Fig. 2

Variations of cumulative hydrogen production, concentrations of cell, glucose, and volatile fatty acid over time. Lactic acid-producing bacteria (LAB) only (LAB concentration = 0.019 g/L) (a); purple non-sulfur photosynthetic bacteria (PNSB) only (PNSB concentration = 0.131 g/L) (b); LAB/PNSB ratio of 1/12 at initial cell concentration of 0.15 g/L (LAB concentration = 0.019, PNSB concentration = 0.131 g/L) (c). Hydrogen (black circle), glucose (red triangle), cell (blue diamond), lactic acid (green square), formic acid (blue cross)