Design of a microbial photoheterotrophic consortia for biohydrogen production under nongrowing conditions: Insight into microbial associations

Physiological and metabolic behavior of photoheterotrophic mixed cultures (PHMCs), monocultures of Rhodopseudomonas palustris, Clostridium pasteurianum and Syntrophomonas wolfei and a designed microbial consortium (DMC), consisting of these microorganisms that emulates natural consortia were studied. Growing and photoheterotrophic nongrowing conditions to simulate the use of dark fermentative effluents were used. Under growing conditions, C. pasteurianum showed higher bioH₂ production (8.5 mmol) and molar bioH₂ yield (21 mmoLH₂/gCOD), while R. palustris did not produce this gas. Under nongrowing conditions, DMC reached the highest bioH₂ production (10 mmol) and bioH₂ yield (78.6 mmoLH₂/gCOD) together with Poly-hydroxy-alkanoates (PHA), followed for PHMC-C2 (7.5; 59.6) and the monocultures. Higher bioH₂ and PHA production of the PHMC and the DMC suggest that these conditions promote the use of nonconventional energy pathways, and interactions among microbial populations that allow for the survival and sustain bioH₂ production. This study forms the basis for more in-depth studies of the metabolic behavior of photosynthetic natural and designed cultures.