For the production of 5'-IMP (inosine 5'-monophosphate) and 5'-GMP (guanosine 5'-monophosphate) which are used as the good flavor enhancers in food industry, the coimmobilization of nuclease from Penicillium sp. and adenyl deaminase from Aspergillus sp. on Sepharose matrix was studied.
By using this coimmobilization system, the yeast RNA (ribonucleic acid) was hydrolyzed to the respective mononucleotides and 5'-AMP (adenosine 5'- monophosphate) among the products was converted into 5'-IMP.
Sepharose 4 B was activated by the conventional CNBr activation method. This CNBr activated matrix was used for the coimmobilization simultaneously and for the immobilization of both enzymes.
The yield of enzyme activity on immobilization was between 10 to 30% in both enzymes depending on the method of immobilization. The theromostability of the coimmobilized adenyl deaminase was increased remarkably. The nuclease activity of the coimmobilized nuclease was increased to 50% than immobilized nuclease.
Being very important to achieve effective the coimmobilized enzyme system in terms of complete conversion of 5'-AMP into 5'-IMP, loading ratic of adenyl deaminase to nuclease on coimmobilization was above 1 as the ratio of protein. In RNA hydrolysis reaction, the longer space time was required than achieved for the complete conversion of RNA into mononucleotides.
The characterization of enzymes in various forms was carried out and the results were summarized in the following table.
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In conclusion, the coimmobilization of enzymes increased the reaction rate and broadened the stable range of pH and temperature in coimmobilized enzyme reactor was between 5 and 6 and around 50℃, respectively. For the complete conversion of RNA into mononucleotides, however, much longer space time was required, and hence the productivity of nucleotides might be decreased. As a result of it, the substrate recycling strategy or impact reactor might be used in order to increase the productivity of 5'-IMP and 5'-GMP.
