(164ai) Metabolic Engineering of Four Host Microbes for the Production of Green Leaf Volatiles and Precursor Molecules

Green leaf volatiles (GLVs) are six carbon aldehydes, alcohols and esters that are released by plant upon physical damage, which are vital to plant defense mechanism. They also serve as plant hormones. Due to their strong grassy odor, they are important aroma compounds in flavors and fragrances. To this date, no microbial production of such compounds using glucose as the carbon source have been reported. We have successfully engineered Saccharomyces cerevisiae and Yarrowia lipolytica to produce mg/L level of trans-2-hexenal (leaf aldehyde) and cis-3-hexenol (leaf alcohol), via genetic integration of plant GLV biosynthetic pathway genes and other auxiliary genes. We have also investigated the GLV degradation pathway in Yarrowia lipolytica and identified candidate enzymes. Furthermore, we will address our current progress on producing GLVs and their precursor molecules, hexenoic acids, in Streptomyces albus and Streptomyces coelicolor by heterologous expression of type I modular polyketide synthases (PKSs). This de novo approach utilizes a rationally designed chimeric PKS that involves an efficient butyryl-CoA/ethylmalonyl-CoA loading module, a FabA-type dehydratase from Shawenella, and a hypothetical terminal reductase domain from Dictyostelium.