In a new research in China, scientists have determined that immobilized microbes can break down potentially harmful phthalates, thus proving useful in treating industrial waste water and preventing these  materials from entering the environment. Phthalic Acid Esters (PAEs), commonly known as phthalates, are widely used as additives in polymer manufacture as plasticizers. They do not readily degrade in the environment and so have become widely distributed in natural water, wastewater, soil, and sediment. Concerns about their suspected ability to cause genetic mutations and cancer have led to their listing as priority pollutants by the US Environmental Protection Agency, the European Union, the China National Environmental Monitoring Centre, and other regulatory authorities. Weizhong Wu of the College of Environmental Sciences and Engineering, at Peking University in Beijing and Xianlin Meng of Harbin Institute of Technology in Nangang District of China, have identified and isolated a microbe that can digest one of the most common PAEs, d-n-butyl phthalate. This compound is widely used and is one of the most frequently found in diverse environmental samples including groundwater, river water, drinking water, open ocean water, soil humates, lake sediments and marine sediments, according to the researchers. They have now used acclimation and enrichment techniques to ferment adequate quantities of the active microbe, which was obtained from the activated sludge from a wastewater treatment plant. It was enriched and acclimated by incubating activated sludge. This involves cultivating the microbes in a solution containing phthalate as the only source of carbon for the microbes. Successive divisions of microbial cells quickly lead to the evolution of a strain that can quickly metabolize the phthalate and convert it into the raw materials for microbial growth and reproduction.

The researchers then tested this phthalate-digesting microbe by immobilizing cells on a new type of ceramic honeycomb support. They then measured the concentration of phthalate  before and after in a stimulated wastewater sample. Initial concentration was 100 milligrams per liter which fell to less than 1.0 milligram per litre within two days of treatment with the microbial honey comb. The team points out that the rate of degradation was two and half times faster with immobilized microbes than with microbes floating free in the sample.

Source:The Times of India, June 20, 2009.

ENVIS CENTRE Newsletter Vol.7,Issue 3 July 2009