More Like this

1. n-Butanol production by Rhodopseudomonas palustris TIE-1

   https://doi.org/10.1038/s42003-021-02781-z  

   Bai, Wei; Ranaivoarisoa, Tahina Onina; Singh, Rajesh; Rengasamy, Karthikeyan; Bose, Arpita (November 2021, Communications Biology)

   Abstract Anthropogenic carbon dioxide (CO₂) release in the atmosphere from fossil fuel combustion has inspired scientists to study CO₂to biofuel conversion. Oxygenic phototrophs such as cyanobacteria have been used to produce biofuels using CO₂. However, oxygen generation during oxygenic photosynthesis adversely affects biofuel production efficiency. To producen-butanol (biofuel) from CO₂, here we introduce ann-butanol biosynthesis pathway into an anoxygenic (non-oxygen evolving) photoautotroph,Rhodopseudomonas palustrisTIE-1 (TIE-1). Using different carbon, nitrogen, and electron sources, we achieven-butanol production in wild-type TIE-1 and mutants lacking electron-consuming (nitrogen-fixing) or acetyl-CoA-consuming (polyhydroxybutyrate and glycogen synthesis) pathways. The mutant lacking the nitrogen-fixing pathway produce the highestn-butanol. Coupled with novel hybrid bioelectrochemical platforms, this mutant producesn-butanol using CO₂, solar panel-generated electricity, and light with high electrical energy conversion efficiency. Overall, this approach showcases TIE-1 as an attractive microbial chassis for carbon-neutraln-butanol bioproduction using sustainable, renewable, and abundant resources. 

   more » « less
2. Magnetite nanoparticle anchored graphene cathode enhances microbial electrosynthesis of polyhydroxybutyrate by Rhodopseudomonas palustris TIE-1

   Karthikeyan R, Ranaivoarisoa TO (January 2020, Nanotechnology)

   null (Ed.)

   Microbial electrosynthesis (MES) is an emerging technology that can convert carbon dioxide (CO2) into value-added organic carbon compounds using electrons supplied from a cathode. However, MES is affected by low product formation due to limited extracellular electron uptake by microbes. Herein, a novel cathode was developed from chemically synthesized magnetite nanoparticles and reduced graphene oxide nanocomposite (rGO-MNPs). This nanocomposite was electrochemically deposited on carbon felt (CF/rGO-MNPs), and the modified material was used as a cathode for MES production. The bioplastic, polyhydroxybutyrate (PHB) produced by Rhodopseudomonas palustris TIE-1 (TIE-1), was measured from reactors with modified and unmodified cathodes. Results demonstrate that the magnetite nanoparticle anchored graphene cathode (CF/rGO-MNPs) exhibited higher PHB production (91.31±0.9 mg l−1). This is ∼4.2 times higher than unmodified carbon felt (CF), and 20 times higher than previously reported using graphite. This modified cathode enhanced electron uptake to −11.7±0.1 μA cm−2, ∼5 times higher than CF cathode (−2.3±0.08 μA cm−2). The faradaic efficiency of the modified cathode was ∼2 times higher than the unmodified cathode. Electrochemical analysis and scanning electron microscopy suggest that rGO-MNPs facilitated electron uptake and improved PHB production by TIE-1. Overall, the nanocomposite (rGO-MNPs) cathode modification enhances MES efficiency. 

   more » « less
3. Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically

   https://doi.org/10.1128/aem.01438-24  

   Ranaivoarisoa, Tahina Onina; Bai, Wei; Karthikeyan, Rengasamy; Steele, Hope; Silberman, Miriam; Olabode, Jennifer; Conners, Eric; Gallagher, Brian; Bose, Arpita (September 2024, Applied and Environmental Microbiology)

   Reguera, Gemma (Ed.)

