Secretion in long-chain dicarboxylic acid fermentation

A new experimental method was established to investigate 1,11- dicarboxylic acid (DCA₁₃) secretion in alkane-assimulating yeast, Candida tropicalis. By this method, phenomenon of acid production in resting cells was observed. The whole process can be divided into two phases: the acid secretion phase and the coupling phase of both acid secretion and alkane bioconversion. Extracellular pH and DCA₁₃/^2- played important roles in this process. High extracellular pH and low DCA₁₃/^2- can facilitate acid secretion. A chemical structured model was proposed to analyze these two factors detailedly. Model parameters were simulated by the random search method. Simulated data fitted the experimental results so well that the maximum error between them was less than 5%. This kind of experimental method and kinetic analysis could also be used in other organic acid fermentation.