Bio-hydrogen production by different operational modes of dark and photo-fermentation: An overview

This article overviews reported studies on bio-hydrogen production from different raw materials by dark and photo-fermentations operated with different modes. Sequential and combined dark and photo-fermentations operated in batch, continuous and fed-batch modes were compared. Operating conditions and modes resulting in the highest hydrogen yield and formation rate were revealed. Relative advantages of sequential and combined dark and photo-fermentations were discussed. Sequential fermentation was found to be preferable due to high H2 yields and productivities. High cell density fed-batch culture with controlled feeding and simultaneous product removal was concluded to be the most suitable operation mode at the optimum environmental conditions.