Sustainable bacterial chitosanase production using soybean meal hydrolysate: Insights into biochemical and hydrolysis characteristics

The chitosanase Csn from Bacillus subtilis 168, previously recombinantly expressed in B. subtilis PT5 called PT5(MT1-Csn) had demonstrated potential for converting chitosan into chitosan-oligosaccharides (COS). Herein, a new fermentation medium containing soybean meal hydrolysate (SMH), an oil byproduct, was used for enhancing PT5(MT1-Csn) chitosanase activity. The purified PT5(MT1-Csn) exhibited activity (1018.58 U mL -1 ) 11.5 times higher than the wild-type (WT) enzyme at pH 5.0 and 50 °C. Both PT5(MT1-Csn) and WT exhibited similar pH stability (3.0-9.0) and thermostability. The melting temperature ( Tm ) values of PT5(MT1-Csn) (51.38 o C ± 0.11) and WT (51.68 o C ± 0.03) were similar. After hydrolysis, chitosan-oligosaccharides (COS) without glucosamine or acetylglucosamine were produced, with a degree of polymerization between 2 and 4. The findings of the current study suggest that SMH can be effectively utilized to not only enhance the PT5(MT1-Csn) activity and reduce enzyme production cost but also to effectively valorize the oil byproducts. • Recombinant PT5(MT1-Csn) chitosanase showed potential for hydrolyzing chitosan. • Soybean meal hydrolysate was used as a nitrogen source for chitosanase production. • Enzyme activity of the purified PT5(MT1-Csn) was superior to that of WT. • COS was produced with a degree of polymerization between 2 and 4.