College of Engineering

BMEBT Seminar Presentation by Prof. Christopher Brigham

Date(s): 2/26/2013 10:00 AM - 2/26/201312:00 PM
Location: Textiles Conference Room - 101E
Contact: Dr. Sankha Bhowmick 508-999-8619


Polyhydroxyalkanoates (PHA) are bio-based, biodegradable polymers that are attractive alternatives to petroleum-based plastics. Recently, a PHA production process has been developed using plant oils as the carbon source and the model PHA-producing organism, Ralstonia eutropha, as the biocatalyst. The principal goal of the project included regular production of high-purity PHA with short chain and medium chain length monomers. The steps in the production process at which we can affect the properties, and therefore the economic potential, of the output polymer, are discussed. There are multiple, interrelated means of controlling the output polymer properties. During production strain genetic construction, we can design R. eutropha to produce PHA with only short chain length monomers (biosynthesis from acetyl-CoA) or a combination of short and medium chain length monomers (typically produced through intermediates of fatty acid metabolism). Also, the choice of carbon feedstock will also significantly affect the type of monomers incorporated into PHA. Further, the strategy of fermentation (batch, extended batch, or fed batch cultures) will alter not only the amount of polymer produced, but also influences the molecular weight and, to a certain extent, its monomer composition. Included in the fermentation strategy’s affects are the choice of nitrogenous compound and the feeding strategy of nitrogen, including when limitation occurs in culture. The means of recovery of polymer from cellular biomass is not often discussed in affecting polymer properties, but we have found a significant influence on molecular weight and the monomer composition of the final PHA product. Therefore, even the choice of recovery method (mechanical vs. solvent-based vs. non-solvent-based) is an important choice in developing a targeted product PHA production process. In effect, alteration of the thermal and mechanical properties of PHA polymers will dictate the applications for which the product polymer is suitable, and hence its economic potential. The polymer production process can be specifically tailored, depending on the target application (agricultural, household, medical, etc.). How a production process can be fine-tuned to anticipate challenges like regulation of molecular weight and monomer ratios will be discussed. With an awareness of how polymer properties can be changed, we can potentially adjust the production process to suit a portfolio of needed applications.

Brief Bio:
Dr. Christopher Brigham is a microbiologist and molecular geneticist with expertise in industrial biotechnology. He received his doctorate from Tufts University School of Medicine in Molecular Microbiology, and arrives at the UMass Dartmouth Bioengineering Department from the Department of Biology at Massachusetts Institute of Technology, where he studied polyhydroxyalkanoate (PHA) bioplastic and alcohol biofuel production in the industrially relevant microorganism Ralstonia eutropha. He has determined the genetic basis for PHA biosynthesis under nitrogen limitation conditions, as well as refined a pilot scale process for producing a unique PHA copolymer using plant oils as the sole carbon source. In recent works, his group has diverted carbon flux in R. eutropha to produce isobutanol, both heterotrophically and autotrophically (using CO2 as the main carbon source). He is continuing bioplastics and biofuels production studies at UMass Dartmouth, and plans to expand into fine chemical biosyntheses using R. eutropha and other organisms.

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