Heat-acclimatised strains of Rhodopseudomonas palustris reveal higher temperature optima with concomitantly enhanced biohydrogen production rates

Toit, Jan-Pierre du

doi:10.1016/j.ijhydene.2021.01.068

Cited by 28 publications

(27 citation statements)

References 48 publications

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“…Purple non-sulfur bacteria have been identified as an attractive prospect for photofermentative hydrogen production, due to their high substrate-to-hydrogen conversion efficiency [ 7 , 8 ] and their potential for the bioremediation of waste streams [ 9 ]. The species R. palustris shows great promise for photofermentative hydrogen production, due to its acclimation ability to light intensity [ 10 , 11 ] and temperature [ 12 ]. Hydrogen production by R. palustris is principally facilitated by the photoheterotrophic metabolic route, meaning metabolism in the presence of light, a suitable carbon substrate, and under an anaerobic atmosphere.…”

Section: Introductionmentioning

confidence: 99%

“…Hydrogen production by R. palustris is principally facilitated by the photoheterotrophic metabolic route, meaning metabolism in the presence of light, a suitable carbon substrate, and under an anaerobic atmosphere. However, strain-dependent R. palustris has been shown to produce hydrogen in the temperature range of 30 to 42 °C, with 42 °C also being its physiological upper limit, beyond which the bacterial cells start to die [ 12 ]. R. palustris is not associated with photoinhibition, due to it not being an oxygen-evolving microorganism, and also due to its ability to dissipate excess energy from high light intensities as heat through the use of carotenoids [ 13 ]; however, productivity has been shown to decrease beyond light intensities of approximately 500–600 W m −2 [ 6 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

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A Thermosiphon Photobioreactor for Photofermentative Hydrogen Production by Rhodopseudomonas palustris

2022

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A thermosiphon photobioreactor (TPBR) can potentially be used for biohydrogen production, circumventing the requirement for external mixing energy inputs. In this study, a TPBR is evaluated for photofermentative hydrogen production by Rhodopseudomonas palustris (R. palustris). Experiments were conducted in a TPBR, and response surface methodology (RSM), varying biomass concentration, and light intensity and temperature were employed to determine the operating conditions for the enhancement of both hydrogen production as well as biomass suspension. Biomass concentration was found to have had the most pronounced effect on both hydrogen production as well as biomass suspension. RSM models predicted maximum specific hydrogen production rates of 0.17 mol m−3h−1 and 0.21 mmol gCDW−1h−1 at R. palustris concentrations of 1.21 and 0.4 g L−1, respectively. The experimentally measured hydrogen yield was in the range of 45 to 77% (±3.8%), and the glycerol consumption was 8 to 19% (±0.48). At a biomass concentration of 0.40 g L−1, the highest percentage of biomass (72.3%), was predicted to remain in suspension in the TPBR. Collectively, the proposed novel photobioreactor was shown to produce hydrogen as well as passively circulate biomass.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Thermosiphon Photobioreactor for Photofermentative Hydrogen Production by Rhodopseudomonas palustris

2022

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“…Vanadium for Vnf nitrogenases was supplied as NaVO 3 at a final concentration of 165 nM, equimolar to molybdenum. Cultures were incubated at 35 °C, previously verified as the optimum temperature for strain CGA009, 63 under illumination from 100 W incandescent light bulbs for anaerobic liquid cultures and in the dark for aerobic agar plates. Irradiance intensity was calibrated in the wavelength range 500−1100 nm using a compact spectrometer and cosine correcting probe (RGB photonics Qmini VIS-NIR).…”

Section: ■ Methodsmentioning

confidence: 99%

Expression of Alternative Nitrogenases in Rhodopseudomonas palustris Is Enhanced Using an Optimized Genetic Toolset for Rapid, Markerless Modifications

et al. 2021

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The phototrophic bacterium Rhodopseudomonas palustris is emerging as a promising biotechnological chassis organism, due to its resilience to a range of harsh conditions, a wide metabolic repertoire, and the ability to quickly regenerate ATP using light. However, realization of this promise is impeded by a lack of efficient, rapid methods for genetic modification. Here, we present optimized tools for generating chromosomal insertions and deletions employing electroporation as a means of transformation. Generation of markerless strains can be completed in 12 days, approximately half the time for previous conjugation-based methods. This system was used for overexpression of alternative nitrogenase isozymes with the aim of improving biohydrogen productivity. Insertion of the pucBa promoter upstream of vnf and anf nitrogenase operons drove robust overexpression up to 4000-fold higher than wild-type. Transcript quantification was facilitated by an optimized high-quality RNA extraction protocol employing lysis using detergent and heat. Overexpression resulted in increased nitrogenase protein levels, extending to superior hydrogen productivity in bioreactor studies under nongrowing conditions, where promoter-modified strains better utilized the favorable energy state created by reduced competition from cell division. Robust heterologous expression driven by the pucBa promoter is thus attractive for energy-intensive biosyntheses suited to the capabilities of R. palustris. Development of this genetic modification toolset will accelerate the advancement of R. palustris as a biotechnological chassis organism, and insights into the effects of nitrogenase overexpression will guide future efforts in engineering strains for improved hydrogen production.

