Biorefinery of avocado seed waste for sustainable production of bioplastics and functionalized silver nanocomposites

Abstract

This study examines the potential of utilizing avocado seeds (AS) waste for sustainable polyhydroxyalkanoates (PHA) production and green synthesis of silver nanoparticles (AgNPs) in an integrated biorefinery approach. Initially, phytochemical compounds were extracted from AS biomass using solvent extraction. The residual AS biomass underwent hydrolysis through acid pretreatment and was subsequently utilized as a sustainable carbon source for PHA synthesis by Lysinibacillus sp. RGS. Various operational conditions and nutrient supplementation were thoroughly studied to achieve maximum biomass productivity (dry cell weight: 9.74 +/- 0.34 g/L), PHA accumulation (76.5 +/- 1.85 %), and PHA yield (7.45 +/- 0.32 g/L). The analytical results showed that the produced PHB possesses physicochemical characteristics comparable to those of standard PHB, with excellent thermal stability. The ethanolic extract of avocado seed (ASE) was utilized for AgNPs synthesis. The analytical results indicated that bioactive phytochemicals of ASE are coated on the exterior of synthesized ASE-AgNPs, with a diameter size ranging from similar to 10-30 nm. ASE-AgNPs demonstrated noteworthy antioxidant activity (against DPPH and ABTS) and also confirmed significant antibacterial activity. Moreover, synthesized NPs exhibited dose-dependent antidiabetic activity restraining enzymes alpha-amylase and alpha-glucosidase. The study introduces a sustainable platform for complete valorization of AS, facilitating the production of multiple valuable bioproducts. This approach offers substantial economic advantages, assisting in mitigating the significant environmental impact associated with AS and promoting long-term sustainability.