Single-stage repeated batch cycles using co-culture of Enterobacter cloacae and purple non-sulfur bacteria for hydrogen production

Hydrogen production by biological routes is a sustainable alternative since it requires a low amount of energy for its products and can use renewable raw materials as substrates. The current work studied the production of hydrogen by photofermentation in a single stage using the co-culture of Enterobacter cloacae and one of the photosynthetic bacteria: Rhodobacter capsulatus or Rhodopseudomonas palustris. A combination of different groups of bacteria grown in a single bioreactor has the advantages of simple handling, reduced fermentation time, and high yield rates. Repeated batch cycle operations evaluating the influence of the addition of glucose or lactose from milk whey permeate (MWP) in an isolated or alternate manner were performed. The addition of glucose and MWP promoted maximum productivity of 319.35 mmol H2/L.day in 180 h of process, using the co-culture (1:1) of E. cloacae and R. capsulatus. Furthermore, the experimental run using E. cloacae and R. palustris reached 262.77 mmol H2/L.day (325 h). Besides, the highest organic acid concentration was of butyric acid, reaching 26.63 g/L in assay 6, followed by lactic acid (17.26 g/L) and acetic acid (11.60 g/L).