Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).
Session 1A: "Biopolymers: Production & Properties"
1:50pm - 3:10pm
Session Chair: Song Liu
1:50pm - 2:10pm
Bio-furan based poly (β-thioether ester) synthesized via Thiol-Michael addition polymerization with tunable structure and properties
daihui zhang, marie josee Dumont
McGill University, Canada
Dimethylphenylphosphine efficiently initiated the thiol-Michael addition polymerization for synthesizing a series of bio-based furan polymers with different structure and properties. The benzene rings or hydroxyl groups present in the polymer chains increased the glass transition temperature (Tg) of poly (β-thioether ester). Additionally, copolymers with various compositions were obtained via adding different ratio of 1,6-hexanedithiols to 1,4-benzenedithiols. 1H NMR analysis revealed that experimental ratios of two dithiols monomers matched well with theoretical ratios. The occurrence of a reversible Diels-Alder reaction between furan rings and maleimide groups allowed poly (β-thioether ester) to be dynamically crosslinked. These polymers offer the potentials to produce materials from biomass that have both practical mechanical properties and reprocessing ability.
2:10pm - 2:30pm
Development of an oxygen-limited high cell density cultivation process for Pseudomonas putida LS46 to increase biopolymer productivity
Warren Blunt1, Chris Dartiailh1, Richard Sparling1, Daniel Gapes2, David B. Levin1, Nazim Cicek1
1University of Manitoba, Canada; 2Scion Research, New Zealand
During production of medium chain length polyhydroxyalkanoates (mcl-PHA) from fatty acids using Pseudomonas putida LS46, it was recently shown that both the polymer content of the cell and synthesis rate are increased under microaerophilic conditions. However, that work was conducted in batch bioreactors with low overall volumetric productivity. In the present study, we have increased the volumetric productivity using an oxygen-limited fed batch strategy. A feeding method was developed in which the carbon source and nitrogen source were fed in small, accurate pulses in response to off-gas CO2 concentrations using a Titrimetric Off-Gas Analyzer (TOGA) sensor system. Carbon and nitrogen were fed to ensure balanced growth as long as the dissolved oxygen remained above 0% air saturation, and subsequently oxygen limited conditions were allowed to prevail in order to increase polymer content. Using this method with maximal mass transfer capability of the bioreactor (aeration at 2 VVM using compressed air, mixing at 1200 rpm), 27.3 ± 3.7 g/L cell dry mass (CDM) was obtained in 27 hours of cultivation, with an average cellular mcl-PHA content of 61.4 ± 9.8 %. The resulting volumetric productivity was 0.68 ± 0.14 g/L/hour. This was nearly a ten-fold improvement in total biomass and productivity from the results obtained in batch experiments. Future work will investigate further improvement to total biomass and overall volumetric productivity by increasing the driving force for oxygen transfer.
2:30pm - 2:50pm
Physical and thermal properties of medium chain length polyhydroxyalkanoates
Chris Datiailh, Franklin Ogidi, Nazim Cicek, David B. Levin
University of Manitoba, Canada
Medium chain length polyhydroxyalkanoates (mcl-PHAs) are naturally occurring polymers produced by various bacteria of the genus Pseudomonas which may find potential applications in plastic markets. These polymers can be cultivated in a bioreactor with renewable carbon substrates and are biodegradable. The composition of mcl-PHAs differ in monomer lengths and functional groups under various growth conditions which ultimately influence the polymer properties. Analysis of mcl-PHA production indicates that compositional differences can be inherited from the choice of bacterial strain, the choice of substrate and growth conditions. These same factors affect the molecular weight, crystallinity and order of the polymers. Taken together, significant differences in polymer properties are observed based on the production conditions for mcl-PHA synthesis. Pseudomonas putida LS46 was used to cultivate mcl-PHAs from various feedstocks. When cultivated using octanoic acid as the substrate, an elastomeric polymer was produced. This polymer had a tensile strength of 2.98 MPa and an elongation at break of 161%. The glass transition point was observed at -36 ˚C, melting point as 53˚C and the degradation temperature as 249 ˚C. In comparison, growth on long-chain fatty acids (LCFAs) present in Canola oil produced polymers demonstrating markedly different properties. The mcl-PHAs produced from LCFAs contain longer monomer units with some unsaturation and as a result are completely amorphous. The glass transition temperature of these polymers -53 ˚C and the degradation temperature observed at 253 ˚C.
2:50pm - 3:10pm
Electrospun nanofibers of blends of microbial biopolymers for biomedical applications.
Wei Li, Nazim Cicek, David B Levin, Song Liu
University of Manitoba, Canada
Polyhydroxyalkanoates (PHAs), a class of microbial biopolymers, have recently attracted significant attention due to their biodegradability, biocompatibility, and renewability. Electrospinning has been used to produce nano-fibrous mats for biomedical applications. Electrospun short chain-length (scl-)PHAs has been extensively investigated. But high crystallinity and brittleness has restricted their applications. Medium chain length (mcl-)PHAs are less crystalline and more flexible, but not suitable for electrospinning since they show tacky and elastomeric at room temperature. Blending (mcl-)PHA with (scl-)PHA is a good way to remain electrospinnable while enhancing their physical and mechanical properties. In this research, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV12, with 12 mol% HV content, (scl-)PHA), PHBV25 (with 25 mol% HV, (scl-)PHA), and blends of PHBV25 with poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHOHHx, (mcl-)PHA) were electrospun into PHBV12, PHBV25 and PHBV25/PHOHHx nano-fibrous mats. PHBV25/PHOHHx blends were carried out at different ratios, among which PHBV25/PHOHHx (75/25 wt%) is the optimal one. Various electrospinning processing parameters affected morphology of as-spun PHBV25/PHOHHx (75/25 wt%) nano-fibers. As concentration increased from 7.5 to 15% (w/v), bead-free and smooth nano-fibers were obtained. Increase in applied voltage (from 15.5 to 33.5 kV) decreased nanofiber average diameter from 660.6±232.6 to 413.3±128.4 nm. Increase in feeding rate (from 0.5 to 4 mL/h) increased nanofiber average diameter from 478.8±154.9 to 761.4±204.2 nm. DSC and X-ray results indicated that the crystallinity of nano-fibrous mats decreased as PHBV12>PHBV25>PHBV25/PHOHHx (75/25 wt%). The improvement in elongation at break makes blends of PHBV25/PHOHH suitable for biomedical applications in contact with soft issues, such as vascular applications, skin regeneration or drug delivery systems.