Aharon Abeliovich

Anaerobic-Aerobic Process for Microbial Degradation of Tetrabromobisphenol A

ABSTRACT Tetrabromobisphenol A (TBBPA) is a flame retardant that is used as an additive during manufacturing of plastic polymers and electronic circuit boards. Little is known about the fate of this compound in the environment. In the current study we investigated biodegradation of TBBPA, as well as 2,4,6-tribromophenol (TBP), in slurry of anaerobic sediment from a wet ephemeral desert stream bed contaminated with chemical industry waste. Anaerobic incubation of the sediment with TBBPA and peptone-tryptone-glucose-yeast extract medium resulted in a 80% decrease in the TBBPA concentration and accumulation of a single metabolite. This metabolite was identified by gas chromatography-mass spectrometry (GC-MS) as nonbrominated bisphenol A (BPA). On the other hand, TBP was reductively dehalogenated to phenol, which was further metabolized under anaerobic conditions. BPA persisted in the anaerobic slurry but was degraded aerobically. A gram-negative bacterium (strain WH1) was isolated from the contaminated soil, and under aerobic conditions this organism could use BPA as a sole carbon and energy source. During degradation of BPA two metabolites were detected in the culture medium, and these metabolites were identified by GC-MS and high-performance liquid chromatography as 4-hydroxybenzoic acid and 4-hydroxyacetophenone. Both of those compounds were utilized by WH1 as carbon and energy sources. Our findings demonstrate that it may be possible to use a sequential anaerobic-aerobic process to completely degrade TBBPA in contaminated soils.

Production of spirulina biomass: Effects of environmental factors and population density

The effects of environmental conditions (solar irradiance and temperature) and population density on the production of Spirulina biomass are reported for cultures grown in outdoor ponds. Both the specific rate of photosynthesis, expressed on a chlorophyll basis, and the rate of respiration, on a protein basis, decreased as algal concentration increased. Higher specific growth rates were observed at lower population densities. Lower growth rates were associated with the light limitation in dense cultures for optimum conditions in the summer. Seasonal variation was observed in productivity. In summer light was the limiting factor whereas in winter the low daytime temperature appeared to impose the major limitation. It was found that the oxygen concentration in the culture can serve as a useful indicator of limiting factors and can also be used as a means of estimating the extent of such limitations.

Biological denitrification of drinking water using newspaper

Microbial denitrification of drinking water was studied in laboratory columns packed with shredded newspapers. Newspaper served as the sole carbon and energy substrate as well as the only physical support for the microbial population. Complete removal of nitrate (100 mg 1−1) was readily achieved, without accumulation of nitrite. The treated water contained low dissolved organic carbon (4–10 mg 1−1). The cellulose-dependent denitrification process was sensitive to changes in temperature: nitrate removal rates at 14°C were approximately one third of the rates observed at 32°C. Pretreatment of newspaper with diluted NaOH or diluted HCl, or by autoclave did not improve the efficiency of the process. A time-dependent decay in denitrification rate was noticeable after several months of operation. The reasons for this phenomenon, which may be due to weakened adhesion of the bacteria to the substrate, are under investigation.

Anaerobic metabolism of Nitrosomonas europaea

Nitrosomonas europaea is capable of maintaining an anaerobic metabolism, using pyruvate as an electron donor and nitrite as an electron acceptor; utilization of nitrite depends upon supply of both pyruvate and ammonia. The role of ammonia in this reaction was not determined. N europaea also assimilates CO2 anaerobically into cell material in the presence of nitrite (0.5–1.0 mM), pyruvate and ammonia. This reaction was partially inhibited by nitrite which apparently competed with CO2 for reducing power. Anaerobic “nitrite respiration” is sensitive to ionophores, FCCP being the most effective.

The Identification and Characterization of Osmotolerant Yeast Isolates from Chemical Wastewater Evaporation Ponds

Ramat Hovav is a major chemical industrial park manufacturing pharmaceuticals, pesticides, and various aliphatic and aromatic halogens. All wastewater streams are collected in large evaporation ponds. Salinity in the evaporation ponds fluctuates between 3% (w/v) and saturation and pH values range between 2.0 and 10.0. We looked for microorganisms surviving in these extreme environmental conditions and found that 2 yeast strains dominate this biotope. 18S rDNA sequence analysis identified the isolates as Pichia guilliermondii and Rhodotorula mucilaginosa. Both isolates grew in NaCl concentrations ranging up to 3.5 M and 2.5 M, respectively, and at a pH range of 2-10. There was a distinct difference between the Rhodotorula and Pichia strains and S. cerevisiae RS16 that served as a control strain with respect to accumulation of osmoregulators and internal ion concentrations when exposed to osmotic stress. The Pichia and Rhodotorula strains maintained high glycerol concentration also in media low in NaCl. Utilization of various carbon sources was examined. Using a tetrazolium-based assay we show that the Rhodotorula and Pichia strains are capable of utilizing a wide range of different carbon sources including anthracene, phenanthrene, and other cyclic aromatic hydrocarbons.

