Remodeling Isoprene Pyrophosphate Metabolism for Promoting Terpenoids Bioproduction

Terpenoids are the largest family of natural products.They are made from the building block isoprene pyrophosphate(IPP),and their bioproduction using engineered cell factories has received a great deal of attention.To date,the insufficient metabolic supply of IPP remains a great challenge for the efficient synthesis of terpenoids.In this work,we discover that the imbalanced metabolic flux distribution between the central metabolism and the IPP supply hinders IPP accumulation in Bacillus subtilis(B.subtilis).Therefore,we remodel the IPP metabolism using a series of genetically encoded two-input-multioutput(TIMO)circuits that are responsive to pyruvate or/and malonyl-CoA,resulting in an IPP pool that is significantly increased by up to four-fold.As a proof-of-concept validation,we design an IPP metabolism remodeling strategy to improve the production of three valuable terpenoids,including menaquinone-7(MK-7,4.1-fold),lycopene(9-fold),andβ-carotene(0.9-fold).In particular,the titer of MK-7 in a 50-L bioreactor reached 1549.6 mg·L^(-1),representing the highest titer reported so far.Thus,we propose a TIMO genetic circuits-assisted IPP metabolism remodeling framework that can be generally used for the synergistic fine-tuning of complicated metabolic modules to achieve the efficient bioproduction of terpenoids.

Quantum chemical descriptors based QSAR modeling of neodymium carboxylate catalysts for coordination polymerization of isoprene

Based on the quantum chemical descriptors and the activities for isoprene polymerization of 12 neodymium carboxylates obtained by authors’earlier work,statistical analysis of data was made and a QSAR model correlating the quantum chemical descriptors and the activity was built with the partial least square(PLS)approach.The model is:A=51602εHOMO+6σ+12546,which indicates that the catalytic activity A is positively correlated with the HOMO energyεHOMOand the ligand polarizabilityσ,with the contribution ofσbeing larger,εHOMO smaller.The model’s coefficient of determination r^2=0.96 and that of cross validation q^2=0.94,both being close to 1,which means that its quality is well and its predictive power is strong.Analysis of the modeling process and the resulted QSAR model,together with the interpretation of the model’s mechanism,also shows that the model obtained from this study is valid and reliable.According to the QSAR model,the mechanism of catalyst activity can be interpreted as that neodymium carboxylates with higher HOMO energy and larger ligand polarizability are easier to react with the co-catalysts so as to produce more active and stable centers of catalyst,resulting in a higher activity.

Biogenic Isoprene and Its Impact on Human Health in Dependence on Meteorological Conditions

Urban green areas have an important implication on the local climate. A cross-linkage of many small green spaces could result in decreasing the effect of the urban heat island, but also increase people’s thermal comfort. By the way, urban green areas could also induce a positive effect on the local urban air quality. But attention has to be paid to the assortment of the tree species. More or less all tree species are emitting biogenic volatile organic compounds in different concentration. These serve as precursors for the formation of ozone near the ground. So near surface ozone has the ability to react with different particulate matters and could become toxic, due to oxidation or nitrification. This causes inflammations and inspired allergens may increase the risk of a respiratory disease. Therefore, an analysis and assessment of the urban green area air quality could help to make a statement about the recreational effect of these areas in dependence of the leading vegetation and for that matter for the exposure to ozone. By the help of these the results can be used as a guidance of urban planning taking into account the influence of biogenic emission as a function of actual weather conditions.

Synthesis and Characterization of Poly(isoprene-b-butyl methacrylate) Block Copolymer in the Presence of Rare Earth Catalyst

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Copolymerization of Butadiene and Isoprene by NdC_6H_6(AlCl_4)_3-AlR_3 System

This paper reported the copolymerization results of butadiene and isoprene catalyzed byNdC6H6（AlCl4）3-AlR3 system.The results show that the catalytic activity is dependent on the weight ratioof butadiene and isoprene,the concentration of comonomers,the nature of alkylaluminium and thepolymerization temperature as well.High contents of 1,4 microstructure of copolymer are obtained by thenovel catalyst system.

Determination of breath isoprene in 109 suspected lung cancer patients using cavity ringdown spectroscopy

Background:Lung cancer is one of the most common malignant tumors worldwide.Currently,effective screening methods for early lung cancer are still scarce.Breath analysis provides a promising method for the pre-screening or early screening of lung cancer.Isoprene is a potential and important breath biomarker of lung cancer.Material and Methods:To investigate the clinical value of isoprene for diagnosing lung cancer patients,a cavity ringdown spectroscopy(CRDS)based near-real time,sensitive analysis method of breath isoprene is developed in our lab.In this paper,92 breath samples from lung cancer patients,17 breath samples from patients with benign lesions,and 107 breath samples from healthy people were collected.Results:Research indicates that breath isoprene concentration is significantly higher in healthy individuals(221:3±122:2 ppbv)than in patients with lung cancer(112:0±36:6 ppbv)and benign lung lesions(127:9±41:2 ppbv).The result of Receiver Operating Characteristic(ROC)curve suggests that the concentration of isoprene is meaningful for the diagnosis of lung cancer(AUC=0:822,sensitivity=63:6%,specificity=90:2%,P<0:01).Conclusion:This study demonstrates that the CRDS breath isoprene analysis system can effectively analyze a large sample of human breath isoprene,and preliminarily confirms the use of breath isoprene as a biomarker for lung diseases.

