Effect of zinc ion on photo-fermentative hydrogen production performance, kinetics and electronic distribution in biohydrogen production by HAU-M1.

• H 2 yield can be promoted by the addition of Zn2+. • Excessive Zn2+ resulted in more substrate electrons transferring to substrate residue. • 26.42% substrates electrons were diverted towards hydrogen at 2 mg/L Zn2+. • The critical Zn2+ concentration was 40.83 mg/L. The aim of this work was to study the characteristics, kinetics and electronic distribution of photo-fermentation hydrogen production (PFHP) with Zn2+ addition then gave the main results that the addition of Zn2+ can effectively improve hydrogen production with an increasing of 1–5 mg/L Zn2+ concentration. The maximum hydrogen yield of 592 ± 13 mL and shortest lag time of 4.67 h were obtained at 2 mg/L Zn2+. 26.42% of the substrate energy was diverted to H 2. Modified Gompertz and Hane-Levenspiel models were applied to evaluate the effect of Zn2+ on PFHP by mixed bacteria HAU-M1, the constants n and m obtained by fitting models were 14.97 and 58.79, respectively, indicating the fermentation system was noncompetitive inhibition, the predicted critical Zn2+ concentration was 40.83 mg/L. [ABSTRACT FROM AUTHOR]