Bioremediation: environmental clean-up through pathway engineering

Given the immense risk posed by widespread environmental pollution by inorganic and organic chemicals, novel methods of decontamination and clean-up are required. Owing to the relatively high cost and the non-specificity of conventional techniques, bioremediation is a promising alternative technology for pollutant clean-up. Advances in bioremediation harness molecular, genetic, microbiology, and protein engineering tools and rely on identification of novel metal-sequestering peptides, rational and irrational pathway engineering, and enzyme design. Recent advances have been made for enhanced inorganic chemical remediation and organic chemical degradation using various pathway-engineering approaches and these are discussed in this review.     

Bioremediation of an industrial effluent containing monocrotophos

Almost 30% of the precious agricultural output of India is lost owing to pest infestation. In India, pesticide consumption for protecting crops is about 3% of the total world consumption. Monocrotophos (MCP), an organophosphorus insecticide, is widely used to control insects on crops. Being readily water soluble and highly toxic, its removal from wastewater generated during manufacture becomes inevitable. Bioremediation of wastewater containing MCP by Arthrobacter atrocyaneus, Bacillus megaterium, and Pseudomonas mendocina was highest at pH 8.0, but maximum reduction in Chemical Oxygen Demand (COD) was at pH 7.0. Removal of MCP and reduction in COD by B. megaterium and Ps. mendocina were highest at 35°C, while with A. atrocyaneus, it was maximum at 30°C, under aerated culture condition and inoculum density of 10⁸ cells/ml. Use of pure cultures for bioremediation of effluent containing MCP appears to be the first such attempt. Received: 26 September 2001 / Accepted: 5 February 2002     

Bioremediation and biovalorisation of olive-mill wastes

Olive-mill wastes are produced by the industry of olive oil production, which is a very important economic activity, particularly for Spain, Italy and Greece, leading to a large environmental problem of current concern in the Mediterranean basin. There is as yet no accepted treatment method for all the wastes generated during olive oil production, mainly due to technical and economical limitations but also the scattered nature of olive mills across the Mediterranean basin. The production of virgin olive oil is expanding worldwide, which will lead to even larger amounts of olive-mill waste, unless new treatment and valorisation technologies are devised. These are encouraged by the trend of current environmental policies, which favour protocols that include valorisation of the waste. This makes biological treatments of particular interest. Thus, research into different biodegradation options for olive-mill wastes and the development of new bioremediation technologies and/or strategies, as well as the valorisation of microbial biotechnology, are all currently needed. This review, whilst presenting a general overview, focusses critically on the most significant recent advances in the various types of biological treatments, the bioremediation technology most commonly applied and the valorisation options, which together will form the pillar for future developments within this field.     

石油污染土壤堆制微生物降解研究

采用异位生物修复技术堆式堆制处理方法 ,对辽河油田原油污染土壤进行了生物修复处理研究 .处理工程设 4个处理料堆单元 ,每个处理单元长 118.5cm ,宽 6 5 .5cm ,高 12 .5cm .研究结果表明 ,当进行处理的石油污染土壤中石油烃总量为 5 .2 2 g·10 0 g-1土时 ,利用黄孢原毛平革菌 (Phanerochaetechrysospori um) ,经过 5 5d的运行 ,石油烃总量去除率达 5 4.2 % .堆制处理中影响污染土壤石油烃总量生物降解的主要变化因子为污染土壤的O2 和CO2 含量、降解石油烃微生物的数量、污染土壤pH的变化 .通过监测这些数据的变化 ,可直接反映该工程的处理石油污染土壤的效果 .本处理工程采用定期通风措施 ,操作简单、运行费用低廉 ,为石油污染土壤生物修复实用化提供了一种简单易行的污染土壤清洁技术 .     

Bioremediation of oil-polluted soil with an association including the fungus Pleurotus ostreatus and soil microflora

The possibility of application of the Pleurotus ostreatus D1-soil microflora to bioremediation of oil-polluted soils was studied. The fungus degraded mainly the aromatic fraction, whereas soil microflora intensely degraded paraffin and naphthene oil fractions. Introduction of the fungus Pleurotus ostreatus D to soil induces degradation of a wider range of oil hydrocarbons. It is reasonable to further investigate the discovered phenomenon in order to improve procedures of remediation of oil-polluted soils.     

Bioremediation of oil-polluted soil with an association including the fungus Pleurotus ostreatus and soil microflora

The possibility of application of the Pleurotus ostreatus D1-soil microflora to bioremediation of oil-polluted soils was studied. The fungus degraded mainly the aromatic fractions, whereas soil microflora intensely degraded paraffin and naphthene oil fractions. Introduction of the fungus Pleurotus ostreatus D1 to soil induces degradation of a wider range of oil hydrocarbons. It is reasonable to further investigate the discovered phenomenon in order to improve procedures of remediation of oil-polluted soils.     

