Project description:The thermophilic anaerobe Clostridium thermocellum is a candidate consolidated bioprocessing biocatalyst for the conversion of lignocellulosic biomass into ethanol. The microorganism expresses enzymes for both cellulose solubilization and fermentation to produce lignocellulosic ethanol making it a good candidate for industrial biofuel production. Intolerance to stresses routinely encountered during industrial fermentations may hinder the commercial development of this organism. A recently published study by Yang et al., (2012) characterized the physiological and regulatory response of C. thermocellum to ethanol supplementation. Significant changes in nitrogen metabolism and an accumulation of carbon sources were identified, revealing potential targets for metabolic engineering. In the current study, the response of C. thermocellum to heat and furfural shock were compared with the known effects of ethanol shock. Improved tolerance to these stresses are desirable traits for C. thermocellum and further understanding of the effects that these particular stresses have on the organism are the focus of this work. A forty one array study using total RNA recovered from wild-type cultures of Clostridium thermocellum at different time points of 10, 30, 60, and 120 min post-treatment with 3.95 g.L-1 ethanol, 4 g.L-1 furfural or 68°C treatment compred to that of control without treatment. At least two biological replicates were performed for each treatment and control condition.
Project description:Clostridium thermocellum is a Gram-positive, anaerobic, thermophilic bacterium that ferments cellulose into ethanol. It is a candidate industrial consolidated bioprocess (CBP) biocatalyst for lignocellulosic bioethanol production to produce bioethanol directly from cellulosic biomass. However, few transcriptomic studies have been reported so far for C. thermocellum using biomass as carbon source. In this study, samples were taken from exponential and stationary phases of C. thermocellum cells growing in MTC media with pretreated switchgrass as carbon source, and transcriptomic profiling change of C. thermocellum during different growth phase was investigated using both expression array and tiling array. This study will help the understanding of gene expression of C. thermocellum using cellulosic biomass as carbon source and the knowledge will facilitate future metabolic engineering effort for strain improvement.
Project description:Clostridium thermocellum forms adherent biofilms on lignocellulosic feedstock in a typical continuous cell-monolayer to efficiently break down and uptake cellulose hydrolysates. The adherent biofilm (i.e., sessile cells) may freely revert to the non-adherent form (i.e., planktonic cells) through generation of offspring cells or microenvironment constraints such as limited surface area. The two interdependent cell populations co-exist and have different contributions to culture activity and growth. We developed a novel bioreactor design to rapidly harvest sessile and planktonic cell populations for omics studies. In RNA-seq analyses, within 3299 protein coding genes, 59% (or 1958 genes) were differentially expressed with a minimum two-fold change between the two cell populations isolated simultaneously at high culture activity. Sessile cells had definitive greater expression of genes involved in catabolism of carbohydrates by glycolysis and pyruvate fermentation, ATP generation by proton gradient, the anabolism of proteins and lipids and cellular functions critical for cell division; planktonic cells had notably higher gene expression for flagellar motility and chemotaxis, cellulosomal cellulases and anchoring scaffoldins, and a range of stress induced homeostasis mechanisms such as oxidative stress protection by antioxidants and flavoprotein co-factors, methionine repair, Fe-S cluster assembly and repair in redox proteins, cell growth control through tRNA thiolation, recovery of damaged DNA by nucleotide excision repair and removal of terminal proteins by proteases. Knowledge of these cellular adaptations will aid the engineering of industrially relevant strains for consolidated bioprocessing of solid lignocellulosic biomass.
Project description:Clostridium thermocellum is a Gram-positive, anaerobic, thermophilic bacterium that ferments cellulose into ethanol. It is a candidate industrial consolidated bioprocess (CBP) biocatalyst for lignocellulosic bioethanol production to produce bioethanol directly from cellulosic biomass. However, few transcriptomic studies have been reported so far for C. thermocellum using biomass as carbon source. In this study, samples were taken from exponential and stationary phases of C. thermocellum cells growing in MTC media with pretreated switchgrass as carbon source, and transcriptomic profiling change of C. thermocellum during different growth phase was investigated using both expression array and tiling array. This study will help the understanding of gene expression of C. thermocellum using cellulosic biomass as carbon source and the knowledge will facilitate future metabolic engineering effort for strain improvement. [HX12 expression array]: A eleven array study using total RNA recovered from wild-type cultures of Clostridium thermocellum at different growth phase of T2 and T3 with switchgrass as carbon source. Two biological replicates used for each phase. [3Plex tiling array]: A six array study using total RNA recovered from wild-type cultures of Clostridium thermocellum at different growth phase of T2 and T3 with switchgrass as carbon source. Two biological replicates used for each phase.
Project description:Producing the fuels and chemicals from renewable plant biomass has been thought as a feasible way for global sustainable development. However, the economical efficiency of biorefinery remains challenges. Here a cellulolytic thermophilic fungus, Myceliophthora thermophila, was constructed into a platform through metabolic engineering, which can efficiently convert lignocellulose to important bulk chemicals for polymers, four carbon 1, 4-diacids (malic and succinic acid), directly from lignocellulose without any extra enzymes addition or complicated pretreatment, with titer of over 200 g/L on cellulose and 110 g/L on plant biomass (corncob) during fed-batch fermentation. Our study represents a milestone of consolidated bioprocessing technology (CBP) and offers a new promising system for cost-effectively production of biomass-based chemicals and potentially fuels.
2021-05-04 | GSE114057 | GEO
Project description:Consolidated bioprocessing of agave bagasse
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.
Project description:The thermophilic anaerobe Clostridium thermocellum is a candidate consolidated bioprocessing (CBP) biocatalyst for cellulosic ethanol production. It expresses enzymes for both cellulose solubilization and its fermentation to produce lignocellulosic ethanol. To gain insights into the C. thermocellum genes, using an updated version of the C. thermocellum ATCC 27405 genome annotation, that are required for specific growth on the cellulosic feedstocks of either pretreated switchgrass or Populus, duplicate fermentations were conducted with a 5 g/L solid substrate loading. High quality RNA was extracted using a method we report for C. thermocellum grown on solid substrates. Transcriptome profiles were obtained at two time points during actively growing fermentations (12 h and 37 h post inoculation). A comparison of two transcriptomic analytical techniques, microarray and RNAseq, was performed and the data analyzed for statistical significance. When thresholds for genes passing significance of FDR>0.05 were applied, microarray (2351 genes) had a greater number of significant genes relative to RNA-seq (280 genes when normalized by KDMM). When a 2-fold difference in expression threshold was applied, seventy-three genes were significantly differentially expressed in common between the two techniques. We identified genes differentially expressed when C. thermocellum ATC 27405 was grown on the two biomass substrates, with two putative efflux/transport systems highly differentially regulated (>5-fold). This study has revealed consistency between these two transcriptomics analytical platforms that gives confidence in our switch from the DNA microarray platform to an RNAseq based platform for routine transcriptomics analyses.