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“…Besides, it can grow under aerobic or anaerobic conditions by using light and organic (e.g., lignin breakdown products) or inorganic compounds as a source of ATP generation (1,2). Using these metabolic versatilities, R. palustris has emerged as a potential biotechnological platform for bioremediation (3)(4)(5), bioplastics production (6,7), Metabolic and expression model of R. palustris 4 bioelectricity generation (8,9), wastewater treatment (10)(11)(12), and hydrogen production (13)(14)(15)(16)(17). Furthermore, R. palustris is the only known bacteria to encode all three known nitrogenase enzymes (2) besides Azotobacter vinelandii (A. vinelandii) (18).…”

Section: Introductionmentioning

confidence: 99%

“…The copyright holder for this preprint this version posted March 4, 2022. ; https://doi.org/10.1101/2022.03.03.482919 doi: bioRxiv preprint bioelectricity generation (8,9), wastewater treatment (10)(11)(12), and hydrogen production (13)(14)(15)(16)(17). Furthermore, R. palustris is the only known bacteria to encode all three known nitrogenase enzymes (2) besides Azotobacter vinelandii (A. vinelandii) (18).…”

Section: Introductionmentioning

confidence: 99%

Characterizing the interplay of rubisco and nitrogenase enzymes in anaerobic-photoheterotrophically grownRhodopseudomonas palustrisCGA009 through a genome-scale metabolic and expression model

Chowdhury

Alsiyabi

Saha

2022

Preprint

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Rhodopseudomonas palustris CGA009 (R. palustris) is a gram negative purple non-sulfur bacteria that grows phototrophically or chemotrophically by fixing or catabolizing a wide array of substrates including lignin breakdown products (e.g., p-coumarate) for its carbon and nitrogen requirements. It can grow aerobically or anaerobically and can use light, inorganic, and organic compounds for energy production. Due to its ability to convert different carbon sources into useful products in anaerobic mode, this study, for the first time, reconstructed a metabolic and expression (ME-) model of R. palustris to investigate its anaerobic-photoheterotrophic growth. Unlike metabolic (M-) models, ME-models include transcription and translation reactions along with macromolecules synthesis and couple these reactions with growth rate. This unique feature of the ME-model led to nonlinear growth curve predictions which matched closely with experimental growth rate data. At the theoretical maximum growth rate, the ME-model suggested a diminishing rate of carbon fixation and predicted malate dehydrogenase and glycerol-3 phosphate dehydrogenase as alternate electron sinks. Moreover, the ME-model also identified ferredoxin as a key regulator in distributing electrons between major redox balancing pathways. Since ME-models include turnover rate for each metabolic reaction, it was used to successfully capture experimentally observed temperature regulation of different nitrogenases. Overall, these unique features of the ME-model demonstrated the influence of nitrogenases and rubiscos on R. palustris growth and predicted a key regulator in distributing electrons between major redox balancing pathways, thus establishing a platform for in silico investigation of R. palustris metabolism from a multi-omics perspective.IMPORTANCEIn this work, we reconstructed the first ME-model for a purple non-sulfur bacterium (PNSB). Using the ME-model, different aspects of R. palustris metabolism were examined. First, the ME-model was used to analyze how reducing power entering the R. palustris cell through organic carbon sources gets partitioned into biomass, carbon dioxide fixation, and nitrogen fixation. Furthermore, the ME-model predicted electron flux through ferredoxin as a major bottleneck in distributing electrons to nitrogenase enzymes. Next, the ME-model characterized different nitrogenase enzymes and successfully recapitulated experimentally observed temperature regulations of those enzymes. Identifying the bottleneck responsible for transferring electron to nitrogenase enzymes and recapitulating the temperature regulation of different nitrogenase enzymes can have profound implications in metabolic engineering, such as hydrogen production from R. palustris. Another interesting application of this ME-model can be to take advantage of its redox balancing strategy to gain understanding on regulatory mechanism of biodegradable plastic production precursors, such as polyhydroxybutyrate (PHB).

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Heat-acclimatised strains of Rhodopseudomonas palustris reveal higher temperature optima with concomitantly enhanced biohydrogen production rates

Cited by 28 publications

References 48 publications

A Thermosiphon Photobioreactor for Photofermentative Hydrogen Production by Rhodopseudomonas palustris

A Thermosiphon Photobioreactor for Photofermentative Hydrogen Production by Rhodopseudomonas palustris

Expression of Alternative Nitrogenases in Rhodopseudomonas palustris Is Enhanced Using an Optimized Genetic Toolset for Rapid, Markerless Modifications

Characterizing the interplay of rubisco and nitrogenase enzymes in anaerobic-photoheterotrophically grownRhodopseudomonas palustrisCGA009 through a genome-scale metabolic and expression model

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