Engineering Pseudomonas putida for efficient production of 4-hydroxyvaleric acid from levullinic acid

Abstract

Hydroxy acids are industrially important chemicals as they can be easily modified into various commodity chemicals because of their two functional moieties, carboxyl and hydroxyl group. 4-hydroxyvaleric acid (4HV) is one among them and used to produce various chemicals and biofuels and can be polymerized into biodegradable polyesters with interesting physical properties. 4HV 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, in the present study, we engineered a Pseudomonas putida strain to produce this valuable monomer from levullinic acid, a potent renewable substrate obtained by treating lignocellulosic wastes, to meet out the global requirement and to curb the environment related issues as well. The endogenous substrate/intermediates-degradation pathway-blocked strain yielded at-least a four-fold increased 4HV (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 optimized level of glycerol instead of glucose in the production medium, the resultant strain produced 25 g/L of 4HV from 30 g/L of LA in 48h of cultivation with a 95% substrate conversion efficiency on molar basis. The present system could serve as an efficient platform strain to produce 4HV from the renewable substrate, LA.