(28c) Turing Waste Cooking Oils into High-Value Products By Metabolic Engineering in Yeast and Bacteria

Ya-Hue Valerie Soong, Na Liu, Dongming Xie*

Massachusetts Biomanufacturing Center, Department of Chemical Engineering, University of Massachusetts Lowell, Lowell, MA, United States.

Abstract:

Substantial quantities of waste cooking oils (WCO) generated during the food application is becoming a worldwide concern due to improper disposal to the environment. There is an urgent need of turning WCO into products with extremely high economical values. Previously, an enormous amount of research effort has been focused on production of biodiesel from WCO for the purpose of converting the waste into energy. However, the sustainability and profit margin of biodiesel from WCO have been limited due to the unpredictable biofuel market and some remaining technical challenges. For example, one of the main challenge of using WCO as feedstock in biodiesel production is the presence of high free fatty acid and water contents that causes the significant adverse effects on the transesterification process. From the perspective of more cost-effective manufacturing, it is conceivable that the WCO could be used for microbial energy substrate without impurities removal process. Turning the waste into higher-value products provides an opportunity for more profitable biomanufacturing with very minimal environmental footprint. In our group at UML biomanufacturing center, we have been developing a new biomanufacturing platform to make a series of high-value products from waste cooking oils.

In this presentation, we will focus on bioconversion of WCO into wax esters, which are widely used as high-performance lubricants, cosmetics and many other industrial applications. Despite the fact that the wax esters are founded in nature universally, the abundance source of wax esters are still low due to the difficulty in accumulating considerable amount of intracellular wax esters. We have metabolically engineered and compared two microbial hosts, the yeast Yarrowia lipolytica ATCC20362 and bacterial Escherichia coli BL21(DE3) for production of wax esters from WCO. We have successfully demonstrated the heterologous biosynthesis of wax esters in both microorganisms by introducing the fatty acyl coenzyme A reductase (FAR) from the Marinobacter hydrocarbonoclasticus strain VT8 and wax ester synthase/acyl-coenzyme A: diacylglycerol acyltransferase (WS/DGAT) from the Acinetobacter calcoaceticus strain ADP1. High bioconversion of WCO to wax eaters was achieved in engineered Y. lipolytica strain under both shake-flask and 1-L bioreactor conditions. For the engineered E. coli, the wax esters were obtained by feeding the glucose and oleic acids as carbon sources in ZYM-based medium. Further expression of lipase and the fatty acid transporter system leads to the product of wax esters directly from WCO. There is a trade-off between the benefits of these two hosts. The oleaginous Y. lipolytica is capable of expressing the intra/extracellular lipases and displaying the high tolerance on lipid accumulation whereas bacterial system exhibits rapid cell growth and higher volumetric productivity. Fermentation optimization for both yeast and E coli and the economical evaluation will also be discussed.

Keywords: Metabolic Engineering, Waste Cooking Oils, Wax Esters, Yarrowia lipolytica, E. coli.