Synthesis of Polylactic Acid from Apple, Pineapple, and Potato Residues

Polylactic acid (PLA), a recyclable and biodegradable polymer, is essential for bioplastic production. Driven by the growing need for sustainable alternatives to petroleum-based plastics and the pressing issue of global food waste, PLA emerges as a promising biodegradable polymer derived from renewable resources such as sugarcane, corn, and biomass. Food waste presents a significant opportunity to produce PLA. While the conversion of food waste into lactic acid (LA), the PLA precursor, has been extensively studied, the subsequent transformation into PLA remains relatively unexplored. This research gap underscores the need for comprehensive investigations to understand the properties, production efficiency, and overall feasibility of producing PLA from food waste. This study aimed to produce PLA from food waste-derived LA. Apple, pineapple, and potato residues, rich in carbohydrates, served as substrates for LA fermentation using Lactobacillus Casei. The resulting LA was polymerized into PLA via ring-opening polymerization (ROP) using zinc oxide and tin (II) 2-ethylhexanoate as catalysts. Fourier Transform Infrared Chromatography (FTIR) confirmed the presence of LA in the fermentation broth, with the carbonyl and hydroxyl groups detected and LA appearing at peak 2.45 minutes in High-Performance Liquid Chromatography (HPLC). Apple residue yielded the highest LA percentage (31.36%), followed by pineapple (23.41%) and potato (20.81%). FTIR also indicated PLA formation due to the carbonyl group being slightly higher and the hydroxyl group being slightly lower than LA. Gel Permeation Chromatography (GPC) results showed potato residue produced PLA with a significantly higher molecular weight (12,662) compared to apple (543). Notably, apple residue PLA exhibited desirable monodisperse properties, which are advantageous for food packaging applications. This study demonstrates the potential of transforming food waste into valuable bioplastics, contributing to waste reduction and environmental sustainability.