Elg1 forms an alternative RFC complex important for DNA replication and genome integrity

Genome-wide synthetic genetic interaction screens with mutants in the mus81 and mms4 replication fork-processing genes identified a novel replication factor C (RFC) homolog, Elg1, which forms an alternative RFC complex with Rfc2-5. This complex is distinct from the DNA replication RFC, the DNA damage checkpoint RFC and the sister chromatid cohesion RFC. As expected from its genetic interactions, elg1 mutants are sensitive to DNA damage. Elg1 is redundant with Rad24 in the DNA damage response and contributes to activation of the checkpoint kinase Rad53. We find that elg1 mutants display DNA replication defects and genome instability, including increased recombination and mutation frequencies, and minichromosome maintenance defects. Mutants in elg1 show genetic interactions with pathways required for processing of stalled replication forks, and are defective in recovery from DNA damage during S phase. We propose that Elg1-RFC functions both in normal DNA replication and in the DNA damage response.     

Nickel and cobalt resistance of various bacteria isolated from soil and highly polluted domestic and industrial wastes

Abstract From enrichment cultures in the presence of 1 mM NiCl₂ 200 strains of aerobic bacteria were isolated from 50 samples collected in the metal-processing industry, waste water treatment plants and from solid waste, highly polluted by heavy metals. The strains isolated were characterized with respect to their substrate spectrum and resistance to nickel, cobalt, zinc and cadmium salts and assigned to 21 groups. One representative of each group was described with respect to cell morphology. All strains were Gram-negative, non-sporing rods or cocci. The highest concentrations of nickel, cobalt, zinc, cadmium, copper, mercury, and silver allowing growth on solid media were estimated. Two strains were able to grow at 20 mM NiCl₂ and CoCl₂, one strain tolerated 12 mM and one 7.5 mM concentrations of these salts.
Fifteen out of 21 strains contained at least one plasmid two contained two plasmids. The plasmid sizes varied between 50 and 340 kbp, except strain 10A, which contained a miniplasmid (2.6 kbp). Attempts to cure four selected strains by exposure to mitomycin C or growth at elevated temperature failed.
By helper-assisted and unassisted conjugation the plasmids of strain 31A were shown to carry nickel and cobalt resistance determinants. Alcaligenes eutrophus strains H16 and N9A and denative of strain CH34 lacking one or both of its native metal resistance plasmids were used as recipients. Both plasmids, p TOM8 and pTOM9, of strain 31A carried resistance properties which were expressed in all recipients except. A. eutrophus H16, in which only nickel resistance was expressed.
Plasmid pTOM3 residing in strain 10A could not be transferred as such. However, transconjugants derived from helper (pULB113)-assisted matings carried co-integrates of various sizes and were resistant to nickel and cobalt.     

Bioremediation of carbofuran contaminated soil under saturated condition: soil column study

Disturbed soil columns, 5.8 cm in diameter and 25 cm in length, were used as a basic model to simulate the movement of carbofuran in rice field soil under saturated conditions. Bioaugmentation using a specific carbofuran degrader, Burkholderia sp. PCL3, in free and immobilized cell forms and biostimulation using rice straw as organic amendment were applied with the aim of enhancing the degradation of carbofuran in soil and to prevent the movement of carbofuran along with the flow through. In the abiotic control and the treatment with only indigenous microorganisms, the mass recovery percentage of carbofuran in the effluent was 52.1 and 22.5%, respectively. The application of bioaugmentation or biostimulation significantly enhanced carbofuran degradation in soil and reduced the movement of carbofuran as indicated by a low mass recovery percentage of carbofuran in the effluent of 14.6–15.5%. A low efficiency of carbofuran removal was obtained from the soil column with bioaugmentation together with biostimulation treatments in which the mass recovery percentage of carbofuran in the effluent was in the range of 22.1–22.6%. Sorption of carbofuran to soil, rice straw and corncob, formation of carbofuran metabolite and colony forming unit (CFU) and pH variation with the time were also investigated during column operation.     

