Sustainable production of oleochemicals requires establishment of cell factory platform strains. The yeast Saccharomyces cerevisiae is an attractive cell factory as new strains can be rapidly ...implemented into existing infrastructures such as bioethanol production plants. Here we show high-level production of free fatty acids (FFAs) in a yeast cell factory, and the production of alkanes and fatty alcohols from its descendants. The engineered strain produces up to 10.4 g l(-1) of FFAs, which is the highest reported titre to date. Furthermore, through screening of specific pathway enzymes, endogenous alcohol dehydrogenases and aldehyde reductases, we reconstruct efficient pathways for conversion of fatty acids to alkanes (0.8 mg l(-1)) and fatty alcohols (1.5 g l(-1)), to our knowledge the highest titres reported in S. cerevisiae. This should facilitate the construction of yeast cell factories for production of fatty acids derived products and even aldehyde-derived chemicals of high value.
Microbial synthesis of medium chain aliphatic hydrocarbons, attractive drop-in molecules to gasoline and jet fuels, is a promising way to reduce our reliance on petroleum-based fuels. In this study, ...we enabled the synthesis of straight chain hydrocarbons (C7–C13) by yeast Saccharomyces cerevisiae through engineering fatty acid synthases to control the chain length of fatty acids and introducing heterologous pathways for alkane or 1-alkene synthesis. We carried out enzyme engineering/screening of the fatty aldehyde deformylating oxygenase (ADO), and compartmentalization of the alkane biosynthesis pathway into peroxisomes to improve alkane production. The two-step synthesis of alkanes was found to be inefficient due to the formation of alcohols derived from aldehyde intermediates. Alternatively, the drain of aldehyde intermediates could be circumvented by introducing a one-step decarboxylation of fatty acids to 1-alkenes, which could be synthesized at a level of 3mg/L, 25-fold higher than that of alkanes produced via aldehydes.
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•Medium chain fatty acids were obtained by engineering fungal fatty acid synthases.•Medium chain alkanes were produced by expressing an alkane biosynthesis pathway.•Among 13 candidates, the ADO from Thermosynechococcus elongatus showed superior activity.•Targeting of the alkane-forming pathway into peroxisomes improved alkane production.•Medium chain 1-alkenes were synthesized by expressing UndA decarboxylase.
The Canadian concept of the Pressure-Tube Super-Critical Water-Reactor (PT-SCWR) uses Pu/Th in a once-through fuel cycle. The implication of using Pu/Th in a PT-SCWR on the safety of the workers in ...the Deep Geological Repository (DGR) facilities as well as on the public after the closure of the DGR was investigated.
A comparison between the Pu/Th and other fuel cycles, namely, U/Th (two U/Th fuels with different enrichments and different UO2/ThO2 ratios), and the regular UO2 was also made. The enrichment of U-235 in U/Th and UO2 was adjusted to give the same exit burnup of the proposed Pu/Th fuel, namely 60 GWd per ton of heavy metals (THM).
The dose rate as a function of distance from the surface of a canister holding different types of spent fuel, and the thickness of the shielding required to reduce this dose rate to 10 μSv/h were estimated.
The dose rate after 50 years of decay for Pu/Th fuel channel is higher than that of uranium by about 8%. This will increase the dose to the workers in DGR facilities unless more shielding is used. Pu/Th will need 13% more thickness of concrete compared to UO2. Using U/Th fuel will also increase the dose received by workers, compared with uranium-only fuel, but less than using Pu/Th. The neutron dose rate of the Pu/Th fuel is the highest dose rate from all fuels studied.
Pu/Th spent fuel will cause the highest dose to the public in case of an accident of the DGR after closure as it will produce the largest amount of I-129 per THM. Although the exact dose received by the critical group is not expected to exceed the dose limit for DGR, it is higher than alternative fuels.
•Pu/Th fuel increased the dose rate to the workers in deep geological repository.•Pu/Th increased the dose rate to the public without exceeding the dose constraint.•U/Th increased the occupational dose rate compared with uranium fuel.•Th-based open fuel cycle did not show better performance compared with uranium.
Children admitted to a pediatric intensive care unit (ICU) are at high risk of developing acute kidney injury (AKI). Although serum creatinine (SCr) levels are used in clinical practice, they are ...insensitive for early diagnosis of AKI. Urinary neutrophil gelatinase-associated lipocalin (uNGAL) and kidney injury molecule-1 (KIM-1) are novel AKI biomarkers whose performance in pediatric ICU patients is largely unknown. In this study, we aimed to characterize uNGAL and KIM-1 patterns in children following ICU admission and to assess their properties in relation to identifying children at risk for AKI development.
From June 2010 until January 2014, we conducted a prospective observational cohort study of term-born children ages 1 day to 1 year on mechanical ventilation. Blood and urine samples were obtained every 6 to 12 hours up to 72 hours post-admission. Blood samples were assayed for SCr, and urine samples were assayed for uNGAL and KIM-1. The RIFLE (risk, injury, failure, loss, end-stage renal disease) classification as 150%, 200% or 300% of median SCr reference values was used to define AKI.
A total of 100 children were included (80 survived). Their median age at admission was 27.7 days (interquartile range (IQR), 1.5 to 85.5). The median duration of mechanical ventilation was 5.8 days (IQR, 3.1 to 11.4). Thirty-five patients had evidence of AKI within the first 48 hours post-admission, of whom 24 (69%) already had AKI when they entered the ICU. uNGAL and KIM-1 concentrations in AKI peaked between 6 to 12 hours and between 12 to 24 hours post-admission, respectively. The maximal area under the receiver operating characteristic curve (AUC) for uNGAL was 0.815 (95% confidence interval (CI), 0.685 to 0.945, P < 0.001) at 0 to 6 hours post-admission. The discriminative ability of KIM-1 was moderate, with a largest AUC of 0.737 (95% CI, 0.628 to 0.847; P < 0.001) at 12 to 24 hours post-admission. At the optimal cutoff point (126 ng/ml), uNGAL concentration predicted AKI development correctly in 16 (84%) of 19 children, up to 24 hours before a rise in SCr became apparent.
