Activation of an indigenous microbial consortium for bioaugmentation of pentachlorophenol/creosate contaminated soils

Soil activation, a concept based on the cultivation of biomass from a fraction of a comtaminated soil for subsequent use as an inoculum for bioaugmentation of the same soil, was studied as a method for the aerobic biodegradation of pentachlorophenol (PCP) and polycyclic hydrocarbons (PAH) in contaminated soils. A microbial consortium able to degrade PCP and PAH in contaminated soil from wood-preserving facilities was isolated and characterized for PCP degradation and resistance. To obtain an active consortium from the contaminated soil in a fed-batch bioreactor, the presence of soil as a support or source of nutrients was found to be essential. During the 35 days of bioreactor operation, residual PCP in solution remained near zero up to a loading rate of 700mg/l per day. The PCP meneralization rate increased from 70 mg/l per day when no PCP was added to the bioreactor to 700 mg/l per day at the maximum loading rate. The consortium tolerated a PCP concentration of 400 mg/l in batch experiments. Production of a PCP-degrading consortium in a fed-batch slurry bioreactor enhanced the activity of PCP biodegradation by a factor of ten. PAH biodegradation increased, during the same time period, by a factor of 30 and 81 for phenanthrene and pyrene, respectively. Preliminary laboratory-scale results indicated that a significant reduction in the time required for degradation of PCP and PAH in contaminated soil could be achieved using activated soil as an inoculum.Issued as NRC 33861 correspondence to: R. Samson     

Phytoremediation of Pentachlorophenol in the Crested Wheatgrass (Agropyron cristatum × desertorum) Rhizosphere

Pentachlorophenol (PCP) is a widespread, highly toxic contaminant of soil and water that is generally recalcitrant to microbial breakdown and thus may be considered a good candidate for phytoremediation. PCP toxicity and rates of mineralization were compared in crested wheatgrass seedlings that were either sterile or root-inoculated with microbial consortia derived from soil at a PCP-contaminated site. Inoculated seedlings were more tolerant to PCP and mineralized threefold more ¹⁴C-PCP than sterile seedlings. Only 10% of the recovered radioactivity from sterile seedlings represented mineralized PCP, indicating that rhizosphere microorganisms are primarily responsible for PCP mineralization. The levels of PCP degradation exhibited by several microbial consortia and isolates in liquid culture were not correlated with their ability to protect crested wheatgrass seedlings from PCP toxicity. Most probable number estimates showed that the presence of crested wheatgrass root exudates enhanced the number of PCP-degrading microorganisms by 100-fold in liquid culture, indicating that exudate components provide some nutritive benefit, possibly as PCP co-metabolites. A close association of plants and rhizosphere microorganisms appears to be necessary for crested wheatgrass survival in PCP-contaminated soil, although understanding the molecular details of this association requires further research.     

Enhancement of Pentachlorophenol Biodegradation Using Organic and Inorganic Supports

The role of soil, straw, and sawdust as supports in enhancing pentachlorophenol (PCP) mineralization by an indigenous soil consortium was examined by assessing the bioavailability of the substrate and other nutrients. PCP sorption tests were conducted in the presence of sterile supports to evaluate PCP bioavailability. Indigenous biomass, practically free of soil particles, was prepared to test the influence of sterile soil and soil components on the mineralization of increasing PCP concentrations. Organic supports such as straw and sawdust were very good sorbents for PCP, resulting in a slow, continuous desorption of substrate, high mineralization rates, and reduced toxicity to the active biomass. Soil and clay retained less PCP and desorbed it in decreasing amounts. Soil was the best amendment to enhance the mineralization of 100 mg/L PCP. Soil, soil extract, and the lowest-molecular-weight fraction of the soil extract facilitated the complete mineralization of 300 mg/L of PCP with a lag time of about 9 days, compared to 21 days for the unamended culture. Addition of soil enhanced PCP mineralization by an indigenous consortium, probably because soil particles served as an adsorbent for the contaminant to decrease its toxicity, as a support for biomass colonization, and as a source of supplementary nutrients for the biomass. This concept is of importance, particularly for the production of active and resistant biomass for the biotreatment of contaminated soils.     

