Ml Britz

Degradation and mineralization of high-molecular-weight polycyclic aromatic hydrocarbons by defined fungal-bacterial cocultures.

ABSTRACT This study investigated the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) in liquid media and soil by bacteria (Stenotrophomonas maltophilia VUN 10,010 and bacterial consortium VUN 10,009) and a fungus (Penicillium janthinellum VUO 10,201) that were isolated from separate creosote- and manufactured-gas plant-contaminated soils. The bacteria could use pyrene as their sole carbon and energy source in a basal salts medium (BSM) and mineralized significant amounts of benzo[a]pyrene cometabolically when pyrene was also present in BSM. P. janthinellum VUO 10,201 could not utilize any high-molecular-weight PAH as sole carbon and energy source but could partially degrade these if cultured in a nutrient broth. Although small amounts of chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene were degraded by axenic cultures of these isolates in BSM containing a single PAH, such conditions did not support significant microbial growth or PAH mineralization. However, significant degradation of, and microbial growth on, pyrene, chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene, each as a single PAH in BSM, occurred when P. janthinellum VUO 10,201 and either bacterial consortium VUN 10,009 or S. maltophilia VUN 10,010 were combined in the one culture, i.e., fungal-bacterial cocultures: 25% of the benzo[a]pyrene was mineralized to CO2 by these cocultures over 49 days, accompanied by transient accumulation and disappearance of intermediates detected by high-pressure liquid chromatography. Inoculation of fungal-bacterial cocultures into PAH-contaminated soil resulted in significantly improved degradation of high-molecular-weight PAHs, benzo[a]pyrene mineralization (53% of added [14C]benzo[a]pyrene was recovered as14CO2 in 100 days), and reduction in the mutagenicity of organic soil extracts, compared with the indigenous microbes and soil amended with only axenic inocula.

Survival of Lactobacillus acidophilus and Bifidobacterium bifidum in Commercial Yoghurt During Refrigerated Storage

Abstract Samples of five brands of commercial yoghurt were obtained directly from the processors and enumeration of viable Lactobacillus acidophilus and Bifidobacterium bifidum and determination of pH was carried out at three-day intervals over a five-week period. Three of the five products contained 10 7 –10 8 g −1 viable cells of L. acidophilus , whereas the other two products contained ⩽ 10 5 of this organism initially. Similarly, the initial count of B. bifidum was 10 6 –10 7 g −1 in two of five products, while the viable numbers of this organism were ⩽ 10 3 in the other three products. All the products showed a constant decline in the viable count of L. acidophilus and B. bifidum during storage. Initial pH values ranged from 4.07 to 4.36 and these declined after five weeks of storage to pH 3.8–4.26.

Surfactant‐enhanced biodegradation of high molecular weight polycyclic aromatic hydrocarbons by Stenotrophomonas maltophilia

The objectives of this study were to isolate and evaluate microorganisms with the ability to degrade high molecular weight polycyclic aromatic hydrocarbons (PAHs) in the presence of synthetic surfactants. Stenotrophomonas maltophilia VUN 10,010, isolated from PAH-contaminated soil, utilized pyrene as a sole carbon and energy source and also degraded other high molecular weight PAHs containing up to seven benzene rings. Various synthetic surfactants were tested for their ability to improve the PAH degradation rate of strain VUN 10,010. Anionic and cationic surfactants were highly toxic to this strain, and the Tween series was used as a growth substrate. Five nonionic surfactants (Brij 35, Igepal CA-630, Triton X-100, Tergitol NP-10, and Tyloxapol) were not utilized by, and were less toxic to, strain VUN 10,010. MSR and log Km values were determined for fluoranthene, pyrene, and benzo[a]pyrene in the presence of these nonionic surfactants and their apparent solubility was increased by a minimum of 250-fold in the presence of 10 g L-1 of all surfactants. The rate of pyrene degradation by strain VUN 10,010 was enhanced by the addition of four of the nonionic surfactants (5-10 g L-1); however, 5 g L-1 Igepal CA-630 inhibited pyrene degradation and microbial growth. The specific growth rate of VUN 10,010 on pyrene was increased by 67% in the presence of 10 g L-1 Brij 35 or Tergitol NP-10. The addition of Brij 35 and Tergitol NP-10 to media containing a single high molecular weight PAH (four and five benzene rings) as the sole carbon source increased the maximum specific PAH degradation rate and decreased the lag period normally seen for PAH degradation. The addition of Tergitol NP-10 to VUN 10,010 cultures which contained a PAH mixture (three to seven benzene rings) substantially improved the overall degradation rate of each PAH and increased the specific growth rate of VUN 10,010 by 30%. Evaluation of the use of VUN 10,010 for degrading high molecular weight PAHs in leachates from surfactant-flushed, weathered, PAH-contaminated sites is warranted. Copyright 1998 John Wiley & Sons, Inc.

