Polyhydroxyalkanoates (PHAs) comprise a group of natural biodegradable polyesters that are synthesized by microorganisms. However, several disadvantages limit their competition with traditional synthetic plastics or their application as ideal biomaterials. These disadvantages include their poor mechanical properties, high production cost, limited functionalities, incompatibility with conventional thermal processing techniques and susceptibility to thermal degradation. To circumvent these drawbacks, PHAs need to be modified to ensure improved performance in specific applications. In this review, well-established modification methods of PHAs are summarized and discussed. The improved properties of PHA that blends with natural raw materials or other biodegradable polymers, including starch, cellulose derivatives, lignin, poly(lactic acid), polycaprolactone and different PHA-type blends, are summarized. The functionalization of PHAs by chemical modification is described with respect to two important synthesis approaches: block copolymerization and graft copolymerization. The expanded utilization of the modified PHAs as engineering materials and the biomedical significance in different areas are also addressed. Polyhydroxyalkanoates Phas,Bacterial Fermentation Pha,Elastomeric Materials Pha,Pha Suture Fasteners Xingbang High Molecular Materials Co., Ltd. , https://www.chemicaladditive.com
First, the habit of raising shrimp. Green prawns live extensively in lakes and ditches. They prefer to inhabit shallow waters of many aquatic plants. It is an omnivorous animal. The larvae are dominated by plankton, and shrimps are mainly stems and leaves of aquatic plants. Green shrimp usually spawn between 7 and 9 months, spawning 800 to 1200 eggs each time. As the fertilized eggs are well protected by the mother, the natural hatching rate is above 92%. The larvae become larvae after three to four peelings. Juveniles need only 2 to 3 months to mature their eggs. Green prawn has a high fertility. After ovulation hatches, female ovulates quickly.
Second, the cultivation of shrimp. There are two kinds of methods for the cultivation of the shrimp: one is to directly lay down the shrimp, 500 to 800 females per acre, and 300 to 500 males. They should be stocked at the end of April and the beginning of May. The second is to stock artificially cultivated juveniles: First, use an acre of pond or pond as a breeding pond. Before the beginning of summer, catch 10 to 12.5 kilograms of brood broodstock from the river, and select individuals with strong, fertile eggs into the pool. , Put the grass or poplar root in the pool. Every morning, during the production period, a small keg of soybean milk (about 1 kilogram of soybeans) is fed, and then a bucket of vegetable cake or syrup (about 5 kilograms of dried product) is poured. Twenty-five days after hatching of the juveniles, 250 liters of pups can be bred. Artificially reared fresh shrimp, the yield per mu can reach 15 to 25 kilograms, and high yield can reach 40 to 50 kilograms.
Third, bait supply. Shrimp are more mixed in the artificial feeding, all kinds of artificial feed can be fed, such as snail, silkworm cocoon, fly maggot, fish meal, etc., plant foods are bean cake, rice bran, wheat bran distiller's grains and so on. Feeding time is appropriate at 5pm, and it can be evenly sprinkled around the shrimp pond in appropriate quantities so that the shrimps will not kill each other due to hunger.
Fourth, artificial breeding ponds. Artificially cultivated shrimp should build shrimp ponds. Shrimp ponds can use common fish ponds, covering an area of ​​2 to 6 mu and a water depth of 1.2 to 1.5 meters. Flat silt mud should not be too much. Shrimp ponds should be convenient for drainage and irrigation near water sources. The shrimps have poor swimming ability. Therefore, some shrimp plants such as shrimp and algae should be propagated in the shrimp ponds for shrimps to inhabit. However, the area should not exceed 25% of the water area. Branches can also be used for hiding shrimps to prevent shrimps from being damaged. • Before the stocking, the tea pods, crotons, bleaching powder, rattan extract or other medicines are usually used to kill harmful fish and large aquatic insects in the pool and avoid enemy invasion. ? Green shrimp ponds should strengthen the usual patrol pond management to prevent pool collapse, leakage or waterfowl, water mice prey on green shrimp. Once a large number of prawns are found jumping, floating on the surface of the water, or climbing on the edge of the pool, it means that the dissolved oxygen in the pool is low, and the metabolites are too high, which will cause a large number of deaths of the prawns. The water must be changed immediately to increase oxygen.
Freshwater shrimp culture technology
Green shrimp is the largest freshwater shrimp produced in China. Its delicate meat, delicious taste, rich nutrition, and medicinal value are also popular among people.