Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China.
Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China; Tianjin Engineering Technology Center of Green Manufacturing Biobased Materials, Tianjin, 300071, China.
Carbohydr Polym. 2018 Jun 1;189:210-217. doi: 10.1016/j.carbpol.2018.02.027. Epub 2018 Feb 12.
Polymer sanxan is a novel microbial polysaccharide produced by Sphingomonas sanxanigenens NX02, which can produce poly-3-hydroxybutyrate (PHB) simultaneously. A strategy of combining rational and random gene manipulation was investigated to improve the yield of sanxan. Several crucial PHB biosynthesis genes were deleted through homologous recombination, then the PHB-deficient mutant was treated with plasma mutagenesis to obtain NXdP, an engineering strain. Ultimately, the yield of purified sanxan produced by strain NXdP increased from 14.88 ± 0.83 g/L to 21.20 ± 0.38 g/L in a 5 L bioreactor, while the cell dry weight (CDW) was decreased from 9.61 ± 0.14 g/L to 3.12 ± 0.15 g/L. The total precipitable material (crude sanxan) produced from NXdP showed higher zero-shear viscosity, light transmittance, and greater gel strength than that from NX02 due to the enhancement of its purity. The engineering strategies explored here are useful for engineering cell factories to produce other valuable metabolites.
聚 3-羟基丁酸酯（PHB）是一种细胞内聚酯，在细菌中作为碳源和能源的储存物质。本研究以 Sphingomonas sanxanigenens NX02 为出发菌株，该菌株能够同时合成新型微生物胞外多糖 sanxan。通过合理的基因敲除策略敲除了几个关键的 PHB 生物合成基因，构建 PHB 缺陷型突变株 NXdP，然后利用等离子体诱变技术进一步提高 sanxan 的产量。最终，在 5 L 发酵罐中，突变株 NXdP 的 sanxan 产量从 14.88 ± 0.83 g/L 提高到 21.20 ± 0.38 g/L，而细胞干重（CDW）从 9.61 ± 0.14 g/L 降低到 3.12 ± 0.15 g/L。由于突变株 NXdP 合成的 sanxan 纯度提高，其总可沉淀物质（粗 sanxan）表现出更高的零剪切黏度、透光率和凝胶强度。本研究中探索的工程策略对于工程细胞工厂生产其他有价值的代谢产物具有重要意义。
