Economic importance of algae

Algae use chlorophyll and sunlight to make food by means of photosynthesis.

Besides making food, algae also give off oxygen. Oxygen is a by-product of photosynthesis. Many animals depend on algae for both food and oxygen. Algae are important to animals for this reason. In fact, some people believe that if there were no algae (both one-celled and many-celled ones), there would not be enough food and oxygen for all the animals on the earth.

Some people depend on algae for food. In Japan, almost everyone eats a food known as nori. It comes from laver, a kind of red algae. The Japanese eat 130 000 tons of this seaweed each year. It is eaten in soups and biscuits. People in Korea, Ireland, Great Britain, and New Zealand also eat it.

Have you ever eaten algae? You might be surprised to find out that you have. In the many countries, algin is used to thicken foods such as ice-cream. Algin comes from brown algae. Some ingredients that may be found in food are gelose, agar, carrageenan, nori (red algae), kombu (brown algae).

Algae are important in other ways too. Some are used as fertilizers. Some are a source of iodine. Some are used to make certain drugs. Others can be used to make paints and soap.

Scientists who study bacteria use algae, too. They grow bacteria on jellylike agar. It comes from red algae.

Algae and products made from algae have a long history of usefulness. Dulse, a red alga, has been used as food for people and domestic animals for centuries. The algae now most widely used for food is nori, grown chiefly by coastal villagers in Japan. Nori is dried into sheets that are used in soups and biscuits and as a flavoring in many foods.

Although most algae are low in protein, they contain concentrated minerals and some starch. In many countries, dried algae are ground into a powder and added to animal feed as a mineral supplement. Algae yield valuable extracts. Agar, an extract taken from red algae, is a jellylike substance that is used for laboratory cultures in which bacteria are grown.

Carrageenin is another extract from red algae that is used to keep small particles in suspension in many foods. For example, carrageenin prevents chocolate from separating out in chocolate milk. Carrageenin is a common ingredient in jams and jellies, instant coffee, honey, wine and ice cream.

Fungi

Fungi are eukaryotic organisms; most species are multicellular. The cell walls of most fungi contain a hard substance called chitin. Chitin is found only in fungi and in the hard outer skeletons of insects.

The body of a typical fungus consists of many individual filaments called hyphae. Hyphae contain cytoplasm and one or more nuclei. Hyphae secrete enzymes that digest food. The fungus then absorbs the nutrients from the food through its cell walls.

Intertwined hyphae form the body of the fungus, or mycelium. Most of a fungus lives under the sub­strate, or material in which the fungus is growing. The visible part contains the spore-producing structures and is called the fruiting body. Saprophytic fungi feed on dead matter. Parasitic fungi feed on living organisms.

Nutrition. Fungi are nonmotile organisms that obtain food by decomposing organic matter. Fungi were once considered plants, but studies later revealed that fungi have none of the characteristics that plants possess. Unlike most plants, fungi lack chloroplasts and cannot carry out photosynthesis. Neither do fungi have many animal characteristics. Because of their unusual combination of traits, fungi are classified in a separate kingdom.

Date: 2014-12-22; view: 863