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Over the last century, energy consumption has increased tremendously due to the growth of world population and industrialization. Interest in the utilization of renewable carbohydrate sources to produce fuel ethanol as an alternative to petroleum is rising around the world to save petroleum and natural gas. The ideal raw materials for ethanol production should be cheap and rich in nutrient. Some renewable feedstock such as sago starch, cellulose materials have been investigated. Few researches are carried out on the utilization of kitchen garbage.

Being a kind of municipal waste with high volume, kitchen garbage is difficult to be handled owning to its high organic content and moisture. On the other hand, it could also be regarded as a valuable resource
due to its content of nutrients. It is reported that hydrogen, lactic acid and other substances could be produced from it. The research taken on by Li12 adopted the organic solid based on European
standard to produce ethanol. The raw materials were a mixture of waste from kitchen garbage and yard waste. Little information showed the utilization of Chinese kitchen garbage, since Chinese have a unique eating habit, the investigation on Chinese kitchen garbage to ethanol could provide valuable information for the recycling technology.

During the fermentation process, suitable production medium and variables optimization are of crucial importance. For ethanol production, researchers have paid much interest in utilizing the Zymomonas mobilis. This kind of facultative anaerobic bacterium has been extensively studied over the last decade due to its efficient production of ethanol
from sucrose and fructose. In order to obtain the maximum yield of ethanol with complete utilization of the substrate to reduce pollution encountered in the spent broth, suitable medium optimization should be carried out. Medium optimization by single factor experiment is laborious and time consuming. Thus the statistical methodology was adopted to optimize the nutrients for the medium to acquire the optimum ethanol yield. Several statistical factorial designs ranging from two-factorial to multi-factorial designs are available for optimization.

Among them, the Plackett-Burman (P–B) statistical method could study n variables in n+1 experimental runs, which means it could screen variables with less time, chemical and manpower. Furthermore, since the design is orthogonal in nature, implying that effect of each variable would not interfere with each other. Thus the P–B design could be a useful tool in optimizing the medium for fermentation.

Another study of the fermentation process involves the optimization of culture parameters. Similar to the nutrient screening process, utilization of statistical designs could get rid of the shortcomings of the traditional single factor experiments. Moreover, it could reveal the relationship between the variables which is of great importance during the fermentation process. Among them, response surface methodology (RSM) is one suitable method for identifying the effect of individual variables and for seeking the optimum conditions for a multivariable system efficiently. This process has been successfully applied to optimize ethanol fermentation and other product fermentation.
The utilization of this method in this study could determine the relations
between the factors as well as the optimal ethanol production conditions.

The aim of this study is to adopt P–B design to optimize the medium composition for ethanol production from kitchen garbage. Different kinds of ingredients were tested for their effect on ethanol production.
The CCD design was applied to reveal the relations between physical parameters such as initial pH, temperature and time, the determination of corresponding optimum conditions would also be investigated.

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