Liquefying alkaline .alpha.-amylase, process for producing the same, and detergent composition containing the same

A liquefying alkaline .alpha.-amylase having the following enzymatic properties:

• 1) action:
• hydrolyzes 1,4-.alpha.-glucosidic linkages in starches, amylose, amylopectin and partial degradation products thereof and from amylose, forms glucose (G1), maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5) and maltohexaose (G6), but does not act on pullulan;
• 2) isoelectric point:
• has an isoelectric point of about 9.2 when measured by isoelectric focusing electrophoresis;
• 3) acting pH:
• acts in a pH range of from 5.0 to 11.0;
• 4) pH stability:
• stable in a pH range of from 6.5 to 10.0;
• 5) acting temperature range:
• acts in a temperature range of from 20.degree. C. to 80.degree. C.;
• 6) thermal stability:
• stable at temperatures of 50.degree. C. or lower when treated for 30 minutes in a glycine-salt-sodium hydroxide buffer having a of pH 8.5;
• 7) molecular weight:
• has a molecular weight of 50,000.+-.5,000 as measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis;
• 8) effect of surfactants:
• substantially free from activity inhibition by surfactants selected from the group consisting of sodium linear alkylbenzene sulfonates, sodium alkylsulfate esters, sodium polyoxyethylene alkylsulfate esters, sodium alkylsulfonates, soaps, and polyoxyethylene alkyl ethers.

A process for the preparation of a liquefying alkaline .alpha.-amylase, comprising the steps of:

• (a) culturing a liquefying-alkaline-.alpha.-amylase-producing bacterium belonging to the genus Bacillus;
• and
• (b) isolating the liquefying alkaline .alpha.-amylase from the resulting culture;
• wherein said liquefying alkaline .alpha.-amylase has the following enzymatic properties:
• 1) action:
• hydrolyzes 1,4-.alpha.-glucosidic linkages in starches, amylose, amylopectin and partial degradation products thereof and from amylose, forms glucose (G1), maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5) and maltohexaose (G6), but does not act on pullulan;
• 2) isoelectric point:
• has an isoelectric point of about 9.2 when measured by isoelectric focusing electrophoresis.

A detergent composition, comprising:

• (a) a surfactant selected from the group consisting of anionic surfactants, nonionic surfactants, and mixtures thereof;
• and
• (b) a liquefying alkaline .alpha.-amylase having the following enzymatic properties:
• 1) action:
• hydrolyzes 1,4-.alpha.-glucosidic linkages in starches, amylose, amylopectin and partial degradation products thereof and from amylose, forms glucose (G1), maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5) and maltohexaose (G6), but does not act on pullulan;
• 2) isoelectric point:
• has an isoelectric point of about 9.2 when measured by isoelectric focusing electrophoresis.