Degradation of fluoranthene, pyrene, benz[a]anthracene and dibenz[a,h]anthracene by Burkholderia cepacia

Microbiological analysis of soils from a polycyclic aromatic hydrocarbon (PAH)‐contaminated site resulted in the enrichment of five microbial communities capable of utilizing pyrene as a sole carbon and energy source. Communities 4 and 5 rapidly degraded a number of different PAH compounds. Three pure cultures were isolated from community 5 using a spray plate method with pyrene as the sole carbon source. The cultures were identified as strains of Burkholderia (Pseudomonas) cepacia on the basis of biochemical and growth tests. The pure cultures (VUN 10 001, VUN 10 002 and VUN 10 003) were capable of degrading fluorene, phenanthrene and pyrene (100 mg l−1) to undetectable levels within 7–10 d in standard serum bottle cultures. Pyrene degradation was observed at concentrations up to 1000 mg l−1. The three isolates were also able to degrade other PAHs including fluoranthene, benz[a]anthracene and dibenz[a,h]anthracene as sole carbon and energy sources. Stimulation of dibenz[a,h]anthracene and benzo[a]pyrene degradation was achieved by the addition of small quantities of phenanthrene to cultures containing these compounds. Substrate utilization tests revealed that these micro‐organisms could also grow on n‐alkanes, chlorinated‐ and nitro‐aromatic compounds.

Microbial degradation and detoxification of high molecular weight polycyclic aromatic hydrocarbons by Stenotrophomonas maltophilia strain VUN 10,003.

The ability of Stenotrophomonas maltophilia strain VUN 10,003 to degrade and detoxify high molecular weight polycyclic aromatic hydrocarbons (PAHs) was evaluated in a basal liquid medium. Using high cell density inocula of strain VUN 10,003, the concentration of pyrene, fluoranthene, benz[a]anthracene, benzo[a]pyrene, dibenz[a,h]anthracene and coronene decreased by 98, 45, 26, 22, 22 and 55% over periods ranging from 5 to 42 d. When a PAH mixture containing three‐ to seven‐ring compounds was used, degradation of both low and high molecular weight compounds occurred concurrently. Mutagenicity assays (Ames Test) demonstrated a decrease in the mutagenic potential of dichloromethane culture extracts from all cultures containing single PAH over the incubation period, corresponding to the decrease in the concentration of the PAH. These observations indicate that strain VUN 10,003 could be used for the detoxification of PAH‐contaminated wastes.

Detection of heavy metal ion resistance genes in Gram-positive and Gram-negative bacteria isolated from a lead-contaminated site

Resistance to a range of heavy metal ions wasdetermined for lead-resistant and other bacteria whichhad been isolated from a battery-manufacturing sitecontaminated with high concentrations of lead. Several Gram-positive (belonging to the genera Arthrobacter and Corynebacterium) andGram-negative (Alcaligenes species) isolateswere resistant to lead, mercury, cadmium, cobalt,zinc and copper, although the levels of resistance tothe different metal ions were specific for eachisolate. Polymerase chain reaction, DNA-DNAhybridization and DNA sequencing were used to explorethe nature of genetic systems responsible for themetal resistance in eight of the isolates. SpecificDNA sequences could be amplified from the genomic DNAof all the isolates using primers for sections of themer (mercury resistance determinant on thetransposon Tn501) and pco (copperresistance determinant on the plasmid pRJ1004) geneticsystems. Positive hybridizations with mer andpco probes indicated that the amplified segmentswere highly homologous to these genes. Some of thePCR products were cloned and partially sequenced, andthe regions sequenced were highly homologous to theappropriate regions of the mer and pcodeterminants. These results demonstrate the widedistribution of mercury and copper resistance genes inboth Gram-positive and Gram-negative isolates obtainedfrom this lead-contaminated soil. In contrast, theczc (cobalt, zinc and cadmium resistance) andchr (chromate resistance) genes could not beamplified from DNAs of some isolates, indicating thelimited contribution, if any, of these genetic systemsto the metal ion resistance of these isolates.

