Metabolic Engineering of Fusarium oxysporum to Improve Its Ethanol-Producing Capability

Abstract

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.

Whole genome structural predictions reveal hidden diversity in putative oxidative enzymes of the lignocellulose-degrading ascomycete Parascedosporium putredinis NO1

“…The genome of P. putredinis NO1 is slightly smaller than that of Fusarium oxysporum at 47 Mb, a phytopathogenic fungus containing an expanded CAZyme repertoire of 1430 domains ( 10 ). The lignocellulose-degrading activities of F. oxysporum have been well investigated in part due to its pathogenicity and ability to ferment sugars from lignocellulose breakdown directly into ethanol ( 11 , 12 ).…”

Bioethanol Production from Lignocellulosic Biomass—Challenges and Solutions

“…The modification goal is to obtain a microorganism able to ferment all sugars in the biomass, tolerating stress conditions, showing high resistance to inhibitors, and producing a mixture of synergistic enzymes necessary for the complete hydrolysis of all lignocellulose carbohydrates [46,134,[138][139][140]. Among the most frequently modified microorganisms are Saccharomyces cerevisiae, Zymomonas mobilis, and Escherichia coli [46,[141][142][143][144], but also other bacterial and fungal species were tested, including Fusarium oxysporum [145],…”

Second Generation Bioethanol Production: On the Use of Pulp and Paper Industry Wastes as Feedstock

“…Some of these microorganisms are capable of fermenting both hexoses and pentoses [84][85][86], and since several of these microorganism have the ability of producing both lignocellulolytic enzymes and ethanol, they could be applied for CBP [87][88][89]. Nevertheless, low ethanol yields, due to the formation of significant amounts of by-products (e.g., acetic acid), low productivity and low growth rates are associated to ethanol production by filamentous fungi [87,[90][91][92].…”