Investigation of the Potential of Using Liquid Rubbers in Rubber Industry

Along with the developing technology in the rubber industry, the use of natural and synthetic rubbers as well as liquid rubbers has increased significantly in recent years. The formulation of the tread compound, which directly affects the performance of a tire, is generally produced from natural and synthetic rubbers. Intensive scientific studies have been carried out on liquid rubbers because they reduce the consumption of process oils used in the tire production phase and increase dispersion. In this study, the rheological and physico-mechanical properties of rubbers developed using only liquid rubber (liquid isoprene and liquid SBR) with four different viscosities and without using process oil (Styrene Butadiene Rubber—SBR) were investigated. It has been observed that the rubber blends produced by adding four different liquid rubbers to the same recipe caused changes in rheological and physico-mechanical properties compared to the reference sample. It was observed that the minimum torque/viscosity (ML), maximum torque/viscosity (MH) and curing time (t90) in some of the formulas tested decreased significantly due to the use of liquid rubber.

非接触式人体气味标志化合物的定性研究

As a base research on intelligentized search technique in seismic ruins,we study on human odor by a portable GC-MS.Qualitative analysis experiment demonstrate that isoprene,acetone and 6-methyl-5-heptene-2-one are symbol of human odor.This research give important data to search survival base on artificial olfaction technique in seismic ruins.

Characteristics and chemical reactivity of biogenic volatile organic compounds from dominant forest species in the Jing-Jin-Ji area,China

Background:Biogenic volatile organic compounds(BVOCs)play an essential role in tropospheric atmospheric chemical reactions.There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-Ji area of China.Based on the field survey,forest resources data and the measured standard emission factors,the Guenther model developed in 1993(G93)was applied in this paper to estimate the emission of BVOCs from several dominant forest species(Platycladus orientalis,Quercus variabilis,Betula platyphylla,Populus tomentosa,Pinus tabuliformis,Robinia pseudoacacia,Ulmus pumila,Salix babylonica and Larix gmelinii)in the Jing-Jin-Ji area in 2017.Then the spatiotemporal emission characteristics and atmospheric chemical reactivity of these species were extensively evaluated.Results:The results showed that the total annual BVOCs emission was estimated to be 70.8 Gg C·year^(−1),consisting 40.5%(28.7 Gg C·year^(−1))of isoprene,36.0%(25.5 Gg C·year^(−1))of monoterpenes and 23.4%(16.6 Gg C·year^(−1))of other VOCs.The emissions from Platycladus orientalis,Quercus variabilis,Populus tomentosa and Pinus tabulaeformis contributed 56.1%,41.2%,36.0% and 31.1%,respectively.The total BVOCs emission from the Jing-Jin-Ji area accounted for 61.9% and 1.8%in summer and winter,respectively.Up to 28.8% of emission was detected from Chengde followed by Beijing with 24.9%,that mainly distributed in the Taihang Mountains and the Yanshan Mountains.Additionally,the Robinia pseudoacacia,Populus tomentosa,Quercus variabilis,and Pinus tabulaeformis contributed mainly to BVOCs reaction activity.Conclusions:The BVOCs emission peaked in summer(June,July,and August)and bottomed out in winter(December,January,and February).Chengde contributed the most,followed by Beijing.Platycladus orientalis,Quercus variabilis,Populus tomentosa,Pinus tabulaeformis and Robinia pseudoacacia represent the primary contributors to BVOCs emission and atmospheric reactivity,hence the planting of these species should be reduced.

Evaluation of Some Insulated Greases Prepared from Rubber and Bitumen Thickeners

The wax gel grease (S0) was prepared from a mixture of 2.3:1 base oil blend (base oil grade 260/290, transformer oil), and microcrystalline wax in the presence of 0.1% - 2% of polyoxyethylene sorption nano-palmitate as antioxidant and 2,2 methylene bis (4-methyle-6-tertiary butyl phenol) as anticorrosion. It was found that the prepared Wax gel grease has inconvenient physico-chemical and dielectric properties, so in order to improve its physico-chemical properties (viscosity, penetration, dropping point and water resistance) and dielectric Properties (dielectric constant, dielectric loss and volume resistivity), Butyl rubber, isoprene rubber and bitumen were added separately as thickening agents to the prepared wax gel in certain proportion at certain frequency range 1 - 1000 KHz at 35°C. The best dielectric properties were achieved by adding butyl rubber to the prepared wax gel.

