Cell Factories For Production Of Biofuels Research Articles

Heterologous glucose-6-phosphate dehydrogenase empowers the biofuel potential of Tetradesmus obliquus via generating lipogenic NADPH

Large-scale production of biofuels from oleaginous microalgal feedstocks in a commercially feasible manner is hampered by their relatively slow growth rates and overall lipid yield than the rapidly proliferating algal species. Therefore, it is pivotal to obviate this bottleneck by augmenting lipid overproduction in fast-growing microalgal species by heterologous overexpression lipogenic genes from model oleaginous species. In this regard, the pentose phosphate pathway of Tetradesmus obliquus was perturbed by heterologous overexpression of glucose-6-phosphate dehydrogenase (PtG6PD) from the model pennate diatom Phaeodactylum tricornutum, known for its oleaginicity. The role of PtG6PD in increasing lipid production was reported in the heterologous T. obliquus. Total lipid content was increased by 2.09- and 2.31-fold in transgenic lines than WT by elevating the lipogenic NADPH, without any negative impact on their growth rates. Interestingly, lipid yields in the transgenic strains reached up to 93 mg/L and 103 mg/L which showed a further 2-fold enhancement under nitrogen-deficient conditions. Furthermore, it was demonstrated that PtG6PD overexpression also altered fatty acid composition, with a specific increment in total monounsaturated fatty acids. Our results uncovered the pivotal role of the pentose phosphate pathway in supplying lipogenic NADPH in T. obliquus and identified key genetic targets for lipid biosynthesis enhancement in alternative hosts. Altogether, these findings open avenues for metabolic engineering in non-model and fast-growing non-oleaginous microalgal species, thereby presenting a promising strategy for empowering commercially viable photosynthetic cell factories for biofuel production.

Biofuel Production Via in Situ Resource Utilization on Mars

This paper is based on the fundamentals and principles of materials science and resource utilization. In-situ resource utilization (ISRU) can make full use of materials in space to produce the resources needed for human survival and even interstellar migration programs. Bio-based biofuel production solutions can address human consumption in space exploration while allowing the production of fuels in a sustainable manner, with minimal inputs and producing cleaner, more environmentally friendly fuels.ISRU biofuel production can be achieved by directly converting inorganic carbon (atmospheric CO2) into target compounds as biofuels by autotrophic microorganisms, or by fixing carbon and then use metabolic engineering to convert biomass or complex substrates into target compounds, completing a two-step biofuel production process. In this paper, we investigate a potential microbial cell factory for biofuel production on Mars via ISRU, leading to some relevant breakthroughs and discoveries. This paper advances the development of the research content through a series of studies.In this paper, we have studied and optimized the use of new energy fuels based on basic fuel performance studies. This paper provides a new way of thinking and research in the field of energy research, based on the previous basic research.

Genome-scale metabolic modeling underscores the potential of Cutaneotrichosporon oleaginosus ATCC 20509 as a cell factory for biofuel production

BackgroundCutaneotrichosporon oleaginosus ATCC 20509 is a fast-growing oleaginous basidiomycete yeast that is able to grow in a wide range of low-cost carbon sources including crude glycerol, a byproduct of biodiesel production. When glycerol is used as a carbon source, this yeast can accumulate more than 50% lipids (w/w) with high concentrations of mono-unsaturated fatty acids.ResultsTo increase our understanding of this yeast and to provide a knowledge base for further industrial use, a FAIR re-annotated genome was used to build a genome-scale, constraint-based metabolic model containing 1553 reactions involving 1373 metabolites in 11 compartments. A new description of the biomass synthesis reaction was introduced to account for massive lipid accumulation in conditions with high carbon-to-nitrogen (C/N) ratio in the media. This condition-specific biomass objective function is shown to better predict conditions with high lipid accumulation using glucose, fructose, sucrose, xylose, and glycerol as sole carbon source.ConclusionContributing to the economic viability of biodiesel as renewable fuel, C. oleaginosus ATCC 20509 can effectively convert crude glycerol waste streams in lipids as a potential bioenergy source. Performance simulations are essential to identify optimal production conditions and to develop and fine tune a cost-effective production process. Our model suggests ATP-citrate lyase as a possible target to further improve lipid production.

