Engineering aspects of the production of sugar alcohols with the osmophilic yeast Moniliella tomentosa var pollinis. Part Ⅰ. Batch and fed-batch operation in stirred tank

摘要

Moniliella tomentosa var pollinis was cultivated on complex medium consisting of glucose as carbon source, urea, (NH_4)_2SO_4, corn steep liquor and yeast extract as nitrogen sources, respectively. The pH and the concentrations of (dry) cell mass, glucose, erythritol, ribitol, glycerol, disaccharides, trisaccharides, polysaccharides, amino acids in medium, oxygen and carbon dioxide in off-gas were monitored during cultivation. Rates of growth, substrate uptake and production, yields and yield coefficients as well as OUR, CPR and RQ were evaluated with different medium composition and operating conditions in a 30 1 stirred tank by batch and fed-batch operation. At high substrate concentrations in batch operation high (dry) cell mass concentrations (65 g l~(-1)), high erythritol concentrations (90 g l~(-1)) erythritol yield (36%) and yield coefficients (0.35 g g~(-1)) as well as polyol concentrations (150 g l~(-1)) polyol yield (62%) and yield coefficients (0.65 g g~(-1)) were obtained under optimal conditions. With fed-batch operation better results were obtained: high (dry) cell mass concentrations (up to 116 g l~(-1)), high erythritol concentrations (up to 170 g l~(-1)), polyol concentrations (up to 188 g l~(-1)) were obtained under optimal conditions. Under oxygen limitation ethanol was formed, and under nitrogen limitation foam formation impaired the production process. By suitable aeration and a fed-batch process using a mixture of glucose and nitrogen source for feeding, ethanol and foam formation could be reduced and eliminated, respectively.