Propionic acid production from glycerol was studied using Propionibacterium acidipropionici DSM 4900 cells immobilized on polyethylenimine-treated Poraver (PEI-Poraver) and Luffa (PEI-Luffa), respectively. Using PEI-Luffa, the average productivity, yield and concentration of propionic acid from 40gL -1 glycerol were 0.29gL -1h -1, 0.74mol PAmol Gly -1 and 20gL -1, respectively, after four consecutive recycle-batches. PEI-Poraver supported attachment of 31 times higher amounts of cells than PEI-Luffa and produced 20, 28 and 35gL -1 propionic acid from 40, 65 and 85gL -1 glycerol, respectively (0.61molPAmolGly-1). The corresponding production rates were 0.86, 0.43 and 0.35gL -1h -1, which are the highest reported from glycerol via batch or fed-batch fermentations for equivalent propionic acid concentrations. Using a continuous mode of operation at a dilution rate of 0.1h -1, cell washout was observed in the bioreactor with free cells; however, propionic acid productivity, yield and concentration were 1.40gL -1h -1, 0.86molPAmolGly-1, and 15gL -1, respectively, using immobilized cells in the PEI-Poraver bioreactor. The choice of the immobilization matrix can thus significantly influence the fermentation efficiency and profile. The bioreactor using cells immobilized on PEI-Poraver allowed the fermentation of higher glycerol concentrations and provided stable and higher fermentation rates than that using free cells or the cells immobilized on PEI-Luffa.
Bibliographical noteFunding Information:
The Swedish Governmental Agency for Innovation Systems (Vinnova) is acknowledged for funding the project. Perstorp AB is thanked for coordinating the project.
- Cell adsorption
- Organic acid
- Platform chemical