不同分子量γ-聚谷氨酸的生物合成

Bioproduction of poly-γ-glutamic acid with diverse molecular weights in Bacillus subtilis

摘要:

【背景】不同分子量的γ-聚谷氨酸在农业、化妆品和医药领域具有重要的应用价值，开发不同分子量γ-聚谷氨酸的生物合成工艺已成为研究热点。【目的】在γ-聚谷氨酸生产菌株枯草芽孢杆菌(Bacillus subtilis) KH2中实现不同分子量γ-聚谷氨酸的合成。【方法】分别克隆表达不同来源的水解酶，包括B.subtilis来源的γ-聚谷氨酸水解酶PgdS和YwtE，以及地衣芽孢杆菌来源的SGH。研究不同来源水解酶对B.subtilisKH2产γ-聚谷氨酸分子量的影响。通过改变水解酶处理条件获得不同分子量γ-聚谷氨酸的生物合成工艺。【结果】PgdS、YwtE和SGH均可降低γ-聚谷氨酸的分子量，其中PgdS水解效果最好，可以将γ-聚谷氨酸分子量由原来的1 600 kDa降低为180 kDa。通过优化PgdS的添加量与添加时间，在B.subtilisKH2中获得了分子量为210–600 kDa的γ-聚谷氨酸。【结论】利用水解酶处理，可以在B.subtilisKH2中实现不同分子量γ-聚谷氨酸的生物合成。该方法反应条件温和、分子量可控区间宽，具有良好的应用前景。

Abstract:

[Background] Poly-γ-glutamic acids (γ-PGAs) with different molecular weights are of high application value in agriculture, cosmetics, and medicine, and biosynthesis of γ-PGA with specific molecular weights has attracted the interest of scholars. [Objective] To synthesize γ-PGAs of different molecular weights in a γ-PGA producer, Bacillus subtilis KH2. [Methods] Three γ-PGA hydrolases of B.subtilis PgdS, B.subtilis YwtE, and B.licheniformis SGH, were heterologously expressed and their hydrolytic capacities were investigated. γ-PGAs with different molecular weights were yielded in B.subtilis KH2 through the modification of enzymatic degradation conditions. [Results] All the three hydrolases can cleave high-molecular-weight γ-PGA into low-molecular-weight γ-PGA, particularly PgdS. The molecular weight of γ-PGA decreased from 1 600 kDa to 180 kDa with the addition of PgdS. Finally, the addition amount and time of PgdS were optimized to yield γ-PGA with the molecular weight of 210-600 kDa in KH2. [Conclusion] γ-PGAs with diverse molecular weights were synthesized in B.subtilis KH2 through the controllable treatment with hydrolase. This study provided a promising approach for the sustainable production of γ-PGA with different molecular weights in a wide range under mild synthesis conditions.