Consolidate Processing for Improvement of Ethanol Production from Food Waste

To improve the performance of ethanol production from food waste, a consolidation process involving both the addition of surfactant and cell immobilization was investigated. Results showed that the optimum glucose concentration was 200 g/L for ethanol fermentation using Saccharomyces cerevisiae as inoculum. With the addition of 0.5% Tween 80, the ethanol production was improved from 68.1 to 79.8 g/L, which was attributed to the increased mass transfer of cells provoked by Tween 80. In a cell-immobilized system, wheat straw was used as the matrix to carry the cells. A high ethanol production of 87.8 g/L was obtained with the sequential fermentation mode due to the high cell density on the cell carrier. The results of a mass balance calculation revealed that the ethanol production of food waste achieved 340.4 kg/t (on a dry basis), which provided an insight that food waste was a suitable substrate for ethanol production. The main cost was spent on energy consumption in the processes of food waste sterilization, hydrolysis, fermentation, and ethanol distillation, and measures for reducing the energy were suggested to improve the economic performance of ethanol production

Metabolic Remodulation of Chassis and Corn Stover Bioprocessing to Unlock 3‑Hydroxypropionic Acid Biosynthesis from Agrowaste-Derived Substrates

Embracing the principles of sustainable development, the valorization of agrowastes into value-added chemicals has nowadays received significant attention worldwide. Herein, Escherichia coli was metabolically rewired to convert cellulosic hydrolysate of corn stover into a key platform chemical, namely, 3-hydroxypropionic acid (3-HP). First, the heterologous pathways were introduced into E. coli by coexpressing glycerol-3-P dehydrogenase and glycerol-3-P phosphatase in both single and fusion (gpdp12) forms, making the strain capable of synthesizing glycerol from glucose. Subsequently, a glycerol dehydratase (DhaB123-gdrAB) and an aldehyde dehydrogenase (GabD4) were overexpressed to convert glycerol into 3-HP. A fine-tuning between glycerol synthesis and its conversion into 3-HP was successfully established by 5′-untranslated region engineering of gpdp12 and dhaB123-gdrAB. The strain was further metabolically modulated to successfully prevent glycerol flux outside the cell and into the central metabolism. The finally remodulated chassis produced 32.91 g/L 3-HP from the cellulosic hydrolysate of stover during fed-batch fermentation