Investigação da produção de Biohidrogênio por Fotofermentação utilizando Bactérias Púrpuras não Sulfurosas na presença de Barita e Basalto

Abstract

Hydrogen stands out as a clean and promising fuel, especially when produced from biomass. The current study aimed to evaluate the biological production of hydrogen using rock (Basalt) and ore (Barite) in a fermentation medium, with the intention of favoring microbial activity or promoting cell stabilization and employing in the medium non-sulfur purple bacteria associated in a 1:1:1 ratio: Rhodobacter capsulatus, Rhodospirillum rubrum, and Rhodopseudomonas palustris. As carbon sources, lactose from whey permeate powder, a co-product of the agro-industry, and glucose P.A., both at a concentration of 20 g/L, were used. The control test with lactose resulted in a productivity of 16.67 ± 0.361 mmol H₂/(L·day)], higher than that of glucose [11.35 ± 0.363 mmol H₂/(L·day)]. The presence of Barite in the culture medium increased hydrogen productivity by 12-fold compared to the control [215.32 ± 3.22 mmol H₂/(L·day)], while Basalt resulted in a 6-fold increase [109.28 ± 4.53 mmol H₂/(L·day)]. The most efficient condition in terms of hydrogen productivity, among the lactose concentrations tested (15, 20, 25 and 30 g/L), using Barite and culture medium with molybdate, was 20 g/L. Next, a factorial design was carried out in which the inoculum density and Barite concentration were evaluated and validated. The central point (0.2 gvs/L of inoculum and 0.27 g/L of Barite) was considered operationally optimal, resulting in 213.40 ± 3.80 [mmol H₂/(L·day)]. The Basalt was also subjected to chemical treatments using NaOH, HCl, and H₂SO₄ to hydrogen productivity increases. Among the treatments evaluated, the treatment with NaOH showed the highest performance, resulting in a productivity of 185.23 ± 4.25 [mmol H₂/(L·day)], higher than the value observed in the control condition 124.95 ± 4.37 [mmol H₂/(L·day)]. Among the chemical treatments with NaOH evaluated (15, 20, 25 and 30%), using Basalt, the treatment with 20% NaOH presented the highest hydrogen productivity. Finally, after carrying out a factorial design in which the inoculum density and the concentration of the treated rock were evaluated and validated, the point corresponding to 0.230 gSV/L of inoculum and 0.365 g/L of treated rock was considered operationally optimal, resulting in a production of 193.89 ± 4.37 [mmol H₂/(L·day)].