Coexpression of xylose isomerase and xylulokinase as strategy to increase xylose conversion rate to poly-3-hydroxybutyrate in Burkholderia sacchari

Abstract

Polyhydroxyalkanoates (PHAs) are potential substitutes for petrochemical plastics, with the advantage of being biodegradable and biocompatible. There are several types of PHA, the most studied being poly-3-hydroxybutyrate (P3HB), differing from each other by the monomer composition. One of the limitations of the mass production of PHAs is the price of raw material. The utilization of xylose (major component of hemicelluloses) from the lignocellulosic waste in ethanol production is considered an alternative path to lower PHAs production cost. In this scenario, Burkholderia sacchari emerges as a potential tool for the production of PHA due to the fact that it is capable of converting xylose into P3HB with high efficiency. Previous studies have shown that higher xylose consumption and P3HB production is possible through the increased expression of genes related to xylose catabolism. In this project, it is proposed an increased expression of the xylulokinase and xylose isomerase simultaneously, both enzymes involved in the isomerase pathway of the xylose catabolism. For this purpose, using molecular biology tools, xylB (xylulokinase) will be amplified from the genome of Burkholderia saccharia and then inserted in the plasmid vector pBBR2-MCS1 that has the Burkholderia xenovorans xylA gene (xylose isomerase), which will be electroporated in B. sacchari. After the presence of the constructed vector in B. sacchari is confirmed, the obtained strain will be evaluated by growth, xylose consumption and P3HB accumulation through experiments in thermostatted shaker.