Enzymatic Production of Chitooligosaccharide Using a GH Family 46 Chitosanase from Paenibacillus elgii and Its Antioxidant Activity

Chitooligosaccharide (COS), a natural antioxidant, is a hydrolysis product of chitosan created using enzymatic or chemical methods. COS has received considerable attention recently, making its efficient bioproduction of great value. This study investigated the optimal conditions for the enzymatic method using a GH family 46 chitosanase from Paenibacillus elgii TKU051 to prepare COS based on the response surface methodology (RSM). The results showed optimal values for chitosan hydrolysis, such as a pH of 5.5, an incubation temperature of 58.3 °C, an [E]/[S] ratio of 118.494 (U/g), and an incubation time of 6.821 h. Under the optimal conditions, the highest reducing sugar level (per substrate, w/w) of the chitosan hydrolysis process that could be reached was 690.587 mg/g. The composition of the obtained COS was analyzed using the thin-layer chromatography (TLC) method, yielding (GlcN)2 and (GlcN)3 as the products. The ascorbic acid equivalent antioxidant capacity (AEAC) of the obtained COS was found to be 1246 mg/100 g (via a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay) and 3673 mg/100 g (via an ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) radical-scavenging assay). This green and efficient bioproduction method may possess excellent potential for application in bioactive COS preparation.