Efficiency and transcriptomic analysis reveal the mechanism of fermentation residue biochar and dosage on enhancing food waste high solid bioethanol fermentation

Abstract

Recovering bioethanol from food waste offers dual benefits of mitigating pollution and producing clean, renewable energy. High solid bioethanol fermentation enhances process sustainability and economic viability, however, hindered by decreased bioethanol yield and limited fermentation residue valorization methods. In this study, the bioethanol fermentation residue was used to produce biochar, which was incorporated into the food waste high solid bioethanol fermentation system to improve process efficiency. The BC produced at 500 °C (BC500) has highest S_BET, with obvious adsorptions observed both on the surface and within the pores. The addition of BC500 increased the bioethanol yield by 14.93% and reduced acetic acid concentration by 37.58%. Increasing the BC500 dosage to 7.5 g/L reached the highest bioethanol concentration of 75.11 g/L (97.56% of the theoretical value), and 38.51% increase in bioethanol yield. The transcriptomic revealed that the BC500 enhanced bioethanol yield by regulating gene expression and enhancing signaling pathways. BC500 provided abundant attachment sites, significantly upregulating the expression of gene SIPA1L2 and MTMR3/4, and upgraded Ras and MAPK signaling pathway of Saccharomyces cerevisiae. These changes promoted cell cycle progression and proliferation, while limiting autophagy and cell death. The optimum BC500 dosage (7.5 g/L) could provide a more stable environment for signal transduction and enhance carbohydrate metabolism. The research enhanced food waste bioethanol conversion efficiency, realize zero discharge of fermentation residues, which advancing the sustainable development and clean production of high solid bioethanol fermentation technology.