Composition for producing tagatose and method of producing tagatose using the same

1. A method of producing tagatose, comprising:

(a) producing tagatose-6-phosphate by contacting fructose-6-phosphate with tagatose-6-phosphate kinase, a microorganism expressing the tagatose-6-phosphate kinase, or a culture of the microorganism,

wherein the tagatose-6-phosphate kinase consists of the amino acid sequence of SEQ ID NO: 3 or 5; and

(b) producing tagatose by contacting the produced tagatose-6-phosphate with tagatose-6-phosphatase, a microorganism expressing the tagatose-6-phosphate phosphatase, or a culture of the microorganism.

2. The method of claim 1 , further comprising converting glucose-6-phosphate into fructose-6-phosphate by contacting glucose-6-phosphate with glucose-6-phosphate-isomerase, a microorganism expressing the glucose-6-phosphate-isomerase, or a culture of the microorganism.

3. The method of claim 2 , further comprising converting glucose-1-phosphate into glucose-6-phosphate by contacting glucose-1-phosphate with phosphoglucomutase, a microorganism expressing the phosphoglucomutase, or a culture of the microorganism.

4. The method of claim 3 , further comprising converting, starch, maltodextrin, or sucrose into glucose-1-phosphate by contacting starch, maltodextrin, sucrose, or a combination thereof with α-glucan phosphorylase, starch phosphorylase, maltodextrin phosphorylase, or sucrose phosphorylase, a microorganism expressing the α-glucan phosphorylase, starch phosphorylase, maltodextrin phosphorylase, or sucrose phosphorylase, or a culture of the microorganism.

5. The method of claim 2 , further comprising converting glucose into glucose-6-phosphate by contacting glucose with glucokinase, a microorganism expressing the glucokinase, or a culture of the microorganism.

6. The method of claim 5 , further comprising convening starch, maltodextrin or sucrose into glucose by contacting starch, maltodextrin, sucrose, or a combination thereof with α-amylase, pullulanase, glucoamylase, sucrase, or isoamylase, a microorganism expressing the α-amylase, pullulanase, glucoamylase, sucrose, or isoamylase, or a culture of the microorganism.

7. The method of claim 1 , wherein the contacting is performed at pH 5.0 to 9.0, 40° C. to 80° C., or for 0.5 hours to 24 hours.

8. A method of producing tagatose, comprising contacting (a) starch, maltodextrin, sucrose, or a combination thereof; with (b) (i) tagatose-6-phosphate phosphatase, (ii) tagatose-6-phosphate kinase consists of the amino acid sequence of SEQ ID NO: 3 or 5, (iii) glucose-6-phosphate-isomerase, (iv) phosphoglucomutase or glucokinase, (v) phosphorylase, and (vi) one or more of α-amylase, pullulanase, isoamylase, glucoamylase, or sucrase; and (c) phosphate.