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Background An important conceptual advance in health and the environment has been recognized that enzymes play a key role in the green processing industries. Of particular interest, chitosanase is beneficial for recycling the chitosan resource and producing chitosan oligosaccharides. Also, chitosan gene expression and molecular characterization will promote understanding of the biological function of bacterial chitosanase as well as explore chitosanase for utilizing chitosan resources. Results A chitosanase-producing bacterium TY24 was isolated and identified as Bacillus cereus. Moreover, the chitosanase gene was cloned and expressed in Escherichia coli. Sequence analysis reveals that the recombinant chitosanase (CHOE) belongs to the glycoside hydrolases 8 family. The purified CHOE has a molecular weight of about 48 kDa and the specific activity of 1150 U/mg. The optimal pH and temperature of CHOE were 5.5 and 65 °C, respectively. The enzyme was observed stable at the pH range of 4.5–7.5 and the temperature range of 30–65 °C. Especially, the half-life of CHOE at 65 °C was 161 min. Additionally, the activity of CHOE was remarkably enhanced in the presence of Mn2+, Cu2+, Mg2+ and K+, beside Ca2+ at 5 mM. Especially, the activity of CHOE was enhanced to more than 120% in the presence of 1% of various surfactants. CHOE exhibited the highest substrate specificity toward colloid chitosan. Conclusion A bacterial chitosanase was cloned from B. cereus and successfully expressed in E. coli (BL21) DE3. The recombinant enzyme displayed good stability under acid pH and high-temperature conditions.

In view of the present situation that the recovery of waste thermosetting plastics and products is difficult and the utilization rate is low, regeneration mechanism, regeneration methods and recycling process of waste thermosetting plastics under mechanical thermal coupling fields are proposed. Regeneration powders of Thermosetting Phenolic plastic are obtained by mechanochemical activated regeneration methods, the molecular structure, properties and crosslink density of phenol regeneration materials are analyzed. Analysis results show that network crosslinked molecular structure was destroyed, reactive groups produced and the crosslink density decreased. The activity of regeneration powders was reinforced and its plasticity was also improving, so the utilization rate was improved. Regeneration composite plastics were manufactured by hot press molding or extrusion compression molding. The microstructure of regeneration composite plastics was analyzed, and its mechanical strength was tested. Results showed that the tensile strength and bending strength of samples (weight ratio ≥ 50%) respectively exceed 15.88 MPa and 33.49 MPa. At last process parameters for regeneration effects were discussed, and these parameters were optimized. When particle size was 80 mesh (size ≤ 0.18 mm), quality proportion was 50~70%, pressure was 10Mpa, heating temperature was 180~190°C, the optimal effects for regenerated composite were achieved.