An optimized cocktail of chitinolytic enzymes to produce N,N′-diacetylchitobiose and N-acetyl-d-glucosamine from defatted krill by-products

Abstract Defatted krill powder (DKP), the byproduct of krill oil industry, is a resource of biological macromolecules. Here, one bacterial protease, three bacterial chitinases and one insect N -acetyl- d -hexosaminidase were integratively used to produce peptide, N , N ′-diacetylchitobiose [(GlcNAc) 2 ] and N -acetyl- d -glucosamine (GlcNAc) from DKP. First, alkaline protease was found to outperform neutral protease in deproteinizing DKP and the resultant krill peptides were rich in essential amino acids (41.4%). Second, the mutant of chitinase A from Serratia marcescens [ Sm ChiA-F232W/F396W ( Sm ChiA-M)] was found to be 32% faster than wild-type Sm ChiA in hydrolyzing the deproteinized DKP (DDKP) and showed significant synergy with chitinase B from S. marcescens ( Sm ChiB) and chitinase C from S. marcescens ( Sm ChiC). Then two Sm ChiA-M-based enzyme combinations [ Sm ChiA-M +  Sm ChiB +  Sm ChiC and Sm ChiA-M +  Sm ChiB +  Sm ChiC +  Of Hex1 (an insect N -acetyl- d -hexosaminidase from Ostrinia furnacalis )] were designed to produce (GlcNAc) 2 and GlcNAc, respectively, from DDKP. A yield of 2.04 g/L (GlcNAc) 2 or 2.71 g/L GlcNAc (each with 95% purity) could be obtained from 20 g/L DDKP in 24 h.