Screening of Kluyveromyces strains for the production of ethyl acetate: Design and evaluation of a cultivation system

摘要

Some members of the yeast Kluyveromyces marxianus are known to convert sugars and ethanol into ethyl acetate. This metabolic activity offers a chance for an economically favorable use of whey. An exemplary batch experiment is presented to demonstratethe formation of ethyl acetate by K. marxianus DSM 5422 on whey-based medium in an aerated 70-L stirred reactor. A screening system was developed to check Kluyveromyces strains regarding their capability to form ethyl acetate. The designed screening system takes the volatility of ethyl acetate and the requirement of oxygen for sugar conversion into account and allows the analysis of ester formation kinetics. Modeling and measurement of the ester stripping from screening bottles guaranteed reliable dataevaluation. Twelve of 23 tested strains produced noteworthy amounts of ethyl acetate with a yield between 0.13 and 0.23 g ester per gram sugar consumed. The productive strains showed individual kinetics of ester formation; some strains had a short interval of intense production while others exhibited a longer period of stable formation. Another factor of interest was the selectivity of product formation expressed as the mass ratio of formed ester and ethanol, which ranged from 0.9 to 3.5 g/g.