A temperature-shift strategy in batch microbial transglutaminase fermentation

Temperature is one of the most important environmental factors for cell gro wth and product formation. Batch microbial transglutaminase (MTG) fermentat ions by Streptoverticillium mobaraense WSH-Z2 at various temperatures, rang ing from 25 to 35 degreesC, were studied. MTG activity and dry cell weight (DCW) reached 2.94 u/ml and 25.1 g/l, respectively at 30 degreesC, which we re higher than those at other temperatures. The lag time was shorter and th e specific cell growth rate (mu (cell)) and specific MTG production rate (m u (MTG)) in the early stages of growth were higher at 32 degreesC or higher temperature. At the mid- and later stages of growth, mu (cell) and mu (MTG ) were higher at 28 degreesC. Based on these results, a two-stage temperatu re control strategy was developed in which 32 degreesC was used for ferment ation for the first 18 h and the temperature was switched to 28 degreesC af ter 18 h. Using this temperature-shift strategy, the maximal MTG activity a nd productivity reached 3.37 u/ml and 80.2 u/l/h, respectively. The average specific cell growth rate and average specific MTC production rate were 3. 02 u/h/g DCW and 0.028 g/h/g DCW, respectively. The MTG fermentation level obtained by the strategy was higher than those in single temperature-contro l experiments. (C) 2001 Elsevier Science Ltd. All rights reserved.