The nucleic acid content in Candidu ntilis was autolytically reduced only after previous lyophilization of yeast cells or pretreatment of the cells with ethyl acetate. These pretreatments provided a sufficient permeability of the cell membrane system and thus enabled a reduction of the nucleic acid content. While deep freezing of the cells (-35 "C) had no positive effect on the degradation of nucleic acids, lyophilization of yeast cells led to a 75 "/, decrease of the nucleic acid content. Furthermore, a 55 "/, reduction of the nucleic acid content was proceeded without a concomitant loss of proteins. Similar results were obtained by using ethyl acetate.
Proteins from microbial sources, particularly yeasts, could significantly compensate for the increasing shortage of food protein. However, the utilization of single-cell protein (SCP) for nurtitional purposes is hindered because of their high nucleic acid (NA) content. A high NA content can evoke high levels of uric acid in blood, which subsequently precipitates due to its low solubility and finally causes diseases (MOUNOLOU 1971, TREVALYAN 1975, DAMODORAN and KINSELLA 1984, KYBAROVA and RUT 1985).
Several chemical, physical and enzymatic methods were developed for depleting microorganisms of their N content (RUT et al. 1978al. . OHRABLO er al. 1985)). The most promising methods, particularly because of their low cost, seem to be autolytic procedures based on an activation of ribonucleases present in microorganisms. However, up to now research results indicate that no such method is generally applicable. Some procedures work efficiently only if a particular strain was grown on a special medium and harvested at a certain stage of the growth phase (LINDBLOM and MOGRAN 1974, TREVELYAN 1976a, 1976b, HUANG and KINSELLA 1986).