The effects of some physical factors, including preculture time, media initial pH and bead concentrations, on the production of gamma-decalactone by immobilized Sporidiobolus salmonicolor CCRC 21975 within calcium alginate beads were investigated. Long-term reuse and stability of the immobilized preparation were also examined. Regardless of the preculture time, no significant difference in the production of gamma-decalactone by immobilized S. salmonicolor cells was observed as long as the initial populations of the entrapped cells were the same. Calcium alginate-immobilized S. salmonicolor cells showed improved tolerance to perturbations in external pH and produced more gamma-decalactone than did free cells. The patterns of changes in S. salmonicolor cells inside or outside the gel beads as well as production of gamma-decalactone by immobilized S. salmonicolor did not vary significantly with bead concentration. Furthermore, after reuse of the calcium alginate-immobilized S. salmonicolor cells for 13 consecutive 4-day batch fermentations, no bead leakage was detected. The production of gamma-decalactone in the 13th cycle was about 58.4% of that in the first cycle.