Metabolic Engineering of Fusarium oxysporum to Improve Its Ethanol-Producing Capability.
Metabolic Engineering of Fusarium oxysporum to Improve Its Ethanol-Producing Capability.
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DOI：
10.3389/fmicb.2016.00632
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发表时间：
2016
影响因子：
5.2
通讯作者：
Christakopoulos P
中科院分区：
文献类型：
--
作者：
Anasontzis GE;Kourtoglou E;Villas-Boâs SG;Hatzinikolaou DG;Christakopoulos P
尖孢镰刀菌是为数不多的能够直接从植物细胞壁生物量中发酵乙醇的丝状真菌之一。它具有将生物质分解为单糖所需的酶工具箱，并在厌氧和微氧条件下将其发酵成乙醇。虽然这些特性可以使其在整合过程中使用，从而绕过了使用酿酒酵母从木质纤维素材料中生产乙醇时遇到的一些瓶颈，即它无法降解木质纤维素和消耗戊糖，但与酵母相比，氧孢子菌的两个主要缺点-其低生长速度和低乙醇产量-阻碍了该过程的进一步发展。我们之前已经确定了葡萄糖分解代谢和戊糖磷酸途径的两种主要酶磷酸糖脲酶和转醛缩酶可能是真菌代谢的瓶颈，我们已经报道了它们的组成产物对真菌生长特性的影响。在本研究中，我们研究了厌氧条件下它们的本构产物对乙醇产量的影响。我们报告了乙醇产量的增加和伴随的醋酸产量的减少。代谢组学分析表明，所应用的遗传修饰不仅仅是加速了微生物的代谢率；它们还影响了各种代谢物的相对浓度，这表明向choris酸途径的通道增加，γ-氨基丁酸分流的激活以及NADPH再生的过剩。
Fusarium oxysporum is one of the few filamentous fungi capable of fermenting ethanol directly from plant cell wall biomass. It has the enzymatic toolbox necessary to break down biomass to its monosaccharides and, under anaerobic and microaerobic conditions, ferments them to ethanol. Although these traits could enable its use in consolidated processes and thus bypass some of the bottlenecks encountered in ethanol production from lignocellulosic material when Saccharomyces cerevisiae is used—namely its inability to degrade lignocellulose and to consume pentoses—two major disadvantages of F. oxysporum compared to the yeast—its low growth rate and low ethanol productivity—hinder the further development of this process. We had previously identified phosphoglucomutase and transaldolase, two major enzymes of glucose catabolism and the pentose phosphate pathway, as possible bottlenecks in the metabolism of the fungus and we had reported the effect of their constitutive production on the growth characteristics of the fungus. In this study, we investigated the effect of their constitutive production on ethanol productivity under anaerobic conditions. We report an increase in ethanol yield and a concomitant decrease in acetic acid production. Metabolomics analysis revealed that the genetic modifications applied did not simply accelerate the metabolic rate of the microorganism; they also affected the relative concentrations of the various metabolites suggesting an increased channeling toward the chorismate pathway, an activation of the γ-aminobutyric acid shunt, and an excess in NADPH regeneration.