Lactase is a disaccharidase present on the surface of mammalian small intestinal mucosal microvilli, and many beneficial intestinal bacteria have the ability to produce lactase. Lactase deficiency is present in most of the world's population, affecting nearly 2/3 of the world's population.

Polylactose is composed of glucose and galactose, these two monosaccharides are easily absorbed by the intestinal lumen and are an important source of human tissue structure and energy. The precondition for lactose to be absorbed and utilized by the human body is hydrolysis by lactase (LCT). Lactase is a disaccharidase present on the surface of the small intestinal mucosa of mammals. It is distributed in foci in the intestinal mucosa. It can degrade lactose into galactose and glucose, and also has the transfer effect of galactosides.

In fact, many people cannot digest and absorb lactose after drinking milk due to the lack of lactase in the small intestinal epithelial cells. After lactose enters the colon, it is decomposed by intestinal bacteria, producing a large amount of short-chain fatty acids such as lactic acid and formic acid and hydrogen gas. The osmotic pressure increases, which increases the water in the intestinal cavity, causing abdominal distension, bowel sounds, colic and even diarrhea, which is medically called lactose intolerance (LI).

In addition to manifesting lactose intolerance, there are people with poor lactose metabolism but no symptoms, commonly referred to as lactose malabsorption (LM). Lactose intolerance and lactose malabsorption are collectively known as lactase deficiency (LD). Lactase deficiency is a widespread worldwide problem that affects nearly two-thirds of the world's population. LD poses a great threat to human health, especially adolescents, so the study of intestinal lactase is particularly important.

The source of human intestinal lactase mainly depends on the body's own synthesis, a small amount of synthesis and secretion of probiotics in the intestinal tract, and supplementation with exogenous lactase. The self-synthesized intestinal lactase is synthesized by the lactase gene and linked to the surface of the intestinal mucosal microvilli by a hydrophobic amino acid sequence at the -COOH end.

Some intestinal bacteria contain lactase, such as Bifidobacterium, Lactobacillus, Escherichia coli, yeast and mold and other lactase from different sources. Its enzymatic properties vary greatly, and many lactase genes from different sources have been cloned. All bifidobacteria contain galactosidase, which can degrade lactose into glucose and galactose, and its activity is significantly higher than that of other intestinal bacteria. Therefore, appropriate supplementation of bifidobacteria can avoid the occurrence of lactose intolerance. Lactase is made into lactase tablets by means of microbial engineering and separation and purification processes.

Intestinal lactase deficiency is caused by genetic causes, and there is currently no cure. Therefore, the regulation technology of intestinal lactase is particularly important. The regulation technology of intestinal lactase mainly includes the following aspects:

1. Avoid drugs that impair the activity of lactase. The abuse of antibiotics is prohibited, because inappropriate use of antibiotics can inhibit the reproduction of normal probiotic flora, hinder the metabolism of lactose by intestinal microorganisms, thereby aggravating the symptoms of lactose intolerance. Supplementing folic acid and zinc preparations can promote the repair of intestinal epithelial cells and the recovery of lactase activity. Such methods are mainly aimed at secondary lactase deficiency caused by diffuse lesions of the small intestinal mucosa.

2. Directly supplement lactase and produce low-lactose products. Oral administration of exogenous lactase and hydrolysis of lactose by lactase to produce low-lactose or lactose-free dairy products to assist the digestion and absorption of lactose are currently widely concerned research hotspots. Certain intestinal microorganisms such as Lactobacillus can produce a small amount of lactase, and high-yielding strains can be obtained through genetic engineering mutation breeding, which enables large-scale production of lactase.

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