Fermentative Polyhydroxybutyrate Production from a Novel Feedstock Derived from Bakery Waste

In this study, Halomonas boliviensis was cultivated on bakery waste hydrolysate and seawater in batch and fed-batch cultures for polyhydroxybutyrate (PHB) production. Results demonstrated that bakery waste hydrolysate and seawater could be efficiently utilized by Halomonas boliviensis while PHB contents between 10 and 30% (w/w) were obtained. Furthermore, three methods for bakery waste hydrolysis were investigated for feedstock preparation. These include: (1) use of crude enzyme extracts from Aspergillus awamori , (2) Aspergillus awamori solid mashes, and (3) commercial glucoamylase. In the first method, the resultant free amino nitrogen (FAN) concentration in hydrolysates was 150 and 250 mg L −1 after 20 hours at enzyme-to-solid ratios of 6.9 and 13.1 U g −1 , respectively. In both cases, the final glucose concentration was around 130–150 g L −1 . In the second method, the resultant FAN and glucose concentrations were 250 mg L −1 and 150 g L −1 , respectively. In the third method, highest glucose and lowest FAN concentrations of 170–200 g L −1 and 100 mg L −1 , respectively, were obtained in hydrolysates after only 5 hours. The present work has generated promising information contributing to the sustainable production of bioplastic using bakery waste hydrolysate.