Key process conditions for production of [C.sub.4] dicarboxylic acids in bioreactor batch cultures of an engineered Saccharomyces cerevisiae strain

The growth and product formation by the engineered strain is studied in bioreactors in order to analyze the effects of pH, calcium and carbon dioxide and oxygen availability. The studies have shown that malic acid production with the engineered Saccharomyces cerevisiae strain is transferred from shake flasks to 1- liter batch bioreactors by simultaneous optimization of four process parameters, pH and concentrations of C[O.sub.2], calcium and [O.sub.2].