Enhancing the Ethanol Fermentation Performance of Food and Fruit Waste Using Mild Acid Hydrolysis in Slurry Mode

This study aimed to improve the saccharification and ethanol fermentation performance from blend of food and fruit waste (FFW) by optimizing mild acid hydrolysis pre-treatment in slurry mode. Valorizing the abundant organic carbon in FFW into bioethanol aligns with efforts towards renewable, green energy alternatives to fossil fuels.

FFW was mixed with water at a 1:1 solid-to-liquid ratio and subjected to dilute acid (HCl or H₂SO₄) hydrolysis at 60 °C for 6 h with agitation at 90 rpm. Reducing sugar yield and nutrient release were monitored to determine optimal pre-treatment conditions. The pre-treated hydrolysates were then fermented under submerged conditions using Saccharomyces cerevisiae to produce ethanol.

Pre-treatment with 1% (v/v) H₂SO₄ resulted in a high ethanol yield of 4.68% (v/v) after 24 h of fermentation. This outperformed all other pre-treatment conditions tested and a thermally-treated control. Detailed characterization confirmed that the pre-treatment successfully enhanced the saccharification of lignocellulosic and starchy components in the FFW.

Combining a low-temperature dilute acid hydrolysis pre-treatment in slurry mode substantially improved the bioethanol production capacity from FFW. This represents a promising approach to valorize FFW’s abundant organic nutrients and carbon into a renewable liquid biofuel, helping transition from fossil fuels towards a greener future.