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Transcriptional profiling of Myceliophthora thermophila on galactose and metabolic engineering for improved galactose utilization

ABSTRACT: Transcriptional landscape of MyceliopTranscriptional profiling of Myceliophthora thermophila on galactose and metabolic engineering for improved galactose utilization thora thermophila responding to soluble starch and the role of regulator AmyR on polysaccharide degradation Efficient biological conversion of all sugars from lignocellulosic biomass is necessary for cost-effective production of biofuels and commodity chemicals. Galactose is the next most abundant sugar in many hemicelluloses and it will be important to capture this carbon for an efficient bioconversion process of plant biomass. Thermophilic fugus Myceliophthora thermophila has been used as cell factory to produce biochemicals directly from renewable polysaccharides. This study determined the transcriptomic profiles of M. thermophila responding to galactose and identified the gene involved in the oxido-reductive pathway for galactose degradation, of which hexokinase might be the rate-limiting enzyme in this thermophilic fungus. Galactokinase was necessary for high induction of galactose transporter and disruption of galK resulted in decreased galactose utilization. Both of galactokinase deletion and sugar transporter overexpression could further activate the oxido-reductive pathway and led to improved galactose utilization. In addition, disruption of the Leloir pathway brought about reduced tolerance to cell wall perturbation, oxidative stress and high osmolality. In order to accelerate galactose consumption, the third galactose-degradation pathway- De Ley-Doudoroff pathway was successfully integrated into M. thermophila and the consumption rate of galactose was increased by 57%. This study will be benefit for the rational design of fungal strains to produce biofuels and biochemical from plant biomass, especially, marine plant biomass with the abundant of galactose, such as red seaweed and molasses.

ORGANISM(S): Thermothelomyces thermophilus

PROVIDER: GSE165516 | GEO | 2021/02/05

REPOSITORIES: GEO

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Project description:Plant biomass holds tremendous potential as a renewable feedstock in the production of biofuels and biochemicals. The effective co-utilization of the main components cellulose and hemicellulose in plant lignocellulose is critical to the economic viability of lignocellulosic biorefineries. Here, we found that the thermophilic cellulolytic fungi Myceliophthora thermophila can utilize cellulose and hemicellulose synchronously. To investigate the underlying molecular mechanisms, we firstly checked the soluble carbohydrate of the culture using plant biomass (corncob) as sole carbon source and revealed the presence of various oligosaccharides including cellodextrin and xylodextrin, both intracellularly and extracellularly in the cultures, in addition to glucose or xylose. Based on these, intracellular oligosaccharide metabolism was proposed and confirmed by identification of cellodextrin and xylodextrin metabolism pathway. Furthermore, sugar consumption assay showed that contrasting with synchronous utilization of mixed cello-/xylo-dextrin, the inhibition effect of glucose for the metabolism of xylose and cello-/xylo-dextrin exists in this fungus, suggesting Carbon Catabolite Repression (CCR) is largely avoided at the form of oligosaccharides. Transporter MtCDT-2 showing preference to xylobiose and the tolerance of cellobiose inhibition also helps to bypass metabolic inhibition. Finally, the expression of cellulase and hemicellulase genes, were found orthogonal induction by cellobiose/Avicel and xylobiose/xylan, which conferred the ability of the strain to synchronously utilize cellulose and hemicellulose. Taken together, the orthogonal oligosaccharide catabolic pathway in this fungus establishes the molecular basis for the synchronous utilization of cellulose and hemicellulose, which sheds new light on understanding the plant biomass degradation by fungi and provides alternative paradigm for development of lignocellulose biorefinery such as consolidated bioprocessing in the future.

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Transcriptional profiling of Myceliophthora thermophila on galactose and metabolic engineering for improved galactose utilization

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