Enzymatic production of ribonucleotides from autolysates of Kluyveromyces marxianus grown on whey

After 20h fermentation of medium containing 5% (w/v) dehydrated whey, at 30 degrees C, pH 4.5, yeast cells were harvested, diluted in 0.1M KH2PO4, and autolyzed at different pHs (6.5-7.5) and temperatures (45-55 degrees C). Phosphodiesterase (0.2-1.0% w/v, 65 degrees C, pH 6.5, 6h) and adenyl deaminase (0.5-1.0% w/v, 60 degrees C, pH 5.5, 4h) were added to the autolysates. After heat treatment (100 degrees C, 15 min), samples were analyzed by RP-HPLC and LC/MS. Production of 5'-ribonucleotides was maximized at 50 degrees C, pH 6.5. Yields of 5'-AMP (800 mu g/g of biomass) and 5'-GMP (2000 mu g/g) increased considerably after addition of 1.0% phosphodiesterase. 5'-IMP increased only after addition of 1.0% adenyl deaminase.