Sequential utilization of Phaseolus lunatus pod (PLP) for the development of pectin and bioethanol: biorefinery approach

Abstract

In recent years, the valorization approach for transforming waste into wealth has attracted researchers to develop value-added products. This work is designed to valorize Phaseolus lunatus pod (PLP), vegetable waste, to extract pectin and bioethanol production through microbial fermentation. With the conventional method, the extraction of pectin from Phaseolus lunatus pod (PLP) was optimized using statistical and artificial neural network techniques. The Box–Behnken design of experiments and artificial neural network design were employed to optimize the extraction process and effect of process variables, namely, temperature (50–100 °C), liquid-to-solid ratio (LSR 10–40 mL/g), extraction time (30–120 min), and concentration of citric acid (30–60% w/v). The maximum yield of crude pectin (0.47 g/g) resulted from optimized process variables such as temperature 75 °C, LSR 40 mL/g, time 30 min, and citric acid 45 (% w/v). The physicochemical composition, such as carbohydrate content, protein, total phenolic content, esterification degree, methoxyl content, and techno-functional properties, was determined. The structural property, functional group analysis, thermal stability, and surface morphology of extracted pectin from PLP under optimum conditions were investigated using ¹H-NMR spectroscopy, FTIR spectroscopy, TGA, and SEM analysis. The hydrolysis obtained from residual biomass was subjected to bioethanol production through microbial fermentation with a yield of 0.11 g/g. Based on the findings, the Phaseolus lunatus pod (PLP) could be explored as a promising, cost-effective alternative for developing value-added products in food and biofuel applications.