1. The body is long, the abdomen is round.
2. The head is large and blunt.
3. The pore is semi-oval and transversely situated.
4. Eyes and ears wide.
5. A pair of slender and slender maxillary barbels is present on the body.
6. It has a pair of pectoral fins, a pair of pelvic fins, a dorsal fin and a digital fin.
7. Caudal fin is homocircular in nature.

Cold-blooded aquatic vertebrates that swim with fins and breathe with gills are called fish. Rui is a carp fish. Small and light carp are called minor carp (bata, ghania) and large and heavy carp are called major carp (rui, katla, mrigel). Under normal conditions, roe fish fry are 35–45 cm (1–1.5 ft) long and weigh 700–800 g. But the fish of Halda river weigh 2-2.5 kg in a year. Therefore, the price of hatching fish or hatching eggs of Halda river is 60-65 thousand taka per kg. Dr. Siddiq Publications

(i) Food processing: Amylase is used to make corn syrup from starch. Protease enzymes are used to reduce the protein content of biscuit dough. Cellulase is needed to process coffee. Catalase enzyme is used in the bakery industry to make sugar from starch.
(ii) Baby food: Trypsin is used to make baby food easier to digest.
(iii) In paper industry: Amylase is used in paper sizing and coating. Xylanase is used to reduce the amount of bleaching when decolorizing paper. Cellulase is needed to smooth the paper and reduce the water content of the paper. Ligninase enzyme is used to remove lignin from paper.
(iv) In Alcohol Industry: Amylase, Gluconase and Protease are used in the preparation of raw materials for alcohol. α amylase and β amylase are used in beer and wine making. Protease enzymes are used to remove turbidity in beer.
(v) In dairy industry: Rennin is used to make cheese from milk protein. In France, lipase is used to ripen sheep’s milk blue cheese. Lactase enzyme is required to make glucose and galactose from lactose.
(vi) In photography industry: Protease is used to clear gelatin from film.
(vii) In rubber industry: Catalase enzyme is required during manufacture of rubber from latex.
(viii) Biological detergents: Protease is used to remove protein stains from fabrics. Amylase is used to remove starch stains from clothes and dishes. Cellulase is used as a biological conditioner for fabrics. Lipase enzyme is used to remove oil and grease stains from fabrics.
(ix) In biofuel industry: Cellulase is used to produce ethanol in fermentation process.
(x) Ice cream making: Soft and malleable ice cream is made using lactase enzyme.
(xi) Candy making: Candy is made using invertase enzyme.
The use of enzymes in various research works including molecular biology is increasing day by day. Metabolism and life cannot exist without enzymes. So it can be said that the systemic activity of enzymes is life.

Enzymes like pepsin, trypsin, chymotrypsin, aminotrypsin, peptidase etc. digest protein food to produce amino acids. Enzymes like tyalin, amylase, maltase, isomaltase, lactase etc. digest carbohydrates and convert them into glucose. Enzymes like lipase, phospholipase, lecithinase, cholesterol esterase, monoglyceridase etc. digest lipids to produce fatty acids and glycerol.

Fruit juice is a popular food these days. Enzymes are used to make juice from fruits like mango, grape, apple, orange, pineapple etc. Cellulase and pectinase enzymes are used to clarify fruit juices.

Today environmental protection has become a global movement. Enzyme technology has made it possible to save the environment. Biosensors are made using enzymes. These biosensors determine the amount of various pollutants present in the environment.

In 1929, Alexander Fleming first produced the antibiotic Penicillin from Penicillium notatum, which saved the lives of many patients. It works against bacterial activity. It revolutionized medicine.

(i) Recombinant DNA is produced using different types of enzymes in gene engineering.
(ii) Determining the base order of DNA and RNA and addition or subtraction of nucleotides.
(iii) DNA cleavage using restriction enzymes and joining of DNA fragments using lipase enzyme.
(iv) Necessary drugs are prepared from milk, blood and urine of animals using enzymes.

(i) Fermin or bromaline enzyme is used as anthelmintic.
(ii) Thrombin stops bleeding in the body. An enzyme called urobilase is used to dissolve blood clots in the brain and arteries.
(iii) The amount of uric acid and urea in the blood is determined by uricase and urease enzymes.
(iv) Enzymes called glucose oxidase and peroxidase are used to determine the blood sugar level of a diabetic patient.
(v) Enzymes like amylase, pepsin, lipase etc. are taken as medicines for stomach pain.
(vi) Trypsin is used in cataract surgery.
(vii) Using proteolytic enzymes can control hypertension and greatly reduce the risk of death.
(viii) Trypsin enzyme is used to clean body wounds.

(i) Pectic enzyme is used in making juice of mango, apple, grape etc.
(ii) It is used to remove large stains from clothes.
(iii) Enzymes are used to separate the hair from the hide in the tannery.