3.4.2.5 pH
The 24-h culture was aliquoted to the same volume and then buffered with 500 mM buffer solution to the final concentration of 50 mM. Acetate salt solution was used as buffer solution at pH 5.25 and 5.75. Citrate was used to buffer the culture at pH 5.9 and 6.4. Tris was used to buffer the solution at pH 7.3, 7.8, 8.3, 8.8 and 9.3. In Figure 3.13, H2 production by Tetraspora sp. CU2551 under light condition showed in broad range and increased when increasing the pH from 5.75 to 9.30. In contrast, the production was dropped when lowering pH to 5.25 where almost no detectable H2 evolution was observed