(107b) Biologically Upgrading Enzymatically Free Hydrolysate Derived From Lignocellulosic Biomass

Chemicals can be produce in a renewable manner from engineered microorganisms from simple sugar feedstocks; however, for these processes to ever be economically viable the feedstocks must be attainable at inexpensive cost.  Currently, sugar feedstocks are obtained through the degradation of renewable lignocellulosic biomass through pretreatment and enzymatic hydrolysis steps, but the costs and inefficiencies associated with the pretreatments and enzymes necessary for deconstruction present hurdles to widespread application.  The opportunity to bypass enzymatic involvement and yet still microbially produce chemicals from biomass would expand the potential of this renewable method. 

Recent work on biomass deconstruction has identified enzymatically free routes that bypass the necessity of enzymatic hydrolysis in the production of potential substitute feedstocks.  One route has been discovered that is capable of generating the biomass byproduct levulinic acid (LA) without the use of enzymes. Recently, the Dumesic Lab of University of Wisconsin has developed a novel technique that utilizes the solvent γ-valerolactone (GVL) to deconstruct biomass into the simple sugars glucose and xylose.  This talk will discuss the efforts made towards biologically upgrading these enzymatically free feedstocks through identifying an LA metabolic route and evaluating the toxicity of these new feedstocks.

For LA to be considered as a substitute feedstock, it must have the capability to support growth as the sole carbon source.  It has been demonstrated that some organisms can grow on LA, such as Pseudomonas putida; however, the metabolic pathway remains unknown.  In order to elucidate the potential genes involved, a library of P. putida mutants was screened and the disrupted genes identified.  Current work is involved in isolating the genes that are necessary and sufficient for growth and determining their function.  The goal is to use these genes to engineer alternative organisms for LA growth capability.