Comparison of several methods for the separation of poly(3-hydroxybutyrate) from Cupriavidus necator H16 cultures

Biopolymers, such as polyhydroxyalkanoates (PHA), are an environmentally friendly alternative to plastics derived from fossil fuels. However, producing PHA in a cost-effective way requires the development of highly efficient separation and purification treatments. In this study, one acid treatment (sulphuric acid combined with a subsequent bleaching step) and three alkaline treatments (sodium hypochlorite, sodium hydroxide and a combination of the latter with an halogenated solvent) were evaluated for recovering poly(3-hydroxybutyrate) (PHB), a type of PHA, from Cupriavidus necator H16 cells with high biopolymer content (65%). Purity, percent of recovery and the properties of the PHB obtained after each treatment, together with the costs and environmental impacts associated with each treatment, were determined and compared. The lowest recovery costs were obtained with the sodium hydroxide and sulphuric acid treatments (1.02 and 1.11 € kg−1, respectively). Estimated CO2 emissions of these two treatments were 18% of those based on the use of sodium hypochlorite. However, the highest purity (98%) and lowest polymer degradation were achieved with the acid treatment. Consequently, the acid treatment was selected as the most effective choice for PHA recovery.