[47] Production of 5′-ribonucleotides using immobilized 5′-phosphodiesterase

This chapter presents the preparation, enzymatic properties, and industrial application of immobilized 5'-phosphodiesterase. 5'-Ribonucleotides are starting substances for the preparation of food additives and drugs. Their preparation by the enzymatic hydrolysis of RNA is well known. However, the 5'-phosphodiesterase enzyme used for this purpose simultaneously hydrolyzes RNA and DNA so that 5'-deoxynucleotides are obtained as by-products in addition to the intended 5'-ribonucleotides. These by-products can only be separated from the 5'-ribonucleotides with great difficulty. For preparing pure 5'-ribonucleotides, it is, therefore, necessary to start from RNA that is practically free of DNA. However, by using an immobilized enzyme, the purification procedure of the reaction products becomes simple and the yield is high. A crude RNA/DNA solution such as is obtained in known manner from microorganisms can be used without an expansive preliminary purification of RNA. Various processes for the preparation of pure RNA are already known, for example, the selective precipitation of pure RNA by heating and subsequent treatment with acid or by precipitation in the presence of bivalent cations.