Transformations of ammonia and the environmental impact of nitrifying bacteria

In the sequence of events leading from ammonia to N2 during the process of biotransformation of inorganic nitrogen compounds, the weakest link, with respect to our knowledge and understanding of the organisms involved, is nitrification. In particular, this is true for the oxidation of ammonia to nitrite. The enzymes have not been thoroughly studied, and the enzymatic mechanisms have not been identified. Almost any biochemical and physiological aspect studied proved to be controversial, and major ecological questions still remain unanswered. Unless the structure and function of the various components of the process are worked out, progress in developing means for controlling nitrification will depend mainly on laborious trial and error and not on knowledgeable manipulation of this group of bacteria.

Cadmium toxicity and resistance in Chlorella sp.

Abstract The Cd 2+ tolerance of Chlorella sp. isolated from an urban waste water treatment plant was studied. The growth of this alga was severely inhibited at 10 μM Cd 2+ with an LD 50 of 3 μM. Addition of 100 μM glutathione or 100 μM cysteine reduced the inhibitory effect of Cd 2+ . The amelioration of Cd 2+ inhibition by GSH was not due to direct complexing of the two compounds in the growth medium, indicating that an intracellular mechanism involving GSH or its metabolites is responsible for Cd 2+ detoxification. A Cd 2+ resistant line (CdR-DK), with an LD 50 of 35 μM, was selected by growing the alga on solid medium in the presence of increasing concentrations of the ion. Phytochelatins (PCs), a family of peptides synthesized by plants in response to cadmium, were detected in extracts of the CdR-DK cells. The possible role that these peptides, which are derived from glutathione, may play in cadmium detoxification in Chlorella is discussed.

Denitrification in laboratory sand columns: Carbon regime, gas accumulation and hydraulic properties

Microbiological denitrification in a sandy matrix was studied by means of laboratory sand columns operated at continuous and pulse feed regimes. Gas production resulting from the biological activity played a major role in modifying the hydraulic properties of the column, leading to decreases in hydraulic conductivity and porosity, higher water velocities through the column, higher dispersion and anomalies in the head difference to flow rates ratios. All of these effects were more pronounced when formate, the carbon source used, was supplied continuously: microbial activity and gas production were concentrated at the top of the column, leading to almost complete clogging. When the formate was supplied in pulses, activity and gas production were dispersed, leading to relative uniformity in the physical parameters measured and a homogeneous appearance of the column. The results suggest that in a futurein situ aquifer denitrification plant, pulse application of the carbon source is prefereable to a continuous supply regime.

Activity and survival of tribromophenol-degrading bacteria in a contaminated desert soil

A strain of bromophenol degrading bacteria was isolated from a contaminated desert soil. The isolate identified as Achromobacter piechaudii and designated as strain TBPZ was able to metabolize both 2,4,6-tribromophenol and chlorophenols. The degradation of halophenols resulted in the stechiometric release of bromide or chloride. Growth and degradation of bromophenol were enhanced in the presence of yeast extract. To follow the survival of an introduced bacteria in the contaminated soil, TBPZ was transformed with a plasmid carrying a gene for kanamycin resistance and the lux CDABE operon from the luminescent bacteria Vibrio fischeri under the control of a constitutive promoter producing strain TBPZ-N61. The activity of the transformed bacteria was not affected by the insertion of the plasmid. Specific detection of the introduced isolate in the contaminated soil samples was achieved by selection on kanamycin. Survival of the introduced bacteria, TBPZ-N61, in the contaminated soil was influenced by soil moisture. Biodegradation of TBP occurred only in soil with at least 25% water content. Addition of yeast extract increased the survival and the activity of the introduced bacteria. The current study demonstrated that the limiting factors controlling pollutant degradation in a contaminated desert soil are water content, nutrient availability and the bioaugmentation of an appropriate microbial population.

The fate of heavy metals in wastewater stabilization ponds

The distribution of toxic heavy metals was studied throughout the process of treatment of domestic wastewater by stabilization ponds. The concentrations and distribution of free and bound zinc, cadmium, lead and copper through the various stages of a treatment plant were analyzed by Anodic Stripping Voltammetry (ASV). Only a slight decrease in the total metals concentration was observed during the various stages of the wastewater treatment plant. However, the distribution among dissolved (free and chelated) and particulate fractions did change towards solubilization of most of the particulate fraction. Within the soluble fraction a significant decrease in the free cations occurred due to a proteinaceous chelating agent(s) released by the microbial population in the ponds. A similar phenomenon was found in simulated laboratory experiments which were carried out with a Chlorella strain isolated from the stabilization ponds.