Bioremediation of pentachlorophenol-contaminated soil by bioaugmentation using activated soil

The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from 10⁵ cfu/g to 10⁸ cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5 weeks at 20 °C and for up to 3 months when kept at 4 °C. The activated attached soil biomass produced in the completely mixed soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor, were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms. Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days) in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached to soil particles or as a flocculent biomass, were similar. Received: 31 March 1997 / Received revision: 22 July 1997 / Accepted: 25 August 1997     

Development of a Microbial Consortium from a Contaminated Soil That Degrades Pentachlorophenol and Wood-Preserving Oil

An indigenous microbial consortium capable of degrading pentachlorophenol (PCP) and petroleum hydrocarbons (C₁₀-C₅₀) was produced from a soil contaminated with wood-preserving oil. Two 10-L stainless steel soil slurry (10% w/v) bioreactors were operated in fed-batch mode. To verify the growth and efficiency of PCP degraders in the presence of other contaminants, one bioreactor was fed with a PCP-based wood-preserving mixture (WPM) and a second reactor was fed with technical-grade NaPCP. During the 90-day period of activation, PCP, C₁₀-C₅₀, Cl^-, pH, and dissolved oxygen levels were monitored. The microbial community was monitored using specific most probably number (MPN) bacterial counts and mineralization tests. PCP degradation rates increased similarly in both reactors, from 19 to 132 mg/L-d in the NaPCP reactor, and from 41 to 112 mg/L-d in the WPM reactor. Contaminant loss calculations showed that 99.5% of PCP and 92.5% of C₁₀-C₅₀ added to the WPM reactor were biodegraded. It also revealed that 83% of polychlorinated dioxins and furans were removed. PCP-degrading bacteria increased from 7×10² to 1.6×10⁶ bacteria/mL in both reactors, and petroleum hydrocarbon degraders increased from 1.7×102 to 3.4×108 bacteria/mL in the WPM reactor, indicating that the activity of PCP degraders was not inhibited by the presence of microorganisms growing on petroleum hydrocarbons.     

Biodegradation of pentachlorophenol in natural soil by inoculatedRhodococcus chlorophenolicus

Rhodococcus chlorophenolicus PCP-1, a mineralizer of polychlorinated phenols, was inoculated into natural sandy loam and peaty soils with pentachlorophenol (PCP) at concentrations usually found at lightly and heavily polluted industrial sites (30 to 600 mg PCP/kg). A single inoculum of 10⁵ to 10⁸ cells per g of peat soil and as little as 500 cells/g sandy soil initiated mineralization of¹⁴C-PCP. The mineralization rates of PCP were 130 to 250 mg mineralized per kg soil in 4 months in the heavily (600 mg/kg) polluted soils and 13 to 18 mg/kg in the lightly (30 mg/kg) polluted soils. There were no detectable PCP mineralizing organisms in the soils prior to inoculation, and also there was no significant adaptation of the indigenous microbial population to degrade PCP during 4 months observation in the uninoculated soils. The inoculum-induced mineralization continued for longer than 4 months after a single inoculation. Uninoculated, lightly polluted soils (30 mg PCP/kg) also showed loss of PCP, but some of this reappeared as pentachloroanisol and other organic chlorine compounds (EOX). Such products did not accumulate in theR. chlorophenolicus-inoculated soils, where instead EOX was mineralized 90 to 98%.R. chlorophenolicus mineralized PCP unhindered by the substrate competition offered by the PCP-methylating bacteria indigenously occurring in the soils or by simultaneously inoculated O-methylatingR. rhodochrous.     

