Tailor‐Made Polyhydroxyalkanoates by Reconstructing Pseudomonas Entomophila

Abstract

Microbial polyhydroxyalkanoates (PHA) containing short‐ and medium/long‐chain‐length monomers, abbreviated as SCL‐co‐MCL/LCL PHAs, generate suitable thermal and mechanical properties. However, SCL‐co‐MCL/LCL PHAs with carbon chain longer than nine are difficult to synthesize due to the low specificity of PHA synthase PhaC and the lack of either SCL‐ or MCL/LCL monomer precursor fluxes. This study succeeds in reprogramming a β‐oxidation weakened Pseudomonas entomophila containing synthesis pathways of SCL 3‐hydroxybutyryl‐CoA (3HB) from glucose and MCL/LCL 3‐hydroxyalkanoyl‐CoA from fatty acids with carbon chain lengths from 9 to 18, respectively, that are polymerized under a low specificity PhaC61‐3 to form P(3HB‐co‐MCL/LCL 3HA) copolymers. Through rational flux‐tuning approaches, the optimized recombinant P. entomophila accumulates 55 wt% poly‐3‐hydroxybutyrate in 8.4 g L−1 cell dry weight. Combined with weakened β‐oxidation, a series of novel P(3HB‐co‐MCL/LCL 3HA) copolymers with over 60 wt% PHA in 9 g L−1 cell dry weight have been synthesized for the first time. P. entomophila has become a high‐performing platform to generate tailor‐made new SCL‐co‐MCL/LCL PHAs.

A Polyhydroxyalkanoates-Based Carrier Platform of Bioactive Substances for Therapeutic Applications

“…Many studies have reported that novel-type PHA containing units of non-natural structures, such as vinyl and azido PHA, have been synthesized using metabolically engineered microbes powered by system and synthetic biology, expanding the possibility of diverse chemical modification and providing new approaches for functional BAS delivery particle fabrication for customized and precise medical treatments in the future ( Pinto et al, 2016 ; Yu et al, 2020a ; Li et al, 2021b ). Besides, the rapid developments of biotechnology have advanced the innovations of designs and fabrications of self-assembled PHA-based BAS carriers for therapeutic applications.…”

“…According to the carbon-atom number of monomers, PHA can be divided into two categories, namely short-chain length (SCL) PHA generally containing 3-5 carbon atoms (C3-C5), such as 3-hydroxybutyrate (3HB), 4-hydroxybutyrate (4HB), 3-hydroxyvalerate (3HV), 3-hydroxypropoinate (3HP), etc., and medium/long-chain length (M/LCL) PHA with over 5 carbon atoms (≥C6) ( Choi et al, 2020b ; Meng et al, 2014 ; Zhang et al, 2018b ). Specifically, MCL PHA (C6-C14) and LCL PHA (≥C15) are generally accumulated by wild-type or recombinant Pseudomonas using fatty acids as carbon source ( Meng et al, 2014 ; Nikel and de Lorenzo, 2018 ; Prieto et al, 2016 ); ( Chen and Hajnal, 2015 ; Choi et al, 2020a ; Li et al, 2021b ; Singh and Mallick, 2009 ), while Ralstonia eutropha, Halomonas bluephagenesis TD01 and Escherichia coli have been developed to be promising workhorses for SCL PHA production with decades of research fundation and several industrial-scale successes. Herein, The major biosynthetic pathways of both SCL- and M/LCL-PHA by recombinant microbes from different structurally related and/or unrelated carbon sources (glucose, glycerol, fatty acids, etc.)…”

“…Generally, MCL-PHA are crystalline elastomers exhibiting entirely different mechanical properties compared to SCL-PHA ( Grigore et al, 2019 ). In previous studies, Li et al has succeeded in producing tailor-made SCL- co -MCL PHA with complementary advantages of mechanics ( Li et al, 2019 ; Li et al, 2021b ). As shown in Table 2 , the introduction of MCL-3HA units in PHB, forming P (3HB- co -MCL 3HA) copolymer, significantly increases the elongation at break of obtained copolymers, turning the brittle PHB into elastic PHA with ignorable variances in thermal properties (Li M. et al, 2021).…”

Post-Transcriptional Control in the Regulation of Polyhydroxyalkanoates Synthesis

“…It is important to continue investing the biotechnological domestication of microorganisms using synthetic biology and metabolic engineering to implement the portfolio of PHAs and improve strategies to lower the costs in industrial production [12,168]. In this review, we have indicated many examples of how post-transcriptional control can be an instrumental tool for the regulation of polyhydroxyalkanoates synthesis.…”

Optimization of a Two-Species Microbial Consortium for Improved Mcl-PHA Production From Glucose–Xylose Mixtures

“…There are many ways to classify PHA. According to the number of carbon atoms in the constituent monomers, PHA can be divided into short-chain-length polyhydroxyalkanoate (scl-PHA) composed of monomers with three to five carbon atoms, medium-chain-length polyhydroxyalkanoate (mcl-PHA) composed of monomers with 6–14 carbon atoms, and long-chain-length polyhydroxyalkanoate (lcl-PHA) composed of monomers with more than 15 carbon atoms ( Singh and Mallick, 2009 ; Li et al, 2021 ). PHAs can also be classified according to the types of monomers, with homopolymers contain only one monomer, and copolymers containing more than one monomer.…”