A series of polyhydroxyalkanoate(PHA)copolymers consisting of short-chain-length(SCL)and medium-chain-length(MCL)3-hydroxyalkanoate(3HA)monomers were synthesized in the recombinant Ralstonia eutropha PHB - 4 harboring...A series of polyhydroxyalkanoate(PHA)copolymers consisting of short-chain-length(SCL)and medium-chain-length(MCL)3-hydroxyalkanoate(3HA)monomers were synthesized in the recombinant Ralstonia eutropha PHB - 4 harboring a low-substrate-specificity PHA synthase PhaC2Ps from Pseudomonas stutzeri 1317. These polyesters,whose monomer compositions varied widely in chain length,were purified and characterized by acetone fractionation,nuclear magnetic resonance(NMR),gel-permeation chromatography(GPC),and differential scanning calorimetry(DSC).This was the first time that the physical properties of PHA copolymers polymerized by PhaC2Ps were characterized.The results indicated that the variation in MCL 3HA contents did not have an obvious influence on the molecular weights of these PHA copolymers but was effective in changing their physical properties. The variation in the thermal property of PHA copolymers with 3-hydroxyoctanoate(3HO)content was also inves- tigated in this study.展开更多
Growing interest in the abatement of greenhouse gases has spurred a surge in research within the field of methanotrophy in recent decades.Certain methanotrophic organisms exhibit the unique ability for the production ...Growing interest in the abatement of greenhouse gases has spurred a surge in research within the field of methanotrophy in recent decades.Certain methanotrophic organisms exhibit the unique ability for the production of biodegradable polymers known as polyhydroxyalkanoates(PHAs)using methane as their solitary carbon source.In this study,we harnessed the capability of Methylocystis suflitae,a Type II methanotroph,for the production of PHA from methane.The genome analysis unveiled the presence of four paralogs of PHA synthase gene in Methylocystis suflitae.Subsequently,we elucidated the catalytic sites of each PHA synthase using protein modeling and molecular docking.Both hydroxybutyrate and hydroxydo-decanoate demonstrated the highest docking energies among all the tested substrates,recording at−7.5,and−7.8 kcal/mol,respectively.The capability of Methylocystis suflitae to synthesize polyhydroxybutyrate(PHB)was evaluated by analyzing the FTIR spectrum,revealing the characteristic carbonyl(C=O)peak at 1723 cm−1.The study included the optimization of the substrate-to-electron acceptor ratio to optimize PHA productivity.Notably,the organism exhibited a productivity value of 11.90±1.34 mg PHA/L/hr.This higher productivity holds significant promise for industrial PHA production,particularly in scenarios where achieving sufficiently high dissolved methane concentrations in industrial fermenters is inherently chal-lenging,potentially enabling more efficient PHA production.Additionally,we determined the melting temperature for PHB produced by Methylocystis suflitae which closely aligns with the standards of commercial-grade PHB,at around 188℃.展开更多
基金Supported by the National Natural Science Foundation of China （No.30225001, No.20334020）. The authors are very grateful to Prof. A. Steinbiichel of the University of Miinster in Germany for the generous donation of strain R. eutropha PHB 4.
文摘A series of polyhydroxyalkanoate(PHA)copolymers consisting of short-chain-length(SCL)and medium-chain-length(MCL)3-hydroxyalkanoate(3HA)monomers were synthesized in the recombinant Ralstonia eutropha PHB - 4 harboring a low-substrate-specificity PHA synthase PhaC2Ps from Pseudomonas stutzeri 1317. These polyesters,whose monomer compositions varied widely in chain length,were purified and characterized by acetone fractionation,nuclear magnetic resonance(NMR),gel-permeation chromatography(GPC),and differential scanning calorimetry(DSC).This was the first time that the physical properties of PHA copolymers polymerized by PhaC2Ps were characterized.The results indicated that the variation in MCL 3HA contents did not have an obvious influence on the molecular weights of these PHA copolymers but was effective in changing their physical properties. The variation in the thermal property of PHA copolymers with 3-hydroxyoctanoate(3HO)content was also inves- tigated in this study.
基金funded by the National Science Foundation in the form of the BuG ReMeDEE initiative(Award#1736255,#2119753,#1849206,and#1920954).
文摘Growing interest in the abatement of greenhouse gases has spurred a surge in research within the field of methanotrophy in recent decades.Certain methanotrophic organisms exhibit the unique ability for the production of biodegradable polymers known as polyhydroxyalkanoates(PHAs)using methane as their solitary carbon source.In this study,we harnessed the capability of Methylocystis suflitae,a Type II methanotroph,for the production of PHA from methane.The genome analysis unveiled the presence of four paralogs of PHA synthase gene in Methylocystis suflitae.Subsequently,we elucidated the catalytic sites of each PHA synthase using protein modeling and molecular docking.Both hydroxybutyrate and hydroxydo-decanoate demonstrated the highest docking energies among all the tested substrates,recording at−7.5,and−7.8 kcal/mol,respectively.The capability of Methylocystis suflitae to synthesize polyhydroxybutyrate(PHB)was evaluated by analyzing the FTIR spectrum,revealing the characteristic carbonyl(C=O)peak at 1723 cm−1.The study included the optimization of the substrate-to-electron acceptor ratio to optimize PHA productivity.Notably,the organism exhibited a productivity value of 11.90±1.34 mg PHA/L/hr.This higher productivity holds significant promise for industrial PHA production,particularly in scenarios where achieving sufficiently high dissolved methane concentrations in industrial fermenters is inherently chal-lenging,potentially enabling more efficient PHA production.Additionally,we determined the melting temperature for PHB produced by Methylocystis suflitae which closely aligns with the standards of commercial-grade PHB,at around 188℃.
