Optimization of bioplastics production from cheese whey

Dissertation presented in partial fulfillment of the requirements for the degree of Master in Biotechnology

Polyhydroxyalkanoates (PHAs) are polyesters produced by a variety of microorganisms. Due to the similarity of chemical and physical properties with the conventional plastics, and full biodegradability, PHAs constitute one of the best alternatives for synthetic polymers replacement. However, the production costs of these biopolymers are very high when compared to synthetic polymers production. One way to reduce the production costs is the utilization of low cost raw materials, such as industrial wastes and by-products as carbon source. An example of raw material is cheese whey, a by-product form cheese industry rich in lactose (4-5%). In this work, cheese whey was supplied to Escherichia coli strains harbouring the PHB synthesis genes from Cupriavidus necator for the production of poly(3hydroxybutyrate) (PHB). During this study, diverse reactor operating strategies were tested: feeding controlled by pH under oxygen limitation, feeding without oxygen limitation and continuous feeding. The best results were achieved in a fed-batch system with feeding controlled by pH and oxygen limitation, where 44.93% of PHB content,33.76 g/L of PHB concentration, 78.65 g/L of active biomass concentration and a volumetric productivity of 0.57 gPHB/L.h, were obtained.