Showing papers on "Microbial biodegradation published in 1985"

Studies on the physiology of microbial degradation of pentachlorophenol

Abstract: The requirements and conditions for pentachlorophenol (PCP) biodegradation by a mixed bacterial culture was studied. The effects of oxygen, nutrients, additional carbon sources, pH and temperature are described. Up to 90% of PCP was degraded into CO2 and inorganic chloride in 1 week at an input concentration of <600 μM. Degradation continued when pO2 was lowered to 0.0002 atm but ceased when pO2 was further decreased to 0.00002 atm. Supplementary carbon sources, such as phenol, hydroxybenzoic acids or complex nutrients did not affect the biodegradation, but the presence of ammonium salts enhanced the rate of PCP degradation without affecting the yield of CO2. The degrading organisms were shown to be procaryotic mesophiles; no degradation was shown at temperatures below +8° and above +50°C. The optimum pH for degradation was from 6.4 to 7.2 and at higher pH value (8.4) degradation was inhibited more than at lower pH (5.6).

Correlation of Microbial Degradation Rates with the Chemical Structure

Abstract: Structure/reactivity relations are investigated experimentally and theoretically for the microbial degradation of 35 substituted phenols and anilines by adapted mixed cultures of bacteria. From the results one can conclude that the initial attack of the aromatic nucleus has an electrophilic character and is ratelimiting. The results are suitable for predictions of biodegradation rates of organic compounds and facilitate understanding of the mechanism of degradation.

Anaerobic Degradation of C1 and C2 Chlorinated Hydrocarbons

Abstract: : This research investigated the potential for anaerobic, biological degradation of five chlorinated C1 and C2 hydrocarbons: tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), chloroform (CF), and dichloromethane (DCM). Attempts were made to delineate the importance of microbial -- as opposed to purely chemical -- mechanisms of degradation; products formed; and pathways involved. The five compounds were studied separately in batch, anaerobic systems employing a diverse community of microflora from a municipal waste treatment plant. The added substrate concentrations ranged from 2-25 mg/L for the C1 compounds, and from 1-2 mg/L for the C2 compounds. Radiotracer studies were conducted with 14C-chloroform and 14C-dichloromethane to investigate their fate, as well as to delineate degradative pathways. PCE was completely converted to TCE, but the product was not further degraded to any significant degree. Results suggest that the microbially mediated reductive dechlorination of PCE is an inducible process. Anaerobic conversion of 1,1,1-trichloroethane did not require acclimation. Anaerobic, microbial utilization of chloroform (CF) proceeded without acclimation. Microbial degradation of DCM occurred readily after an acclimation period of variable length. CF inhibits utilization of DCM in a manner that is slowly reversible. Inhibition persists long after levels of CF in the solution are depleted. Keywords: Biological Treatment; Hazardous Wastes; Solvents; Microbial Metabolism.

Microbial degradation of polyurethanes

Abstract: Results of research on degradation of polyurethanes by microflora in landfills, by soil microorganisms and micro-fungi. The biodegradation includes utilisation of different structural constituents; infrared spectroscopy was used to determine structural changes. Polyurethanes based on polyester are more biodegradable than those based on polyether. References.