Degradation of p-nitrophenol and pentachlorophenol mixtures by Sphingomonas sp. UG30 in soil perfusion bioreactors

The degradation of mixtures of pentachlorophenol (PCP) and p-nitrophenol (PNP) were evaluated in pure cultures of Sphingomonas sp. UG30, statically incubated soils (60% water-holding capacity) and soil perfusion bioreactors where encapsulated cells of UG30 were used as a soil inoculant. In pure-culture studies, conditions were optimized for mineralization of PCP and PNP mixtures at concentrations of 30 mg l⁻¹ each. Optimum in vitro mineralization of PCP and PNP mixtures by UG30 was facilitated using ammonium phosphate as a nitrogen source, while inhibition was observed with ammonium nitrate. The bioreactor system used columns containing soil treated with mixtures of 100, 225 or 500 mg kg⁻¹ of PCP and PNP. Rapid dissipation of both substrates was observed at the 100 mg kg⁻¹ level. Inoculation with UG30 enhanced PCP degradation at the 100 mg kg⁻¹ level in bioreactors but not in static soil microcosms. At higher PCP and PNP concentrations (225 mg kg⁻¹), occasional complete degradation of PNP was observed, and PCP degradation was about 80% compared to about 25% in statically incubated soils after 20 days at 22°C. There was no additional degradation of the PCP and PNP mixtures attributable to inoculation with encapsulated cells of UG30 in either soil system at concentrations of 225 or 500 mg kg⁻¹. Journal of Industrial Microbiology & Biotechnology (2000) 25, 93–99. Received 25 February 2000/ Accepted in revised form 07 June 2000     

Impact of chlorophenols on microbiota of an unpolluted acidic soil: microbial resistance and biodegradation

The impact of 2-monochlorophenol (MCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) on the microbial community of an acidic forest soil was studied under controlled laboratory conditions by spiking microcosms with the pollutants at concentrations ranging from 0.1 to 5000 mg kg(-1). A decrease in the cumulative respirometric values and changes in the bacterial and fungal community composition were detected at 1000 mg MCP kg(-1), 100 mg TCP kg(-1) and 100 and 1000 mg PCP kg(-1). However, drastic effects on the microbial community were revealed only at higher concentrations of MCP and TCP, although the toxicity of PCP was expected to be stronger. The acidic condition of the soil presumably reduces bioavailability of PCP, leading to less pronounced effects than the other pollutants. This finding highlights the consideration of pollutant bioavailability in each environment to adequately assess contamination effects. Twenty-two different chlorophenol-resistant and potentially degrading microorganisms were isolated from highly polluted microcosms. The most resistant isolates were related to Burkholderia arboris, Bacillus circulans, Paenibacillus taichungensis, Luteibacter rhizovicina and Janibacter melonis. These isolates also showed the capacity to reduce the concentration of TCP or PCP between 15% and 35% after 5 days of incubation (initial concentration of 50 mg L(-1)). The isolate related to B. circulans is an atypical case of a member of the Firmicutes group for which chlorophenol-degrading capacities have been described.     

Anaerobic mineralization of pentachlorophenol (PCP) by combining PCP-dechlorinating and phenol-degrading cultures

The dechlorination and mineralization of pentachlorophenol (PCP) was investigated by simultaneously or sequentially combining two different anaerobic microbial populations, a PCP-dechlorinating culture capable of the reductive dechlorination of PCP to phenol and phenol- degrading cultures able to mineralize phenol under sulfate- or iron-reducing conditions. In the simultaneously combined mixture, PCP (about 35 microM) was mostly dechlorinated to phenol after incubation for 17 days under sulfate-reducing conditions or for 22 days under iron-reducing conditions. Thereafter, the complete removal of phenol occurred within 40 days under both conditions. In the sequentially combined mixture, most of the phenol, the end product of PCP dechlorination, was degraded within 12 days of inoculation with the phenol degrader, without a lag phase, under both sulfate- and iron-reducing conditions. In a radioactivity experiment, [14C-U]-PCP was mineralized to 14CO2 and 14CH4 by the combined anaerobic microbial activities. Analysis of electron donor and acceptor utilization and of the production and consumption of H2, CO2, and CH4 suggested that the dechlorinating and degrading microorganisms compete with other microorganisms to perform PCP dechlorination and part of the phenol degradation in complex anoxic environments in the presence of electron donors and acceptors. The presence of a small amount of autoclaved soil slurry in the medium was possibly another advantageous factor in the successful dechlorination and mineralization of PCP by the combined mixtures. This anaerobic-anaerobic combination technology holds great promise as a cost-effective strategy for complete PCP bioremediation in situ.     

