Current efforts to improve xanthan gum (XG) production by Xanthomonas have focused on the growth medium, operating parameters, and downstream steps. However, a key aspect is the development of optimal strains. The present work aimed to investigate the formation of XG monomers, using kinetic and stoichiometric models to identify possible bottlenecks, and to engineer a recombinant strain to overcome such limitations. The galU and ugd genes involved in thebiosynthesis of the UDP-glucose and UDP-glucuronic acid monomers were overexpressed in Xanthomonas campestris pv. campestris. The strains were cultivated in shake flasks and bioreactor. As predicted by in silico analysis, overexpression of the ugd gene resulted in a significant increase in gum synthesis, up to 50% higher volumetric productivity in thebioreactor. To a lesser extent, galU overexpression was also shown to improve product formation. These findings validated the hypothesis that metabolic engineering of the monomer biosynthesis can enhance XG production.

中文翻译：

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油菜黄原胶的产生通过有利于其单体的生物合成而增加


目前改善黄原胶 （XG） 生产的努力主要集中在生长培养基、操作参数和下游步骤上。然而，一个关键方面是最佳菌株的开发。目前的工作旨在研究 XG 单体的形成，使用动力学和化学计量模型来识别可能的瓶颈，并设计重组菌株来克服这些限制。参与 UDP-葡萄糖和 UDP-葡萄糖醛酸单体生物合成的 galU 和 ugd 基因在油菜黄单胞菌 pv 中过表达。坎佩斯特里斯。菌株在摇瓶和生物反应器中培养。正如计算机分析所预测的那样，ugd 基因的过表达导致树胶合成显著增加，生物反应器中的体积生产率提高了 50%。在较小程度上，galU 过表达也被证明可以改善产物形成。这些发现验证了单体生物合成的代谢工程可以增强 XG 产生的假设。