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The objective of this work was to evaluate a thermotolerant yeast Issatchenkia orientalis DY252 as a microbial feed additive for ruminants. In the present study, the influence of volatile fatty acids (VFA) and temperature on oxygen uptake rate by I. orientalis DY 252 was investigated. It was evident that the oxygen uptake rate was decreased gradually as the VFA concentrations increased in a range of 30 to 120 mM. Although the oxygen uptake rate was not greatly affected by temperature in the range 37 to 43°C, a maximum value of 0.45 mg O 2 /g cell/ min was obtained at 39°C. With regard to the oxygen uptake rate by yeast, viability was found to be less important than the metabolic activity of yeast.

Aims:The purpose of the present investigation was to develop a novel method for cell immobilization. Methods and Results: Aureobasidium pullulans cells were mixed with an alginate solution, and the mixture was extruded to form small gel beads as hydrated-immobilized cells. The beads were then placed at )15°C for 6-24 h to induce freeze-dehydration. The freeze-dehydration resulted in shrinkage of beads as a result of water removal reducing bead volume by 82% and bead weight by 85%. The dehydrated beads were successfully used for the production of fructo-oligosaccharides in a model reactor system. Conclusions: Dehydrated beads may provide some commercial advantages over conventional immobilized cells. Significance and Impact of the Study: This study shows that bioreactor performance can be improved up to two times by the use of the dehydrated beads.