A new approach to optimization of the constructive parameters of laboratory fermenters is proposed in the paper. A non-iterative algorithm for problem solving is developed on the basis of a generalized approach for fuzzy optimization. It allows to take into account non-stochastic uncertainties. Influence of the parameters of the fuzzy sets to the result is investigated. Fuzzy optimization allows to determine such values of the constructive parameters under which KLa have greater value with about 5%.