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

Exo-b-D-glucosaminidase is an enzyme acting on b-(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-b-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-b-D-glucosaminidase were 22 ± 1 �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-b-D-glucosaminidase production. Statistical optimization resulted
in an overall increase of exo-b-D-glucosaminidase activity from 116.7 ± 4.6 to 2335.1 ± 12.4 unit/g initial
dry substrate. Crude exo-b-D-glucosaminidase was found to have optimum activity at 42 ± 1 �C and pH
5.6. Crude exo-b-D-glucosaminidase produced the maximum D-glucosamine yield of 410e546 mM from
different a-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-b-D-glucosaminidase employing the cost-effective SSF process
and the significance of the exo-b-D-glucosaminidase for the preparation of commercially important Dglucosamine
and to cope seafood processing chitinous biomaterials.