PRODUCTION OF POLYHYDROXYALKANOATES FROM FATTY WASTES

Polyhydroxyalkanoates are a family of polyhydroxyesters synthesized by numerous bacteria as an intracellular carbon and energy storage compounds under nutrient-limiting conditions, in the presence of available carbon sources. They are biodegradable thermoplastics that could be used in many fields, including new emerging and interesting potential applications. In order to effectively and economically produce PHAs, one of the most promising strategies to follow is the use of waste material as carbon source. Wastewaters from food processing and food service industries and activities contain considerable amounts of fat, oil and grease (FOG), that need to be treated for their disposal. These low-cost materials could be converted into value-added products, like polyhydroxyalkanoates (PHAs). In this work the biosynthesis of polyesters from triglyceride substrates was investigated. A number of bacterial isolates from different environmental samples were selected and tested for polymer production. A first filter step based on lipolitic activity was followed and those bacteria potentially able to degrade oils or animal fats were kept for futher studies. In a second step, bacteria were directly grown on animal fats and vegetal oils, and polymer accumulation was analyzed. Each triglyceride, whether of animal or vegetable derivation, supported the growth of a number of the newly isolated strains to relatively high cell yields. PHA production was also reasonably high, at least in some cases. The repeat-unit composition of the bioproducts was determined by gas chromatography (GC) analysis of the ß-hydroxyalkanoate methyl esters from the hydrolyzed polymers. Each polyester produced was composed of ß-hydroxyacyl moieties with chain lengths ranging from C4 to C14, with C8 and C10 being the predominant methyl esters.