Four marine-derived fungi for bioremediation of raw textile mill effluents

Textile dye effluents pose environmental hazards because of color and toxicity. Bioremediation of these has been widely attempted. However, their widely differing characteristics and high salt contents have required application of different microorganisms and high dilutions. We report here decolorization and detoxification of two raw textile effluents, with extreme variations in their pH and dye composition, used at 20–90% concentrations by each of the four marine-derived fungi. Textile effluent A (TEA) contained an azo dye and had a pH of 8.9 and textile effluent B (TEB) with a pH of 2.5 contained a mixture of eight reactive dyes. The fungi isolated from mangroves and identified by 18S and ITS sequencing corresponded to two ascomycetes and two basidiomycetes. Each of these fungi decolorized TEA by 30–60% and TEB by 33–80% used at 20–90% concentrations and salinity of 15 ppt within 6 days. This was accompanied by two to threefold reduction in toxicity as measured by LC₅₀ values against Artemia larvae and 70–80% reduction in chemical oxygen demand and total phenolics. Mass spectrometric scan of effluents after fungal treatment revealed degradation of most of the components. The ascomycetes appeared to remove color primarily by adsorption, whereas laccase played a major role in decolorization by basidiomycetes. A process consisting of a combination of sorption by fungal biomass of an ascomycete and biodegradation by laccase from a basidiomycete was used in two separate steps or simultaneously for bioremediation of these two effluents.     

Potential use of environmental cyanobacterial species in bioremediation of lindane-contaminated effluents

This study investigated the potential degradation of lindane [γ-hexachlorocyclohexane (γ-HCH)], resulting from agricultural runoff, by environmental species of cyanobacteria. Cyanobacterial species isolated from the Egyptian Lakes Qaroun and Mariut were exposed, either individually or as mixtures, to 5 and 10 ppm lindane for 7 days. Growth inhibition or stimulation percentage, as well as the percentage of lindane removal efficiency (RE), were calculated, and factors controlling both were discussed. Lindane exhibited different degrees of toxicity or stimulation for the selected cyanobacteria. Stimulation of growth ranged between 0.0- and 13.16-fold higher than controls, while inhibition ranged between 0.0% and 100%. Results also proved that Mariut species were more resistant to lindane toxicity than were Qaroun species. Resistance to lindane among Qaroun spp. was in the order Oscillatoria sp. 12>Oscillatoria sp. 13>Synechococcus sp.>Nodularia sp.>Nostoc sp.>Cyanothece sp.>Synechococcus sp. Among Mariut spp., it was Microcystis aeruginosa MA1>Anabaena cylindrica>Microcystis aeruginosa MA15>A. spiroides>A. flos-aquae. Mixed cultures showed varying sensitivity. Lindane was removed by all the species, either as individuals or mixtures, at both concentrations. The lindane RE percentage of Qaroun species ranged between 71.6% and 99.6% with a maximum of 98.0–99.6% at 5 ppm, 83.9% and 99.7% at 10 ppm, and maximum between 95.5% and 99.7%. Mariut species showed an RE percentage of 45.23–100.0% with maximum between 99.23% and 100.0% at 5 ppm and 43.15% and 100.0% at 10 ppm with maximal RE percentage between 99.67% and 100.0%. Mixed culture RE percentages ranged between 91.6% and 100% at 5 ppm with a maximum range of 99.3–100%, while at 10 ppm, the RE percentage ranged between 90.4% and 100%, with a maximum range of 96.0–100%. Results indicate the potential of natural resources as efficient agents for pollution control.     

Feasibility of bioremediation by white-rot fungi

The ligninolytic enzymes of white-rot fungi have a broad substrate specificity and have been implicated in the transformation and mineralization of organopollutants with structural similarities to lignin. This review presents evidence for the involvement of these enzymes in white-rot fungal degradation of munitions waste, pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, bleach plant effluent, synthetic dyes, synthetic polymers, and wood preservatives. Factors relating to the feasibility of using white-rot fungi in bioremediation treatments for organopollutants are discussed.     

