Self-adhesive PMIA membranes with chitosan porous beads immobilized pullulanase for efficient biological aging of beer.

A novel pulluanase@chitosan porous beads/Poly (m-phthaloyl-m-phenylenediamine) (PULL@CPB/PMIA) membrane with good separation and biocatalysis properties was prepared by a self-adhesive method by introducing an immobilized enzyme (PULL@CPB) onto the PMIA membrane. The combination of PULL@CPB and PMIA could increase the one-step refining of protoplasmic beer as well as the ability of biocatalysis to lower the alcohol-to-ester ratio. The experimental results showed that the addition of PULL@CPB and the increase in the ratio of EtOH/water in the coagulation bath both increased the load of pullulanase on the membrane surface, while excessive addition decreased the activity of pullulanase. Under the amount of PULL@CPB is 0.5 g·L and the ratio of EtOH/water is 60%, the relative activity of pullulanase in PULL@CPB modified PMIA membrane was the highest, which was 91.7% of the initial activity. The interception rates of protein and macromolecular β-glucan were 92.2% and 87.3%, respectively, under the condition of beer flux (162.3 L·m·h). At the same time, the PULL@CPB/PMIA membrane has strong antibacterial performance and thus plays a role in extending the shelf life of beer. Compared with free pullulanase, the thermal stability, pH stability, organic solvent stability, and storing stability of immobilized pullulanase were significantly improved. The effects of PULL@CPB dosage and operating temperature on biocatalysis efficiency were discussed. The immobilized pullulanase activity on the membrane remained at 70.8% after 10 continuous uses. Therefore, the PMIA membrane is an excellent carrier of pullulanase, so its bioactive membrane has a wide range of prospects in food, medicine, and other fields.