Full Length Research Paper

Production of organic acids in an immobilized cell reactor using Propionibacterium acidi-propionici

M. Mohammadi¹, G.D. Najafpour¹*, M. Asadi², M. Rahimnejad¹, S. Najafpour³ M. Pazouki⁴

¹Faculty of Chemical Engineering, Noushirvani University of Technology, Babol, Iran.

²Faculty of Civil Engineering, Noushirvani University of Technology, Babol, Iran.

³Ecological Academy of Caspian Sea P.O.Box 961, Sari, Iran.

⁴Environment Group, Department of Energy, Materials and Energy Research Center, Karaj, Iran.

*Corresponding author. E-mail: najafpour@nit.ac.ir, najafpour8@yahoo.com. Fax: 0098-111-3234204.

Accepted 1 August, 2008

Immobilized cell reactor (ICR) was developed as a novel bioreactor to convert hydrolyzed sugars to organic acids. Sugar fermentation by Propionibacterium acid-propionici entraped by calcium alginate was carried out in continuous mode to produce propionic and acetic acids. In continuous fermentation, more than 90 percent of glucose conversion and 60 percent conversion of xylose were obtained at a retention time of 28 h.  The present research has demonstrated that the microorganism preferred glucose as carbon source over other carbon sources. The highest sugar concentration (120 g/L) in the ICR column was successfully converted to propionic acid. The achieved results in ICR with high substrate concentration are promising for scale up operation.

Key words: Enzyme, whole cell, immobilized cell reactor, bioreactor, entrapment.