| EFFECTS OF PH AND REPEATED HEAT-SHOCK TREATMENT ON HYDROGEN FERMENTATION OF SUCROSE BY A MIXED CULTURE |
| Sun-Kee Han1†, Sang-Hyoun Kim1, Shihwu Sung2, and Hang-Sik Shin1 |
1Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
2Department of Civil and Construction Engineering, Iowa State University, Town Engineering Building, Ames, Iowa 50011-3232, USA |
Corresponding Author:
Sun-Kee Han ,Tel: +82-42-869-3697, Fax: +82-42-869-3610 , Email: skhan003@kaist.ac.kr
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Received: June 14, 2003; Accepted: September 14, 2003. |
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| ABSTRACT |
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This study was conducted to investigate the effects of pH and repeated heat-shock treatment on the production of hydrogen and metabolites in hydrogen fermentation of sucrose by a mixed culture. The batch experiments were repeatedly performed three times using the same sludge as a seed microorganism in each serum bottle. Initial pH 6.5 led to the maximum hydrogen production from sucrose with only initial heat-shock treatment. The sucrose degradation efficiency increased up to 98.0%. The maximum values of the hydrogen yield and the specific hydrogen production rate were 2.0 mol H2 (mol hexose)"1 and 103.2 ml H2 (g VSS • day)"1, respectively. However, at initial pH 7.0 or higher, methane was detected so that repeated heat-shock treatment was needed. Butyrate and acetate were the two most abundant species in hydrogen fermentation. At initial pH 6.5, butyrate production reached the maximum while acetate production reached the minimum, resulting in the highest butyrate/acetate (B/A) ratio of 5.0. Compared with the value of stoichiometric reaction, the hydrogen yield of 2.0 mol H2 (mol hexosef1 meant that most of the sucrose was converted to butyrate, instead of acetate. Thus, Clostridium species are considered to be the dominant microorganisms because these bacteria are responsible for butyrate fermentation. The high concentrations of butyrate indicate that the hydrogen- and acid-producing pathway dominated the metabolic flow. In this study using sucrose as a substrate by a mixed culture, the optimum initial pH of 6.5 was a dividing line between acid and alcohol production for an undefined inoculum. |
| Keywords:
initial pH | heat-shock treatment | hydrogen yield | butyrate | Clostridium species |
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