Carboxylic acids soils, polymers

Intensive research is underway to invent a truly biodegradable trash bag. One of the more creative methods is to make plastic sheets from lactic acid. Lactic add is a natural carboxylic acid produced by fermentation of sugars, particularly in milk and working muscle. Many soil bacteria can degrade polymers of lactic acid. Thus these trash bags would be easily broken down in landfill soil. 

Another, more promising, method of reducing the accumulation of polymers in the environment is to develop polymers that are biod adable and can be recycled by natural processes. Biodegradable polymers are polymers that can be broken down by enemies produced by soil microorganisms. Much research is directed at the development of such polymers, and many have aheady been developed. Most biod adable polymers exhibit ester or amide moieties, which can be hydrolyzed by enzymes. Examples include a class of compounds called polyhydroxyalkano-ates (PHAs), which are polymers of 3-hydroxy carboxylic acids. 

Dubach and Mehta (1963) define humic substances as a series of predominantly aromatic-phenolic polymers, whose acidity is mainly due to carboxyl groups, and which are free of carbohydrates and probably of nitrogen. They state that the presence of quinonic structures cannot be confirmed or excluded. They are of the opinion that there are ether linkages between the aromatic monomers, but humic substances are too nonhomogeneous to justify an attempt to write a structural formula for them, as was done in the past. The humic substances constitute over 50% of the organic matter of mineral soils. At the present time few workers would have any doubt that these substances contain nitrogen. 

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