Formulation of filamentous fungi for bioremediation

Mycelia of Marasmiellus troyanus embedded in calcium alginate granules with corn cob grits as a nutritive amendment were viable after one year with refrigeration but inviable when stored at room temperature. With refrigeration, Phanerochaete chrysosporium mycelia and spores embedded in alginate were both viable after one year. At room temperature, spores encapsulated in alginate granules gave good viability while mycelial formulations did not. In all trials, corn cob grits was superior to saw dust for extending shelf life. Corn cob grits-amended granules of both species were able to germinate and grow in both uncontaminated soil and chemical waste-contaminated soil. © Rapid Science Ltd. 1998     

Evaluation of holocellulase production by plant-degrading fungi grown on agro-industrial residues

Agaricus brasiliensis CS1, Pleurotus ostreatus H1 and Aspergillus flavus produced holocellulases when grown in solid and submerged liquid cultures containing agro-industrial residues, including sugar cane bagasse and dirty cotton residue, as substrates. These isolates proved to be efficient producers of holocellulases under the conditions used in this screening. Bromatological analysis of agro-industrial residues showed differences in protein, fiber, hemicellulose, cellulose and lignin content. Maximal holocellulase activity (hemicellulase, cellulase and pectinase) was obtained using solid-state cultivation with 10% substrate concentration. In this case, remarkably high levels of xylanase and polygalacturonase activity (4,008 and 4,548 IU/l, respectively) were produced by A. flavus when grown in media containing corn residue, followed by P. ostreatus H1 with IU/l values of 1,900 and 3,965 when cultivated on 5% and 10% sugar cane bagasse, respectively. A. brasiliensis CS1 showed the highest reducing sugar yield (11.640 mg/ml) when grown on medium containing sugar cane bagasse. A. brasiliensis was also the most efficient producer of protein, except when cultivated on dirty cotton residue, which induced maximal production in A. flavus. Comparison of enzymatic hydrolysis of sugar cane bagasse and dirty cotton residue by crude extracts of A. brasiliensis CS1, P. ostreatus H1 and A. flavus showed that the best reducing sugar yield was achieved using sugar cane bagasse as a substrate.     

Degradation of high molecular weight compounds of Kraft pulp mill effluents by a combined treatment with fungi and bacteria

Pretreatment of Kraft pulp mill effluents by mycelial pellets or extracellular ligninolytic liquid from Phanerochaete chrysosporium enhanced the anaerobic degradation of high molecular weight (HMW) compounds up to 79% and 72% respectively, against 45% when only anaerobic digestion was considered. Decolourization was obtained only after fungal pretreatment, since both anaerobic digestion and ligninolytic liquid pretreatment of Kraft effluent slightly increased colour.     

Potential treatment alternative for laboratory effluents

The Chemical Analysis Laboratory under study weekly generates 46.5 L effluent with low pH (0.7), high COD concentration (6535 mg O2/L), sulphate (10390 mg/L) and heavy metals (213 mg Hg/L, 55 mg Cr/L, 28 mg Al/L, 22 mg Fe/L, 10mg Cu/L, 4 mg Ag/L). A treatment sequence has been proposed using a physical chemical step (coagulation/flocculation or chemical precipitation) followed by a biological step (anaerobic treatment). Removals of COD (18%), turbidity (76%) and heavy metals (64-99%) were attained only after adjusting pH to 6.5, without requiring the addition of Al2(SO4)3 and FeCl3. Due to the low COD:sulphate ratio (0.9-1.3), it was possible to efficiently operate the UASB reactor (at the biological step) only upon mixing the effluent with household wastewater. COD, sulphate and heavy metals removals of 60%, 23% and 78% to 100%, respectively, were attained for 30% effluent in the reactor feed. The results pointed to the need of a pretreatment step and mixing the effluent in household wastewater prior to the biological step. This alternative is feasible as this can be achieved using sanitary wastewater generated in the university campus.     

Toxicity and bioremediation of pesticides in agricultural soil

Pesticides are one of the persistent organic pollutants which are of concern due to their occurrence in various ecosystems. In nature, the pesticide residues are subjected to physical, chemical and biochemical degradation process, but because of its high stability and water solubility, the pesticide residues persist in the environment. Moreover, the prevailing environmental conditions like the soil characteristics also contribute for their persistence. Bioremediation is one of the options for the removal of pesticides from environment. One important uncertainty associated with the implementation of bioremediation is the low bioavailability of some of the pesticides in the heterogeneous subsurface environment. Bioavailability of a compound depends on numerous factors within the cells of microorganism like the transportation of susbstrate across cell membrane, enzymatic reactions, biosurfactant production etc. as well as environment conditions such as pH, temperature, availability of electron acceptor etc. Pesticides like dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), Endosulfan, benzene hexa chloride (BHC), Atrazine etc. are such ubiquitous compounds which persist in soil and sediments due to less bioavailability. The half life of such less bioavailable pesticides ranges from 100 to 200 days. Most of these residues get adsorbed to soil particles and thereby becomes unavailable to microbes. In this review, an attempt has been made to present a brief idea on ‘major limitations in pesticide biodegradation in soil’ highlighting a few studies.     

