Aerobic biodegradation of vinyl chloride in groundwater samples

Studies were conducted to examine the biodegradation of 14C-labeled vinyl chloride in samples taken from a shallow aquifer. Under aerobic conditions, vinyl chloride was readily degraded, with greater than 99% of the labeled material being degraded after 108 days and approximately 65% being mineralized to 14CO2.     

Characterization of a highly enriched dehalococcoides-containing culture that grows on vinyl chloride and trichloroethene

A highly enriched culture that reductively dechlorinates trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), and vinyl chloride (VC) to ethene without methanogenesis is described. The Dehalococcoides strain in this enrichment culture had a yield of (5.6 +/- 1.4) x 10(8) 16S rRNA gene copies/micromol of Cl(-) when grown on VC and hydrogen. Unlike the other VC-degrading cultures described in the literature, strains VS and BAV1, this culture maintained the ability to grow on TCE with a yield of (3.6 +/- 1.3) x 10(8) 16S rRNA gene copies/micromol of Cl(-). The yields on an electron-equivalent basis measured for the culture grown on TCE and on VC were not significantly different, indicating that both substrates supported growth equally well. PCR followed by denaturing gradient gel electrophoresis, cloning, and phylogenetic analyses revealed that this culture contained one Dehalococcoides 16S rRNA gene sequence, designated KB-1/VC, that was identical (over 1,386 bp) to the sequences of previously described organisms FL2 and CBDB1. A second Dehalococcoides sequence found in separate KB-1 enrichment cultures maintained on cDCE, TCE, and tetrachloroethene was no longer present in the VC-H(2) enrichment culture. This second Dehalococcoides sequence was identical to that of BAV1. As neither FL2 nor CBDB1 can dechlorinate VC to ethene in a growth-related fashion, it is clear that current 16S rRNA gene-based analyses do not provide sufficient information to distinguish between metabolically diverse members of the Dehalococcoides group.     

Aerobic biodegradation of vinyl chloride in groundwater samples.

Studies were conducted to examine the biodegradation of 14C-labeled vinyl chloride in samples taken from a shallow aquifer. Under aerobic conditions, vinyl chloride was readily degraded, with greater than 99% of the labeled material being degraded after 108 days and approximately 65% being mineralized to 14CO2.     

Biodegradation of polyethylene glycol by symbiotic mixed culture (obligate mutualism)

Neither Flavobacterium sp. nor Pseudomonas sp. grew on a polyethylene glycol (PEG) 6000 medium containing the culture filtrate of their mixed culture on PEG 6000. The two bacteria did not grow with a dialysis culture on a PEG 6000 medium. Flavobacterium sp. grew well on a dialysis culture containing a tetraethylene glycol medium supplemented with a small amount of PEG 6000 as an inducer, while poor growth of Pseudomonas sp. was observed. Three enzymes involved in the metabolism of PEG, PEG dehydrogenase, PEG-aldehyde dehydrogenase and PEG-carboxylate dehydrogenase (ether-cleaving) were present in the cells of Flavobacterium sp. The first two enzymes were not found in the cells of Pseudomonas sp. PEG 6000 was degraded neither by intact cells of Flavobacterium sp. nor by those of Pseudomonas sp., but it was degraded by their mixture. Glyoxylate, a metabolite liberated by the ether-cleaving enzyme, inhibited the growth of the mixed culture. The ether-cleaving enzyme was remarkably inhibited by glyoxylate. Glyoxylate was metabolized faster by Pseudomonas sp. than by Flavobacterium sp., and seemed to be a key material for the symbiosis.     

Methane production from propionate by methanogenic mixed culture

Abstract The association of Desulfobulbus sp. with Methanosarcina barkeri 227 was able to produce CH₄ from propionate in the presence of sulfate, if a sufficient amount of ferrous iron was added to the media in order to trap the soluble sulfides produced from sulfate. In the absence of ferrous iron, soluble sulfides inhibited the acetoclastic reaction. Attempts to cultivate Desulfobulbus sp. with H₂-utilising methanogenic bacteria in the absence of sulfate did not succeed.     

Aerobic mineralization of vinyl chloride by a bacterium of the order Actinomycetales

A gram-positive branched bacterium isolated from a trichloroethylene-degrading consortium mineralized vinyl chloride in growing cultures and cell suspensions. Greater than 67% of the [1,2-14C]vinyl chloride was mineralized to carbon dioxide, with approximately 10% of the radioactivity appearing in cell biomass and another 10% appearing in 14C-aqueous-phase products.     

