Enhancing photo-fermentative biohydrogen production using different zinc salt additives.

The kinetic properties of the hydrogen yield of photosynthetic bacteria were investigated using Han-Levenspiel and modified Gompertz models to determine the effects of different zinc salts on the growth and hydrogen production of the photosynthetic bacterium HAU-M1. Inorganic zinc salts (zinc standard solution and zinc sulfate) inhibited bacterial growth by 1-4-fold higher than organic zinc salts (zinc lactate and zinc gluconate). Among these four zinc salts, 5 mg/L zinc lactate displayed the weakest inhibition performance. This compound increased cumulative hydrogen production by approximately 57.81% (80.44 mL/g) and maximum hydrogen production rate by 58.27% (3.43 mL/[g·h]). The Han-Levenspiel model with parameters m > n > 0 indicated that the addition of zinc salts influenced the hydrogen production process of the bacterium in a noncompetitive manner. Compared with the inorganic zinc, the organic zinc salts were more suitable as exogenous zinc supplements to promote bacterial growth and its hydrogen production.