Amylase is a general term for enzymes that hydrolyze starch and glycogen with the specificity of enzyme preparation. Its main mechanism of action is to hydrolyze starch into maltose, glucose, dextrin, etc. To understand amylase, we must first understand starch, which is a storage polysaccharide stored in cells as starch granules during plant growth, and exists in seeds and tubers. Starch is not a simple molecule, but a mixture of two different types of starch, divided into two categories: amylose and amylopectin.
Amylose: The amylose content in starch is about 10-30%. It is a chain-like compound made of glucose bonded by a -1,4-glycosidic bond that can be dissolved in hot water without forming a paste. It is blue when exposed to iodine and can be hydrolyzed by amylase into maltose and a small amount of glucose.
Amylopectin: The content of starch is relatively high, about 65% to 81%, and it is composed of thousands of glucose residues, also known as gum starch. The molecule is relatively large, and its molecule has many non-reducing ends, but only one reducing end, so it does not show reducing. It is insoluble in cold water, but expands into a paste when it reacts with hot water. When it encounters iodine, it turns purple or reddish-purple. It can be hydrolyzed by amylase to produce a mixture called dextrin.
What are the types of amylase?
According to the different positions of hydrolyzed starch: α-amylase, β-amylase, γ-amylase, isoamylase
According to microbial sources: bacterial amylase, fungal amylase, fungal amylase
According to the reaction temperature: medium temperature amylase and high temperature amylase, medium temperature amylase at 70 degrees, high temperature amylase at 90 to 105 degrees
Alpha-amylase is mainly purified by fermentation of Bacillus subtilis, Aspergillus niger, Aspergillus oryzae and Rhizopus. Due to different sources, it is divided into fungal α-amylase and bacterial α-amylase, which are called starch 1,4-dextrinase according to their functions. The host mechanism is to cut the α-1,4-glycosidic bond inside the starch chain. The starch is hydrolyzed into maltose, oligosaccharides containing 6 glucose units and oligosaccharides with branched chains. For example, in the processing of flour products, adding fungal α-amylase can enhance the reproductive capacity of yeast and shorten the fermentation time of bread dough.
β-amylase is mainly purified by fermentation of Aspergillus, Rhizopus and Endosporium, also known as starch 1,4-maltosidase and high maltase. It can cut 1,4-glycosidic bond from the non-reducing end of starch molecule to generate maltose. The products of this enzyme acting on starch are maltose and limit dextrin. It is used to produce starch sugar, maltose syrup, caramel, high maltose syrup and maltitol, and it can replace the fungus alpha amylase to save cost.
Glucoamylase is mainly purified by fermentation of Aspergillus niger, Rhizopus, Endosporium and Monascus, also known as starch α-1,4-glucosidase and glucoamylase. This enzyme acts on the non-reducing end of starch molecules, taking glucose as the unit, and acts on the α-1,4-glycosidic bonds in starch molecules in turn to generate glucose. The products acting on amylopectin include glucose and oligosaccharides with α-1,6-glycosidic bonds, and the products acting on amylose are almost all glucose. For example, in the production of liquor, adding saccharification enzyme can make the saccharification of starch more thorough, and can increase the yield of wine by 5%.
Isoamylase is mainly fermented and purified by anaerobic bacillus, bacillus and some pseudomonas, also known as starch α-1,6-glucosidase, branching enzyme. This enzyme acts on the α-1,6-glycosidic bond at the branch point of the amylopectin molecule, cutting the entire side chain of amylopectin into amylose. For example, in the grain starch of the feed, the amylose content only accounts for 20%, and the amylopectin content is as high as 80%. However, α-amylase, β-amylase, and saccharification enzymes cannot hydrolyze amylopectin rapidly and thoroughly. Adding an appropriate amount of isoamylase to convert it into amylose makes it more conducive to the hydrolysis of other amylases and improves the utilization rate of grain starch.
