Some observations on immobilized hydrogen‐producing bacteria: Behavior of hydrogen in gel membranes

A hydrogen‐producing bacterium, Clostridium butyricum, was immobilized in polyacrylamide gel membrane, agar gel membrane, and collagen membrane. The apparatus consisted of a compartment(I or II) and a whole‐cell‐entrapped gel membrane which was placed in the center of the two compartments. The behavior of hydrogen through whole‐cell‐entrapped gel membrane was examined for improving the sensitivity of a microbial BOD sensor and the efficiency of biochemical fuel cells. The bacteria‐polyacrylamide gel membrane produced a higher amount of hydrogen in compartment II than the other bacteria‐entrapped gel membranes. The apparent diffusion constant decreased with increasing bacteria contents in the gel membrane. As a result, 100 mg wet cells/g gel was the maximal bacteria content in the membrane for the production of hydrogen. Twenty percent of the hydrogen evolved by the whole cells diffused to compartment II, and there was a linear relationship between the glucose concentration in a bulk solution (compartment I) and the rate of hydrogen diffused to compartment II.