Aug 2026· Biotechnology Advances· pp.
109019
· 0 citations· 75 references
Medicine
TL;DR
This review consolidates current progress in plastic deconstruction, substrate conditioning, microbial metabolism, fermentation control, polymer recovery, and techno-economic and life-cycle considerations and identifies priorities for scalable and environmentally sustainable PHA production from plastic-derived substrates.
Abstract
Polyhydroxyalkanoate (PHA) production from plastic-derived substrates offers a promising route to mitigate plastic pollution while reducing dependence on conventional PHA feedstocks. Plastic waste represents an abundant carbon source for microbial fermentation, but efficient conversion remains limited by incomplete deconstruction, inhibitory intermediates, low carbon recovery, and challenges in process integration. Plastic-derived streams contain diverse compounds, including fatty acids, hydrocarbons, fatty alcohols, aldehydes, esters, and aromatic compounds generated during depolymerization. These intermediates can be metabolized by selected microorganisms, particularly Pseudomonas species with versatile fatty-acid and hydrocarbon pathways, as well as Cupriavidus necator and mixed microbial cultures. Unlike reviews that address plastic upcycling or PHA biosynthesis separately, this review focuses on the deconstruction-fermentation interface that governs plastic-to-PHA conversion. It consolidates current progress in plastic deconstruction, substrate conditioning, microbial metabolism, fermentation control, polymer recovery, and techno-economic and life-cycle considerations. By emphasizing substrate composition, biological compatibility, plastic‑carbon recovery, and final polymer quality, the review identifies priorities for scalable and environmentally sustainable PHA production from plastic-derived substrates.
Polyhydroxyalkanoates (PHAs) are biodegradable microbial polyesters with strong potential as sustainable alternatives to petroleum-derived plastics. Oil-derived substrates, including free fatty acids, triglycerides, and waste cooking oil (WCO), are attractive feedstocks due to their high degree of reduction and favorable theoretical yields; however, their utilization remains limited by challenges in substrate accessibility, compositional variability, and process scalability. This work investigates the influence of substrate type and lipid composition on PHA production using Pseudomonas putida as a model medium-chain-length PHA (mcl- PHA) producer. A systematic experimental approach assessed the effects of various carbon sources--free fatty acids, triglycerides, and complex oils--on biomass formation and PHA accumulation. Co-substrate supplementation strategies were also examined to assess their impact on fermentation performance. The results show that substrate type strongly affects both growth and PHA accumulation. Free fatty acids supported higher biomass formation than triglycerides, indicating that hydrolysis and substrate accessibility are key limiting factors. Among the substrates tested, oleic acid yielded the highest biomass (5.75 g/L), while palmitic acid resulted in the highest intracellular PHA content (51.6 wt percent), reflecting more efficient carbon allocation toward storage. In contrast, linoleic acid exhibited reduced performance, suggesting metabolic constraints associated with increased unsaturation. Complex substrates such as WCO and hydrolyzed WCO (HWCO) provided balanced performance, supporting both growth and polymer accumulation. Scale-up studies demonstrated that oxygen transfer, substrate delivery, and inoculum strategy are critical parameters in oil-based fermentation systems. In a 2 L bioreactor, the optimized process achieved a maximum PHA titer of 52.40 g/L, confirming the feasibility of scaling oil-based PHA production under controlled conditions. A twostage fermentation strategy further improved performance by separating biomass growth from PHA accumulation. Overall, this work demonstrates that substrate type and composition are key determinants of PHA production from oil-derived feedstocks. The findings provide practical insights for the development and scale-up of sustainable PHA bioprocesses using low-cost, waste-derived substrates.
Global plastic production is expected to continue rising in the next few decades, with packaging accounting for roughly one quarter of the total volume of plastic and intensifying interest in biodegradable alternatives such as polylactic acid (PLA). One approach towards bioplastic production is lactic acid fermentation. Lactic acid (LA) can be produced from waste and by-products, such as food and agricultural waste, and then polymerised into PLA. This review provides an overview of LA production from waste-derived feedstocks, covering substrate composition, pretreatment and hydrolysis strategies, fermentation modes, and downstream operations, and highlights key performance indicators (yield, final LA concentration, and volumetric productivity). This review examines technological bottlenecks associated with waste heterogeneity, mixed sugar utilisation, inhibitor formation, pH and temperature control, contamination risks, high cost, and complexity of LA recovery and purification. Recent advances in pre-treatment, robust or engineered microbial strains, mixed microbial cultures, process integration, and intensified downstream schemes are also discussed to increase productivity and purity while reducing energy and chemical inputs. Finally, techno-economic assessment studies on waste-based PLA are synthesised, showing that both economic and environmental performance depend on feedstock logistics, process configuration, and end-of-life options for PLA products.