Bulk sparkling wine production by external encapsulated yeast bioreactor

Summary A new method for bulk sparkling wine production is proposed. The use of an external bioreactor with high immobilized yeast loading for second fermentation was studied. The new process is much faster than the traditional one and the sparkling wines obtained are perfectly clear without showing quality faults.     

UASB反应器中影响污泥颗粒化的工程因素

研究了具有不同微生物群系的接种污泥、流动方式和流速对上流式厌氧污泥床(UASB)反应器中活性污泥粒化的影响。颗粒化过程包括：微生物絮凝体的形成、亚核的形成,亚核增长和颗粒成熟四个阶段。微絮凝体的形成取决于酸化菌的作用。流体的动量传递和流体对悬浮物的剪切作用是影响亚核形成的关键性工程因素。为此提出最低流速概念,即形成污泥膨胀床的最低流速。合适的进料速率、污泥负荷、布水均匀性以及碱度控制是UASB反应器工程放大和过程控制的四大要素。     

Changes in the microbial community during repeated anaerobic microbial dechlorination of pentachlorophenol

Pentachlorophenol (PCP) has been widely used as a pesticide in paddy fields and has imposed negative ecological effect on agricultural soil systems, which are in typically anaerobic conditions. In this study, we investigated the effect of repeated additions of PCP to paddy soil on the microbial communities under anoxic conditions. Acetate was added as the carbon source to induce and accelerate cycles of the PCP degradation. A maximum degradation rate occurred at the 11th cycle, which completely transformed 32.3 μM (8.6 mg L^?1) PCP in 5 days. Illumina high throughput sequencing of 16S rRNA gene was used to profile the diversity and abundance of microbial communities at each interval and the results showed that the phyla of Bacteroidates, Firmicutes, Proteobacteria, and Euryarchaeota had a dominant presence in the PCP-dechlorinating cultures. Methanosarcina, Syntrophobotulus, Anaeromusa, Zoogloea, Treponema, W22 (family of Cloacamonaceae), and unclassified Cloacamonales were found to be the dominant genera during PCP dechlorination with acetate. The microbial community structure became relatively stable as cycles increased. Treponema, W22, and unclassified Cloacamonales were firstly observed to be associated with PCP dechlorination in the present study. Methanosarcina that have been isolated or identified in PCP dechlorination cultures previously was apparently enriched in the PCP dechlorination cultures. Additionally, the iron-cycling bacteria Syntrophobotulus, Anaeromusa, and Zoogloea were enriched in the PCP dechlorination cultures indicated they were likely to play an important role in PCP dechlorination. These findings increase our understanding for the microbial and geochemical interactions inherent in the transformation of organic contaminants from iron rich soil, and further extend our knowledge of the PCP-transforming microbial communities in anaerobic soil conditions.     

Straw Compost and Bioremediated Soil as Inocula for the Bioremediation of Chlorophenol-Contaminated Soil

We evaluated the use of straw compost and remediated soil as inocula for bioremediation of chlorophenol-contaminated soil. The in situ biotransformation of pentachlorophenol (PCP) and mineralization of radiolabeled [U-(sup14)C]PCP by straw compost and remediated soil were studied under field-simulating conditions before and after 3 months of adaptation with PCP in a percolator. After PCP adaptation, the straw compost mineralized up to 56% of the [(sup14)C]PCP. No partial dechlorination of PCP was found. The native straw compost did not mineralize PCP, but partial dechlorination of PCP occurred (i) at pH 8 under near-thermophilic conditions (45(deg)C) and (ii) at pH 7 under aerobic and mesophilic conditions. No biotransformation reactions occurred at room temperature (25(deg)C) at pH 8. Enrichment in the percolator enhanced the mineralization rate of remediated soil to 56% compared with that of the native remediated soil, which mineralized 24% of [(sup14)C]PCP added. Trace amounts of chloroanisoles as the only biotransformation products were detected in PCP-adapted remediated soil. Both inoculants studied here showed effective mineralization of PCP when they were adapted to PCP in the percolator. No harmful side reactions, such as extensive methylation, were observed.     

