betaamilase

Beta-amylase is an enzyme with the EC number 3.2.1.2 that catalyzes the hydrolysis of alpha-1,4 glycosidic bonds in starches from the nonreducing end, releasing maltose as the main product. It is primarily found in plants, especially barley endosperm, and is also produced by some microorganisms. In plants, beta-amylase participates in starch degradation during seed germination and grain maturation.

Mechanism and properties: Beta-amylase is an exo-acting enzyme that cleaves maltose units successively from the nonreducing end of starch molecules. It is classified in glycoside hydrolase family 14 (GH14). The active site typically contains catalytic glutamate residues. The enzyme generally operates best in mildly acidic conditions and at elevated temperatures, with pH optima around 4.0–5.5 and temperature optima that depend on the source, often in the range of 50–70°C for industrial preparations. In starch with branched points, beta-amylase can produce a limit dextrin that contains alpha-1,6 linkages.

Substrates and products: The primary substrates are soluble starch, amylose, and to a lesser extent amylopectin. The principal product is maltose, which is a fermentable sugar, and the extent of maltose production is influenced by the presence of branching points and other enzymes such as alpha-amylase.

Applications: Beta-amylase is widely used in brewing and distilling to increase maltose production for yeast fermentation. It also finds use in starch processing and maltose syrup production, as well as in some baking and fruit juice clarification processes. Commercial preparations may be derived from barley malt or produced recombinantly in microorganisms. Regulatory status varies by jurisdiction, but many enzyme preparations are approved as processing aids.