Conversion of waste cooking oil into medium chain polyhydroxyalkanoates in a high cell density fermentation

Biodegradable and biocompatible polymers polyhydroxyalkanoates (PHAs) have a wide range of applications from packaging to medical. For the production of PHA at scale it is necessary to develop a high productivity bioprocess based on the use of a cheap substrate. The objective of the current study was to develop a high cell density bioreactor-based process for the production of medium chain length polyhydroxyalkanoate (mclPHA) with waste cooking oil as the sole carbon and energy source. A number of substrate feeding strategies for bacterial growth and polymer production were investigated. Pseudomonas chlororaphis 555 achieved high biomass of 73 g/l medium and a good biomass yield (including PHA in the cell) of 0.52 g/g substrate. P. chlororaphis 555 accumulated 13.9 g mclPHA/L and achieved polymer productivity of 0.29 g mclPHA/(L h). The mclPHA contained predominantly (R)-3-hydroxyoctanoic acid and (R)-3-hydroxydecanoic acid monomers, with a high fraction of (R)-3-hydroxydodecanoic acid monomers. This polymer is of low molecular weight (18 324 kDa), low polydispersity, it is amorphous, and has a glass transition temperature of -64 °C.