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

• Isolation of a new Penicillium decumbens strain for exo-β-d-glucosaminidase production.
• Solid state fermentation process for exo-β-d-glucosaminidase production by P. decumbens
• Optimized the exo-β-d-glucosaminidase production from P. decumbens by Box-Behnken design.
• We achieved highest level of enzyme activity of 2335.1 ± 12.4 U/g IDS after optimization.
• The crude enzyme formed (μM) 410–546 of d-glucosamine from different chitosan substrates.

Exo-β-d-glucosaminidase is an enzyme acting on β-(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-β-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-β-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-β-d-glucosaminidase production. Statistical optimization resulted in an overall increase of exo-β-d-glucosaminidase activity from 116.7 ± 4.6 to 2335.1 ± 12.4 unit/g initial dry substrate. Crude exo-β-d-glucosaminidase was found to have optimum activity at 42 ± 1 °C and pH 5.6. Crude exo-β-d-glucosaminidase produced the maximum d-glucosamine yield of 410–546 μM from different α-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-β-d-glucosaminidase employing the cost-effective SSF process and the significance of the exo-β-d-glucosaminidase for the preparation of commercially important d-glucosamine and to cope seafood processing chitinous biomaterials.