微生物发酵法制备结冷胶的研究进展

目前,微生物发酵法是结冷胶生产的最佳方法。结冷胶的生物合成途径包括胞内糖活化前体的合成、四糖重复单元的合成、重复单元的移位、聚合及结冷胶分泌到膜外等过程。UDP-葡萄糖焦磷酸化酶、TDP-葡萄糖焦磷酸化酶、UDP-葡萄糖脱氢酶等是结冷胶合成的关键酶。生产结冷胶的菌种可以通过诱变、基因重组和支路基因敲除等方法获得。最佳的碳源、氮源及C/N、最适的发酵温度及溶氧控制、发酵动力学模型建立及响应面实验设计方法等新技术方法逐渐应用于结冷胶的生产。本文对结冷胶的生物合成代谢途径及重要酶的研究进展进行了综述,并对近年来构建结冷胶产生菌的研究及发酵工业进行了总结,展望了未来构建结冷胶基因工程菌的研究方向。 

Research progress in productions of gellan gum by fermentation of microorganism

Gellan is used in the food, pharmaceutical and industries and produced by Sphingomonas paucimobilis. Fermentation is the optimal production of gellan gum.The gellan biosynthetic pathway consists of three sequential steps:intracellular synthesis of sugar-activated precursors, assembly of the tetrasaccharide repeat units linked to the inner membrane, and translocation of the repeat united to the periplasmic space followed by their polymerization and export through the outer membrane.Some enzymes, such as UDP-glucose pyrophosphorylase (UGP) , TDP-glucose pyrophosphorylase (TGP) and UDP-glucose dehydrogenase (UGD) , are critical for gellan gum biosynthesis.Strains used for gellan gum production could be acquired by mutagenesis, gene recombining and gene knockout.Some new technologies, such as the optimal carbon and nitrogen sources and C/N, the optimal fermentation temperature and dissolved oxygen control, the fermentation kinetics model and response surface experimental design methods, were being used in gellan gum production gradually.In this paper, the research progress related to biosynthesis pathway of gellan and biosynthetic enzymes in microorganisms were reviewed, and the latest research of gellan producing strains was summarized. At last, we concluded an outlook for research directions in building gellan genetically engineered strains.