Proteomic tracking and analysis of a bacterial mixed culture

To improve the understanding of microbial behaviors in communities, proteomic tracking, an approach for relative quantification of species-specific population dynamics of mixed cultures, was developed. Therefore, a bacterial mixed culture was analyzed during batch cultivations with and without addition of the antibiotic Ceftazidime. The community was composed of Burkholderia cepacia, Pseudomonas aeruginosa, and Staphylococcus aureus, pathogens causing infections in cystic fibrosis patients. Gel-based proteomics and mass spectrometry were used to obtain qualitative and quantitative proteomic data. During cultivation, P. aeruginosa became dominant within the mixed culture while S. aureus was inhibited in growth. Analysis of samples - taken along cultivation - revealed about 270 differentially expressed proteins. Some of those proteins are related to bacterial interactions, response to antibiotic treatment or metabolic shifts. For instance, the enzymes PhzS(flavin-containing monooxygenase), PhzD (phenazine biosynthesis protein), and PhzG2 (pyridoxamine 5'-phosphate oxidase) indicated the production of the antibiotic pigment pyocyanine by P. aeruginosa that is related to oxidative stress and therefore, might inhibit growth of S. aureus. Overall, the strategy applied not only allows species-specific tracking of the community composition but also provides valuable insights into the behavior of mixed cultures.     

Treatment of high strength organic wastewater by a mixed culture of photosynthetic microorganisms

The growth characteristics and nutrient removal fromsynthetic wastewater by Rhodobacter sphaeroides,Chlorella sorokiniana and Spirulinaplatensis were investigated under aerobic dark(heterotrophic) and aerobic light (photoheterotrophic)conditions. Both in terms of economy and efficiency,aerobic dark conditions were the best for wastewatertreatment using R. sphaeroides and C.sorokiniana, but light was necessary with S.platensis. Neither growth nor nutrient removalcharacteristics of the cells were affected insynthetic wastewater with as high as 10 000 ppmacetate, 1000 ppm propionate, 700 ppm nitrate and 100 ppmphosphate. Although R. sphaeroides and C. sorokiniana showed good growth in syntheticwastewater containing 400 ppm of ammonia, S.platensis was completely inhibited.When grown as a monoculture, none of thestrains could simultaneously remove acetate,propionate, ammonia, nitrate and phosphate from thewastewater. R. sphaeroides could remove allthe above nutrients except nitrate, but the rate of removal was relatively low. The rate of nutrientsremoval by C. sorokiniana was higher, but theorganism could not remove propionate; S.platensis could efficiently remove nitrate, ammoniaand phosphate, but none of the organic acids. A mixedculture of R. sphaeroides and C.sorokiniana was therefore used for simultaneousremoval of organic acids, nitrate, ammonia andphosphate. The optimum ratio of the cells depended onthe composition of the wastewater.     

Control of an Escherichia coli mixed culture via affinity binding

A chemostat with population specific recycle was employed to alter the dynamics of a competitive mixed culture of Escherichia coli. Based on differential expression of a functional maltoporin, the two populations were separated by specific adhesion on starch-Sepharose. The slower growing population was the recycled to the reactor. The specific recycle was successful in maintaining the slower growing population at a high level than in comparable reactors without recycle.     

Aerobic mineralization of vinyl chloride by a bacterium of the order Actinomycetales.

A gram-positive branched bacterium isolated from a trichloroethylene-degrading consortium mineralized vinyl chloride in growing cultures and cell suspensions. Greater than 67% of the [1,2-14C]vinyl chloride was mineralized to carbon dioxide, with approximately 10% of the radioactivity appearing in cell biomass and another 10% appearing in 14C-aqueous-phase products.     

Polyhydroxybutyrate production from lactate using a mixed microbial culture

In this study we investigated the use of lactate and a lactate/acetate mixture for enrichment of poly-3-hydroxybutyrate (PHB) producing mixed cultures. The mixed cultures were enriched in sequencing batch reactors (SBR) that established a feast-famine regime. The SBRs were operated under conditions that were previously shown to enable enrichment of a superior PHB producing strain on acetate (i.e., 12 h cycle length, 1 day SRT and 30°C). Two new mixed cultures were eventually enriched from activated sludge. The mixed culture enriched on lactate was dominated by a novel gammaproteobacterium. This enrichment can accumulate over 90 wt% PHB within 6 h, which is currently the best result reported for a bacterial culture in terms of the final PHB content and the biomass specific PHB production rate. The second mixed culture enriched on a mixture of acetate and lactate can produce up to 84 wt% PHB in just over 8 h. The predominant bacterial species in this culture were Plasticicumulans acidivorans and Thauera selenatis, which have both been reported to accumulate large amounts of PHB. The data suggest that P. acidivorans is a specialist on acetate conversion, whereas Thauera sp. is a specialist on lactate conversion. The main conclusion of this work is that the use of different substrates has a direct impact on microbial composition, but has no significant effect on the functionality of PHB production process.     

