Plastic pollution is a pressing environmental issue, with global plastic production exceeding 400 million tonnes annually, a significant portion of which accumulates in landfills and marine ecosystems [1]. To address this, biobased and biodegradable polymers have gained attention as sustainable alternatives to petrochemical-derived plastics. Among them, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a member of the polyhydroxyalkanoates (PHA) family, has demonstrated significant potential due to its biobased origin, biodegradability, and thermoplastic properties [2], [3]. Despite these advantages, bioplastics currently account for only a small share of global plastic production; however, their production is expected to grow significantly – from around 2.47 million tonnes in 2024 to approximately 5.73 million tonnes by 2029 [1]. To address environmental concerns associated with plastic waste and promote circular economies, it is essential to enhance the production and use of bioplastics such as PHBV. Strategies to enhance bioplastics adoption include advancing material properties, enacting supportive policies, investing in recycling infrastructure, and promoting market competitiveness [4].
PHBV is synthesized by bacterial fermentation of renewable carbon sources, such as sugars and fatty acids, and has found applications in packaging, biomedical materials, and other sustainable products [5], [6]. However, the large-scale commercialization of PHBV is challenged by the use of open culture systems for bacterial production, which complicates the extraction process and impacts polymer purity, yield, and the overall sustainability of the production process [7]. Conventional extraction methods – such as the use of organic solvents, enzymatic treatments, or mechanical disruption – are widely employed for polymer recovery, but they offer limited insight into the real-time molecular events that occur during the extraction process. A deeper understanding of these molecular mechanisms will improve the efficiency, selectivity, and environmentally friendliness of extraction strategies, ultimately improving further the viability of PHBV production at industrial scale [7].
Conventional analytical tools for assessing and optimizing polymer extraction are limited by their inability to capture real-time, molecular-level interactions, hindering mechanistic understanding. Conventional Nuclear Magnetic Resonance (NMR) spectroscopy, though widely used for polymer characterization, requires homogeneous samples and uniform magnetic fields, making it unsuitable for heterogeneous systems like biomass-polymer mixtures [8]. This often necessitates extensive sample preparation, disrupting native structural and dynamic properties. Other common techniques – such as chromatography, microscopy, and Magnetic Resonance Imaging (MRI) – also have limitations. Chromatography offers compositional and purity analysis but faces challenges with polymer solubility, method complexity, and sample loss [9]. Microscopy provides morphological insights but lacks chemical specificity and is limited to post-process analysis [10]. MRI, while non-invasive and spatially resolved, lacks the chemical resolution needed to reveal molecular-level extraction mechanisms [11].
To overcome these limitations, this study presents a novel approach to studying the extraction of PHBV from wastewater-derived biomass in real time, utilizing slice-selective NMR spectroscopy for in situ observation and mechanistic analysis. Slice-selective NMR merges the chemical specificity of traditional NMR spectroscopy with the spatial resolution characteristic of MRI, offering precise, spatially resolved chemical information directly within heterogeneous systems without requiring sample homogenization. This technique uniquely captures dynamic interactions, molecular transformations, and solvent diffusion processes occurring during extraction, enabling real-time mechanistic insights [12], [13]. For this study, PHBV extraction was performed using model solvents within a temperature range of 25 °C to 120 °C, monitored over a maximum period of 24 hours using a 600 MHz NMR spectrometer. These studies provided insights into kinetics, thermodynamics and formation of side products in the process, which are essential for optimizing solvent selection, minimizing polymer degradation, and improving overall extraction efficiency.
Moreover, the versatility and robustness of slice-selective NMR spectroscopy suggest broader applicability in other biodegradable and bio-based polymer extraction studies. In conclusion, integrating slice-selective NMR spectroscopy significantly advances biopolymer extraction characterization methodologies. By delivering superior chemical specificity, spatial resolution, and temporal insights compared to traditional analytical techniques, this method substantially enhances the mechanistic understanding necessary for optimizing sustainable polymer extraction processes. In this study, preliminary kinetic insights were obtained, along with insights into the possible impurities present, further demonstrating the method’s capacity to reveal subtle yet critical aspects of the extraction mechanism. The adoption of such advanced analytical techniques in polymer research has the potential to drive innovation in sustainable materials processing, ultimately contributing to the broader goal of reducing reliance on petrochemical-based plastics and promoting circular economy principles.