Enhancing bioethanol yield from food waste: Integrating decontamination strategies and enzyme dosage optimization for sustainable biofuel production

Abstract

• Bioethanol production from consumer food waste aided by decontamination strategies. • Applied engineered strain to minimise exogenous enzyme dosage to produce ethanol. • Thermal sterilisation improved ethanol yields by 49% over chemical sterilisation. • Application of amylase-secreting yeast reduced enzyme dosages by 33 %. • High solids, fed-batch fermentation improved ethanol titres compared to batch. Amidst the global surge in energy demand, the public’s focus has shifted from fossil fuels to more sustainable and eco-friendly fuels like bioethanol. Thus, the prospect of producing bioethanol from food waste (FW) is gaining traction, offering a sustainable solution to both waste management and energy needs. However, increasing bioethanol yields during food waste fermentation requires an approach that addresses the variability of these heterogeneous feedstocks in terms of chemical composition, microbial contamination, enzyme dosage requirements, and high moisture content. Hence, this study evaluated thermal and chemical decontamination strategies for pre- and post-consumer food waste and minimised the exogenous enzyme dosage by applying an engineered, amylase-producing strain ( Saccharomyces cerevisiae ER T12). Results show that thermal sterilisation at an elevated liquefaction temperature significantly improved ethanol yields (from pre-and post-consumer food waste) more than chemical decontamination methods. Also, key findings show that applying the amylase-secreting yeast reduced enzyme dosages by up to 33 %. During fed-batch fermentation with strain ER T12, the highest possible solids loading increased the final ethanol concentrations by 96 % (for pre-consumer FW) and 85 % (for post-consumer FW) compared to batch fermentation. Also, the pre-consumer to post-consumer FW fed-batch fermentation maintained acceptable volumetric production rates of 2.35 to 1.57 g/l.h and yielded 87.6 to 61.2 % of the theoretical maximum. Although the maximum solids loadings, ethanol titres and yields achievable in food waste fermentations were still limited by the inherent moisture contents of the feed, they demonstrated performances that may be appropriate for industrial implementation, considering the negative feedstock costs.