Thermal pre-processing before extraction of polyhydroxyalkanoates for molecular weight quality control

Past studies have repeatedly demonstrated the technical feasibility to produce polyhydroxyalkanoate (PHA) using bacterial biomass of mixed microbial cultures (MMCs). Commercial quality grades poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, can be produced with control average monomer composition. However, demonstration PHBV production and recovery molecular weight (MW) distribution has been lacking in research literature. Towards this goal, a workflow developed for characterizing by thermal treatment pre-processing dried PHA-rich before solvent extraction. Dimethyl carbonate (DMC) was suitable routine evaluation extractable PHA. From assessments DMC extraction differential scanning calorimetry, 125 °C selected nominally 100 percent yield independent polymer 3-hydroxyvalerate (3HV) content (2 41 wt.% 3HV) (100 1400 kDa). Intrinsic viscosity measurements at 60 used monitoring. Mark-Houwink constants, α (0.738 ± 0.010) LogK (-2.016 0.025), were estimated co-polymer blend having 36 3HV. A model random scission supported that (Mw) more robust metric, compared number (Mn), assessing rates. During isothermal heat given batch, interpreted rate reproducible commonly, but not always, constant time. Scission rates between batches also variable. Measured properties (thermal stability, PHA content, grade, initial moisture content) could correlated observed batch-to-batch variation rate. Molecular loss did influence melting temperatures blends evaluated over wide sub-eutectic range 3HV content. changes these considered likely influenced nature distribution, consequently, crystallization behaviour. effects on behaviour then contributed variability glass transition enthalpies. correlation MW change observed.