Branched α-glucan, α-glucosyltransferase which forms the glucan, their preparation and uses

1. A purified α-glucosyltransferase, which forms a saccharide having α-1,4 linkages which is branched when the said α-glucosyltransferase acts on maltose and α-1,4 glucan having a glucose polymerization degree of 3 or higher;

wherein said branched α-1,4 glucan saccharide is composed of glucose molecules linked to each other with α-glucosidic linkages and having the following characteristics upon methylation analysis:

(1) Ratio of 2,3,6-trimethyl-1,4,5-triacetyl-glucitol to 2,3,4-trimethyl-1,5,6-triacetyl-glucitol, which indicates the ratio of glucose residues with α-1,4 linkages to α-1,6 linkages, is in the range of 1:0.6 to 1:4;

(2) Total content of 2,3,6-trimethyl-1,4,5-triacetyl-glucitol and 2,3,4-trimethyl-1,5,6-triacetyl-glucitol, which indicates that the total content of glucose residues with α-1,4 linkages and glucose residues with 1,6 linkages, is 60% or higher in the partially methylated glucitol acetates;

(3) Content of 2,4,6-trimethyl-1,3,5-triacetyl-glucitol, which indicates that the content of glucose residues with α-1,3 linkages, is 0.5% or higher but less than 10% in the partially methylated glucitol acetates; and

(4) Content of 2,4-dimethyl-1,3,5,6-tetraacetyl-glucitol, which indicates that the content of glucose residues with α-1,3 linkages and α-1,6 linkages, is 0.5% or higher in the partially methylated glucitol acetates; and

wherein said α-glucosyltransferase has the following physicochemical properties:

(a) Molecular weight

90,000±10,000 daltons on SDS-polyacrylamide gel electrophoresis;

(b) Optimum temperature

50 to 55° C. when reacted at pH 6.0 for 30 min;

(c) Optimum pH

pH 5.0 to 6.3 when reacted at 40° C. for 30 min;

(d) Thermal stability

Stable up to the temperature of 40° C. when incubated at pH 6.0 for 60 min; and

(e) pH Stability

Stable at least in the range of pH 4.0 to 8.0 when incubated at 4° C. for 24 hours.

2. The α-glucosyltransferase of claim 1 , which is derived from a microorganism of the genus Bacillus or Arthrobacter.

3. The α-glucosyltransferase of claim 1 , which is derived from a microorganism of the genus Bacillus is of the strain Bacillus circulans PP710, International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology Accession No. FERM BP-10771, or a mutant thereof capable of producing the α-glucosyltransferase of claim 1 .

4. The α-glucosyltransferase of claim 1 , which is derived from a microorganism of the strain Arthrobacter globiformis PP349, International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology Accession No. FERM BP-10770, or a mutant thereof capable of producing the α-glucosyltransferase of claim 1 .

5. A process for producing the α-glucosyltransferase of claim 1 , comprising the steps of:

culturing a microorganism selected from the strains of Bacillus circulans , FERM BP-10771 , Arthrobacter globiformis , FERM BP-10770, and mutants thereof capable of producing the α-glucosyltransferase of claim 1 ; and

collecting the produced α-glucosyltransferase from the resulting culture.