Enzymatic preparation of seasoning 5'-nucleotides from baker's yeast

Chemical phosphorylation with sodium trimetaphosphate (STMP) as a modifying agent was used to prepare functional protein isolate and dissociated nucleic acid (mostly RNA) from baker's yeast. The majority of protein-RNA complex in the disintegrated yeast cells was first extracted with an aqueous alkaline solution (pH 12, 40 degrees C) followed by phosphorylation with STMP under the same condition for 6 hrs. An apparent dissociation of protein-RNA complex occurred due to the covalent attachment of anionic phosphate groups onto yeast protein molecules. The nucleic acid residued in the supernatant after removal of modified protein isolate by isoelectric precipitation was recovered by reprecipitating at pH 2 followed by converting it to 5'-nucleotides with malt rootlets 5'-phosphodiesterase as well as red marine algal adenylate deaminase. This coherent process provided a preparation of food-usable functional protein isolate and 5'-nucleotides from baker's yeast.