Ethanol Production from Kitchen Garbage by Zymomonas mobilis: Optimization of Parameters through Statistical Experimental Designs

H. Ma, Q. Wang, L. Gong, X. Wang, X. Wang and W. Yin

Abstract
Plackett-Burman design was employed to screen 8 parameters for ethanol production from kitchen garbage by Zymomonas mobilis in simultaneous saccharification and fermentation. The parameters were divided into two parts, four kinds of enzymes and supplementation nutrients. The result indicated that the nutrient inside kitchen garbage could meet the requirement of ethanol production without supplementation, only protease and glucoamylase were needed to accelerate the ethanol production. The optimum usages for both enzymes were determined to be A = 100 U g–1 by single factor experiment. Then the parameters including initial pH, time and temperature were optimized during the fermentation by using central composite experimental design (CCD). The results second-order polynomial model indicated that interactions between the factors showed no crucial effect on ethanol production. The optimum conditions were determined to be initial pH of 4.95, time of t = 30.69 h, temperature of θ = 31.22 °C, the corresponding maximum ethanol was γ = 53.20 g L–1. Ethanol production from kitchen garbage enjoyed the advantages of simple process, low cost and short fermentation time, which should be further studied to make it applicable.

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Keywords
Zymomonas mobilis, ethanol fermentation, kitchen garbage, Plackett-Burman experimental design, central composite experimental design