Bioremediation of creosote-contaminated soil: a pilot-scale landfarming evaluation

A pilot-scale landfarming investigation of the effects of biostimulation and bioaugmentation on a creosote-contaminated (258.3 g kg^–1) mispah form (FAO: lithosol) soil, with a view to developing a cost-effective bioremediation methodology for creosote-contaminated soils was conducted in nine duplicate reactors, including two controls (Treatments 1 and 2). Treatments 3–9 were watered and aerated daily and Treatment 4–9 were monthly amended with mono-ammonium phosphate. Treatment 5–9 received further amendments as follows: Treatment 5, hydrogen peroxide; Treatment 6, indigenous microbial biosupplement; Treatment 7, sewage sludge; Treatment 8, cow manure; Treatment 9, poultry manure. Residual concentrations of creosote ranged between 29 and 215 g kg^–1 after sixteen weeks. The phenolics and the 2- and 3-ringed polyaromatic hydrocarbons (PAHs) were removed below detectable levels or to very low levels. The 4- and 5-ringed PAHs were removed by between 68 and 83%. Indigenous microbial biosupplement and sewage sludge were the most effective in creosote removal. Hydrogen peroxide did not significantly enhance microbial population and creosote removal. There was no significant difference between the results obtained from the treatments amended with organic manures. However, there was a significant difference between the effects of the organic manures and the indigenous microbial biosupplement. Results from this study suggests that a combination of the two treatment techniques (biostimulation and bioaugmentation) would be a better approach to treating soil contaminated with very high concentrations of creosote.     

Feeding approaches for biogas production from animal wastes and industrial effluents

Different feeding approaches were applied to a 5 l anaerobic digester in order to improve the biogas production. During operation, the reactor was fed with a mixture (9.7% w/v total solids (TS) and 7.6% w/v volatile solids (VS) in average) of pig manure with fish oil waste and waste from bentonite of edible oil filtration process, at different intervals of 24, 12 and 4 h at 15 days of hydraulic retention time. Production and quality of the biogas were practically constant at 183.7 ml (average) of biogas per gram of volatile solids available in the reactor per day, and the best biogas composition was 73.6% v/v CH₄ and 26.4% v/v CO₂.     

Phytoremediation-biorefinery tandem for effective clean-up of metal contaminated soil and biomass valorisation

During the last few decades, phytoremediation process has attracted much attention because of the growing concerns about the deteriorating quality of soil caused by anthropogenic activities. Here, a tandem phytoremediation/biorefinery process was proposed as a way to turn phytoremediation into a viable commercial method by producing valuable chemicals in addition to cleaned soil. Two agricultural plants (Sinapis alba and Helianthus annuus) were grown in moderately contaminated soil with ca. 100 ppm of Ni and further degraded by a fungal lignin degrader—Phanerochaete chrysosporium. Several parameters have been studied, including the viability of plants, biomass yield, and their accumulating and remediating potentials. Further, downstream processing showed that up to 80% of Ni can be easily extracted from contaminated biomass by aqueous extraction at mild conditions. Finally, it was demonstrated that the growth of plants on the contaminated soil could be degraded by P. chrysosporium, and the effect of nickel and biomass pretreatment on the solid-state fermentation was studied. The proposed and studied methodology in this work could pave the way for successful commercialization of the phytoremediation process in the near future.     

石油污染土壤的生物修复与土壤酶活性关系

研究了不同油浓度污染土壤经过两个为期125d的生物修复后的土壤中过氧化氢酶、多酚氧化酶和脂肪酶的酶活变化,分析了土壤中3种酶活性的变化特征与规律。结果表明,随着油浓度的增加,土壤中过氧化氢酶和多酚氧化酶的活性下降,脂肪酶活性增加;经过生物修复后,土壤中的过氧化氢酶和多酚氧化酶的活性在第二周期要比第一周期提高,而脂肪酶活性下降;这3种土壤酶活性变化受污染物浓度影响不显著,但不同浓度油污染土壤的修复对过氧化氢酶的影响要大于对多酚氧化酶和脂肪酶的影响。     

Distillery and curd whey wastes as viable alternative sources for biosurfactant production

Biosurfactant production from synthetic medium and industrial waste, viz. distillery and whey wastes was investigated by using an oily sludge isolate Pseudomonas aeruginosa strain BS2. In synthetic medium separately supplemented with glucose and hexadecane as water-soluble and -insoluble carbon sources, respectively, strain BS2 reduced the surface tension of the fermentation broth from 57 to 27 mN/m. The culture produced biosurfactant during the stationary growth phase and its yield was 0.97 g/l. The culture utilized distillery and whey wastes for its growth, as maximum cell counts reached to 54 × 10⁸ and 64 × 10⁹ c.f.u./ml from an initial inoculum size of 1 × 0⁵ c.f.u./ml, respectively, within 48 h of incubation and in these wastes the yields of biosurfactant obtained were 0.91 and 0.92 g/l, respectively. In synthetic medium, distillery and whey wastes, strain BS2 produced a crystalline biosurfactant which belonged to the category of secondary metabolites and its maximum production occurred after the onset of nitrogen-limiting conditions. After recovering biosurfactant from the fermented waste, the chemical oxygen demand (COD) of distillery and whey wastes was significantly reduced by 81 and 87%, respectively. Total acids, nitrogen and phosphate levels in distillery waste were reduced by 90, 92 and 92%, respectively, while in case of whey waste the concentration of these nutrients was reduced by 88, 95 and 93%, respectively. The isolated biosurfactant possessed potent surface active properties, as it effectively reduced the surface tension of water from 72 to 27 mN/m and formed 100% stable emulsions of a variety of water-insoluble compounds such as hydrocarbons, viz. hexadecane, crude oil, kerosene and oily sludge and pesticides, viz. dichlorodiphenyltrichloroethane (DDT) and benzene hexachloride (BHC). The effectiveness of biosurfactant was also evident from its low critical micellar concentration (CMC) which was 0.028 mg/ml.     

