolase family 5 (GH5) and two carbohydrate- binding modules (CBM6s). In this study, we compared HcCel5-CD with the CD of Saccharophagus degradans Cel5H (SdCel5H-CD), which is a processive EG reported previously. Our results showed that in comparison to SdCel5H-CD, HcCel5-CD has more suitable characteristics for cellulose hydrolysis, such as higher hydrolytic activity, thermostability (40-80 degrees C), and processivity. Noticeably, HcCel5-CD is capable of hydrolyzing cellotriose, unlike HcCel5. These features of HcCel5-CD for cellulose hydrolysis could be employed for efficient saccharification of lignocellulose to produce cellobiose and glucose, which may be used to produce renewable fuels and chemicals.