Pretreatment with KOH and KOH-urea enhanced hydrolysis of α-chitin by an endo-chitinase from Enterobacter cloacae subsp. cloacae

Abstract

Chitin is the second most abundant and renewable polysaccharide, next to cellulose. Hydrolysis of abundant and highly crystalline α-chitin, pretreated with KOH and KOH-urea aqueous solutions, by a single modular endo-chitinase from Enterobacter cloacae subsp. cloacae (EcChi1) was investigated. The hydrolysis of untreated α-chitin and colloidal chitin by EcChi1 produced N-acetylglucosamine and N, N’-diacetylchitobiose, whereas, hydrolysis of treated substrates generated N, N’, N’’-triacetylchitotriose, in addition to N-acetylglucosamine and N, N’-diacetylchitobiose. The total amount of chitooligosaccharides (COS) generated by EcChi1 from pretreated substrates was 10 to 25-fold higher compared to untreated α-chitin at 24 h (depending on the solvent type and state of substrate). EcChi1 released higher amount of DP1 and DP2 products on treated α-chitin, with a fold change of 45 and 18, respectively. Treatment of α-chitin with KOH/KOH-urea is, therefore, a promising approach for an efficient conversion of rich source of chitin to soluble COS by chitinases like EcChi1.