Effects of media sterilization and variable carbon-loading on medium-chain length PHA (bio-plastics) production by Pseudomonasputida LS46 using biodiesel derived glycerol

Abstract

<abstract> <bold>Abstract. </bold>In recent years, the market for bio-products has been growing rapidly. This is largely attributed to widespread concerns over the environment. Numerous bio-products have been developed and discussed throughout literature, one of which includes Polyhydroxyalkanoates (PHAs) commonly known as bio-plastics. PHAs are considered a promising alternative to the petrochemical derived plastics in wide use today. Sustainable fermentation strategies are being developed which incorporate industrial waste streams as carbon source feedstock for eventual commercial-scale manufacturing of such products. In this study, a novel mcl-PHA producing strain of the gram-negative bacterium Pseudomonas putida (P. putida) LS46, was grown on minimal media containing 1g/L of nitrogen in flask-batch with varying concentrations of waste glycerol (WG) obtained from a biodiesel production plant at 1%, 3%, 6%, 9%, and 12% v/v. Sterilized vs. non-sterilized media conditions were studied to evaluate the need for media pretreatment. One batch of flasks was subjected to autoclaving, while another batch remained unautoclaved. Conditions were monitored over a 72 hour period to investigate effects of media sterilization and carbon loading on cell biomass production and mcl-PHA accumulation. Overall, highest mcl-PHA accumulation occurred in the sterilized media conditions containing 1% WG at ~15% cdw of the 3.94g/L cell biomass achieved. In contrast, despite the 12% WG non-sterilized media conditions exhibiting highest cell biomass production at 10.18g/L, a significantly lower amount of mcl-PHA accumulation was detected at 0.36% cdw. Overall, sterilized media conditions containing 1% WG proved ideal for mcl-PHA accumulation in this study.