Inactivation of lytic enzymes by heat treatment in ultrafiltration-coupled acetonobutylic fermentation

• Published in: Applied microbiology and biotechnology Vol. 33; no. 3; pp. 274 - 279
• Main Authors: Minier, M, Soucaille, P, Blanc-Ferras, E, Izard, A, Goma, G
• Format: Journal Article
• Language: English
• Published: 01.06.1990
• Subjects: Clostridium; enzyme inhibitors; fermentation; growth rate; heat treatment; inactivation
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/BF00164521

Clostridium acetobutylicum cultures were grown in batch mode, using mineral ultrafiltration membranes to confine the microbial cells in the fermentor while the permeate was subject to heat treatment (70 degrees C for 20 min) before recycling. The extracellular lytic activity in the broth, measured by the initial rate of lysis of a buffered suspension of Clostridium cell walls, was strongly decreased by a factor of 6.7 at pH 5.5, and 3.9 at pH 4.8. This caused an enhancement of the growth rate during the course of fermentation and an increase in the maximal cell concentration, which was practically doubled in heat-treatment assays. The solvent production results obtained were less positive in terms of productivity and final butanol concentration, since there was no significant improvement, despite elimination of lytic enzyme inhibition. The heat-inactivation of lytic enzymes influenced the culture more than the suppression of product inhibition, particularly concerning the activity and orientation of this bacterial metabolism.