Availability and metabolism of purines of single-cell proteins in monogastric animals.

Single-cell protein (SCP) consisting of the more or less processed cell mass of bacteria, yeasts, fungi or algae is considered to be a potential source of protein for the nutrition of animals and man. However, the high content of nucleic acids, which may attain 10-1570 in fast-growing microbes, is one of the main factors limiting the use of SCP for human nutrition because of hyperuricemia (Anon. 1976). Processing of SCP in order to reduce the content of nucleic acids appears to result in loss of protein and reduction of the nutritive value (Kharatyan, 1978), increase of allergic factors (Scrimshaw & Dillon, 1979) or increase of free bases (Tiemeyer et al. 1980). Animal feeding and metabolism experiments are necessarily associated with the development of SCP products for evaluating inter alia the various criteria of protein quality, the utilization and/or uricogenic potency of nucleic acids and possible influences on animal productivity. In most of such experiments performed up to now the nucleic acid fraction of SCP has not been analyzed and important physiological characteristics of the experimental animals have frequently been ignored. This paper discusses some of the recent developments in the evaluation of nucleic acids in SCP.