ReviewBiochemical and biotechnological trends in chitin, chitosan, and related enzymes produced by Paenibacillus IK-5 Strain

We review studies on biochemical characterization of the structures and functions of chitinase, chitosanase, and chitobiase produced by cells of the bacterium, Paenibacillus sp. IK-5. The IK-5 chitinases comprise two GH18 chitinases (ChiA and ChiB), an auxiliary activity family 10 (AA10) chitin oxydehydrolase (ChiC), and a GH19 chitinase (ChiD). The IK-5 chitosanase (ChiE) has a glycosyl hydrolase family 8 (GH8) catalytic domain at the amino-terminus and two discoidin domains (DD) at the carboxyl-terminus. The IK-5 cells also produce chitobiase, containing carbohydrate hydrolase H-20 and S-layer homology domains. Together, these ChiA∼ChiE proteins form a huge complex, designated the “chitinasome”. The DD domains bind specifically and tightly to chitosan, suggesting that they are chitosan-specific carbohydrate-binding modules (CBM32); indeed, CBM32 modules have been confirmed to bind to chitosan oligosaccharides (GlcN)2-6. A high-yield secretion system for Ik-5 chitosanase has been constructed using plasmid pNY301 expressed in Bacillus brevis.We also review biotechnological research using chitin, chitosan, crab shell, and IK-5 chitinase and chitosanase. Chitosan has been shown to be useful for efficient gene transfer into microbial and animal cells. IK-5 cell culture and crab shells were effective for the growth of plants and seaweeds.