Protein-glutaminase (EC 3.5.1.44, PG) converts protein glutamine residues in proteins and peptides into glutamic acid residue, and markedly improves the solubility, emulsification, and foaming properties of food proteins. However, the source bacteria, Chryseobacterium proteolyticum, have low enzyme production ability, inefficient genetic operation, and high production cost. Therefore, it is critical to establish an efficient expression system for active PG. Here, combinatorial engineering was developed for high-yield production of PG in Bacillus subtilis. First, we evaluated different B. subtilis strains for PG self-activation. Then, combinatorial optimization involving promoters, signal peptides, and culture medium was applied to produce active recombinant PG in a B. subtilis expression system. Through combinatorial engineering, PG enzyme activity reached 3.23 U/mL in shaken-flask cultures. Active PG with the yield of 7.07 U/mL was obtained at 40 h by the P_SecA-YdeJ combination in fed-batch fermentation, which is the highest yield of PG in existing reports.

蛋白质-谷氨酰胺酶（EC 3.5.1.44，PG）将蛋白质和肽中的蛋白质谷氨酰胺残基转化为谷氨酸残基，显着提高食品蛋白质的溶解性、乳化性和起泡性。然而，来源菌Chryseobacterium proteolyticum产酶能力低，遗传操作效率低，生产成本高。因此，建立活性PG的高效表达系统至关重要。在这里，开发了用于在枯草芽孢杆菌中高产生产 PG 的组合工程。首先，我们评估了不同的枯草芽孢杆菌PG自激活菌株。然后，应用涉及启动子、信号肽和培养基的组合优化以在枯草芽孢杆菌表达系统中产生活性重组 PG。通过组合工程，PG酶活性在摇瓶培养中达到3.23 U/mL。_{P SecA} -YdeJ组合在补料分批发酵中40 h获得活性PG，产量为7.07 U/mL ，是现有报道中PG产量最高的。