Acedos Miguel G, De la Torre Isabel, Barriuso Jorge, García José L
Department of Biotechnology, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
Advanced Biofuels and Bioproducts Unit, Department of Energy, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain.
J Biol Eng. 2025 Apr 14;19(1):32. doi: 10.1186/s13036-025-00503-1.
Rhodococcus jostii RHA1 is an oleaginous bacterium that has attracted considerable attention due to its capacity to use different carbon sources to accumulate significant levels of triacylglycerols that might be converted into biofuels. However, this strain cannot transform xylose into lipids reducing its potential when growing on saccharified lignocellulosic biomass. In this work, we demonstrate that wild type R. jostii RHA1 can be evolved by adaptive laboratory evolution (ALE) to metabolize xylose without engineering heterologous metabolic pathways in the host. We have generated a phenotypically adapted ALE-xyl strain able to use xylose as the sole carbon and energy source more efficiently that an engineered recombinant strain harbouring heterologous xylA and xylB genes encoding a xylose isomerase metabolic pathway. The R. jostii RHA1 ALE-xyl strain accumulates lipids very efficiently using xylose as substrate, but even more importantly it can consume glucose and xylose at the same time. Transcriptomic analyses of ALE-xyl strain growing with glucose or xylose revealed the existence of a silent pentose metabolizing operon that is overexpressed in the presence of xylose. The detection of a xylose reductase activity together with the presence of xylitol in the cytoplasm of ALE-xyl strain suggests that xylose is consumed by a reductase pathway. This study demonstrates that, in cases where a clear phenotypic selection method is available, ALE can be used to improve very efficiently industrial microbial strains without using genetic engineering tools. Strategies focused to exploit the silent phenotypic flexibility of microorganisms to metabolize different carbon sources are powerful tools for the production of microbial value-added products using saccharified lignocellulosic wastes.
约氏红球菌RHA1是一种产油细菌，因其能够利用不同碳源积累大量可转化为生物燃料的三酰甘油而备受关注。然而，该菌株无法将木糖转化为脂质，这降低了其在糖化木质纤维素生物质上生长时的潜力。在这项研究中，我们证明野生型约氏红球菌RHA1可以通过适应性实验室进化（ALE）进行进化，从而在不构建宿主异源代谢途径的情况下代谢木糖。我们已经构建了一种表型适应的ALE-xyl菌株，该菌株能够比携带编码木糖异构酶代谢途径的异源xylA和xylB基因的工程重组菌株更有效地利用木糖作为唯一碳源和能源。约氏红球菌RHA1 ALE-xyl菌株以木糖为底物非常有效地积累脂质，但更重要的是它可以同时消耗葡萄糖和木糖。对在葡萄糖或木糖上生长的ALE-xyl菌株进行转录组分析，发现存在一个沉默的戊糖代谢操纵子，该操纵子在木糖存在时过表达。在ALE-xyl菌株的细胞质中检测到木糖还原酶活性以及木糖醇的存在，表明木糖是通过还原酶途径被消耗的。这项研究表明，在有明确表型选择方法的情况下，ALE可用于非常有效地改良工业微生物菌株，而无需使用基因工程工具。专注于利用微生物沉默的表型灵活性来代谢不同碳源的策略是利用糖化木质纤维素废料生产微生物增值产品的有力工具。