Screening and selection of fungi for bioremediation of olive mill wastewater

Olive mill wastewater (OMWW) is a significant pollutant and its phytotoxicity is attributed mostly to the phenols present. 220 fungi were screened for their ability to produce detoxifying enzymes and/or grow in OMWW. Four isolates, species of Cerrena, Byssochlamys, Lasiodiplodia and Bionectria were selected and compared against Phanerochaete chrysosporium for their ability to bioremediate OMWW in the presence of a competing indigenous microflora. For the first time we report that a Cerrena sp. achieved a 75% reduction of phenolics in OMWW and that, unusually, the reduction occurred within 2 h of the addition to the OMWW.     

Potential for anaerobic bioremediation of BTEX in petroleum-contaminated aquifers

Laboratory incubations of aquifer material or enrichments derived from aquifer material as well as geochemical data have suggested that, under the appropriate conditions, BTEX components of petroleum (benzene, toluene, ethylbenzene and xylene) can be degraded in the absence of molecular oxygen with either Fe(III), sulfate, or nitrate serving as the electron acceptor. BTEX degradation under methanogenic conditions has also been observed. However, especially for benzene, the BTEX contaminant of greatest concern, anaerobic degradation is often difficult to establish and maintain in laboratory incubations. Although studies to date have suggested that naturally occurring anaerobic BTEX degradation has the potential to remove significant quantities of BTEX from petroleum-contaminated aquifers, and mechanisms for stimulating anaerobic BTEX degradation in laboratory incubations have been developed, further study of the organisms involved in this metabolism and the factors controlling their distribution and activity are required before it will be possible to design rational strategies for accelerating anaerobic BTEX degradation in contaminated aquifers. Received 21 November 1995/ Accepted in revised form 20 February 1996     

Degradation of anthracene by selected white rot fungi

Abstract Approximately 60% of the originally supplied anthracene (AC) was degraded in ligninolytic stationary cultures of selected white rot fungi within 21 days. All the white rot fungi tested oxidized AC to anthraquinone (AQ). Unlike Phanerochaete chrysosporium and strain Px, with Pleurotus ostreatus, Coriolopsis polyzona and Trametes versicolor , AQ did not accumulate in the cultures, indicating that AQ was degraded further and its degradation did not appear to be a rate-limiting step. However, P. ostreatus and C. polyzona failed to degrade AQ in the absence of AC. P. ostreatus, T. versicolor and strain Px did not produce lignin peroxidase (ligninase) (LIP) under the test conditions but oxidized AC to AQ suggesting that white rot fungi produce enzyme(s) other than LIP capable of oxidizing compounds with high ionization potential like AC. Moreover, in the case of Ph. chrysosporium and C. polyzona , AC degradation started earlier than the production of LIP. Veratryl alcohol (VA) seemed to be playing a role in AC oxidation catalyzed by LIP in Ph. chrysosporium .     

Random mutants of a Pleurotus ostreatus laccase as new biocatalysts for industrial effluents bioremediation

Aims: To select better performing laccase variants among the 2300 randomly mutated variants of Pleurotus ostreatus POXA1b laccase to develop improved laccase‐based biocatalysts. Methods and Results: Screening of collections of 2300 randomly mutated variants of POXA1b was performed by assaying activity towards the phenolic substrate 2,6‐dimethoxyphenol. Two new variants endowed with higher enzyme activity than the wild‐type laccase were characterized, and their ability to decolourize industrial dyes with complex trisazo‐, polyazo‐ and stilbene‐type structures, in the absence of mediators, was demonstrated. One of the mutants (2L4A) was also proved to be highly stable at both acidic and alkaline pH values (displaying a half‐life of around 1 month at the pH levels of both 5 and 10). Conclusions: In comparison with the wild‐type laccase, the new selected 2L4A mutant shows a significant increase in stability at acidic pH, whilst storing its high stability at alkaline pH. This variant also represents a more versatile enzyme with respect to both the variety of xenobiotics degraded and the operative conditions. Significance and Impact of the Study: This work represents the first example of improvement of a basidiomycete laccase for industrial effluents bioremediation by directed evolution.     

