CO-dependent hydrogen production by the facultative anaerobe Parageobacillus thermoglucosidasius

The overreliance on dwindling fossil fuel reserves and the negative climatic effects of using such fuels are driving the development of new clean energy sources. One such alternative source is hydrogen (H₂), which can be generated from renewable sources. Parageobacillus thermoglucosidasius is a facultative anaerobic thermophilic bacterium which is frequently isolated from high temperature environments including hot springs and compost.

Comparative genomics performed in the present study showed that P. thermoglucosidasius encodes two evolutionary distinct H₂-uptake [Ni-Fe]-hydrogenases and one H₂-evolving hydrogenases. In addition, genes encoding an anaerobic CO dehydrogenase (CODH) are co-localized with genes encoding a putative H₂-evolving hydrogenase. The co-localized of CODH and uptake hydrogenase form an enzyme complex that might potentially be involved in catalyzing the water-gas shift reaction (CO + H₂O → CO₂ + H₂) in P. thermoglucosidasius. Cultivation of P. thermoglucosidasius DSM 2542^T with an initial gas atmosphere of 50% CO and 50% air showed it to be capable of growth at elevated CO concentrations (50%). Furthermore, GC analyses showed that it was capable of producing hydrogen at an equimolar conversion with a final yield of 1.08 H₂/CO.

This study highlights the potential of the facultative anaerobic P. thermoglucosidasius DSM 2542^T for developing new strategies for the biohydrogen production.