Factors affecting nitrogen dynamics in a semiarid woodland (Dry Chaco,Argentina)

In an effort to elucidate the factors affecting soil N dynamics in the Dry Chaco ecosystem, soil respiration and microbial biomass N were measured for one year underneath 5 vegetation types: a leguminous tree (Prosopis flexuosa DC), a non-leguminous tree (Aspidosperma quebracho-blanco Schlecht.), a non leguminous shrub (Larrea spp.), the open interspaces, and a pure grassland. Ammonifier and nitrifier densities and N content in litter were also measured in some cases. Results were compared with previously reported N mineralization rates and soil fertility.During the dry season microbial biomass N and net N mineralization were low, while accretion of easily mineralizable C occurred (estimated through soil respiration rates in lab under controlled temperature and moisture). With the onset of rain, microbial biomass N and N mineralization increased markedly, resulting in a decrease in easily mineralizable C. Throughout the wet season N mineralization varied with soil moisture while microbial biomass N remained consistently high. Mean values of immobilized N in this ecosystem were high (20–140 mg kg^–1), of about the same order of magnitude as accumulated net N mineralization (50–150 mg kg^–1 yr^–1). Microbial decay in the dry season, considered as a source of easily mineralizable N, accounted for only 40% of gross N mineralization increase at the beginning of the wet season. Ammonifier densities correlated significantly with soil moisture and N mineralization, but nitrifiers did not.The highest values of total N, N mineralization, inorganic N, microbial biomass N, nitrifier densities, N content in litter, total organic C and easily mineralizable C were found under Prosopis and the lowest values under shrubs and the interspaces. The main differences between tree species were in N mineralization at the beginning of the wet season, in total and inorganic N pools, and in nitrifier densities; all of which were significantly lower under Aspidosperma than under Prosopis.N mineralization in the pure grassland was very low despite high values of total N and C sources. Although N immobilized in microbial biomass was similarly high under Aspidosperma, Prosopis and the pure grassland, net N mineralization rates were quite different.     

Bacterial Community Dynamics during Start-Up of a Trickle-Bed Bioreactor Degrading Aromatic Compounds

