MtgA Deletion-Triggered Cell Enlargement of Escherichia coli for Enhanced Intracellular Polyester Accumulation

Abstract

Bacterial polyester polyhydroxyalkanoates (PHAs) have been produced in engineered Escherichia coli, which turned into an efficient and versatile platform by applying metabolic and enzyme engineering approaches. The present study aimed at drawing out the latent potential of this organism using genome-wide mutagenesis. To meet this goal, a transposon-based mutagenesis was carried out on E. coli, which was transformed to produce poly(lactate-co-3-hydroxybutyrate) from glucose. A high-throughput screening of polymer-accumulating cells on Nile red-containing plates isolated one mutant that produced 1.8-fold higher quantity of polymer without severe disadvantages in the cell growth and monomer composition of the polymer. The transposon was inserted into the locus within the gene encoding MtgA that takes part, as a non-lethal component, in the formation of the peptidoglycan backbone. Accordingly, the mtgA-deleted strain E. coli JW3175, which was a derivate of superior PHA-producing strain BW25113, was examined for polymer production, and exhibited an enhanced accumulation of the polymer (7.0 g/l) compared to the control (5.2 g/l). Interestingly, an enlargement in cell width associated with polymer accumulation was observed in this strain, resulting in a 1.6-fold greater polymer accumulation per cell compared to the control. This result suggests that the increase in volumetric capacity for accumulating intracellular material contributed to the enhanced polymer production. The mtgA deletion should be combined with conventional engineering approaches, and thus, is a promising strategy for improved production of intracellularly accumulated biopolymers.

Enhanced production of poly(3-hydroxybutyrate) in recombinant Escherichia coli and EDTA–microwave-assisted cell lysis for polymer recovery

“…For an industrial production process, the recombinant strain used should be capable of accumulating very high polymer content in their cells than the normal laboratory strains. Genetically engineered E. coli , with some deletions such as mtgA and mreB were observed to be improving PHB production via enhanced inclusion body accumulation and cell enlargement (Jiang et al 2015 ; Kadoya et al 2015 ). Integration of amylase gene into recombinant E. coli is a strategy to make use of starch as the sole carbon source for PHB production (Bhatia et al 2015 ).…”

Microbial Polyhydroxyalkanoates and Nonnatural Polyesters

“…Deletion of mtgA increased production of poly(3HB-co-LA) by enlarging the E. coli cells. [170] The mtgA deleted strain showed increased cell size (1.4-fold) only when cells produced polymers. [170] These results suggest that cell morphology engineering can be employed for enhanced PHA production in several different ways.…”

Microbial Production of Biodegradable Lactate-Based Polymers and Oligomeric Building Blocks From Renewable and Waste Resources

“…From more than 10,000 mutants generated, a mutant (Δ mtgA ) was generated that produced significantly higher (5.1 g/L) P(LA- co -3HB) than the recombinant parent strain (2.9 g/L). The Δ mtgA strain was found to be enlarged in size during P(LA- co -3HB) production, and this mutation in E. coli BW25113 (JW3175) was evaluated for P(LA- co -3HB) production ( Kadoya et al, 2015c ). The Δ mtgA mutation was found to be effective in P(LA- co -3HB) accumulation (7.0 g/L) as compared with its parental strain, E. coli BW25113 (5.2 g/L), without significant alteration of the LA/3HB ratio.…”