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The authors examined the effects of operating parameters on the H2 production by dark fermentation of the wastewater generated from food waste recycling facilities, in short “food waste wastewater (FWW)”. Central composite design based response surface methodology was applied to analyze the effect of initial pH (5.5-8.5) and substrate concentration (2-20 g Carbo. COD/L) on H2 production. The experiment was conducted under mesophilic (35oC) condition and a heat-treated (90oC for 20min)anaerobic digester sludge was used as a seeding source. Although there was a little difference in carbohydrate removal, H_2 yield was largely affected by the experimental conditions, from 0.38 to 1.77 mol H_2/mol hexoseadded. By applying regression analysis, H_2 yield was well fitted based on the coded value to a second order polynomial equation (p = 0.0243): Y = 1.78 - 0.17X_1 + 0.30X_2 + 0.37 X_1X_2 - 0.29X_1^2 - 0.35X_2^2, where X_1, X_2, and Y are pH,substrate concentration (g Carbo. COD/L), and hydrogen yield (mol H2/mol hexoseadded), respectively. The 2-D response surface clearly showed a high inter-dependency between initial pH and substrate concentration,and the role of these two factors was to control the pH during fermentation. According to the statistical optimization, the optimum condition of initial pH and substrate concentration were 7.0 and 13.4 g Carbo. COD/L, respectively, under which predicted H_2 yield was 1.84 mol H_2/mol hexose_added. Microbial analysis using 16S rRNA PCR-DGGE showed that Clostridium sp. such as Clostridium perfringens, Clostridium sticklandii, and Clostridium bifermentans were main H_2-producers.