Valorization of rendering industry wastes and co-products for industrial chemicals,materials and energy: review

Over the past decades, strong global demand for industrial chemicals, raw materials and energy has been driven by rapid industrialization and population growth across the world. In this context, long-term environmental sustainability demands the development of sustainable strategies of resource utilization. The agricultural sector is a major source of underutilized or low-value streams that accompany the production of food and other biomass commodities. Animal agriculture in particular constitutes a substantial portion of the overall agricultural sector, with wastes being generated along the supply chain of slaughtering, handling, catering and rendering. The recent emergence of bovine spongiform encephalopathy (BSE) resulted in the elimination of most of the traditional uses of rendered animal meals such as blood meal, meat and bone meal (MBM) as animal feed with significant economic losses for the entire sector. The focus of this review is on the valorization progress achieved on converting protein feedstock into bio-based plastics, flocculants, surfactants and adhesives. The utilization of other rendering streams such as fat and ash rich biomass for the production of renewable fuels, solvents, drop-in chemicals, minerals and fertilizers is also critically reviewed.     

Bioremediation of PAH-contaminated soil by composting: A case study

Composting technique was used for bioremediation of industrial soil originating from a former tar-contaminated site. The composting process was regulated by aeration to keep optimal temperature gradient and concentrations of O₂ and CO₂ inside the composting pile. The efficiency of bioremediation was evaluated by performing analysis of 11 individual three- to six-ring unsubstituted aromatic hydrocarbons (PAH) and estimating of changes in ecotoxicity of the contaminated soil. After 42 d of composting, PAH with 3–4 rings were removed from 42 to 68%, other higher-molar mass PAH from 35 to 57%. Additional 100 d of compost maturation in open-air field did not result in a further decrease of PAH. Ecotoxicity tests performed with bioluminescent bacteriaVibrio fischerii showed a decrease in toxicity both after composting and maturation phases. However, toxicity tests on mustard-seed germination did not reveal any significant changes during composting and maturation phases.     

Biogas production from plant biomass used for phytoremediation of industrial wastes

In present study, potentials of water hyacinth (Eichhornia crassipes) and water chestnut (Trapa bispinnosa) employed for phytoremediation of toxic metal rich brass and electroplating industry effluent, were examined in terms of biogas generation. Inability of the plants to grow in undiluted effluent directed to select 20%, 40% and 60% effluent concentrations (with deionized water) for phytoremediation experiments. Slurry of both the plants used for phytoremediation produced significantly more biogas than that by the control plants grown in unpolluted water; the effect being more pronounced with plants used for phytoremediation of 20% effluent. Maximum cumulative production of biogas (2430c.c./100gdm of water hyacinth and 1940c.c./100gdm of water chest nut) and per cent methane content (63.82% for water hyacinth and 57.04% for water chestnut) was observed at 5mm particle size and 1:1 substrate/inoculum ratio, after twenty days incubation. Biogas production was quicker (maximum from 8-12days) in water hyacinth than in water chestnut (maximum from 12-16days). The qualitative and quantitative variations in biogas production were correlated with COD, C, N, C/N ratio and toxic metal contents of the slurry used.     

Growth of Jatropha curcas on heavy metal contaminated soil amended with industrial wastes and Azotobacter. A greenhouse study

The aims of the study were to evaluate the effect of organic wastes (biosludge and dairy sludge) and biofertilizer (Azotobacter chroococcum) on the planting conditions of Jatropha curcas in metal contaminated soils. Results showed that the plants survival rate in heavy metal contaminated soil increased with addition of amendments. Treatment T6 (heavy metal contaminated soils+dairy sludge+biofertilizer) observed to be the best treatment for growth (height and biomass) as compared with the treatment T5 (heavy metal contaminated soils+biosludge+biofertilizer). In addition, organic amendments provided nutrients such as carbon, N, P and K to support plant growth and reduced the metal toxicity to plant. The present study showed that metal contaminated lands/soils could be suitably remediated by adapting appropriate measures.