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VLB120在通过魏姆伯格途径利用D-木糖生长过程中的代谢瓶颈。

Metabolic bottlenecks of VLB120 during growth on d-xylose via the Weimberg pathway.

作者信息

Nerke Philipp, Korb Jonas, Haala Frederick, Hubmann Georg, Lütz Stephan

机构信息

Chair for Bioprocess Engineering, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Straße 66, 44227, Dortmund, Germany.

出版信息

Metab Eng Commun. 2024 Jun 6;18:e00241. doi: 10.1016/j.mec.2024.e00241. eCollection 2024 Jun.

Abstract

The microbial production of value-added chemicals from renewable feedstocks is an important step towards a sustainable, bio-based economy. Therefore, microbes need to efficiently utilize lignocellulosic biomass and its dominant constituents, such as d-xylose. VLB120 assimilates d-xylose via the five-step Weimberg pathway. However, the knowledge about the metabolic constraints of the Weimberg pathway i.e., its regulation, dynamics, and metabolite fluxes, is limited, which hampers the optimization and implementation of this pathway for bioprocesses. We characterized the Weimberg pathway activity of VLB120 in terms of biomass growth and the dynamics of pathway intermediates. In batch cultivations, we found excessive accumulation of the intermediates d-xylonolactone and d-xylonate, indicating bottlenecks in d-xylonolactone hydrolysis and d-xylonate uptake. Moreover, the intermediate accumulation was highly dependent on the concentration of d-xylose and the extracellular pH. To encounter the apparent bottlenecks, we identified and overexpressed two genes coding for putative endogenous xylonolactonases PVLB_05820 and PVLB_12345. Compared to the control strain, the overexpression of PVLB_12345 resulted in an increased growth rate and biomass generation of up to 30 % and 100 %, respectively. Next, d-xylonate accumulation was decreased by overexpressing two newly identified d-xylonate transporter genes, PVLB_18545 and (PVLB_13665). Finally, we combined xylonolactonase overexpression with enhanced uptake of d-xylonate by knocking out the repressor gene (PVLB_13655) and increased the growth rate and biomass yield by 50 % and 24 % in stirred-tank bioreactors, respectively. Our study contributes to the fundamental knowledge of the Weimberg pathway in pseudomonads and demonstrates how to encounter the metabolic bottlenecks of the Weimberg pathway to advance strain developments and cell factory design for bioprocesses on renewable feedstocks.

摘要

利用可再生原料通过微生物生产增值化学品是迈向可持续生物基经济的重要一步。因此,微生物需要高效利用木质纤维素生物质及其主要成分,如D-木糖。VLB120通过五步魏伯格途径同化D-木糖。然而,关于魏伯格途径的代谢限制,即其调控、动力学和代谢物通量的知识有限,这阻碍了该途径在生物过程中的优化和应用。我们从生物量生长和途径中间体的动力学方面对VLB120的魏伯格途径活性进行了表征。在分批培养中,我们发现中间体D-木糖内酯和D-木糖酸盐过度积累,表明D-木糖内酯水解和D-木糖酸盐摄取存在瓶颈。此外,中间体的积累高度依赖于D-木糖的浓度和细胞外pH值。为了克服明显的瓶颈,我们鉴定并过表达了两个编码假定内源性木糖内酯酶PVLB_05820和PVLB_12345的基因。与对照菌株相比,PVLB_12345的过表达分别使生长速率和生物量生成增加了30%和100%。接下来,通过过表达两个新鉴定的D-木糖酸盐转运蛋白基因PVLB_18545和PVLB_13665,减少了D-木糖酸盐的积累。最后,我们通过敲除阻遏基因PVLB_13655,将木糖内酯酶过表达与增强D-木糖酸盐摄取相结合,在搅拌罐生物反应器中分别使生长速率和生物量产量提高了50%和24%。我们的研究有助于了解假单胞菌中魏伯格途径的基础知识,并展示了如何克服魏伯格途径的代谢瓶颈,以推进基于可再生原料的生物过程的菌株开发和细胞工厂设计。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/166e/11252243/75e2cd1f3a9b/gr1.jpg

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