Has Antimicrobial Properties Of Chitosan Composite Membrane Research And Applications

The Chitosan (CTS), a kind of natural polysaccharide biological macromolecule, has many outstanding properties and potential application in various areas. Its film forming ability and antibacterial preservation for vegetable and fruit are the most important features, which make it extremely important in the field of the coating to maintain fruits fresh, the film separation, eatable film carrier, the film for biological degradation and so on. So it is required that the CTS films must have different properties when used for different purposes. When the CTS is used to coat on fruits and vegetable to prolong their storage life, it has been forced to be associated with some shortcomings, such as a low moisture-holding rate, fruits dehydration due to its typical molecular structural feature. Moreover, simultaneous maintenance of quality of fruits and vegetabales, moisture control at room temperature cannot be achieved along with the desired anticorrosive microbial properties. When CTS is used as a film carrier, the mechanical strength of CTS film is weak, easily chapped or staved. The above mentioned limitations of CTS film are attributed to the structure of CTS molecule and its nature, therefore, in order to extend the application of CTS it is imperative to improve and enhance the moisture-keeping and the mechanical strength of the membrane. Nano-SiOx is non-toxic, tasteless, non-polluting. It is one of the most extensively used inorganic nano-materials in the present modification of application of organic materials. When its particle size is reduced to nanometer level, SiOx displays a series of special functions. Moreover, nano-SiOx has a large quantity of unsaturated linkage and hydroxyl functionality in the different linkage state, and the molecules within cluster is in the form of three dimensional chain structure, leading to some interaction between SiOx with certain groups or bases of high polymer material. This may help to improve the performances of the material to a great extent.Therefore, using nano-SiOx to carry molecular modification to Chitosan to enhance the film obdurabihty and antibacterial property, improve water penetration rate and permeability, and make it apply to the fruits and vegetables' before harvestry and after harvestry. Fruits and vegetables from growing to postharvest storage all gain safe and effective protection. Primary coverage and main conclusions of the present research are as follows.1. Performance researches of Chitosan nano-SiOx composite films. Chitosan was modified by adding nano-SiOx, and then Chitosan nano-SiOx mixture (CTS-Fh) was coated to obtain films. Characteristics of the composite films were investigated by Infra-red spectroscopy (IR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The results indicated that strong hydrogen bonds were formed between Chitosan and nano-SiOx. Compared with the non-modified Chitosan films, the tensile strength, elongation-at-break and orthogonal tear strength of modified composite films(CTS-Fh) increased by about 63.29%, 45.38% and 11.58% respectively. At the same time, transmittivity and permeability of CTS-Fh were also improved. The performance of the CTS-Fh films obviously surpassed that of the pure CTS films.2. Researches on antibacterial properties of Chitosan nano-SiOx composite films. The antibacterial property experiments of the CTS-Fh and the CTS indicated that modified Chitosan films had a more obvious effect than pure CTS films against bacterium such as Gram-negative bacteria E. coli (Escherichia coli.) and Gelanshi masculine fungus subtilis bud spore bacillus (Bacillus subtilis), and fungus like yeast (Saccharomyces) and blue mildew (Penicillium), the antibacterial rate reaching 22.34%,6.50%,36.49%å’Œ53.76%, respectively. Simultaneously CTS-Fh had an obvious function to control the growth of agricultural pathogenic bacteria like late blight of potato (Phytophthora infestans), the tomato grey mold (Botrytis cinerea Pers) and the hot pepper wilt disease (Fusarium wilt).3. The application in the storage of fruits and vegetables. Taking the permeation rate of water as objective function, the orthogonal rotation experimental design methods based on single quadratic regression were used for investigation and established a quadratic regression model, obtaining an optimal formula of CTS-Fh for coating Jinqiu pear and cucumber to prolong their storage life at room temperature. The rate of water loss, vitamin C content, respiratory strength, polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), good fruit ratio and fresh-keeping life were determined separately. At the same time, the influence of the composited Chitosan film on the surface morphology and the waxy no-smooth character of Jinqiu pear were analyzed. Research results indicated that when the ratio of Chitosan and SiOx and monoglyceride was 1.547 : 0.028 : 0.015, the permeation rate of composite films failed were 73.1% as compared to the pure membrane; the preservative life of treated fruits and vegetables had been significantly prolonged at room temperature. Various indexes had been improved, such as the preservative life of the Jinqiu pear was extended from 20 days to 60 days, and good fruit rate was up to 80.00%, and the preservative life of Cucumber was extended to 12 days from 6 days, and good fruit rate was 95.12%.4. Research on insectieidal activity of Chitosan nano-SiOx composite films against Aphid. The toxicity testing in laboratory showed: CTS-Fh films had good insectieidal activity against aphid. Its anti-insect (aphis) effect was higher than that of CTS (57.41%), reaching to 62.93%, increasing by 15%. Field experiments showed that after pure CTS solution, CTS-Fh composite solution, CTS/AWei (a compound) mixture solution and 0.18% AWei (pesticide) were spayed on to Jinqiu pear trees, the levels of insects decreased evidently and fell to 53.04%, 68.66%, 90.52% and 87.60 respectively during 1-7 days after application. Results indicated that CTS/nano-SiOx composite films can strengthen the drug efficacy and the duration of pesticide.5. Acute toxicity test of Chitosan composite films. By adding an acceptable maximum amount of nano-SiOx to the Chitosan films following the formula, acute toxicity test of the film was carried on the Kunming second-level mouse. Results indicated that when the applied dosage was 10.0 g/kg BW, LD₅₀>10.0 g/kg BW after 2 weeks. It was discovered neither any presented animals died nor any were under intoxication. CTS-Fh composite film is safe and an innocuous material.6. Pesticide formulation rsearch of Chitosan nano-SiOx composite films. Whether the indoor toxicity tests, or the field pharmacodynamic experiments, CTS-Fh films had a certain degree of insectieidal activity. In conclusion, CTS-Fh films could be used as a pesticide to control diseases and insect pests of fruits and vegetables, and proved to be a green pesticide which was at a lower residual level. When CTS-Fh films mixed with pesticides, taking advantage of the function of chitosan's film isformation, CTS-Fh films as a pesticide agent can be more widely used in agriculturalproduction.