51 research outputs found
Bioproduction of Linalool From Paper Mill Waste
A key challenge in chemicals biomanufacturing is the maintenance of stable, highly productive microbial strains to enable cost-effective fermentation at scale. A âcookie-cutterâ approach to microbial engineering is often used to optimize host stability and productivity. This can involve identifying potential limitations in strain characteristics followed by attempts to systematically optimize production strains by targeted engineering. Such targeted approaches however do not always lead to the desired traits. Here, we demonstrate both âhit and missâ outcomes of targeted approaches in attempts to generate a stable Escherichia coli strain for the bioproduction of the monoterpenoid linalool, a fragrance molecule of industrial interest. First, we stabilized linalool production strains by eliminating repetitive sequences responsible for excision of pathway components in plasmid constructs that encode the pathway for linalool production. These optimized pathway constructs were then integrated within the genome of E. coli in three parts to eliminate a need for antibiotics to maintain linalool production. Additional strategies were also employed including: reduction in cytotoxicity of linalool by adaptive laboratory evolution and modification or homologous gene replacement of key bottleneck enzymes GPPS/LinS. Our study highlights that a major factor influencing linalool titres in E. coli is the stability of the genetic construct against excision or similar recombination events. Other factors, such as decreasing linalool cytotoxicity and changing pathway genes, did not lead to improvements in the stability or titres obtained. With the objective of reducing fermentation costs at scale, the use of minimal base medium containing paper mill wastewater secondary paper fiber as sole carbon source was also investigated. This involved simultaneous saccharification and fermentation using either supplemental cellulase blends or by co-expressing secretable cellulases in E. coli containing the stabilized linalool production pathway. Combined, this study has demonstrated a stable method for linalool production using an abundant and low-cost feedstock and improved production strains, providing an important proof-of-concept for chemicals production from paper mill waste streams. For scaled production, optimization will be required, using more holistic approaches that involve further rounds of microbial engineering and fermentation process development
Consolidated Bioprocessing: Synthetic Biology Routes to Fuels and Fine Chemicals
From MDPI via Jisc Publications RouterHistory: accepted 2021-05-14, pub-electronic 2021-05-18Publication status: PublishedFunder: Biotechnology and Biological Sciences Research Council; Grant(s): BB/S011684/1Funder: Engineering and Physical Sciences Research Council; Grant(s): EP/S01778X/1Funder: Office of Naval Research Global; Grant(s): N62909-18-1-2137The long road from emerging biotechnologies to commercial âgreenâ biosynthetic routes for chemical production relies in part on efficient microbial use of sustainable and renewable waste biomass feedstocks. One solution is to apply the consolidated bioprocessing approach, whereby microorganisms convert lignocellulose waste into advanced fuels and other chemicals. As lignocellulose is a highly complex network of polymers, enzymatic degradation or âsaccharificationâ requires a range of cellulolytic enzymes acting synergistically to release the abundant sugars contained within. Complications arise from the need for extracellular localisation of cellulolytic enzymes, whether they be free or cell-associated. This review highlights the current progress in the consolidated bioprocessing approach, whereby microbial chassis are engineered to grow on lignocellulose as sole carbon sources whilst generating commercially useful chemicals. Future perspectives in the emerging biofoundry approach with bacterial hosts are discussed, where solutions to existing bottlenecks could potentially be overcome though the application of high throughput and iterative Design-Build-Test-Learn methodologies. These rapid automated pathway building infrastructures could be adapted for addressing the challenges of increasing cellulolytic capabilities of microorganisms to commercially viable levels
Chemoautotrophic production of gaseous hydrocarbons, bioplastics and osmolytes by a novel <i>Halomonas</i> species
BackgroundProduction of relatively low value, bulk commodity chemicals and fuels by microbial species requires a step-change in approach to decrease the capital and operational costs associated with scaled fermentation. The utilisation of the robust and halophilic industrial host organisms of the genus Halomonas could dramatically decrease biomanufacturing costs owing to their ability to grow in seawater, using waste biogenic feedstocks, under non-sterile conditions.ResultsWe describe the isolation of Halomonas rowanensis, a novel facultative chemoautotrophic species of Halomonas from a natural brine spring. We investigated the ability of this species to produce ectoine, a compound of considerable industrial interest, under heterotrophic conditions. Fixation of radiolabelled NaH14CO3 by H. rowanensis was confirmed in mineral medium supplied with thiosulfate as an energy source. Genome sequencing suggested carbon fixation proceeds via a reductive tricarboxylic acid cycle, and not the Calvin-Bensen-Bassham cycle. The mechanism of energy generation to support chemoautotrophy is unknown owing to the absence of an annotated SOX-based thiosulfate-mediated energy conversion system. We investigated further the biotechnological potential of the isolated H. rowanensis by demonstrating production of the gaseous hydrocarbon (bio-propane), bioplastics (poly-3-hydroxybutyrate) and osmolytes (ectoine) under heterotrophic and autotrophic CO2 fixation growth conditions.ConclusionsThis proof-of-concept study illustrates the value of recruiting environmental isolates as industrial hosts for chemicals biomanufacturing, where CO2 utilisation could replace, or augment, the use of biogenic feedstocks in non-sterile, industrialised bioreactors
Are quasars accreting at super-Eddington rates?
