BIOHYDROGEN PRODUCTION POTENTIAL USING VARIABLE NATURAL INOCULA
Four different types of bacterial inocula were collected from nature to determine if hydrogen production could be achieved using mixed cultures of bacteria. These sources were agricultural soils where both potatoes and soybeans were grown in as well as two different kinds of compost.
The inocula were baked for two hours or boiled for fifteen minutes to inactivate non-sporeforming bacteria and to select for sporeforming, hydrogen-producing bacteria. Twelve batch experiments were conducted using a fractional factorial experimental design to study the effects of initial sucrose
concentration and initial pH on hydrogen production potential and rate. The hydrogen production potential and rate were both used as key parameters to determine how well these initial conditions influenced the potential of the spores to produce hydrogen after heat shock treatment. The results
obtained in this study conclude that natural inocula could be heat shocked to develop their H2- producing capability. The two heat shock methods, boiling and baking, were sufficient to inactivate hydrogen-consuming methanogens in this study. The hydrogen-producing bacteria responsible
in this study may be from the genus Clostridium. A high initial pH tended to yield higher hydrogen production potentials, hydrogen production rates, and conversion efficiencies. The initial sucrose concentration tended to have little effect on hydrogen production potentials, hydrogen
production rates, and conversion efficiencies. An average hydrogen percentage in the biogas was 55 + 4.0 % using both heat shock treatments while a high hydrogen percentage of 82% in the biogas occurred using boiling as the heat shock treatment. On average, it was
found that the two kinds of compost produced the most hydrogen while the potato soil treatments had the highest hydrogen production rate. The highest conversion efficiencies of the potato, soybean, compost one, and compost two inocula were 11.7%, 14.2%, 17.0%, and 18.1%,
respectively. The highest values of hydrogen production potential using potato soil, soybean soil, compost one, and compost two as inocula were 270, 318, 507, and 401 mL H2, respectively. The highest values of hydrogen production rate using potato soil, soybean soil, compost one,
and compost two as inocula were 5.9, 2.8, 3.3, and 2.0 mL H2 / hr, respectively. The results revealed that biohydrogen production using natural inocula is achievable. The batch experiments confirm that the results measured in this study possessed high reliability and the natural
inocula had significant potential of biohydrogen production.
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