Method for isomerizing glucose syrups

Abstract

The present invention is directed to a method for enzymatically isomerizing glucose in glucose-containing liquors. The presence of relatively small amounts of water-soluble salts of sulfurous acids during the enzymatic isomerization of glucose in glucose-containing liquors reduces color formation therein and increases the stability of the glucose-isomerizing enzyme.

What is claimed is: 
     
       1. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose comprising providing a glucose-isomerizing enzyme in a glucose-containing liquor and subjecting the liquor to isomerizing conditions, there being present in the glucose-containing liquor during isomerization a small amount of a water-soluble salt of sulfurous acid sufficient to measurably reduce the formation of color bodies below that level obtained by carrying out the enzymatic isomerization without the presence of the water-soluble salt of sulfurous acid. 
     
     
       2. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 1, wherein the amount of a water-soluble salt of sulfurous acid provided in the glucose-containing liquor during isomerizaton is sufficient to provide a level of SO 2  in the liquor of from about 0.02 to about 0.3 percent by weight based on the dry substance content of the liquor. 
     
     
       3. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 2, wherein the amount of a water-soluble salt of sulfurous acid provided in the glucose-containing liquor during isomerization is sufficient to provide a level of SO 2  in the liquor of from about 0.03 to 0.08 percent by weight based on the dry substance content of the liquor. 
     
     
       4. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 2, wherein the glucose-isomerizing enzyme is produced from a micro-organism of the Streptomyces genus. 
     
     
       5. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 4, wherein cellular material containing glucose-isomerizing enzyme is provided in the liquor. 
     
     
       6. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 5, wherein the pH of the glucose-containing liquor during isomerization is maintained at a value from about 6.5 to about 7.5. 
     
     
       7. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 6, wherein the temperature of the glucose-containing liquor during isomerization is maintained at a level of from about 50° to about 65° C. 
     
     
       8. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 7, wherein the glucose-isomerizing enzyme is produced from Streptomyces sp. ATCC 21175 or Streptomyces ATCC 21176. 
     
     
       9. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 8, wherein the water-soluble salt of sulfurous acid provided in the glucose-containing liquor during the isomerization is selected from the group consisting of magnesium sulfite, magnesium bisulfite and mixtures thereof. .Iadd. 10. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose comprising providing a glucose-isomerizing enzyme in a glucose-containing liquor and subjecting the liquor to isomerizing conditions, there being present in the glucose-containing liquor during isomerization an amount of a water-soluble salt of sulfurous acid sufficient to reduce denaturation of the glucose-isomerizing enzyme below that level occurring when the enzymatic isomerizaton is carried out without the presence of the water-soluble salt of sulfurous acid. .Iaddend..Iadd. 11. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 10, wherein the glucose-isomerizing enzyme is derived from microorganisms of the Streptomyces genus. .Iaddend..Iadd. 12. A process for enzymatically isomerizing glucose in a glucose-containing liquor to fructose as defined in claim 11, wherein the microorganisms of the Streptomyces genus are Streptomyces sp. ATCC 21175. .Iaddend.