Microbial Production of Bioplastics from Renewable Carbon Sources: Synthesis, Characterisation and Future Perspectives

Abstract

The transition from petrochemical plastics to lower-impact materials requires more than substitution of fossil carbon with biomass. It requires production routes that integrate renewable feedstocks, efficient biocatalysis, controlled material properties, credible end-of-life performance and economically realistic downstream processing. This critical narrative review evaluates microbial routes to bioplastics with emphasis on polyhydroxyalkanoates (PHAs), direct biosynthesis of lactate-containing polyesters, and bacterial cellulose as a structurally distinct microbial polymer relevant to bioplastic applications. Literature published principally from 2000 to 9 August 2026 was examined, while earlier foundational work was retained when necessary to explain PHA enzymology and polymerisation. The strongest evidence base concerns PHA production, for which Cupriavidus necator, Pseudomonas spp., halophilic Halomonas spp., methanotrophs, autotrophs and mixed microbial cultures offer complementary advantages. Renewable carbon sources now extend from purified sugars to lignocellulosic hydrolysates, waste oils, crude glycerol, whey-derived sugars, food-waste carboxylates, algal biomass, methane and carbon dioxide. Yet feedstock "renewability" does not by itself guarantee environmental or economic superiority: pretreatment severity, inhibitor formation, nutrient requirements, gas-transfer demand, sterilisation, polymer recovery and solvent use can dominate process burdens. Synthetic biology has broadened monomer spectra and enabled lactate-based and other non-natural polyesters, but many demonstrations remain less mature than conventional PHA fermentation. Characterisation must therefore connect monomer composition and molecular mass with crystallinity, thermal transitions, mechanical behaviour, barrier performance and biodegradation under specified environments rather than relying on generic claims of biodegradability. Across the field, scale-up is constrained by feedstock heterogeneity, oxygen and mass transfer, product recovery, reproducible polymer quality and incomplete techno-economic and life-cycle evidence. Future progress will depend on integrated strain-process-material design, standardised reporting, low-impact recovery, continuous or non-sterile production where appropriate, and application-specific end-of-life testing. Microbial bioplastics are technically versatile, but their sustainability advantage is conditional and must be demonstrated at the level of the complete production and use system.