Production of (2R, 3R)-2,3-butanediol using engineered Pichia pastoris: strain construction, characterization and fermentation

Background2,3-butanediol (2,3-BD) is a bulk platform chemical with various potential applications such as aviation fuel. 2,3-BD has three optical isomers: (2R, 3R)-, (2S, 3S)- and meso-2,3-BD. Optically pure 2,3-BD is a crucial precursor for the chiral synthesis and it can also be used as anti-freeze agent due to its low freezing point. 2,3-BD has been produced in both native and non-native hosts. Several pathogenic bacteria were reported to produce 2,3-BD in mixture of its optical isomers including Klebsiella pneumoniae and Klebsiella oxytoca. Engineered hosts based on episomal plasmid expression such as Escherichia coli, Saccharomyces cerevisiae and Bacillus subtilis are not ideal for industrial fermentation due to plasmid instability.ResultsPichia pastoris is generally regarded as safe and a well-established host for high-level heterologous protein production. To produce pure (2R, 3R)-2,3-BD enantiomer, we developed a P. pastoris strain by introducing a synthetic pathway. The alsS and alsD genes from B. subtilis were codon-optimized and synthesized. The BDH1 gene from S. cerevisiae was cloned. These three pathway genes were integrated into the genome of P. pastoris and expressed under the control of GAP promoter. Production of (2R, 3R)-2,3-BD was achieved using glucose as feedstock. The optical purity of (2R, 3R)-2,3-BD was more than 99%. The titer of (2R, 3R)-2,3-BD reached 12 g/L with 40 g/L glucose as carbon source in shake flask fermentation. The fermentation conditions including pH, agitation speeds and aeration rates were optimized in batch cultivations. The highest titer of (2R, 3R)-2,3-BD achieved in fed-batch fermentation using YPD media was 45 g/L. The titer of 2,3-BD was enhanced to 74.5 g/L through statistical medium optimization.ConclusionsThe potential of engineering P. pastoris into a microbial cell factory for biofuel production was evaluated in this work using (2R, 3R)-2,3-BD as an example. Engineered P. pastoris could be a promising workhorse for the production of optically pure (2R, 3R)-2,3-BD.

Function and Regulation of Ferredoxins in the Cyanobacterium, Synechocystis PCC6803: Recent Advances.

Ferredoxins (Fed), occurring in most organisms, are small proteins that use their iron-sulfur cluster to distribute electrons to various metabolic pathways, likely including hydrogen production. Here, we summarize the current knowledge on ferredoxins in cyanobacteria, the prokaryotes regarded as important producers of the oxygenic atmosphere and biomass for the food chain, as well as promising cell factories for biofuel production. Most studies of ferredoxins were performed in the model strain, Synechocystis PCC6803, which possesses nine highly-conserved ferredoxins encoded by monocistronic or operonic genes, some of which are localized in conserved genome regions. Fed1, encoded by a light-inducible gene, is a highly abundant protein essential to photosynthesis. Fed2-Fed9, encoded by genes differently regulated by trophic conditions, are low-abundant proteins that play prominent roles in the tolerance to environmental stresses. Concerning the selectivity/redundancy of ferredoxin, we report that Fed1, Fed7 and Fed9 belong to ferredoxin-glutaredoxin-thioredoxin crosstalk pathways operating in the protection against oxidative and metal stresses. Furthermore, Fed7 specifically interacts with a DnaJ-like protein, an interaction that has been conserved in photosynthetic eukaryotes in the form of a composite protein comprising DnaJ- and Fed7-like domains. Fed9 specifically interacts with the Flv3 flavodiiron protein acting in the photoreduction of O2 to H2O.

The Role of Synthetic Biology in the Design of Microbial Cell Factories for Biofuel Production

Insecurity in the supply of fossil fuels, volatile fuel prices, and major concerns regarding climate change have sparked renewed interest in the production of fuels from renewable resources. Because of this, the use of biodiesel has grown dramatically during the last few years and is expected to increase even further in the future. Biodiesel production through the use of microbial systems has marked a turning point in the field of biofuels since it is emerging as an attractive alternative to conventional technology. Recent progress in synthetic biology has accelerated the ability to analyze, construct, and/or redesign microbial metabolic pathways with unprecedented precision, in order to permit biofuel production that is amenable to industrial applications. The review presented here focuses specifically on the role of synthetic biology in the design of microbial cell factories for efficient production of biodiesel.