Performance intensification of a stirred bioreactor for fermentative biohydrogen production

<p>In this study, the biohydrogen (bioH<sub>2</sub>) production of a microbial consortium was optimized by adjusting the type and configuration of two impellers, the mixing regimen and the mass transfer process (<i>K</i><sub>L</sub><i>a</i> coefficients). A continuous stirred-tank reactor (CSTR) system, with a nonstandard geometry, was characterized. Two different mixing configurations with either predominant axial (PB4 impeller) or radial pumping (Rushton impeller) were assessed and four different impeller configurations to produce bioH<sub>2</sub>. The best configuration for an adequate mixing time was determined by an ANOVA analysis. A response surface methodology was also used to fully elucidate the optimal configuration. When the PB4 impellers were placed in best configuration, c/Dt = 0.5, s/Di = 1, the maximum bioH<sub>2</sub> productivity obtained was 440 mL L<sup>−1</sup> hr<sup>−1</sup>, with a bioH<sub>2</sub> molar yield of 1.8. The second best configuration obtained with the PB4 impellers presented a bioH<sub>2</sub> productivity of 407.94 mL L<sup>−1</sup> hr<sup>−1</sup>. The configurations based on Rushton impellers showed a lower bioH<sub>2</sub> productivity and bioH<sub>2</sub> molar yield of 177.065 mL L<sup>−1</sup> hr<sup>−1</sup> and 0.71, respectively. The experiments with axial impellers (PB4) showed the lowest <i>K</i><sub>L</sub><i>a</i> coefficient and the highest bioH<sub>2</sub> production, suggesting that mixing is more important than <i>K</i><sub>L</sub><i>a</i> for the enhanced production of bioH<sub>2.</sub></p>