This study was performed with a laboratory-scale fixed-bed bioreactor degrading a mixture of aromatic compounds (Solvesso100). The starter culture for the bioreactor was prepared in a fermentor with a wastewater sample of a car painting facility as the inoculum and Solvesso100 as the sole carbon source. The bacterial community dynamics in the fermentor and the bioreactor were examined by a conventional isolation procedure and in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotides. Two significant shifts in the bacterial community structure could be demonstrated. The original inoculum from the wastewater of the car factory was rich in proteobacteria of the alpha and beta subclasses, while the final fermentor enrichment was dominated by bacteria closely related to Pseudomonas putida or Pseudomonas mendocina, which both belong to the gamma subclass of the class Proteobacteria. A second significant shift was observed when the fermentor culture was transferred as inoculum to the trickle-bed bioreactor. The community structure in the bioreactor gradually returned to a higher complexity, with the dominance of beta and alpha subclass proteobacteria, whereas the gamma subclass proteobacteria sharply declined. Obviously, the preceded pollutant adaptant did not lead to a significant enrichment of bacteria that finally dominated in the trickle-bed bioreactor. In the course of experiments, three new 16S as well as 23S rRNA-targeted probes for beta subclass proteobacteria were designed, probe SUBU1237 for the genera Burkholderia and Sutterella, probe ALBO34a for the genera Alcaligenes and Bordetella, and probe Bcv13b for Burkholderia cepacia and Burkholderia vietnamiensis. Bacteria hybridizing with the probe Bcv13b represented the main Solvesso100-degrading population in the reactor.Many branches of industry produce waste gases which contain odorous organic and inorganic components. Apart from the conventional thermal and physicochemical techniques for removal of pollutants from exhaust air, biological waste gas treatment is becoming more and more important. This kind of treatment is advantageous in cases in which the recovery of the components (e.g., absorption in liquids and adsorption in solids) or the utilization of a thermal process (thermal or catalytic combustion) is not economical. Today three different process variations for biological waste gas treatment are used: biofilters, bioscrubbers, and trickle-bed bioreactors. In biofilters and trickle-bed reactors, the pollutant-degrading microorganisms are immobilized on a carrier material, whereas in bioscrubbers the microorganisms are dispersed in the liquid phase. Biofilters and bioscrubbers are preferred in industry, while biofilters are common in compost production and sewage plants (10).Biological waste gas treatment has a long tradition. Already in 1953, a soil system was employed for the treatment of odorous sewer exhaust gases in Long Beach, Calif. (25), and although up to now a lot of efforts have been funneled into process engineering (14, 17, 18, 24), current knowledge of the involved microorganisms is still very limited. Diversity of the microbial communities in the bioreactors for the exhaust gas purification have mostly been analyzed by culture-dependent methods (9, 12, 28, 31). However, there is a large discrepancy between the total (direct) microscopic cell counts and viable plate counts in many ecosystems and every cultivation medium selects for certain microorganisms. Therefore, cultivation-based studies of bacterial populations may give wrong impressions of the actual community structure in an ecosystem (35). A possible means of avoiding qualitative and quantitative errors in the analysis of microbial community structure in complex ecosystems is the use of fluorescently labeled, rRNA-targeted oligonucleotides (5) for the in situ identification and enumeration of bacteria. This method has already been used successfully in complex microbial communities, such as multispecies biofilms (6, 22, 26), trickling filters (27), and activated sludge (37).The current study was performed with a laboratory-scale trickle-bed bioreactor degrading a mixture of aromatic compounds (Solvesso100). The starter culture for the inoculation of the bioreactor was an enrichment prepared in a fermentor which was itself started with a wastewater sample from a car painting factory as the inoculum and Solvesso100 as the sole carbon source. The goal of our study was to use for the first time fluorescent in situ hybridization (FISH) to investigate the microbial community structure and dynamics in the fermentor and the bioreactor during start-up. One of the open questions was whether the fermentor enrichment, which is done in suspension, indeed selects for those bacteria that later are immobilized in the bioreactor. In the course of this study, new 16S as well as 23S rRNA-targeted probes for phylogenetic groups within the beta subclass of the class Proteobacteria have been developed and applied in order to obtain a higher taxonomic resolution of the molecular techniques. The molecular data were compared to those obtained by traditional cultivation-dependent techniques.     

Understanding fungal functional biodiversity during the mitigation of environmentally dispersed pentachlorophenol in cork oak forest soils

Pentachlorophenol (PCP) is globally dispersed and contamination of soil with this biocide adversely affects its functional biodiversity, particularly of fungi – key colonizers. Their functional role as a community is poorly understood, although a few pathways have been already elucidated in pure cultures. This constitutes here our main challenge – elucidate how fungi influence the pollutant mitigation processes in forest soils. Circumstantial evidence exists that cork oak forests in N. W. Tunisia – economically critical managed forests are likely to be contaminated with PCP, but the scientific evidence has previously been lacking. Our data illustrate significant forest contamination through the detection of undefined active sources of PCP. By solving the taxonomic diversity and the PCP‐derived metabolomes of both the cultivable fungi and the fungal community, we demonstrate here that most strains (predominantly penicillia) participate in the pollutant biotic degradation. They form an array of degradation intermediates and by‐products, including several hydroquinone, resorcinol and catechol derivatives, either chlorinated or not. The degradation pathway of the fungal community includes uncharacterized derivatives, e.g. tetrachloroguaiacol isomers. Our study highlights fungi key role in the mineralization and short lifetime of PCP in forest soils and provide novel tools to monitor its degradation in other fungi dominated food webs.     

