Microbial biodegradation

About: Microbial biodegradation is a research topic. Over the lifetime, 1647 publications have been published within this topic receiving 75473 citations.

Aerobic and anaerobic microbial degradation of poly-β-hydroxybutyrate produced by Azotobacter chroococcum

Abstract: Food industry wastewater served as a carbon source for the synthesis of poly-β-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5° C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11°C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3–7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.

Anaerobic biodegradation of polychlorinated biphenyls by a microbial consortium originated from uncontaminated paddy soil

Abstract: Polychlorinated biphenyls (PCBs) in Kanechlor-300 and -400 mixtures dissipated significantly compared with a sterilized control under anaerobic conditions in three Japanese paddy soils with no history of PCB contamination, demonstrating the anaerobic microbial degradation of PCBs. The PCB-degrading activity was maintained successfully in a static flooded soil medium for more than 3 years by serial transfer at intervals of 56 days (13 transfers). Ortho-, meta-, and para-substituted PCBs, 15.2 ± 9.9 mol% in total, were significantly degraded after 56 days of incubation. Analysis of menaquinones-6 and -7 and cloning of 16S rRNA gene fragments from a polymerase chain reaction denaturing gradient gel electrophoresis (DGGE) profile indicated the predominance of Firmicutes in the consortium. A PCR-based identification of the gene fragments showed the frequent presence of Desulfitobacterium sp., but not Dehalobacter sp. or Dehalococcoides sp., in the consortium. It is proposed that Japanese paddy soils with no history of PCB contamination contain an anaerobic microbial consortium consisting predominantly of Firmicutes that have the potential for anaerobic degradation of PCB.

Biodegradation of Dinoseb (2-sec-Butyl-4,6-Dinitrophenol) in Several Idaho Soils with Various Dinoseb Exposure Histories.

Abstract: We examined the ability of native microorganisms in various Idaho soils to degrade dinoseb and studied some physical and chemical soil characteristics which might affect the biodegradation process. Dinoseb biodegradation rates were higher in silt-loam soils than in loamy-sand soils. Biodegradation rates were not influenced by previous exposure of the soils to dinoseb. Bacterial numbers, measured by standard plate counts on soil extract agar, were the best predictors of biodegradation rates, accounting for 53% of the variability between soils. Soil nitrate-N inhibited dinoseb biodegradation and accounted for 39% of the variability. Sorption of dinoseb to soil surfaces also appeared to influence biodegradation rates. No other soil parameter contributed significantly to the variability in biodegradation rates. Persistence of dinoseb in one soil was due to inhibition of biodegradation by nitrate, while in another soil persistence appeared to be due to lack of native degradative microorganisms.