Avaliação da influência do espectro luminoso na produção de hidrogênio por bactérias fotossintetizantes

Abstract

Considering the environmental impacts caused by the combustion of fossil fuels, researchers have been seeking technologies for sustainable energy generation. Hydrogen is seen as a clean and non-polluting alternative, whose production can be carried out biologically through photosynthetic processes, employing photosynthetic bacteria. Some parameters are important to optimize hydrogen synthesis, and evaluating light influence on the photofermentation process is crucial. In this work, the biological production of hydrogen by photofermentation using the purple non-sulfur bacteria Rhodobacter capsulatus and Rhodospirillum rubrum was studied, using lactose from powdered whey permeate at a concentration of 10 g/L as the carbon source. Small-scale assays were conducted with 50 mL reactors, varying light sources, with cold white LEDs, infrared, and spectrum-directed LEDs. It was found that both the visible and infrared ranges produced hydrogen, however, a saturation effect was observed with the combination of the two ranges. The Tukey test was performed to evaluate which light source achieved the best performance, and it was observed that the cold white LED achieved the highest maximum productivity of 8.23 ± 0.10 mmol H2/(L.day). Large-scale assays were also carried out with a 2.1 L plate-type photobioreactor under the same conditions as the small scale, but with the LEDs that achieved the best performance in the small scale. For these assays, the maximum productivity and light conversion efficiency obtained were 10.33 mmol H2/(L.day) and 1.67% for the spectrum-directed LED, and 18.64 mmol H2/(L.day) and 3.26% for the cold white LED, respectively. The condition for large-scale was also evaluated by increasing the light intensity to 5000 lx for the cold white LED and using the revitalization system, achieving a maximum value of 26.93 mmol H2/(L.day) and 4.49% ECL.