Herein, we established a repeated-batch process for ethanol production from glycerol by immobilized Pachysolen tannophilus. The aim of this study was to develop a more practical and applicable ethanol production process for biofuel. In particular, using industrial-grade medium ingredients, the microaeration rate was optimized for maximization of the ethanol production, and the relevant metabolic parameters were then analyzed. The microaeration rate of 0.11 vvm, which is far lower than those occurring in a shaking flask culture, was found to be the optimal value for ethanol production from glycerol. In addition, it was found that, among those tested, Celite was a more appropriate carrier for the immobilization of P. tannophilus to induce production of ethanol from glycerol. Finally, through a repeated-batch culture, the ethanol yield (Ye/g) of 0.126 ± 0.017 g-ethanol/g-glycerol (n = 4) was obtained, and this value was remarkably comparable with a previous report. In the future, it is expected that the results of this study will be applied for the development of a more practical and profitable long-term ethanol production process, thanks to the industrial-grade medium preparation, simple immobilization method, and easy repeated-batch operation.

We investigated ethanol production from glycerol after screening of the yeast Pachysolen tannophilus ATCC 32691. For yeast to produce ethanol form glycerol, it is important that aeration is finely controlled. Therefore, we attempted to produce ethanol using a surface-aerated fermentor. When 880 ml of YPG medium (1% yeast extract, 2% peptone, 2% glycerol) was used to produce ethanol, the optimal aeration conditions for ethanol production were a surface aeration rate and agitation speed of 500 ml/min and 300 rpm, respectively. In a fed-batch culture, the maximum ethanol production and the maximum ethanol yield from glycerol (Ye/g) was 5.74 g/l and 0.166, respectively, after 90 hr using the surface-aerated fermentor.