Improving k(L)a determination in fungal fermentation, taking into account electrode response time

An alternative way for determining the oxygen mass transfer coefficient, k( L)a, based upon the traditional dynamic method, is proposed. The oxygen mat erial balance equation in the liquid phase is integrated after insertion of the oxygen probe response time (first order type), and k(L)a values are de termined by employing Marquardt's algorithm, considering as a weighting fac tor the model's sensitivity with respect to k(L)a. Bench-scale fermentation s of Aspergillus awamori, performed under different agitation (300-700 rpm) and aeration conditions (0.2-0.6 vvm), were utilized for calculating k(L)a values (0.0283-0.0874 s(-1)), employing three methods: two so-called tradi tional, the gas balancing and the dynamic methods, and the one proposed her e. The latter method is shown to be as reliable as the aforementioned metho ds but is easier to apply when the oxygen level in the reactor is above the critical value. (C) 2000 Society of Chemical Industry.