   ABSTRACT With the rising demand for sustainable renewable resources, microorganisms capable of producing bioproducts such as bioplastics are attractive. While many bioproduction systems are well-studied in model organisms, investigating non-model organisms is essential to expand the field and utilize metabolically versatile strains. This investigation centers onRhodopseudomonas palustrisTIE-1, a purple non-sulfur bacterium capable of producing bioplastics. To increase bioplastic production, genes encoding the putative regulatory protein PhaR and the depolymerase PhaZ of the polyhydroxyalkanoate (PHA) biosynthesis pathway were deleted. Genes associated with pathways that might compete with PHA production, specifically those linked to glycogen production and nitrogen fixation, were deleted. Additionally, RuBisCO form I and II genes were integrated into TIE-1’s genome by a phage integration system, developed in this study. Our results show that deletion ofphaRincreases PHA production when TIE-1 is grown photoheterotrophically with butyrate and ammonium chloride (NH₄Cl). Mutants unable to produce glycogen or fix nitrogen show increased PHA production under photoautotrophic growth with hydrogen and NH₄Cl. The most significant increase in PHA production was observed when RuBisCO form I and form I & II genes were overexpressed, five times under photoheterotrophy with butyrate, two times with hydrogen and NH₄Cl, and two times under photoelectrotrophic growth with N₂. In summary, inserting copies of RuBisCO genes into the TIE-1 genome is a more effective strategy than deleting competing pathways to increase PHA production in TIE-1. The successful use of the phage integration system opens numerous opportunities for synthetic biology in TIE-1.IMPORTANCEOur planet has been burdened by pollution resulting from the extensive use of petroleum-derived plastics for the last few decades. Since the discovery of biodegradable plastic alternatives, concerted efforts have been made to enhance their bioproduction. The versatile microorganismRhodopseudomonas palustrisTIE-1 (TIE-1) stands out as a promising candidate for bioplastic synthesis, owing to its ability to use multiple electron sources, fix the greenhouse gas CO₂, and use light as an energy source. Two categories of strains were meticulously designed from the TIE-1 wild-type to augment the production of polyhydroxyalkanoate (PHA), one such bioplastic produced. The first group includes mutants carrying a deletion of thephaRorphaZgenes in the PHA pathway, and those lacking potential competitive carbon and energy sinks to the PHA pathway (namely, glycogen biosynthesis and nitrogen fixation). The second group comprises TIE-1 strains that overexpress RuBisCO form I or form I & II genes inserted via a phage integration system. By studying numerous metabolic mutants and overexpression strains, we conclude that genetic modifications in the environmental microbe TIE-1 can improve PHA production. When combined with other approaches (such as reactor design, use of microbial consortia, and different feedstocks), genetic and metabolic manipulations of purple nonsulfur bacteria like TIE-1 are essential for replacing petroleum-derived plastics with biodegradable plastics like PHA. 

   more » « less
4. Emerging opportunities and research questions for green ammonia adoption in agriculture and beyond

   https://doi.org/10.1038/s44359-024-00012-2  

   Garvey, Sarah M; Davidson, Eric A; Wagner-Riddle, Claudia; Collins, Adrian; Houser, Matthew; Li, Tongzhe; MacDonald, Graham K; Tenuta, Mario; Kanter, David; Kyle, Page; et al (January 2025, Nature Reviews Clean Technology)

   Synthetic ammonia production by the Haber–Bosch process revolutionized agriculture by making relatively inexpensive nitrogen (N) fertilizer widely available and enabling a rise in global food production1,2. The Haber–Bosch process relies on fossil fuels (known as grey ammonia production) and emits more than 450 Mt of CO2 annually3. Green ammonia, which is produced using renewable energy, offers a pathway to decouple ammonia production from fossil fuels and reduce CO2 emissions. As a carbon-free fuel, green ammonia could partially replace fossil fuels to decarbonize hard-to-abate sectors such as maritime shipping4. However, the widespread use of green ammonia could have complex environmental and social consequences, as it threatens to add reactive N into the biosphere3 and could disrupt fertilizer markets. In this Comment, we identify opportunities, barriers and open questions related to green ammonia production and usage as a fertilizer and beyond. We then recommend research priorities to avoid unforeseen consequences through research, monitoring and adaptation in real time. 

   more » « less
5. Techno-economic analysis and network design for CO₂ conversion to jet fuels in the United States

   https://doi.org/10.1016/j.rser.2024.115191  

   Zhou, Rui; Jin, Mingzhou; Li, Zhenglong; Xiao, Yang; McCollum, David; Li, Alicia (March 2025, Renewable and Sustainable Energy Reviews)

   The conversion of carbon dioxide (CO2) into jet fuel holds significant potential for reducing CO2 emissions, providing an alternative to carbon-based resources, and offering a renewable means of energy storage. The objective of this study is to conduct a techno-economic analysis and optimize the supply chain network for converting CO2 to jet fuel in the United States, aiming to minimize total costs while assessing the environmental and economic feasibility of two CO2 conversion pathways. This first pathway is based on Fischer-Tropsch synthesis (FTS), and the other one is based on the valorization and upgrading of light methanol (MeOH). Incorporating spatial and techno-economic data, a mixed-integer linear programming model was developed to select source plants and conversion pathways, locations of conversion refinery sites, and the amount of captured CO2 across the United States. The optimal results indicate that the FTS pathway is adopted at all selected refineries when the hydrogen price is $1000/t and the operating cost, mainly electricity used in conversion, is reduced to 5 % of its current level. Under this scenario, the total annual profit is $8B and the net carbon emissions are −88,783,284 tons. The sensitivity analyses reveal that the prices of electricity and hydrogen significantly contribute to total production costs. The CO2 recycle percentage of the FTS pathway influences the choice of applied pathways at refineries. Additionally, a higher conversion rate holds a substantial promise for reducing the total production cost and can make the MeOH pathway a viable choice.Not Available 

   more » « less