Biocatalysis of Corn Starch with Thermostable α-amylase in Twin-screw Extruder

Traditional technical solutions in the field of enzymatic hydrolysis of starch and starch-containing raw materials involve multi-stage water-enzymatic treatment of the substrate including the stages of cooking, liquefaction, dextrinization, evaporation and drying. As an alternative to this multistage technology, the use of extruders is proposed, which, in addition to the production of food, ingredients and feed, can be used as chemical reactors, replacing traditional batch reactors. The study of the influence of operating extrusion parameters, moisture content and dosage of a thermostable amylolytic enzyme on the process of starch extrusion and the degree of its hydrolysis in the chamber of a twin-screw extruder was carried out. It was found that the temperature range 112-122 ° C is optimal for the biocatalysis process. The maximum dextrose equivalent of 13.6 was achieved with a moisture content of 36% and a dosage of α-amylase of 6 amylolytic units per 1 g of starch. It has been shown that the dextrose equivalent during the extrusion of starch with a given amount of enzyme at a moisture content of 20% was 12.6. The residual amylolytic activity of the extrudates varied in the range from 0.2 to 0.55 units and depended on the initial enzyme dosage. It indicates incomplete inactivation of α-amylase during extrusion even at temperature conditions exceeding the α-amylase temperature optimum. It was found that, in contrast to the extrusion of starch without an enzyme, an increase in the moisture content upon the addition of α-amylase promotes an increase in solubility and a decrease in the water-holding capacity of extrudates. The results of the study showed the possibility of carrying out a continuous biocatalytic reaction of starch hydrolysis directly in the extruder chamber. It makes it possible to obtain hydrolysates with low moisture content in one stage, excluding the stages of water-heat treatment of low-concentrated starch media, their evaporation and subsequent spray drying.

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