Bioremediation of a Chilean Andisol contaminated with pentachlorophenol (PCP) by solid substrate cultures of white-rot fungi

This study provides a first attempt investigation of a serie of studies on the ability of Anthracophyllum discolor, a recently isolated white-rot fungus from forest of southern Chile, for the treatment of soil contaminated with pentachlorophenol (PCP) to future research on potential applications in bioremediation process. Bioremediation of soil contaminated with PCP (250 and 350 mg kg⁻¹ soil) was investigated with A. discolor and compared with the reference strain Phanerochaete chrysosporium. Both strains were incorporated as free and immobilized in wheat grains, a lignocellulosic material previously selected among wheat straw, wheat grains and wood chips through the growth and colonization of A. discolor. Wheat grains showed a higher growth and colonization of A. discolor, increasing the production of manganese peroxidase (MnP) activity. Moreover, the application of white-rot fungi immobilized in wheat grains to the contaminated soil favored the fungus spread. In turn, with both fungal strains and at the two PCP concentrations a high PCP removal (70–85%) occurred as respect to that measured with the fungus as free mycelium (30–45%). Additionally, the use of wheat grains in soil allowed the proliferation of microorganisms PCP decomposers, showing a synergistic effect with A. discolor and P. chrysosporium and increasing the PCP removal in the soil.     

Pentachlorophenol degradation: a pure bacterial culture and an epilithic microbial consortium.

The steady-state growth of a Flavobacterium strain known to utilize pentachlorophenol (PCP) was examined when cellobiose and PCP simultaneously limited its growth rate in continuous culture. A concentration of 600 mg of PCP per liter in influent medium could be continuously degraded without affecting steady-state growth. We measured specific rates of PCP carbon degradation as high as 0.15 +/- 0.01 g (dry weight) of C per h at a growth rate of 0.045 h-1. Comparable specific rates of PCP degradation were obtained and maintained by PCP-adapted, natural consortia of epilithic microorganisms. The consortium results suggest that a fixed-film bioreactor containing a PCP-adapted natural microbial population could be used to treat PCP-contaminated water.     

Pentachlorophenol degradation: a pure bacterial culture and an epilithic microbial consortium

The steady-state growth of a Flavobacterium strain known to utilize pentachlorophenol (PCP) was examined when cellobiose and PCP simultaneously limited its growth rate in continuous culture. A concentration of 600 mg of PCP per liter in influent medium could be continuously degraded without affecting steady-state growth. We measured specific rates of PCP carbon degradation as high as 0.15 +/- 0.01 g (dry weight) of C per h at a growth rate of 0.045 h-1. Comparable specific rates of PCP degradation were obtained and maintained by PCP-adapted, natural consortia of epilithic microorganisms. The consortium results suggest that a fixed-film bioreactor containing a PCP-adapted natural microbial population could be used to treat PCP-contaminated water.     

A new continuous biofilm bioreactor for immobilized oil-degrading filamentous fungi

A new type of horizontal biofilm bioreactor for continuous bioconversion of emulsified oily substrate by immobilized growing biofilm of filamentous fungi was designed, constructed, and feasibility tested. The new reactor design provides "self"-immobilization of homogenized mycelium leading to even biofilm development. This was accomplished by using stainless steel screens of optimal mesh, mounted in parallel and stretching outward from a main rotating axis of a biological rotating contractor. Each screen was equipped with a pair of stainless steel blades mounted on supports allowing for continuous biofilm "shaving" beyond a predetermined thickness, thus retaining freshly growing active biofilm surface. The feasibility of the new bioreactor was demonstrated by decalactone production from emulsified castor oil by immobilized filamentous fungi (Tyromyces sambuceus). The combination of oriented metal screens and moving blades was found to be highly effective for a model system in maintaining stable substrate emulsion in the reactor in either batchwise or continuous processing, as well as maintaining biofilm thickness with continuous removal of excess growing hyphae. (c) 1996 John Wiley & Sons, Inc.