Levels of uNGAL and KIM-1 increase in patients with AKI following ICU admission and peak at 6 to 12 hours and 12 to 24 hours post-admission, respectively. uNGAL seems to be a reliable marker for identifying children who will develop AKI 24 hours later.
Low catalytic activities of pathway enzymes are often a limitation when using microbial based chemical production. Recent studies indicated that the enzyme activity of aldehyde decarbonylase (AD) is ...a critical bottleneck for alkane biosynthesis in Saccharomyces cerevisiae. We therefore performed functional screening to identify efficient ADs that can improve alkane production by S. cerevisiae.
A comparative study of ADs originated from a plant, insects, and cyanobacteria were conducted in S. cerevisiae. As a result, expression of aldehyde deformylating oxygenases (ADOs), which are cyanobacterial ADs, from Synechococcus elongatus and Crocosphaera watsonii converted fatty aldehydes to corresponding C
alkanes and alkenes. The CwADO showed the highest alkane titer (0.13 mg/L/OD
) and the lowest fatty alcohol production (0.55 mg/L/OD
). However, no measurable alkanes and alkenes were detected in other AD expressed yeast strains. Dynamic expression of SeADO and CwADO under GAL promoters increased alkane production to 0.20 mg/L/OD
and no fatty alcohols, with even number chain lengths from C8 to C14, were detected in the cells.
We demonstrated in vivo enzyme activities of ADs by displaying profiles of alkanes and fatty alcohols in S. cerevisiae. Among the AD enzymes evaluated, cyanobacteria ADOs were found to be suitable for alkane biosynthesis in S. cerevisiae. This work will be helpful to decide an AD candidate for alkane biosynthesis in S. cerevisiae and it will provide useful information for further investigation of AD enzymes with improved activities.
•Gamma heating measurement using gamma thermometer in irradiation.•Nine axial gamma heating measurements were performed each site.•Serpent-2 code was used and compared against ...measurement.•Uncertainty quantification of the gamma heating are presented.
Interaction of radiation with matter results in heat generation and in effect, changes in the irradiation sample’s quality. Knowledge about heat deposition within the irradiation sites can go a long way in enhancing the safety and quality of the irradiation condition. To measure such results, SCK-CEN Gamma Thermometer (GT) is used for experimentally measuring Gamma Heating (GH) during the operation of McMaster Nuclear Reactor (MNR) at three irradiation sites. In addition, Monte Carlo reactor physics code (Serpent-2) is also used for modeling the MNR in order to compare as well as validate it against experimental and operational measured data such as the multiplication factor (keff) during the operational day against the actual values (unity), the experimentally measured GH values. After finding a difference of 0.45% at the beginning of the day and 0.32% at the end of the day in the keff, a comparable GH profile was observed between the measurement and the calculation. Additionally, the average axial differences of GH results found in the beryllium irradiation site (2A), and the graphite irradiation sites (8B and 8E) are 4.71%, 10.71%, and 11.72%.
•Moving valine biosynthetic pathway to the cytosol improved isobutanol productivity.•Manipulation iron–sulfur cluster synthesis machinery enhances isobutanol production.•Increased isobutanol yield by ...deletion of all three pyruvate decarboxylase.•Expression of sesquiterpene synthases in mitochondria improved amorphadiene titer.
Replacement of conventional transportation fuels with biofuels will require production of compounds that can cover the complete fuel spectrum, ranging from gasoline to kerosene. Advanced biofuels are expected to play an important role in replacing fossil fuels because they have improved properties compared with ethanol and some of these may have the energy density required for use in heavy duty vehicles, ships, and aviation. Moreover, advanced biofuels can be used as drop-in fuels in existing internal combustion engines. The yeast cell factory Saccharomyces cerevisiae can be turned into a producer of higher alcohols (1-butanol and isobutanol), sesquiterpenes (farnesene and bisabolene), and fatty acid ethyl esters (biodiesel), and here we discusses progress in metabolic engineering of S. cerevisiae for production of these advanced biofuels.
Water ferns of the genus
Azolla
and the filamentous cyanobacteria
Nostoc azollae
constitute a model symbiosis that enabled the colonization of the water surface with traits highly desirable for the ...development of more sustainable crops: their floating mats capture CO
2
and fix N
2
at high rates using light energy. Their mode of sexual reproduction is heterosporous. The regulation of the transition from the vegetative phase to the spore forming phase in ferns is largely unknown, yet a prerequisite for
Azolla
domestication, and of particular interest as ferns represent the sister lineage of seed plants. Sporocarps induced with far red light could be crossed so as to verify species attribution of strains from the Netherlands but not of the strain from the Anzali lagoon in Iran; the latter strain was assigned to a novel species cluster from South America. Red-dominated light suppresses the formation of dissemination stages in both gametophyte- and sporophyte-dominated lineages of plants, the response likely is a convergent ecological strategy to open fields. FR-responsive transcripts included those from MIKC
C
homologues of CMADS1 and miR319-controlled GAMYB transcription factors in the fern, transporters in
N. azollae
, and ycf2 in chloroplasts. Loci of conserved microRNA (miRNA) in the fern lineage included miR172, yet FR only induced miR529 and miR535, and reduced miR319 and miR159. Phylogenomic analyses of MIKC
C
TFs suggested that the control of flowering and flower organ specification may have originated from the diploid to haploid phase transition in the homosporous common ancestor of ferns and seed plants.
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