The isolation of chitinase from Streptomyces thermocarboxydus and its application in the preparation of chitin oligomers

Abstract

Microbial chitinase has received great attention due to its medical, biological, and agricultural applications. In this study, over 50 bacterial strains were isolated from Taiwanese soils using medium containing squid pen powder (SPP) as the sole source of carbon/nitrogen. Based on chitinolytic activity, Streptomyces thermocarboxydus TKU045 was selected for further study. Optimized culture conditions revealed that S. thermocarboxydus TKU045 could produce the highest chitinase activity (52.985 U/mL) when cultured in a medium containing 1% (w/v) SPP at 45 °C for 36 h. Characterized TKU045 chitinase showed novel properties with a smallest molecular weight (12.8 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis) and more acidic optimal pH (pH 4) than those of other Streptomyces chitinases. A combination of high-performance liquid chromatography and matrix-assisted laser desorption ionization time of flight mass spectrometer data revealed that chitin oligomers (COS) obtained from the hydrolysis of colloidal chitin by TKU045 chitinase comprise oligomers with multiple degrees of polymerization (DP) varying from 1 to 7. The COS with low DP exhibited enhanced 2,2-diphenyl-1-picrylhydrazyl radical scavenging capability and promoted the growth of Lactobacillus lactis. Taken together, the COS obtained by hydrolyzing colloidal chitin with TKU045 chitinase could have the potential to be used in medicine or nutraceuticals due to its active anti-oxidant and prebiotic contents.