Valorization of the Crude Glycerol for Propionic Acid Production Using an Anaerobic Fluidized Bed Reactor with...

This study evaluated the propionic acid (HPr) production from crude glycerol (CG) (5000 mg L^-1) in an anaerobic fluidized bed reactor (AFBR). Grounded tire particles (2.8-3.35 mm) were used as support material for microbial adhesion. The reactor was operated with hydraulic retention times (HRT) varying from 8 to 0.5 h under mesophilic (30 °C) conditions. The HPr was the main metabolite produced, increasing in composition from 66.5 to 99.6% by decreasing the HRT from 8 to 0.5 h. Other metabolic products were 1,3-propanediol, with a maximum of 29.4% with an HRT of 6 h, ethanol, acetic, and butyric acids. The decrease in HRT from 8 to 0.5 h decreased the HPr yield, with a maximum of 0.48 ± 0.06 g HPr g COD^-1 and an HRT of 6 h, and favored HPr productivity, with a maximum of 4.09 ± 1.24 g L^-1 h^-1 and HRT of 0.5 h. In the biogas, the H₂ content increased from 12.5 to 81.2% by decreasing the HRT from 8 to 0.5 h. These results indicate the potential application of the AFBR for HPr production using an immobilized mixed culture.