Sustainable production of polyhydroxyalkanoates from agricultural wastes within a circular economy framework

Abstract

The current environmental crisis associated with fossil fuel-based plastics has driven the search for sustainable alternatives, among which polyhydroxyalkanoates (PHA) emerge as promising biodegradable biopolymers. The present article provides a comprehensive review of the recent advances and challenges in the sustainable production of PHA from agricultural waste via a circular economy approach. Agricultural waste feedstocks such as rice straws, wheat straws, fruit peels, husks, bagasse, and food processing byproducts serve as abundant, renewable, and cost-effective materials for microbial PHA production. The importance of this study lies in addressing a significant concern of recycling and valorisation of agricultural waste. Waste valorisation can be integrated with bioprocess optimization to support the conversion of agro-wastes into PHA for resource recovery and recycling of waste. The present review systematically evaluates the role of pretreatment techniques, high-yielding strains, genetic engineering approaches, and mixed microbial cultures (MMCs) in improving yield and sustainability. Significant attention has been directed towards exploring novel downstream recovery approaches for minimizing chemical waste generation and operational cost. The systematic approach adopted in this review highlights how the closed-loop recycling of agricultural waste can significantly reduce environmental pollution and promote biopolymer synthesis. Further, the review article would attempt to provide environmental and economic implications of agricultural waste-derived PHA as eco-friendly materials and their future perspectives in replacing petrochemical-based plastics. Sustainable approaches in PHA production from agricultural wastes are summarized. Latest developments on genetic engineering and pathway optimization are discussed. Novel bioreactor designs and mixed microbial consortia approaches are reviewed. Recent advances in downstream processing are discussed for cost-effective PHA production. The environmental and economic implications of the circular economy are highlighted.