In a previous paper, Collin & Hur\'e (2001), using a sample of Active
Galactic Nuclei (AGN) where the mass has been determined by reverberation
studies (Kaspi et al. 2000), have shown that if the optical luminosity is
emitted by a steady accretion disc, about half of the objects are accreting
close to or higher than the Eddington rate. We conclude here that this result
is unavoidable, unless the masses are strongly underestimated by reverberation
studies, which does not seem to be the case. There are three issues to the
problem: 1. Accretion proceeds at Eddington or super-Eddington rates through
thick discs. Several consequences follow: an anti-correlation between the line
widths of the lines and the Eddington ratios, and a decrease of the Eddington
ratio with an increasing black hole mass. Extrapolated to all quasars, these
results imply that the amount of mass locked in massive black holes should be
larger than presently thought. 2. The optical luminosity is not produced
directly by the gravitational release of energy, and super-Eddington rates are
not required. The optical luminosity has to be emitted by a dense and thick
medium located at large distances from the center (10 to
gravitational radii). It can be due to reprocessing of the X-ray photons from
the central source in a geometrically thin warped disc, or in dense "blobs"
forming a geometrically thick system, which can be a part of the accretion flow
or the basis of an outflow. 3. Accretion discs are completely "non standard".
Presently neither the predictions of models nor the observed spectral
distributions are sufficient to help choosing between these solutions.Comment: 16 pages, 11 figures, accepted in A&
Renewable and tuneable bio-LPG blends derived from amino acids
From Springer Nature via Jisc Publications RouterHistory: received 2020-05-21, accepted 2020-07-08, registration 2020-07-08, pub-electronic 2020-07-14, online 2020-07-14, collection 2020-12Publication status: PublishedFunder: C3 Biotechnologies LtdFunder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/S01778X/1, EP/J020192/1Funder: Biotechnology and Biological Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000268; Grant(s): BB/M017702/1, BB/L010798/1Funder: Newton-Mosharafa fundAbstract: Background: Microbial biorefinery approaches are beginning to define renewable and sustainable routes to clean-burning and non-fossil fuel-derived gaseous alkanes (known as âbio-LPGâ). The most promising strategies have used a terminal fatty acid photodecarboxylase, enabling light-driven propane production from externally fed waste butyric acid. Use of Halomonas (a robust extremophile microbial chassis) with these pathways has enabled bio-LPG production under non-sterile conditions and using waste biomass as the carbon source. Here, we describe new engineering approaches to produce next-generation pathways that use amino acids as fuel precursors for bio-LPG production (propane, butane and isobutane blends). Results: Multiple pathways from the amino acids valine, leucine and isoleucine were designed in E. coli for the production of propane, isobutane and butane, respectively. A branched-chain keto acid decarboxylase-dependent pathway utilising fatty acid photodecarboxylase was the most effective route, generating higher alkane gas titres over alternative routes requiring coenzyme A and/or aldehyde deformylating oxygenase. Isobutane was the major gas produced in standard (mixed amino acid) medium, however valine supplementation led to primarily propane production. Transitioning pathways into Halomonas strain TQ10 enabled fermentative production of mixed alkane gases under non-sterile conditions on simple carbon sources. Chromosomal integration of inducible (~ 180 mg/g cells/day) and constitutive (~ 30 mg/g cells/day) pathways into Halomonas generated production strains shown to be stable for up to 7 days. Conclusions: This study highlights new microbial pathways for the production of clean-burning bio-LPG fuels from amino acids. The use of stable Halomonas production strains could lead to gas production in the field under non-sterile conditions following process optimisation
Flavin oxidation state impacts on nitrofuran antibiotic binding orientation in nitroreductases
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