Primary biodegradation of a series of alkyl sulfosuccinates by mixed bacterial culture

A mixed bacterial culture capable of primary biodegradation of sodium alkyl sulfosuccinates R¹-OOC−CH(SO₃Na)−CH₂−COO−R² was obtained from soil microorganisms by enrichment cultivation and adaptation in the presence of mono-n-dodecyl sulfosuccinate. Gram-negative psychrophilic bacteria with proteolytic, lipolytic and ammonifying activities were prevalent in the culture. The process of primary biodegradation of alkyl sulfosuccinates can be described by firstorder reaction kinetics. The rate constants for linear esters were ascending in the order C₄<C₅<C₆ (45 μmol/min per g cell protein) and further descending with increasing length of the carbon chain C₆>C₈>=C₁₃. Substitution of cyclohexyl for n-hexyl group resulted in fourfold decrease in biodegradation rate. Terminal branching of alkyl chain does not affect the rate of primary biodegradation.     

Aerobic biodegradation of dinitrotoluenes in batch systems by pure and mixed cultures

Biodegradation characteristics of 2,4- and 2,6-dinitrotoluenes (DNTs) individually by pure strains and defined mixed cultures obtained from a mixed culture isolated from a slate packed bed bioreactor is described. Batch degradation experiments were carried out with free cells in submerged cultivations. The degradation rate and efficiency of five best individual bacterial strains, bacterial consortia comprising three and five of these strains, and the complete mixed culture were evaluated and compared. All the strains showed ability to degrade both the DNTs. All but one strain degraded both DNTs at the same rate. The degradation rate as well as the degradation efficiency by the mixed cultures was higher than that by the individual strains. The complete mixed culture showed 15-20x higher degradation rate than the individual bacterial strains.     

Kinetic analysis of high-concentration isopropanol biodegradation by a solvent-tolerant mixed microbial culture

The ability of a previously enriched microbial population to utilize isopropanol (IPA) as the sole carbon source within a minimal salts medium is studied. The advantage of prior enrichment procedures for the improvement of IPA biodegradation performance is demonstrated for an IPA concentration of up to 24 g L(-1). Results showing the interrelationship between temperature and substrate utilization and inhibition levels at temperatures of between 2 degrees C and 45 degrees C are examined. Models of inhibition based on enzyme kinetics are assessed via nonlinear analysis, in order to accurately represent the growth kinetics of this solvent-tolerant mixed culture. The model that best describes the data is the Levenspiel substrate inhibition model, which can predict the maximum substrate level above which growth is completely limited. This is the first report of IPA treatment of up to 24 g L(-1) by an aerobic solvent-tolerant population.     

Modeling product formation in anaerobic mixed culture fermentations

The anaerobic conversion of organic matter to fermentation products is an important biotechnological process. The prediction of the fermentation products is until now a complicated issue for mixed cultures. A modeling approach is presented here as an effort to develop a methodology for modeling fermentative mixed culture systems. To illustrate this methodology, a steady-state metabolic model was developed for prediction of product formation in mixed culture fermentations as a function of the environmental conditions. The model predicts product formation from glucose as a function of the hydrogen partial pressure (P(H2)), reactor pH, and substrate concentration. The model treats the mixed culture as a single virtual microorganism catalyzing the most common fermentative pathways, producing ethanol, acetate, propionate, butyrate, lactate, hydrogen, carbon dioxide, and biomass. The product spectrum is obtained by maximizing the biomass growth yield which is limited by catabolic energy production. The optimization is constrained by mass balances and thermodynamics of the bioreactions involved. Energetic implications of concentration gradients across the cytoplasmic membrane are considered and transport processes are associated with metabolic energy exchange to model the pH effect. Preliminary results confirmed qualitatively the anticipated behavior of the system at variable pH and P(H2) values. A shift from acetate to butyrate as main product when either P(H2) increases and/or pH decreases is predicted as well as ethanol formation at lower pH values. Future work aims at extension of the model and structural validation with experimental data.     