Hydrolysis of bile acid conjugates by selected fungi

Summary Fungi which have been previously shown to hydrolyse glycocholic acid, with liberation of the free bile acid, have now been shown to be similarly capable of hydrolysing glycodeoxycholic acid. Sodium taurocholate, however, is much less susceptible and its hydrolysis has been demonstrated with only one of the selected fungi, Penicillium chrysogenum, growing in a medium containing the conjugate as the sole sulphur source. It is concluded that the nature of the amino acid moiety is important in determining the ease of hydrolysis of bile acid conjugates by whole cells of the fungi under test.     

Screening of white-rot fungi for efficient decolourization of bleach pulp effluents

Summary Several white-rot fungi collected in the South of Chile were evaluated for their ability to decolourize kraft pulp bleached effluents. Strain 158, recently identified as aRamaria sp., showed the highest potential for the biological treatment of E1 effluent: 90% of the colour was removed by this strain grown under air, with a similar rate and extent of decolourization asPhanerochaete chrysosporium, under oxygen.     

Development of anaerobic filters for treatment of high strength agro-industrial wastewaters

The suitability and advantages of anaerobic filters for the treatment of various agro-industrial wastewaters are discussed. Recent developments in reactor design and typical operating parameters and performance data are given for reactors operated in the up- and downflow mode. The distribution of the most important process parameters throughout the reactor height is discussed and methods for process optimization are presented.     

Evaluation of solid substrates for enzyme production by Coriolus versicolor, for use in bioremediation of chlorophenols in aqueous effluents

In the development of a system for the removal of chlorophenols from aqueous effluents, a range of solid substrates for the growth of Coriolus versicolor were investigated. Substrates included wood chips, cereal grain, wheat husk and wheat bran. Suitability for transformation of chlorophenols depended on laccase production by the fungus. The greatest amount of laccase (<25 Units g⁻¹ substrate) was produced on wheat husk and wheat bran over 30 days colonisation. Aqueous extracts of laccase from wheat husk and wheat bran cultures removed 100% of 2,4-dichlorophenol (50 ppm) from solution within 5 h and 75–80% of pentachlorophenol (50 ppm) within 24 h. Wheat bran was formulated into pellets with biscuit flour to provide a compact substrate for fungal immobilisation. Addition of 8–12% yeast extract to the pellets increased laccase production five-fold. Colonised pellets were added to chlorophenol solutions in 200–4000-ml bioreactors, resulting in >90% removal of chlorophenols within 100 min. Received: 10 April 2000 / Received revision: 4 July 2000 / Accepted: 10 July 2000     

Oxalate production by fungi: significance in geomycology,biodeterioration and bioremediation

Oxalate is a key metabolite that plays a significant role in many metal and mineral transformations mediated by fungi. Metal and mineral transformations are central to geomycological processes including nutrient and element cycling, rock, mineral and metal transformations, bioweathering and mycogenic biomineral formation. Some fungal transformations have potential applications in environmental biotechnology, e.g. metal and radionuclide leaching, biorecovery, detoxification and bioremediation, and in the production or deposition of biominerals or metallic elements with catalytic or other properties. Metal and mineral transformations may also result in adverse effects when these processes result in biodeterioration of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment. Oxalate is ubiquitous in all these contexts. This paper seeks to draw together salient information from environmental and applied research to emphasize the importance of oxalate in geomycology, biodeterioration, environmental biotechnology and bioremediation.     

Potential for bioremediation of fuel‐contaminated soil in Antarctica

A preliminary investigation was conducted to identify the presence of bacteria in fuel‐contaminated Antarctic soil that could potentially be used to bioremediate the contaminated soil at McMurdo Station and other sites in Antarctica. The ability of soil microorganisms to metabolize fuels under the extreme climatic and oligotrophic conditions of Antarctica was of concern. Bacteria were isolated from fuel‐contaminated soil on site at McMurdo Station. Bacteria from noncontaminated soil near the station were also studied for comparison. The Antarctic soil microorganisms exhibited the ability to endure cold and oligotrophic environments. Experiments also showed that bacteria from the fuel spill site were active in their contaminated environment and that acclimation to xenobiotic compounds was necessary. Application of bioremediation in the extreme environmental conditions found at McMurdo Station, Antarctica, were also considered. The possibility of altering environmental factors necessary to adequately support in situ bioremediation in this extreme climate is discussed.