Thermal Degradation Products of α-Pinene in a Tubular Furnace in the Temperature Range from 300°C to 900°C: Contribution to Wildfire Flashovers

Induced BVOC emissions from pyrolyzed plants that may accumulate in confined topographies have been a controversy for their role in wildfire eruptions or flashovers. α-pinene (C10H16) is one of the most abundant monoterpenes emitted from pyrolyzed Mediterranean vegetation in wildfires. Its thermal degradation under fire thermal stresses produces a range of highly flammable gases. In order to identify these products, thermal degradation experiments were performed on α-pinene in a tubular furnace in an inert atmosphere and a high-temperature range (300°C - 900°C). The pyrolysis products were identified using gas chromatography (GC) linked to a tubular furnace outlet by which their retention times were compared with those of reference standards. The degradation products were mainly terpenoids, aliphatic hydrocarbons (methane, ethane, ethene, propane, propene, 1,3-butadiene, isoprene), and aromatics (benzene, toluene) in addition to hydrogen. The radical mechanisms of the chemical reactions associated with the formation of the products at different experimental temperatures were addressed and compared with the literature. Monoterpenes, butadiene, isoprene, aliphatic hydrocarbons, and aromatics formations from α-pinene were consistent with the literature. However, even if benzene has been identified in our experiments, we cannot support with certainty the mechanisms of its formation described in the literature since acetylene was not observed.

Manganese porphyrin-mediated aerobic epoxidation of propylene with isoprene: A new strategy for simultaneously preparing propylene epoxide and isoprene monoxide

The direct epoxidation of propylene by O_(2) is a significant and challenging topic. The key factor for this homogeneous aerobic epoxidation is the activation of molecular oxygen under mild conditions. In this work,the aerobic epoxidation of propylene catalyzed by manganese porphyrins was achieved in the presence of isoprene. Isoprene contains an allyl methyl group, and the α-H can be easily removed to achieve the activation of molecular oxygen. The conversion of propylene was 38% and the selectivity toward propylene oxide(PO) was up to 87%. The role of isoprene was demonstrated, and a plausible mechanism was proposed. The protocol reported herein is expected to provide a strategy for the simultaneous preparation of propylene oxide and isoprene monoxide.

The block copolymerization of isoprene with epichlorohydrin by rare earth coordination catalyst

The block coordination copolymerization of isoprene （Ip） with epichlorohydrin （ECH）has not been reported yet. Deore once studied the anionic type copolymerization ofdiene with ethylene oxide by naphthalene-potassium catalyst and obtained the solid polymerelectrolytes. Based on the coordination polymerization of Ip and ring-openingpolymerization of alkene oxide by rare earth catalysts, we first studied the blockcopolymerization of Ip and ECH in the presence of rare earth coordination catalysts:RE(P204)3-Al （i-Bu）3-halide. The block copolymer which has high molecular weight with

Neodymium-catalyzed Polymerization of C5 Fraction: Efficient Synthesis of 1,3-Pentadiene-isoprene Copolymer Rubbers

The polymerization of C5 fraction without separation and concentration by using a commercial available Nd(P204)3/ AliBu3/AlEt2Cl has afforded for the first time a new kind of 1,3-pentadiene-isoprene random copolymers as rubber materials. Isoprene (IP) and E-1,3-pentadiene (EPD) acted as polymerization monomers, cyclopentadiene acted as poison, and other substances like alkanes, monoolefins, Z-1,3-pentadiene acted as solvents in this multicomponent C5 fraction polymerization system. The data of kinetic experiments, NMR, and DSC indicated that the polymerization of C5 fraction by Nd(P204)3/AliBu3/AlEt2Cl afforded the IP-EPD random copolymers. By controlling polymerization conditions such as [Al]/[Nd]/[Cl] molar ratio and polymerization temperature, the random EPD-IP copolymers containing high cis-1,4-poly(IP)(with selectivity 96%) and moderate cis-1,4-poly(EPD)(with selectivity 60%) units with a low glass transition temperature (about 60 ℃), controllable molecular weight (Mn = 3.8 × 10^4-14.3 × 104), and moderate molecular weight distribution (Mw/Mn = 2.17-2.78) were obtained in a high yield.

