In order to explore the feasibility of immobilized neutral urease for the degradation of urea in Huangjiu (Chinese rice wine), the enzymatic properties of free neutral urease were measured and compared with that of the acid urease. The covalent bonding method was used to immobilize neutral urease with chitosan, and the immobilized neutral urease was used for the degradation of urea in Huangjiu. The results showed that the free neutral urease retained very low enzyme activity under acidic conditions (pH=4.0), while high ethanol volume fraction (24%) had little effect on its activity. After immobilization, the optimal pH of neutral urease was lowered down from 7.0 to 5.0, and acid resistance was also significantly improved. Compared with the free enzyme, temperature and alcohol had little effect on the activity and stability of the immobilized enzyme. This immobilized neutral urease was used to treat Huangjiu at 30 ℃ with dosage of 1 000 U/L for 24 hours, which could degrade more than 95% of urea in Huangjiu. Reusing immobilized enzymes also had a certain effect on the treatment of Huangjiu. This study provides a basis for the future application of immobilized neutral urease for the degradation of urea in Huangjiu.
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