Heterologous Expression of Transaldolase Gene Tal from Saccharomyces cerevisiae in Fusarium oxysporum for Enhanced Bioethanol Production

Abstract

The filamentous fungus Fusarium oxysporum is known for its ability to ferment xylose-producing ethanol. However, efficiency of xylose utilization and ethanol yield was low. In this study, the transaldolase gene from Saccharomyces cerevisiae has been successfully expressed in F. oxysporum by an Agrobacterium tumefaciens-mediated transformation method. The enzymatic activity of the recombinant fungus (cs28pCAM-Sctal4) was 0.195 times higher than that of the wild-type strain (cs28). The recombinant strain also exhibited a 28.83% increase in ethanol yield on xylose media compared to the parental strain. Enhanced ethanol production and a reduction in the biomass were observed during xylose fermentation. Ethanol yield from rice straw by simultaneous saccharification and fermentation with cs28pCAM-Sctal4 was 0.25 g g⁻¹ of rice straw. The transgenic strain of F. oxysporum cs28pCAM-Sctal4 might therefore have potential applications in industrial bioenergy production.

Constitutive homologous expression of phosphoglucomutase and transaldolase increases the metabolic flux of Fusarium oxysporum

“…Also, the recombinant strain had even lower biomass yields than the wild type. Although the transaldolase activity was only 0.195 times higher than the wild type, this different effect, compared to our results, can be attributed to either the different experimental layout or the increased enzyme production in our work [25]. In a very similar study, the same group showed that final biomass in a F. oxysporum strain overexpressing a transaldolase from P. stipitis was lower than that of a wild type strain during growth on xylose [26].…”

“…g substrate −1 are normally found for aerobic growth of filamentous fungi [32], but lower yields are also reported for some filamentous fungi due to extensive byproduct formation [33]. Fan et al [25] reported lower biomass yields for wild type strain F. oxysporum cs28 and the recombinant strain overexpressing the S. cerevisiae sctal. Also, the recombinant strain had even lower biomass yields than the wild type.…”

“…Overexpression of the native transaldolase of S. cerevisiae in a xylose fermenting strain, improved aerobic growth substantially [23] and enhanced anaerobic xylose metabolism [24]. Also, Fan et al reported that the overexpression of two transaldolases, from Pichia stipitis and S. cerevisiae, in F. oxysporum had increased the xylose consumption and ethanol production when grown with glucose and xylose as carbon sources [25,26]. …”

Challenges in ethanol production withFusarium oxysporumthrough consolidated bioprocessing

“…For example, in two very similar studies, Fan et al showed that heterologous overexpression of a transaldolase resulted in lower biomass yields than when using the parental strain. 10,11 On the other hand, our homologous overexpression of both phosphoglucomutase and transaldolase resulted in an increase in the maximum specific growth rate and a biomass yield similar to that of the parental strain, when using glucose as the sole carbon source. With xylose, the same strain had much higher biomass yields and a slightly higher maximum specific growth rate.…”

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

“…Also, the accumulation of sedoheptulose-7-P when the microorganism was grown in glucose-xylose mixtures under oxygen-limiting conditions, and of erythrose-4-P during xylose consumption (Panagiotou et al, 2005b ), indicated a second bottleneck in the F. oxysporum metabolism. Fan et al reported the effect on F. oxysporum of the overexpression of transaldolase genes from Pichia stipitis and S. cerevisiae , which increased both xylose consumption and ethanol production when either glucose or xylose was used as carbon source (Fan et al, 2011a , b ) in shake flask batch cultures.…”