Aerobic mineralization of chlorobenzoates by a natural polychlorinated biphenyl-degrading mixed bacterial culture

A natural mixed aerobic bacterial culture, designated MIXE1, was found to be capable of degrading several low-chlorinated biphenyls when 4-chlorobiphenyl was used as a co-substrate. MIXE1 was capable of using all the three monochlorobenzoate (CBA) isomers tested as well as 2,5-, 3,4- and 3,5-dichlorobenzoate (dCBA) as the sole carbon and energy source. During MIXE1 growth on these substrates, a nearly stoichiometric amount of chloride was released: 0.5 g/l of each chlorobenzoate was completely mineralized by MIXE1 after 2 or 3 days of culture incubation. Two strains, namely CPE2 and CPE3, were selected from MIXE1: CPE2, referred to the Pseudomonas genus, was found to be capable of totally degrading both 2-CBA and 2,5-dCBA, whereas Alcaligenes strain CPE3 was capable of mineralizing 3-, 4-CBA and 3,4-dCBA. Substrate uptake studies carried out with whole cells of strain CPE2 suggested that 2-CBA was metabolized through catechol, while 2,5-dCBA was degraded via 4-chlorocatechol. 3-CBA, 4-CBA, and 3,4-dCBA appeared to be degraded through 3,4-dihydroxybenzoate by the CPE3 strain. MIXE1, which is capable of degrading several chlorobenzoates, should therefore be able to mineralize a number of low-chlorinated congeners of simple and complex polychlorinated biphenyl mixtures. Correspondence to: F. Fava     

Rapid biodegradation of calcium lignosulfonate by means of a mixed culture of microorganisms

In this paper we discuss the aerobic biodegradation of calcium libnosulfonate (CLS) in a beechwood sulfite waste liquor by means of a mixed culture of microorganisms consisting of two Trichosporn Years and bacteria in the Arthrobacter (two species), Psedomonas, and Chromobacterium genera. Under the established parameters 50% CLS was biodegraded in 24 hr accompanied by the demethylation of methoxyl groups, the splitting of sulpher–carbon bonds, and the appearance of carbonyl and carboxyl groups. The achieved results by determination of phenolic OH groups, as well as established changes of the absorption bands of IR spectra of the CLS molecule and the results of the shortening of the analyses of the C, H, O, and S, show that the degradation of the aromatic nuclei-culture biodegradation, which confirms the increase in the concentration of conjugated carbonyl groups and carboxyl groups.     

Design of bacterial defined mixed cultures for biodegradation of specific crude oil fractions, using population dynamics analysis by DGGE

Hydrocarbon-degrading bacteria isolated from oil-polluted soils, were used to design three defined mixed cultures (DMC) for biodegradation of Maya crude oil fractions. The first degrading culture, DMC A was made up with 10 strains. Design of DMC B (six strains) and DMC C (three strains) was based on DGGE profiles obtained throughout biodegradation assays of different petroleum fractions. Biodegradation of the aliphatic fraction (10 000 mg l⁻¹) and an aromatic–polar mixture (5000 mg l⁻¹) was evaluated for the DMC B. Biodegradation of total hydrocarbons (10 000 mg l⁻¹) and its fractions was evaluated for DMC B and DMC C. During biodegradation assays, O₂ consumption and CO₂ production were assessed by respirometry, while population dynamics of predominant strains was based on PCR-DGGE profiles of partial 16S rDNA. Aliphatic fraction was completely biodegraded by DMC B, while degradation of the aromatic–polar mixture was 12.5% and for total hydrocarbons 40.5%. DMC B was able to degrade the aromatic fraction (31%) and even the polar fraction (19.6%) present in total hydrocarbons. DMC C degraded the aromatic and polar fractions (5.6% and 2%, respectively) present in total hydrocarbons. DGGE profiles of the DMCs indicated that Pseudomonas sp., Gordonia rubripertincta and a non-identified strain were predominant and probably responsible of the hydrocarbons biodegradation. The use of DGGE-fingerprinting to track microbial populations, allowed selecting strains to design efficient oil-degrading defined mixed cultures.     

Improvement of acetate production from lactose by growing Clostridium thermolacticum in mixed batch culture

AIMS: The objective of this study was to increase the acetate production by Clostridium thermolacticum growing on lactose, available as a renewable resource in the milk and whey permeate from the cheese industry. METHODS AND RESULTS: Experiments for increased acetate productivity by thermophilic anaerobes grown on lactose were carried out in batch cultures. Lactose at concentration of 30 mmol l(-1) (10 g l(-1)) was completely degraded by Cl. thermolacticum and growth rate was maximal. High concentrations of by-products, ethanol, lactate, hydrogen and carbon dioxide were generated. By using an efficient hydrogenotroph, Methanothermobacter thermoautotrophicus, in a defined thermophilic anaerobic consortium (58 degrees C) with Cl. thermolacticum and the acetogenic Moorella thermoautotrophica, the hydrogen partial pressure was dramatically lowered. As a consequence, by-products concentrations were significantly reduced and acetate production was increased. CONCLUSION: Through efficient in situ hydrogen scavenging in the consortium, the metabolic pattern was modified in favour of acetate production, at the expense of reduced by-products like ethanol. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of this thermophilic anaerobic consortium opens new opportunities for the efficient valorization of lactose, the main waste from the cheese industry, and production of calcium-magnesium acetate, an environmentally friendly road de-icer.