Scalable Step-by-Step Approach of Sustainable Bioplastic Production from Food Waste

The global microplastic crisis, coupled with the growing challenges of food waste disposal, necessitates innovative solutions to address these environmental issues together. Polyhydroxyalkanoates (PHAs) are unique bioplastics that are fully biodegradable in all environments, including marine ecosystems, offering a sustainable alternative to petroleum-based plastics. At the same time, utilizing food waste as a feedstock for PHA production provides an effective strategy for mitigating the challenges of food waste disposal while producing high-value biodegradable plastics. This study provides a step-by-step protocol for producing PHA from food waste, emphasizing the critical care required to ensure high cellular PHA content and quality. The process begins with arrested anaerobic digestion, which converts food waste into microbially assimilable volatile fatty acids (VFA) by maintaining an anaerobic environment and optimizing parameters, such as solid retention time, to maximize VFA production, a key precursor for PHA synthesis. The VFA-rich digestate is then used to cultivate Haloflex mediterranei, a halophilic microorganism capable of accumulating PHA up to 66% ± 5% of its dry cell weight. The high salinity cultivation environment of H. mediterranei prevented culture contamination, ensuring optimal PHA production. Cell growth is monitored by measuring optical density to determine the ideal time for PHA harvesting. Cells are lysed using a chemical-free, water-based method leveraging an osmotic pressure gradient, achieving 93% ± 3% PHA recovery, followed by solvent-based PHA purification to obtain a PHA purity of 96% ± 2%. Each step is vital to ensure the production of high-quality, biodegradable plastics. This paper provides detailed methods for arrested anaerobic digestion, pure culture fermentation, chemical-free cell lysis, and solvent-based PHA purification, offering a scalable and sustainable approach for converting food waste into biodegradable bioplastics suitable for pilot- and full-scale applications.