Comparison of mcl-Poly(3-hydroxyalkanoates) synthesis by different Pseudomonas putida strains from crude glycerol: citrate accumulates at high titer under PHA-producing conditions

Abstract

BackgroundAchieving a sustainable society requires, among other things, the use of renewable feedstocks to replace chemicals obtained from petroleum-derived compounds. Crude glycerol synthesized inexpensively as a byproduct of biodiesel production is currently considered a waste product, which can potentially be converted into value-added compounds by bacterial fermentation. This study aimed at evaluating several characterized P. putida strains to produce medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHA) using raw glycerol as the only carbon/energy source.ResultsAmong all tested strains, P. putida KT2440 most efficiently synthesized mcl-PHA under nitrogen-limiting conditions, amassing more than 34% of its cell dry weight as PHA. Disruption of the PHA depolymerase gene (phaZ) in P. putida KT2440 enhanced the biopolymer titer up to 47% PHA (%wt/wt). The low biomass and PHA titer found in the mutant strain and the wild-type strain KT2440 seems to be triggered by the high production of the side-product citrate during the fermentation process which shows a high yield of 0.6 g/g.ConclusionsOverall, this work demonstrates the importance of choosing an appropriate microbe for the synthesis of mcl-PHA from waste materials, and a close inspection of the cell metabolism in order to identify undesired compounds that diminish the availability of precursors in the synthesis of biopolymers such as polyhydroxyalkanoates. Future metabolic engineering works should focus on reducing the production of citrate in order to modulate resource allocation in the cell’s metabolism of P. putida, and finally increase the biopolymer production.

Perspectives of Polyhydroxyalkanoate (PHAs) Biopolymer Production Using Indigenous Bacteria: Screening and Characterization

“…Increase in the PHA accumulation may be attributed to the large cell sizes 13 . Comparable pictures for visualisation of PHA particles inside the bacterial cells are shown by 47,48 . There's coating of phospholipids and proteins monolayer over these particles and also the linked proteins are concerned within the creation of granule and in the production and degeneration of PHA.…”

Recent strategies for efficient production of polyhydroxyalkanoates by micro-organisms

“…Bacteria have a different capability to synthesis PHAs (Poblete‐Castro et al . ). Taking advantage of these bacterial traits of naturally accumulates PHAs; commercialized PHAs have been produced by using fermentation engineering and enzyme engineering technology, such as PHBV is commercially marketed (Hankermeyer and Tjeerdema ).…”

“…Among the most extensively studied bacterial species producing these biopolymers are genus Pseudomonas reported to accumulate intracellular PHAs Letters in Applied Microbiology 62, 9--15 © 2015 The Society for Applied Microbiology (Gumel et al 2012). Bacteria have a different capability to synthesis PHAs (Poblete-Castro et al 2014). Taking advantage of these bacterial traits of naturally accumulates PHAs; commercialized PHAs have been produced by using fermentation engineering and enzyme engineering technology, such as PHBV is commercially marketed (Hankermeyer and Tjeerdema 1999).…”

Engineering the Osmotic State of Pseudomonas putida KT2440 for Efficient Cell Disruption and Downstream Processing of Poly(3-Hydroxyalkanoates)

“…The highly versatile metabolism of P. putida KT2440 endows the bacterium to harness a wide spectrum of substrates -waste oils, raw glycerol, lignin derivatives and further aromaticswhich allows reducing the production costs (Poblete-Castro et al, 2014;Kohlstedt et al, 2018;Borrero-De Acuña et al, 2019;Poblete-Castro et al, 2019). Additionally, downstream processing procedures also contribute to increasing the overall production expenses due to the use of lytic enzymes, mechanical cell disruptors, high pressure, or temperature for recovery of the added-value products from the intracellular space of the cell.…”