FED-BATCH FERMENTATION DEALING WITH NITROGEN LIMITATION IN MICROBIAL TRANSGLUTAMINASE PRODUCTION BY STREPTOVERTICILLIUM MOBARAENSE

In the later stages of a batch fermentation for microbial transglutami nase production by Streptoverticillium mobaraense the availability of a nitrogen source accessible to the microorganism becomes critical. Fe d-batch fermentation is investigated with the aim of avoiding this sub strate limitation. When peptone is used as a nitrogen source in the fe ed, no significant improvement of growth and transglutaminase producti on is observed. This is probably due to crosslinking of the nitrogen s ource by the transglutaminase produced. Using an inorganic nitrogen so urce alone does not give satisfactory growth and production. A fed-bat ch fermentation method has thus been developed to deal with this probl em. In the batch phase of the fermentation, an initial medium containi ng peptone, designed on the basis of the stoichiometric requirements o f the microorganism, is used to ensure optimal growth. In the feeding phase, ammonium sulphate is used instead to avoid the crosslinking eff ect. The feed composition, mainly the amount of nitrogen and carbon so urce, is also based on the stoichiometric requirements of the organism , taking into account the replacement of peptone by ammonium sulphate. By using this fed-batch fermentation technique. cell-mass dry weight and transglutaminase production could be increased by 33% and 80% resp ectively, compared to those in a batch fermentation.