Production of Gamma-hydroxyvaleric acid (GHV) from levullinic acid in engineered Pseudomonas putida

Abstract

Gamma-hydroxyvaleric acid (GHV) is one of the industrial important hydroxy acids used to produce various commodity chemicals and biofuels and can be polymerized into biodegradable polyesters with interesting physical properties. GHV production by the conventional methods such as chemical synthesis or depolymerisation of polymers by chemical or biological means have a number of disadvantages including unwanted byproducts, low-yield, labourious etc. Therefore, it is essential to develop an eco-friendly production method from renewable resources to meet out the global requirement of this monomer and to curb the environment related issues as well. In the present study, we employed a Pseudomonas putida strain to produce GHV from levulllinic acid (LA), a potent renewable substrate obtained by treating lignocellulosic wastes. We have engineered P. putida strain to block the substrate degradation by its native degradation pathway and thus directed it to solely produce the product. An expression system induced by the substrate was developed to produce GHV. The resultant strain yielded at-least a four-fold increased GHV (8 g/L) than the wild type (2 g/L) from 20 g/L of LA in 48h of cultivation and also a higher substrate conversion efficiency (98% on molar basis) over the control strain (15%). In addition, when using glycerol instead of glucose in the production medium, the resultant strain produced 15 g/L of GHV from 20 g/L of LA in 48h of cultivation with a 98% substrate conversion efficiency on molar basis. The present system could serve as an efficient platform strain to produce GHV from the renewable substrate, LA.