Development of a dual temperature control system for isoprene biosynthesis in Saccharomyces cerevisiae

Conflict between cell growth and product accumulation is frequently encountered in the biosynthesis of secondary metabolites. To address the growth-production conflict in yeast strains harboring the isoprene synthetic pathway in the mitochondria, the dynamic control of isoprene biosynthesis was explored. A dual temperature regulation system was developed through engineering and expression regulation of the transcriptional activator Gal4p. A cold-sensitive mutant, Gal4ep19, was created by directed evolution of Gal4p based on an internally developed growth-based high-throughput screening method and expressed under the heat-shock promoter PSSA4 to control the expression of PGAL-driven pathway genes in the mitochondria. Compared to the control strain with constitutively expressed wild-type Gal4p, the dual temperature regulation strategy led to 34.5% and 72% improvements in cell growth and isoprene production, respectively. This study reports the creation of the first cold-sensitive variants of Gal4p by directed evolution and provides a dual temperature control system for yeast engineering that may also be conducive to the biosynthesis of other high-value natural products.

Well-defined phosphate yttrium dialkyl complexes for catalytic stereo-controllable 1,4-polymerization of isoprene

Oxygen ligation is envisioned to provide a stable and distinctive coordination environment to the strongly oxophilic rare-earth metals. However, the well-defined dialkyl complexes bearing oxyanion ancillary ligand had been rarely addressed for the instability of the complexes and the shortage of easily available ligands. Herein, we report the synthesis of phosphate ligated dialkyl yttrium complexes(PYR2) featuring a high stability and a tunable ligand. Treated with the borate reagent, the phosphate yttrium complex displays high activity and selectivity in the catalytic cis-1,4-polymerization of isoprene(up to 96.5%). Furthermore, using AlMe_(3) as an additive, the stereoselectivity switches to trans-1,4-polymerization(up to 92.0%).

Polymerization of Isoprene by Amidinate-Ligated Yttrium Catalysts.Unprecedented Switching of the Regio-and Stereoselectivity with an Alkyl Aluminum Compound

1 Results Search for catalysts which can control the regio- and stereoselectivity for olefin polymerization is a very important research subject.For the polymerization of isoprene,we have recently achieved,for the first time,the isospecific 3,4 polymerization by using a cationic rare earth metal alkyl catalyst bearing a silylene-linked cyclopentadieny-phosphido ligand[1], and the cis-1,4 living polymerization by a bis(phosphinophenyl)amido-ligated rare earth metal catalyst[2]. In addition to these ligan...

STUDY ON THE POLYMERIZATION OF ISOPRENE CATALYZED BY NEUTRAL ARENE ORGAN-OLANTHANOIDS-AIR_3 SYSTEM

It has been known that the neutral arene complexes of transition metal are important complexes. These complexes can catalyze alkylation of aryl compound and polymerization and oligomerization of olefins in the presence of alkylaluminium. Since 1986, study on

Rare-earth Metal Dialkyl Complexes Supported by 1,3-Disubstituted Indolyl Ligand: Synthesis, Characterization and Catalytic Activity for Isoprene Polymerization

Rare-earth metal dialkyl complexes[1-Bn-3-(DippN=CH)C_(8)H_(4)N]RE(CH_(2)SiMe_(3))2(thf)2(Dipp=2,6-iPr_(2)C_(6)H_(3),RE=Y(1)and Er(2))were prepared through the cyclometalation reactions of the N-Bn-3-imino-functionalized indolyl ligand 1-Bn-3-(DippN=CH)C8H5N with one equivalent of rare-earth metal trialkyl precursors.The structures of compounds 1 and 2 were confirmed by X-ray crystal analyses and characterized by elemental analysis,IR,NMR spectroscopy wherein applicable.In the presence of cocatalysts,these rare-earth metal dialkyl complexes initiated isoprene polymerization with a high activity(95% conversion of 2000 equivalent of isoprene in 360 min),producing polymers with high regioselectivity(1,4-polymers up to 91%).

Formation mechanism of isoprene compounds degraded from carotenoids during fermentation of goji wine

Fermented goji wine as a functional wine is made from yeast fermentation.To our knowledge,fermented goji wine still has a problem with insufficient characteristic aroma.Research has shown that some isoprene compounds with characteristic aromas may improve the aroma of goji wine.Therefore,the present study aimed to investigate the mechanism of isoprene compound production by carotenoid degradation during the fermentation of goji wine.It was found that C1-C6,C5-C6,C6-C7,C7-C8,C8-C9 and C9-C10 were the most easily degraded sites in carotenoids under seven different pretreatment conditions(mechanical treatment,pectinase treatment,adjustment of pH,autoclave treatment,SO_(2) treatment,oxidation treatment and light treatment).Meanwhile,breaking different sites,different aroma contributions such as woody,rose,fruity and grassy aromas were found.Single-factor simulation experiments of goji wine during the fermentation showed that the metabolites in the fermentation process caused the degradation of carotenoids and most were volatile aroma compounds.These results may help improve the brewing process to enhance the aroma of goji wine.