Kann Y.,Metabolix Inc.
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2013
Blends of biobased polyhydroxyalkanoates (PHAs) with PVC have been developed and demonstrated very unique properties when added between 5 and 30 phr. These blends promise to improve both mechanical and environmental performance of PVC. The breakthrough is based on the miscibility of PHA and PVC resins and similar processing windows. Based on the miscibility and performance requirements, specific compositions of PHA copolymers were created to improve plasticization, impact and processing modification. In impact modification, PHA rubber copolymers outperform the best available MBS core/shell impact modifiers and do not compromise PVC transparency and UV stability. In plasticization, PHA copolymers perform as high molecular weight, readily dispersible plasticizers and enable formulation of compounds with low additive migration, low extractables, volatile loss and staining. As a processing aid, the metal adhering properties of PHA copolyesters promote homogeneous shear melting of PVC particles and prevent overheating and degradation. It will be shown that due to their multifunctional performance, the PHA modifiers could significantly simplify the formulation of PVC compounds and reduce the overall amount of required additives. The PHA rubber copolymers are commercially biosynthesized by fermentation technology from renewable resources. They satisfy requirements on sustainability and biodegradability.
Sun X.,Metabolix Inc.
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2011
Biodegradable plastics have attracted much attention in the last decade, not only because they can divert waste from landfill, but also because the biodegradable functionality meets the requirement of many applications. Poly (hydroxy butanoic acid) or PHB copolymers is one such class of plastics. This paper will review the biodegradability of these polymers in various environments including soil, fresh water, seawater, compost and anaerobic digesters. Testing methods and variables influencing biodegradation will also be discussed.
Snell K.D.,Metabolix Inc. |
Singh V.,University of North Texas |
Brumbley S.M.,University of North Texas
Current Opinion in Biotechnology | Year: 2015
The production of novel biopolymers in plants has the potential to provide renewable sources of industrial materials through agriculture. In this review we will highlight recent progress with plant-based production of polyhydroxyalkanoates (PHAs), silk, elastin, collagen, and cyanophycin with an emphasis on the synthesis of poly[(R)-3-hydroxybutyrate] (PHB), a renewable biodegradable PHA polymer with potential commercial applications in plastics, chemicals, and feed markets. Improved production of PHB has required manipulation of promoters driving expression of transgenes, reduction in activity of endogenous enzymes in competing metabolic pathways, insertion of genes to increase carbon flow to polymer, and basic plant biochemistry to understand metabolic limitations. These experiments have increased our understanding of carbon availability and partitioning in different plant organelles, cell types, and organs, information that is useful for the production of other novel molecules in plants. © 2014 Elsevier Ltd.
Sangurdekar D.P.,Princeton University |
Zhang Z.,University of Minnesota |
Zhang Z.,Metabolix Inc. |
Khodursky A.B.,University of Minnesota
BMC Genomics | Year: 2011
Background: Trimethoprim is a widely prescribed antibiotic for a variety of bacterial infections. It belongs to a class of anti-metabolites - antifolates - which includes drugs used against malarial parasites and in cancer therapy. However, spread of bacterial resistance to the drug has severely hampered its clinical use and has necessitated further investigations into its mechanism of action and treatment regimen. Trimethoprim selectively starves bacterial cells for tetrahydrofolate, a vital cofactor necessary for the synthesis of several metabolites. The outcome (bacteriostatic or bactericidal) of such starvation, however, depends on the availability of folate-dependent metabolites in the growth medium. To characterize this dependency, we investigated in detail the regulatory and structural components of Escherichia coli cellular response to trimethoprim in controlled growth and supplementation conditions.Results: We surveyed transcriptional responses to trimethoprim treatment during bacteriostatic and bactericidal conditions and analyzed associated gene sets/pathways. Concurrent starvation of all folate dependent metabolites caused growth arrest, and this was accompanied by induction of general stress and stringent responses. Three gene sets were significantly associated with the bactericidal effect of TMP in different media including LB: genes of the SOS regulon, genes of the pyrimidine nucleotide biosynthetic pathway and members of the multiple antibiotic resistance (mar) regulon controlled by the MarR repressor. However, the SOS response was identified as the only universal transcriptional signature associated with the loss of viability by direct thymine starvation or by folate stress. We also used genome-wide gene knock-out screen to uncover means of sensitization of bacteria to the drug. We observed that among a number of candidate genes and pathways, the effect of knock-outs in the deoxyribose nucleotide salvage pathway, encoded by the deoCABD operon and under the control of the DeoR repressor, was most informative.Conclusion: Transcriptional induction of DNA damage response is an essential feature of the bactericidal effect of trimethoprim. Either the observation of the transcriptional response or DNA damage itself, or both, is made possible by thymine starvation when other folate-dependent metabolites are not limited. The effect of DNA damage by the drug takes place prior to its bactericidal effect, at the beginning of the lag stage of the treatment. Mutations in the deoxyribose nucleotide salvage pathway can affect duration of the lag as well as the rate of killing. This information can be used to postulate certain mechanistic differences between direct thymine starvation in thymidylate synthase deficient mutants and thymine starvation by anti-folate inhibitors. © 2011 Sangurdekar et al; licensee BioMed Central Ltd.
Ambavaram M.M.R.,Virginia Polytechnic Institute and State University |
Ambavaram M.M.R.,Metabolix Inc. |
Basu S.,University of Arkansas |
Krishnan A.,Virginia Polytechnic Institute and State University |
And 8 more authors.
Nature Communications | Year: 2014
Plants capture solar energy and atmospheric carbon dioxide (CO 2) through photosynthesis, which is the primary component of crop yield, and needs to be increased considerably to meet the growing global demand for food. Environmental stresses, which are increasing with climate change, adversely affect photosynthetic carbon metabolism (PCM) and limit yield of cereals such as rice (Oryza sativa) that feeds half the world. To study the regulation of photosynthesis, we developed a rice gene regulatory network and identified a transcription factor HYR (HIGHER YIELD RICE) associated with PCM, which on expression in rice enhances photosynthesis under multiple environmental conditions, determining a morpho-physiological programme leading to higher grain yield under normal, drought and high-temperature stress conditions. We show HYR is a master regulator, directly activating photosynthesis genes, cascades of transcription factors and other downstream genes involved in PCM and yield stability under drought and high-temperature environmental stress conditions.