[Nuclease P1 production by immobilized Penicillium citrinum cells]

Mycelia of Penicillium citrinum were adsorbed and immobilized efficiently within porous polyurethane. Nuclease P1 produced by the immobilized cells were studied in shaking flasks. The suitable glucose and peptone contents in medium were 10 g/L and 1 g/L, respectively. And the shaking speed was 180-200 r/min. After 48 h fermentation, the nuclease P1 activity reached 513.3 U/ml, the productivity was 3.6 times higher than that of the free cells. The production cost is obviously reduced. In repeated batch fermentation, the immobilized cells kept the capacity after 28 batches for 56 days with an average nuclease P1 activity of 507.4 U/ml.