Enzymatic degradation of chitosan and production of D-glucosamine by solid substrate fermentation of exo-β-D-glucosaminidase (exochitosanase) by Penicillium decumbens CFRNT15

Exo-beta-D-glucosaminidase is an enzyme acting on beta-(1 -> 4) linkage of chitosan from its non-reducing end and produces D-glucosamine as the exclusive end product. Solid substrate fermentation (SSF) production of exo-beta-D-glucosaminidase by a novel isolate of Penicillium decumbens (CFRNT15) was optimized employing Box-Behnken design and response surface methodology. The optimized conditions for maximal production of exo-beta-D-glucosaminidase were 22 +/- 1 degrees C temperature, 75% (w/w) moisture, 120 h fermentation, 5.0% (w/w) chitosan, 0.05% (w/w) CaCl2, 0.5% (w/w) MgSO4, and 15.1% (w/v) inoculum. The close agreement of experiential results with the model prediction showed that the model was precise and dependable for predicting the exo-beta-D-glucosaminidase production. Statistical optimization resulted in an overall increase of exo-beta-D-glucosaminidase activity from 116.7 +/- 4.6 to 2335.1 +/- 12.4 unit/g initial dry substrate. Crude exo-beta-D-glucosaminidase was found to have optimum activity at 42 +/- 1 degrees C and pH 5.6. Crude exo-beta-D-glucosaminidase produced the maximum D-glucosamine yield of 410-546 M from different alpha-chitosan substrates hydrolysis. Thin layer chromatography analysis revealed that D-glucosamine was the sole end product of the chitosan hydrolysis. These results indicated the potential of P. decumbens for the production of the exo-beta-D-glucosaminidase employing the cost-effective SSF process and the significance of the exo-beta-D-glucosaminidase for the preparation of commercially important D-glucosamine and to cope seafood processing chitinous biomaterials. (C) 2014 Elsevier Ltd. All rights reserved.