Degradation of high molecular weight polycyclic aromatic hydrocarbons by Pseudomonas cepacia

SummaryWhen inoculated at high cell densities, three strains of Pseudomonas cepacia degraded the polycyclic aromatic hydrocarbons (PAHs) benzo[a]pyrene, dibenz[a,h]anthracene and coronene as sole carbon and energy sources. After 63 days incubation, there was a 20 to 30% decrease in the concentration of benzo[a]pyrene and dibenz[a,h]anthracene and a 65 to 70% decrease in coronene concentration. The three strains were also able to degrade all the PAHs simultaneously in a PAH substrate mixture containing three-, four-, five- and seven-benzene ring compounds. Furthermore, improved degradation of the five- and seven-ring PAHs was observed when low molecular weight PAHs were present.

The effect of growth-conditions of corynebacterium-glutamicum on the transformation frequency obtained by electroporation

SUMMARY: A rapid and efficient method of transforming Corynebacterium glutamicum by electroporation is described. A number of factors are important in determining the level of transformation obtained. Cells grown in the presence of glycine and isonicotinic acid hydrazide and harvested in early exponential growth phase were much easier to transform. The recovery medium on which transformants were isolated also had a significant effect on the number of transformants obtained because cells were osmotically or electrochemically sensitive following electroporation. Transformation efficiencies of up to 5 x 105 transformants per μg plasmid DNA with homologously derived DNA and 2 x 103 transformants per μg of DNA derived from Escherichia coli were obtained.

Isolation and Properties of Metronidazole-Resistant Mutants of Bacteroides fragilis

Metronidazole-resistant mutants of Bacteroides fragilis, isolated after mutagenesis, had diminished ability to take up and metabolize the drug. All the metronidazole-resistant strains had depressed levels of pyruvate dehydrogenase compared with parent cultures. Their end products of glucose metabolism also differed from normal B. fragilis products and were consistent with deficiencies in pyruvate dehydrogenase activity.

Degradation of High Molecular Weight PAHs in Contaminated Soil by a Bacterial Consortium: Effects on Microtox and Mutagenicity Bioassays

Bioaugmentation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil was investigated using a mixed bacterial culture (community five) isolated from an abandoned industrial site. Community five was inoculated into contaminated soil containing a total PAH (two- to five-ring compounds) concentration of approximately 820 mg/kg soil. PAH degradation by the indigenous microbial population was restricted to the lower molecular weight compounds (naphthalene, acenaphthene, fluorene and phenanthrene) even with yeast extract addition: these compounds decreased by 14 to 37%, in soil hydrated to 50% water capacity, following 91 days of incubation at 24°C. Inoculation of community five into this PAH-contaminated soil resulted in significant decreases in the concentration of all PAHs over the incubation period: greater than 86% of naphthalene, acenaphthene, fluorene, and phenanthrene were degraded after 91 days, while anthracene, fluoranthene, and pyrene were degraded to lesser extents (51.7 to 57.6%). A lag period of 48 to 63 days was observed before the onset of benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene removal. However, significant decreases in the concentration of these compounds (32.6, 25.2, and 18.5%, respectively) were observed after 91 days. No significant decrease in the mutagenic potential of organic soil extracts (as measured by the Ames Test) was observed after incubation of the soil with the indigenous microflora; however, the Microtox toxicity of aqueous soil extracts was reduced sevenfold. In contrast, extracts from contaminated soil inoculated with community five underwent a 43% decrease in mutagenic potential and the toxicity was reduced 170-fold after 91 days incubation. These observations suggest that community five could be utilised for the detoxification of PAH-contaminated soil.