Mariana C. Pedrosa, Sandrina A. Heleno, Manuela Pintado et al.· Sustainability· 0 citations
Polyhydroxyalkanoates (PHAs) are a promising class of bio-based, biodegradable polymers that offer a sustainable alternative to conventional fossil-based plastics. However, their commercialization is hindered by high production costs, primarily due to expensive feedstock and complex downstream processing. While valorizing organic waste is a clear path to economic viability, recent research has shown that the two primary feedstocks, food waste (FW) and lipid-rich waste (LRW), demand fundamentally divergent bioprocessing strategies rooted in their distinct biochemical composition and microbial utilization pathways. This review provides a critical, mechanism-based comparative analysis of these two waste-derived PHA platforms: the multi-stage FW-to-volatile fatty acids (VFA) and sugar platform, which is limited by costly pretreatment and mixed culture challenges, and the LRW-to-PHA platform, which offers a high-yield pathway constrained by mass transfer and the need for sterile fermentation. This review further examines advances in microbial metabolism and bioprocess design, highlighting how strain selection and fermentation strategies align with feedstock-specific challenges. It also evaluates modern downstream extraction and purification methods for their impact on polymer quality, cost, and scalability, demonstrating the potential of waste-derived PHAs for applications in packaging, biomedical devices, and agriculture. Finally, the review proposes an evidence-based, application-driven decision-support framework to guide platform selection based on feedstock composition and target polymer specifications.
Lijun Luo, P. Dessì, R. Tyagi et al.· Bioresource Technology· 0 citations
Plastic waste presents a persistent environmental burden, yet its constituent polymers represent structurally valuable chemical feedstocks. Mechanical recycling remains limited due to polymer degradation, additive contamination, and material downcycling, underscoring the need for alternative strategies. Chemical upcycling offers pathways to convert post-consumer plastics into higher-value monomers, functional chemicals, and bioactive or pharmaceutical precursors by exploiting inherent structural motifs such as aromatic rings, ester linkages, and heteroatom-containing backbones. Approaches such as catalytic depolymerization, molecular functionalization, microbial and enzymatic transformation, and scaffold repurposing enable the recovery of polymer-derived building blocks with improved functional value. Case studies illustrating the conversion of discarded plastics into advanced materials and biologically relevant small molecules demonstrate the potential of these approaches to stimulate innovation and expand sustainable chemical practices. Collectively, such developments align with green chemistry principles, support emerging circular chemical economies, and contribute to global sustainability priorities reflected in the United Nations Sustainable Development Goals. This review aims to outline the guiding principles of chemical upcycling and highlight the challenges in chemical design, encouraging the modern chemistry community to tap into the hidden potential of waste plastics.
Biomass–plastic co-pyrolysis has emerged as a promising thermochemical route for the valorization of mixed biomass and plastic waste streams, addressing growing challenges in waste management and resource efficiency. This review summarizes current knowledge on feedstock interactions, reactor technologies, operating conditions, and resulting product distributions. The literature indicates that co-processing biomass with plastics can enhance process performance compared to single-feedstock pyrolysis. Improvements are mainly observed in liquid product quality, increased energy content of gaseous fractions, and modified char properties, although outcomes strongly depend on feedstock composition and process conditions. Beyond technical aspects, the review highlights the relevance of co-pyrolysis within circular economy systems. Oil can be considered a secondary feedstock for the refining and chemical industries, process gas can support internal energy integration, and char may be utilized in material or environmental applications, contributing to partial closure of carbon and resource loops. Despite these advantages, the transition from laboratory-scale studies to large-scale implementation remains the major challenge for biomass–plastic co-pyrolysis. This limitation is associated with feedstock heterogeneity, contamination issues, scale-up difficulties, regulatory uncertainty, and the need for downstream upgrading of products. Overall, biomass–plastic co-pyrolysis represents a promising pathway toward circular waste valorization, but its practical relevance depends on successful system-level integration rather than laboratory-scale performance alone.
Max Lewandowski, Krzysztof Pikoń· Applied Sciences· 0 citations
The global plastic pollution crisis demands a fundamental re-evaluation of materials systems beyond incremental improvements to fossil fuel-based polymers. Bioplastics, polymers derived from renewable biological feedstocks, biodegradable under defined conditions, or both, offer a chemically diverse and rapidly evolving platform for transitioning toward circular materials economies in which the value of carbon, energy, and material is retained across multiple use cycles. This review provides a comprehensive and critically organized account of the bioplastics field, spanning three generations of feedstock development from food crops through lignocellulosic residues to algae and waste streams; primary production pathways including microbial fermentation, ring-opening polymerization, and biosynthesis; forming processes from extrusion and injection molding to additive manufacturing; and the mechanical, thermal, and barrier properties that determine application fitness. Particular emphasis is placed on life cycle assessment, which reveals that bioplastics’ climate benefits are conditional on feedstock choice, land-use management, energy source at manufacturing, and end-of-life pathway, and that burden-shifting from greenhouse gas emissions to land use, water consumption, and eutrophication is a systematic risk requiring integrated LCA evaluation rather than single-metric optimization. The review further examines end-of-life recycling, composting, and biodegradation pathways; market applications across packaging, agriculture, automotive, biomedical, and electronics sectors; and the growing role of artificial intelligence and machine learning in accelerating materials design, process optimization, and lifecycle data management. Critical barriers to scale, such as cost premiums of 20–75% over conventional plastics, inadequate composting infrastructure, recycling stream contamination, regulatory fragmentation, and consumer labeling confusion, are systematically analyzed alongside mitigation strategies. The review concludes with a forward-looking discussion of emerging feedstocks, smart and functional bioplastics, and the policy and infrastructure investments required to translate the environmental promise of bio-based polymers into realized circular economy impact.
