Biodegradable substances

The increase in public environmental awareness and the recognition of the urgent need to control and reduce pollution are leading factors in the recent augment of scientific research for new biodegradable compounds. Biodegradable compounds could replace others that harm the environment and pose hazards to public health , and animal and plant survival. Biodegradation, i.e., the metabolization of substances by bacteria , yeast , fungi , from which these organisms obtain nutrients and energy, is an important natural resource for the development of new environmental-friendly technologies with immediate impact in the chemical industry and other economic activities. Research efforts in this field are two-fold: to identify and/or develop transgenic biological agents that digest specific existing compounds in polluted soils and water, and to develop new biodegradable compounds to replace hazardous chemicals in industrial activity. Research is, therefore, aimed at bioremediation , which could identify biological agents that rapidly degrade existing pollutants in the environment, such as heavy metals and toxic chemicals in soil and water, explosive residues, or spilled petroleum. Crude oil however, is naturally biodegradable, and species of hydrocarbon-degrading bacteria are responsible for an important reduction of petroleum levels in reservoirs, especially at temperatures below 176° F (80° C). The selection , culture , and even genetic manipulation of some of these species may lead to a bioremediation technology that could rapidly degrade oil accidentally spilled in water.

The search for a biodegradable substitute for plastic polymers, for instance, is of high environmental relevance, since plastic waste (bags, toys, plastic films, packing material, etc.) is a major problem in garbage disposal and its recycling process is not pollution-free. In the 1980s, research of polyhydroxybutyrate, a biodegradable thermoplastic derived from bacterial metabolism was started and then stalled due to the high costs involved in fermentation and extraction. Starch is another trend of research in the endeavor to solve this problem, and starch-foamed packing material is currently in use in many countries, as well as molded starch golf tees. However, physical and chemical properties of starch polymers have so far prevented its use for other industrial purposes in replacement of plastic. Some scientists suggest that polyhydroxybutyrate research should now be increased to benefit from new biotechnologies, such as the development of transgenic corn, with has the ability to synthesize great amounts of the compound. This corn may one day provide a cost-effective biodegradable raw material to a new biodegradable plastics industry.

Another field for biodegradable substances usage is the pharmaceutical industry, where biomedical research focuses on non-toxic polymers with physicochemical thermo-sensitivity as a matrix for drug delivering. One research group at the University of Utah at Salt Lake City in 1997, for instance, synthesized an injectable polymer that forms a non-toxic biodegradable hydro gel that acts as a sustained-release matrix for drugs.

Transgenic plants expressing microbial genes whose products are degradative enzymes may constitute a potential solution in the removal of explosive residues from water and soils. A group of University of Cambridge and University of Edinburgh scientists in the United Kingdom developed transgenic tobacco plants that express an enzyme (pentaerythritol tetranitrate reductase) that degrades nitrate ester and nitro aromatic explosive residues in contaminated soils.

Another environmental problem is the huge amounts of highly stable and non-biodegradable hydrocarbon compounds that are discarded in landfills, and are known as polyacrylates. Polyacrylates are utilized as absorbent gels in disposable diapers, and feminine hygiene absorbents, as well as added to detergents as dispersants, and are discharged through sewage into underwater sheets, rivers, and lakes. A biodegradable substitute, however, known as polyaspartate, already exists, and is presently utilized in farming and oil drilling. Polyaspartate polymers are degradable by bacteria because the molecular backbone is constituted by chains of amino acids; whereas polyacrylates have backbones made of hydrocarbon compounds.

The main challenge in the adoption of biodegradable substances as a replacement for existing hazardous chemicals and technologies is cost effectiveness. Only large-scale production of environmental friendly compounds can decrease costs. Public education and consumer awareness may be a crucial factor in the progress and consolidation of "green" technologies in the near future.

See also Amino acid chemistry; Biotechnology; Economic uses and benefits of microorganisms; Transgenics; Waste water treatment