Tuesday, May 10, 2011


Plastics, most of them made from by-products of fossil fuel industry is ubiquitous by its presence in practically every activity modern man is pursuing and it is very difficult to imagine a world without this synthetic marvel. Though during its early stages of popularity, not much of a problem was foreseen in expanding the use of plastics, it is now that the world is facing a crisis on two fronts in continuing with plastics without any moderation. While exhaustible fossil fuel supply and its ever escalating cost make it impossible to produce and use plastics same way as before, disposal of the used plastics poses an environmental danger of immense dimension because of their lack of bio-degradable credentials.

By far the most critical issue to day is the need to curb use of thin disposable plastic bags ( less than 40 microns thickness), used by millions of households all over the world to ferry their purchases from the market to their homes. As more and more restrictions are put in place against use of plastic shopping bags, consumers are forced to carry with them re-usable cloth bags and according to some reports these reusable cloth bags can be a dangerous source of pathogenic microorganisms as they are not cleaned regularly. Now comes the news that an enterprising entrepreneur has created a reusable carry bag made from fabric which is treated with Chitin, a by-product of Shrimp processing industry.

Chitin is the second most abundant polymer occurring naturally and though it was known that chitin is a component of cell wall of fungi, exoskeletons of anthropoids such as crustaceans including crabs, lobsters and shrimps, its industrial importance emerged only during the last 3-4 decades. Like cellulose which is a polymer of glucose, chitin is a polymer of N-acetylglucosamine with structure similar to cellulose while functionally it resembles more like the protein keratin. The deacetylated product from chitin, achieved through reaction with sodium hydroxide has found several uses in food, pharmaceutical, medical and other industries. Establishment of shrimp processing industry has opened up an avenue for profitable commercial extraction of chitin from the inedible parts of the crustacean and both chitin and chitosan are globally traded industrial chemicals.

Use of chitin/chitosan as a thickener and stabilizer is common in foods and pharmaceuticals. It also finds use as a binder in dyes, fabrics and adhesives. Besides these bio-degradable substances also find extensive use as plant protectants in agriculture and in fertilizers. As chitosan is water soluble, surgical sutures made from it are preferred by the medical industry, avoiding the need for post surgical procedure to remove sutures. Though many people are allergic to shell fish and crustaceans, chitin extracted from them do not possess the proteins responsible for the allergy. Chitosan at levels of 50-200 ppm has significant antimicrobial activity which has been made use of for making reusable fabric bags into which the material is woven.

According to scientific findings chitosan can be effective against microorganisms like B.cereus, E.coli, Listeria, Psuedomonas, Shigella, Staphylococcus aureus and Vibriocholerae though higher concentrations only can have any effect against fungal infection. This property of chitosan has been exploited to make reusable cloth bags that will be resistant to bacterial contamination and proliferation during repeated use. Most people keep the reusable bags in their scooters, motor bikes and cars and under the hot and humid climate prevalent in tropical countries like India , right environment is created for the breeding of undesirable bacteria. When such pre-contaminated bags are used again and again to bring purchased foods to homes where they may or may not go into the refrigerator immediately, there exists the possibility of cross contamination, seriousness of which depends on the moisture and nutrient content of the products.

According to commercial claims made by the manufacturers of safe reusable cloth bags using chitosan, unlike others these new innovative bags are lead-free and triclosan-free. Triclosan is an antibacterial and anti-fungal agent that's used in a number of consumer products like soaps, deodorants, toothpastes, cleaning supplies, even trash bags, though its safety credentials are still suspect and may become a part of reusable bags also if laws involving ban of plastic bags are enforced rigorously. Whether a product containing chemicals derived from shrimp can be acceptable to consumers in India, many of them vegetarians, may put a damper to any plans to bring the technology to this country. Of course the best and the least costly approach to the problem of cross contamination from reusable bags is to wash them regularly after every use.


No comments: