Optimization of cello-oligosaccharides production by enzymatic hydrolysis of hydrothermally pretreated sugarcane straw using cellulolytic and oxidative enzymes

Abstract

Enzymatic hydrolysis of lignocellulosic biomass accounts for 20–30% of the total cost of second-generation bioethanol production and many efforts have been made in recent years to overcome the high cost of enzymes. Using cello-oligosaccharides (COS), intermediates in cellulose conversion to glucose, may provide advantages over monomeric glucose fermentation, such as lower risk of growth of process contaminants, shorter fermentation time and limited process inhibition by high concentrations of glucose. In addition, COS are also useful as functional oligosaccharides in the food and feed sectors. This study aimed to optimize COS production for further industrial applications. To the best of our knowledge, this is the first study that has used a design of experiments approach to analyze the synergism between endoglucanases, lytic polysaccharide monooxygenase (LPMO), cellobiose dehydrogenase (CDH) and different additives during the hydrolysis of a pretreated sugarcane straw for COS production. After optimization of enzymatic hydrolysis, a combination of the endoglucanases CaCel and CcCel9m, the LPMO TrCel61A, the CDH NcCDHIIa, with lactose and copper as additives, produced 60.49 mg of COS per g of pretreated sugarcane straw, 1.8–2.7-fold more than the commercial enzyme cocktails Cellic® Ctec2 and Celluclast® 1.5 L. The COS/glucose ratio achieved was 298.31, an increase of 3314 and 2294-fold over the commercial enzymatic cocktails, respectively. These results open a new perspective regarding COS production and its industrial application.