1,3-Propanediol production from glycerol in polyurethane foam containing anaerobic reactors: performance and biomass cultivation and retention.

The use of batch and upflow anaerobic reactors filled with polyurethane foam for pure glycerol fermentation was evaluated. The best reactor operational conditions to obtain high yield and productivity of 1,3-propanediol (1,3-PDO) as the main product and the role of the polyurethane foam in the growth and retention of suspended and attached biomass in the reactors were investigated. In the experiment at 30 °C with a batch reactor (700 mL), biomass growth was mostly as immobilized attached cells, and the achieved 1,3-PDO yield was up to 0.58 mol mol-gly. In the experiment (30 °C) with an upflow anaerobic reactor (717 mL), glycerol loading rates (gly-LR) ranging from 6.94 to 15.47 g gly L day were applied during a 102-day period. During the operation, average 1,3-PDO yield was 0.47 mol mol-gly, reaching a maximum of 0.51 mol mol-gly at gly-LR of 13.57 g gly L day. High 1,3-PDO productivity (5.35 to 5.44 g L day) was obtained when gly-LR was 13.57 to 15.47 g gly L day. Comparing the close yield values in both batch and continuous reactors and based on microbial evaluation, it is concluded that most of the 1,3-PDO generated in the continuous reactor was due to the suspended biomass retained by the foam cubes. The Clostridium genus was the predominant 1,3-PDO producer. Good yields and productivities with packed reactors were attributed to polyurethane foam used for mixed culture growth and retention. Consequently, they are worth considering for 1,3-PDO production from pure glycerol.