초록
To determine the optimal scenario for mixed-acid fermentations, an array of batch fermentations were performed that independently varied the C/N ratio (adjusted using urea) and the blend of carbohydrate (office paper) and nutrient (wet chicken manure (CM)). A blend of 93% paper and 7% wet CM (dry basis) with a C/N ratio of 37gC<SUB>NA</SUB>/gN had the highest culture yield (0.21gacid<SUB>produced</SUB>/gNAVS<SUB>initial</SUB>), total acid productivity (0.84g acid<SUB>produced</SUB>/(L<SUB>liq</SUB>d)), and conversion (0.43gNAVS<SUB>consumed</SUB>/gNAVS<SUB>initial</SUB>). Compared to a control blend of 80% paper and 20% wet CM (dry basis, no urea) the culture yield, productivity, and conversion improved 53%, 44%, and 70%, respectively. Selectivity was a strong function of C/N ratio and varied from 0.167 to 0.667 acid<SUB>produced</SUB>/g NAVS<SUB>consumed</SUB>. Nitrogen supplementation with urea improves performance and reduces costs of (1) capital, (2) nutrients, and (3) downstream processing by reducing impurities from nutrient-rich wastes (e.g., manures, sewage sludge).