RESUMO
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 [SmChiA-F232W/F396W (SmChiA-M)] was found to be 32% faster than wild-type SmChiA in hydrolyzing the deproteinized DKP (DDKP) and showed significant synergy with chitinase B from S. marcescens (SmChiB) and chitinase C from S. marcescens (SmChiC). Then two SmChiA-M-based enzyme combinations [SmChiA-Mâ¯+â¯SmChiBâ¯+â¯SmChiC and SmChiA-Mâ¯+â¯SmChiBâ¯+â¯SmChiCâ¯+â¯OfHex1 (an insect N-acetyl-d-hexosaminidase from Ostrinia furnacalis)] were designed to produce (GlcNAc)2 and GlcNAc, respectively, from DDKP. A yield of 2.04â¯g/L (GlcNAc)2 or 2.71â¯g/L GlcNAc (each with 95% purity) could be obtained from 20â¯g/L DDKP in 24â¯h.