Investigação da produção de hidrogênio por fotofermentação empregando cultura pura e co-cultura

Abstract

The use of bio-hydrogen as an energy source to replace fossil fuels is a promising alternative. The hybrid system for hydrogen production by combining the dark fermentation followed by photo-fermentation has great potential because it allows the total substrate conversion. In this work, the production of hydrogen was studied in batch and fed batch processes using dark fermentation effluent and pure culture and co-culture purple non-sulfur bacteria Rhodopseudomonas palustris and Rhodobacter capsulatus. Initially, tests were carried out in 50 mL reactors in order to test the influence of synthetic RCV medium and the effluent from dark fermentation for hydrogen. Lactose, glucose or soybean molasses as a sugar source were supplemented. The showed that effluent containing organic acids produces better results than synthetic medium. This fact shows there is a synergism between metabolites formed in dark fermentation and the sugar source. The assay of photo-fermentation, containing soy molasses in the effluent showed better results in the production of hydrogen, with a productivity of 8.34 mmol H2 / L·day. Subsequently, tests were performed in large scale (1.5 L) to observe the biogas production. During the process the influence of sugar (glucose and lactose) supplementation was studied for that, it was used an inoculum with the pure culture (R. palustris) and co-culture (R. palustris and R. capsulatus). The results showed that the system employing the co-culture and glucose kept the culture activity for a long time (679 h). In this assay, the amount of accumulated hydrogen was 0.51 mol and the maximum productivity was 287.39 mmol of H2/L·day. This study indicated that photo-fermentation by using co-culture of R. palustris and R capsulatus, from dark fermentation effluent supplemented with sugars, is a viable biological route to produce hydrogen.