Mycelium of Actinoplanes teichomyceticus ATCC 31121 was immobilized or co-immobilized with soybean meal in calcium-alginate beads. Immobilized mycelium was used to deacylate A40926 antibiotic complex in a batch and repeated-batch system and the results were compared with the performance of a suspension culture as well as washed mycelium. The specific deacylation rate of suspended cells was 0.19 mg g(-1) h(-1) while that of washed and immobilized mycelium was found to be much higher; i.e., 0.62 and 0.67 mg g(-1) h(-1), respectively. Biotransformation with suspended mycelium proved not to be attractive in a repented-batch system. After 8 days, i.e., two batch cycles, only 40% of the initial biomass was recovered with a decrease in the specific deacylation rate of 50%. In contrast to that, repeated-batch biotransformation with immobilised mycelium could be successfully maintained for longer than 30 days. During the first 15 days of operation, i.e., three batch cycles, the deacylation rates were rather constant, but gradually decreased after the third consecutive batch cycle. Coimmobilization with soybean meal as a in situ nutrient source improves the deacylation capability of immobilized mycelium.