Overexpressing atpXF enhanced photo-fermentative hydrogen production performance of Rhodobacter sphaeroides

Abstract

The effects of overexpressing atpXF genes encoding b2 subunits of F0F1-ATPase in Rhodobacter sphaeroides HY01 on ATPase, nitrogenase and photo-fermentative hydrogen production activities were studied. The results showed that the expression levels of atpXF and f1 operon in ZTHBB (F0P+atpXF+) enhanced by 1870% and 40% while its expression levels of f0 operon and nif decreased by 20% and 50% compared with those of ZTH, respectively; and the expression levels of b2 subunits, f0 operon, f1 operon and nif in ZTHCB (pucP+atpXF+) enhanced by 370%, 60%, 130% and 160% compared with those of ZTH, respectively. The ATP contents of ZTHBB and ZTHCB increased by 41.5% and 52.8% compared with that of ZTH, and their nitrogenase activities were increased by 30.0% and 41.0% compared with that of ZTH, respectively. When 25 mM acetic acid and 34 mM butyric acid were employed as carbon source and 6 mM l-glutamate was employed as nitrogen source, their hydrogen yields were 7677 ± 176 mL/L (ZTHBB) and 8458 ± 129 mL/L (ZTHCB), which increased by 16.0% and 29.1% compared with that of ZTH, and their maximum hydrogen production rates were 98.0 ± 4.3 mL/(L·h) (ZTHBB) and 100.1 ± 5.1 mL/(L·h) (ZTHCB) under the same conditions, which increased by 14.6% and 17.1% compared with that of ZTH, respectively. The results suggest that overexpressing atpXF could enhance the expression level of F0F1-ATPase and hydrogen production performance of purple non-sulfur bacteria.