ABSTRACT:Recently, research on the production of ethanol from waste has been accelerating for both ecological and economical reasons, primarily for its use as an alternative to petroleum based fuels. In this study, response surface methodology based 2 3 -full factorial central composite design was employed to optimize the parameters of ethanol production from Korean food waste leachate. The reducing sugar concentration of the food waste leachate determined by the dinitrosalicylic acid method was 75 g/L. A second order polynomial model was developed to evaluate the quantitative effects of temperature, pH and reducing sugar concentration in order to find an optimum condition for the ethanol production from food waste leachate. From the experimental result, maximum ethanol concentration of 24.17 g/L was obtained at the optimum condition of temperature (38 ºC), pH (5.45) and reducing sugar concentration (75 g/L). The experimental value (24.17 g/L) agreed very well with the predicted one (23.66 g/L), indicating the suitability of the model employed and the success of response surface methodology in optimizing the conditions of ethanol production from food waste leachate. Canonical analysis indicated that the stationary point was a saddle point for the ethanol yield. Despite being a waste, an ethanol yield of 0.32 g ethanol/g reducing sugar demonstrated the potential of food waste leachate as a promising biomass resource for the production of ethanol.

In the city of Ulsan, South Korea, Food-Waste Leachate (FWL) is let off into the ocean, which eventually poses a severe threat to the marine environment. Preliminary results suggest that this leachate, when subjected to an optimized fermentation process can generate ethanol. A 2 3 -factorial design was employed, and the effects of temperature (30-40 o C), pH (4-6), and reducing sugar concentration (RSC, 45-75 g L −1 ) on ethanol yield was investigated through controlled batch experiments using Saccharomyces cerevisiae (KCTC-7904), a species of budding yeast. A maximum yield of 0.31 g ethanol g −1 RSC corresponding to an ethanol concentration of 23.56 g L −1 was achieved under the following test conditions: temperature -40 o C, pH -4.0, and RSC -75 g L −1 . Among the different parameters studied, both temperature and RSC had a strong synergistic effect on ethanol yield, while the effects due to changes in pH values were minimal. Anew, under the test conditions, the 2-way interaction effect between temperature × pH and the 3-way interaction between temperature × pH × RSC were negative, while all other interactions, were positive and also found to be statistically significant at 5% probability (p value < 0.05). The results were represented by a suitable model equation, which could be easily applied for scale-up to produce value-added ethanol, by sterilizing FWL prior to fermentation. The practical implications of this research have been stated.