Journal Article

Bacterial species-structure-property relationships of polyhydroxyalkanoate biopolymers produced on simple sugars for thin film applications

Banaszak Holl, Mark M., van ‘t Hag, Leonie, Attenborough, Edward, Nosrati, Reza, Yazdan Parast, Farin

2025

Overview

Background The bacterial production of polyhydroxyalkanoates (PHAs), a class of non-toxic, biodegradable, and bio-based polymers, has gained increasing attention as a sustainable alternative to petrochemical plastics. Among PHA producers, Cupriavidus necator H16 and Pseudomonas putida KT2440 are used for their ability to synthesise short- and medium-chain-length PHAs, respectively. While PHAs have been produced from simple hexoses like glucose and fructose, there remains a lack of systematic and integrated analysis linking carbon source, strain selection, monomer composition, and polymer crystallinity to blend behavior in ultrathin films. Results PHB and mcl-PHA production using Cupriavidus necator H16 and Pseudomonas putida KT2440 on glucose and fructose were compared herein. C. necator accumulated PHB up to 60 wt% on fructose and 45 wt% on glucose, with high molecular weight (0.7–1.3 MDa), while P. putida produced mcl-PHA up to 22 wt% on fructose and 18 wt% on glucose, with lower molecular weight (46–47 kDa) and a C6 – C12 monomer profile. Notably, C. necator exhibited extreme cell elongation (up to 30 μm) during PHB accumulation on fructose. Extracted polymers were systematically solvent-blended at defined ratios (100:0, 80:20, 60:40, 40:60, and 20:80 PHB:mcl-PHA) and cast into ultrathin films (~ 20 μm) with varying composition. Crystallinity was modelled using a Gaussian fitting approach on FTIR spectra via custom MATLAB code, enabling localised phase analysis and offering a rapid alternative to DSC for thin film crystallinity estimation. While film blends exhibited tunable crystallinity and multiple melting transitions, elongation at break was consistent across compositions, with increases observed at higher mcl-PHA content. Conclusions This study provides a systematic comparison of PHAs from C. necator H16 and P. putida KT2440 grown on common hexoses, with full characterisation of monomer composition, molecular weight, and thermal behaviour to guide thin film bioplastic design. Blending PHB and mcl-PHA in ultrathin films revealed reduced melting points and crystallinity, likely due to reduced crystal size from film thickness constraints. This work offers a comparative reference for microbial PHA production and presents a strategy to design bioplastics with tunable properties for temperature-responsive packaging and drug delivery applications. Graphical abstract

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Applied Microbiology / Bacteria / Biodegradation / Bioplastics / Biopolymers / Biopolymers - biosynthesis / Biopolymers - chemistry / Bioprocessing / Biotechnology / Carbohydrates / Carbon / Carbon sources / Chemical properties / Chemistry / Chemistry and Materials Science / Composition / Crystallinity / Cupriavidus necator / Cupriavidus necator - metabolism / Cupriavidus necator H16 / Dielectric films / Drug delivery / Elongation / Enzymology / Film thickness / Fructose / Fructose - metabolism / Genetic Engineering / Glucose / Glucose - metabolism / Glycerol / Gram-negative bacteria / Hexoses / Investigations / Materials / Materials research / Melting point / Melting points / Metabolism / Microbial Genetics and Genomics / Microbiological synthesis / Microbiology / Microorganisms / Molecular Weight / Monomers / Petrochemicals / Physiological aspects / Plastics / Polyhydroxyalkanoate / Polyhydroxyalkanoates / Polyhydroxyalkanoates - biosynthesis / Polyhydroxyalkanoates - chemistry / Polyhydroxyalkanoates - metabolism / Polyhydroxyalkanoic acid / Polyhydroxybutyrate / Polymer blends / Polymers / Production processes / Pseudomonas putida / Pseudomonas putida - metabolism / Pseudomonas putida KT2440 / Structure-Activity Relationship / Thermodynamic properties / Thin films / Trace elements