High Cell Density Conversion of Hydrolysed Waste Cooking Oil Fatty Acids Into Medium Chain Length Polyhydroxyalkanoate Using Pseudomonas putida KT2440

Carolina Ruiz,Shane T Kenny,Ramesh Babu P,Kevin E O’Connor,Tanja Narancic,Meg Walsh

doi:10.3390/catal9050468

Carolina Ruiz, Shane T Kenny + Show 4 more

Open Access

https://doi.org/10.3390/catal9050468

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Abstract

Waste cooking oil (WCO) is a major pollutant, primarily managed through incineration. The high cell density bioprocess developed here allows for better use of this valuable resource since it allows the conversion of WCO into biodegradable polymer polyhydroxyalkanoate (PHA). WCO was chemically hydrolysed to give rise to a mixture of fatty acids identical to the fatty acid composition of waste cooking oil. A feed strategy was developed to delay the stationary phase, and therefore achieve higher final biomass and biopolymer (PHA) productivity. In fed batch (pulse feeding) experiments Pseudomonas putida KT2440 achieved a PHA titre of 58 g/l (36.4% of CDW as PHA), a PHA volumetric productivity of 1.93 g/l/h, a cell density of 159.4 g/l, and a biomass yield of 0.76 g/g with hydrolysed waste cooking oil fatty acids (HWCOFA) as the sole substrate. This is up to 33-fold higher PHA productivity compared to previous reports using saponified palm oil. The polymer (PHA) was sticky and amorphous, most likely due to the long chain monomers acting as internal plasticisers. High cell density cultivation is essential for the majority of industrial processes, and this bioprocess represents an excellent basis for the industrial conversion of WCO into PHA.

Highlights

Petrochemical based plastics have been used in a variety of applications for more than seventy years and have replaced materials like glass and metal due to their high performance, low price, versatility, and durability [1,2]
The aim of the current study was to develop a bioprocess to achieve high cell density and high medium chain length PHA productivity using the fatty acid fraction of hydrolysed waste cooking oil as the sole carbon source and P. putida KT2440, a generally recognised as safe (GRAS) and robust organism used in many biotechnological applications [35]
To address the feeding challenge, the hydrolysed waste cooking oil fatty acids (HWCOFA) mixture was maintained at a temperature of 40 ◦ C so that it could be poured into the bioreactor

Summary

Introduction

Petrochemical based plastics have been used in a variety of applications for more than seventy years and have replaced materials like glass and metal due to their high performance, low price, versatility, and durability [1,2]. The worldwide annual production of plastics was 335 million tonnes in. The vast majority of petrochemical based plastics are not biologically degraded [3]. Plastic recovery and recycling rates are low [4], and millions of tonnes of plastics end up in landfills and in the environment [5,6,7,8]. Given the environmental damage caused by non-degradable plastics, there is an urgent need for solutions. Biodegradable plastics can be part of the plethora of solutions to address

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