Dark fermentative bio-hydrogen production: Effects of substrate pre-treatment and addition of metal ions or L-cysteine
2013
Bao, M.D. | Su, H.J. | Tan, T.W.
H₂ is regarded as a promising energy resource because of its high energy content (122kJ/g), and since capable of replacing fossil energy sources. To enhance the hydrogen production, two pure bacterial strains were jointly applied as mixed cultures in a single fermenter, thus combining the starch hydrolysis process and H₂ production process. Strain A1 was responsible for starch hydrolysis by producing amylase and strain B1 was in charge of hydrogen production. Since the starch pre-treatment conduces to starch hydrolysis and the metal ions are the important elements of hydrogenase, the hydrogen production using corn starch was moreover assessed when either pre-treating the starch feed, or by adding Fe²⁺ or Mg²⁺, possibly in association with L-cysteine. The cumulative H₂ production increased as average of triplicate experiments from 838 to 1186mL when the corn starch was pre-treated by boiling. The H₂ production rate of pre-treated corn starch was much higher than that of untreated corn starch. The H₂ yield of pre-treated corn starch reached 1.19mol H₂/mol glucose, 40% higher than using untreated corn starch (0.85mol H₂/mol glucose). By adding trace elements (Fe²⁺ and Mg²⁺) and L-cysteine, the H₂ yields were higher than for the control, except when adding Mg²⁺. The enhancement of the H₂ production by the sole addition of Fe²⁺ and L-cysteine was significant (by 105% and 60%, respectively). The sole addition of Fe²⁺ to the system had the highest effect with a maximum cumulative H₂ production of 1928mL and H₂ yield of 1.94mol H₂/mol glucose.
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