Paracoccus sp. Strain LL1 as a Single Cell Factory for the Conversion of Waste Cooking Oil to Polyhydroxyalkanoates and Carotenoids

Background and objective: Polyhydroxyalkanoates have drawn significant attention as alternative to petroleum-based plastics; however, their industrial production is still hindered by the costly feed materials. Co-generation of other high-value products in addition to polyhydroxyalkanoate by the same microbial strains can be helpful in alleviating overall production cost up to 50%. This study for the first time demonstrates that polyhydroxyalkanoate and astaxanthin-rich carotenoids can be co-produced by Paracoccus sp. LL1 using waste cooking oil as substrate. Material and methods: The halophilic strain of Paracoccus sp. LL1 was grown under batch fermentation using mineral media supplemented with 1% (v v^-1) waste cooking oil. Different surfactants were used to improve substrate utilization. Polyhydroxyalkanoate obtained after the fermentation was characterized by fluorescent microscopy, gas chromatography, and Fourier Transform Infra-Red spectroscopy. Results and conclusion: Oil as a substrate, led to 1.0 g l^-1 poly (3-hydroxybutyrate-co-3- hydroxyvalerate) with concomitant production of 0.89 mg l^-1 of carotenoids after 96 h. An enhancement of 2.7-folds in total cell dry mass was achieved when 0.1% (v v^-1) Tween-80 was used as surfactant for ease in oil metabolism. Paracoccus sp. LL1 has the potential to serve as a single cell factory for bioconversion of cheap substrates into high value products.