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     

Production,isolation and characterization of extracellular protease of an alkaliphilic strain of Arthrobacter ramosus,MCM B-351 isolated from the alkaline lake of Lonar,India

An extracellular protease was produced by Arthrobacter ramosus isolated from the alkaline lake of Lonar, Buldhana District of Maharashtra, India when grown on a synthetic medium of pH 10 containing casein. The optimum conditions for production were 3.0% initial casein concentration, 2% inoculum of 1 × 10⁸ cells/ml, pH 9.0, temperature 30 °C and shaken culture conditions. The protease was purified by ammonium sulphate precipitation followed by Sephadex G-100 chromatography. Two proteases viz. Arthro I and Arthro II, having molecular weights 21 and 11.4 kDa respectively were isolated. The Arthro II fraction had K _m 395 g/ml and V _max 10.55 g/min for azocasein. The maximum activity of enzyme was at 55 °C and pH 8. It was thermostable (up to 80 °C), alkali stable (pH 12) and stable in commercial detergent. The enzyme may contain a thiol group at the active site.     

Bioremediation of ε-Caprolactam from Nylon-6 Waste Water by Use of Pseudomonas aeruginosa MCM B-407

Nylon-6, a man-made polymer that finds its application in the manufacture of car tires, ropes, fabrics, automobile parts etc., is manufactured with ε-caprolactam. Waste water generated during production of nylon-6 contains the unreacted monomer. Owing to the polluting and toxic nature of ε-caprolactam, its removal from waste streams is necessary. Pseudomonas aeruginosa MCM B-407 was isolated from activated sludge used to treat waste from a factory producing nylon-6. This organism was able to remove ε-caprolactam with simultaneous reduction in chemical oxygen demand (COD). The degradation of ε-caprolactam in waste water was found to be optimal over a wide range of pH from 5.0 to 9.0, temperature of 30°C, and under shake or aerated conditions, with an inoculum density of 10⁵ cells/ml and with an incubation period of 24 – 48 h. Thus, Pseudomonas aeruginosa MCM B-407 isolated from the activated sludge exposed to ε-caprolactam may play an important role in the bioremediation of ε-caprolactam from the waste waters of industries manufacturing nylon-6. Received: 13 November 1997 / Accepted: 9 April 1998     

Production and partial characterization of dehairing protease from Bacillus cereus MCM B-326

Bacillus cereus MCM B-326, isolated from buffalo hide, produced an extracellular protease. Maximum protease production occurred (126.87+/-1.32 U ml(-1)) in starch soybean meal medium of pH 9.0, at 30 degrees C, under shake culture condition, with 2.8 x 10(8) cells ml(-1) as initial inoculum density, at 36 h. Ammonium sulphate precipitate of the enzyme was stable over a temperature range of 25-65 degrees C and pH 6-12, with maximum activity at 55 degrees C and pH 9.0. The enzyme required Ca(2+) ions for its production but not for activity and/or stability. The partially purified enzyme exhibited multiple proteases of molecular weight 45 kDa and 36 kDa. The enzyme could be effectively used to remove hair from buffalo hide indicating its potential in leather processing industry.     

Optimization of Dimethoate Degradation by Brevundimonas sp. MCM B-427 Using Factorial Design: Studies on Interactive Effects of Environmental Factors

Microbial cultures were isolated from soil exposed to dimethoate, an organophosphorus insecticide. The isolate that showed maximum degradation of dimethoate was identified as Brevundimonassp. MCM B-427. The curve relating biomass accumulation and degradation revealed that aeration appeared to enhance growth rather than degradation. For optimization of environmental factors, a 2⁴ factorial experimental design was used, wherein four factors namely pH, temperature, inoculum density and aeration condition were varied simultaneously. The interaction between the factors was analyzed using MINITAB package. Degradation of dimethoate was affected by a large number of factors interacting in a complex way. Six two-way and two three-way interactions of various environmental factors were found to be statistically significant. In all the two-way interactions, the effect of one factor was more pronounced when the other was at its optimum. The three-way interactions revealed that optimization of pH, inoculum size and aeration was more critical at 40 °C than at 30 °C.The results imply the importance of studying interactions of parameters rather than optimizing individual parameters one by one. These results demonstrate complexity of the interaction and thereby imply the need for better experimental and statistical models.     

Biomineralization of an organophosphorus pesticide,Monocrotophos, by soil bacteria

AIMS: To study biomineralization of Monocrotophos (MCP) and identify the metabolites formed during biodegradation. METHODS AND RESULTS: Two cultures, namely Arthrobacter atrocyaneus MCM B-425 and Bacillus megaterium MCM B-423, were isolated by enrichment and adaptation culture technique from soil exposed to MCP. The isolates were able to degrade MCP to the extent of 93% and 83%, respectively, from synthetic medium containing MCP at the concentration of 1000 mg x l(-1), within 8 d, under shake culture condition at 30 degrees C. The cultures degraded MCP to carbon dioxide, ammonia and phosphates through formation of one unknown compound--Metabolite I, valeric or acetic acid and methylamine, as intermediate metabolites. The enzymes phosphatase and esterase, reported to be involved in biodegradation of organophosphorus compounds, were detected in both the organisms. CONCLUSIONS:Arthrobacter atrocyaneus MCM B-425 and B. megaterium MCM B-423 isolated from soil exposed to MCP were able to mineralize MCP to carbon dioxide, ammonia and phosphates. SIGNIFICANCE AND IMPACT OF THE STUDY: Pathway for biodegradation of MCP in plants and animals has been reported. A microbial metabolic pathway of degradation involving phosphatase and esterase enzymes has been proposed. The microbial cultures could be used for bioremediation of wastewater or soil contaminated with Monocrotophos.     

Bioremediation of nitroexplosive wastewater by an yeast isolate <Emphasis Type="Italic">Pichia sydowiorum</Emphasis> MCM Y-3 in fixed film bioreactor

Nitroexplosives are essential for security and defense of the nation and hence their production continues. Their residues and transformed products, released in the environment are toxic to both terrestrial and aquatic life. This necessitates remediation of wastewaters containing such hazardous chemicals to reduce threat to human health and environment. Bioremediation technologies using microorganisms become the present day choice. High Melting Explosive (HMX) is one of the nitroexplosives produced by nitration of hexamine using ammonium nitrate and acetic anhydride and hence the wastewater bears high concentration of nitrate and acetate. The present investigation describes potential of a soil isolate of yeast Pichia sydowiorum MCM Y-3, for remediation of HMX wastewater in fixed film bioreactor (FFBR). The flask culture studies showed appreciable growth of the organism in HMX wastewater under shake culture condition within 5–6 days of incubation at ambient temperature (28 ± 2°C). The FFBR process operated in both batch and continuous mode, with Hydraulic Retention Time (HRT) of 1 week resulted in 50–55% removal in nitrate, 70–88% in acetate, 50–66% in COD, and 28–50% in HMX content. Continuous operation of the reactor showed better removal of nitrate as compared to that in the batch operation, while removal of acetate and COD was comparable in both the modes of operation of the reactor. Insertion of baffles in the reactor increased efficiency of the reactor. Thus, FFBR developed with baffles and operated in continuous mode will be beneficial for bioremediation of high nitrate and acetate containing wastewater using the culture of P. sydowiorum.     

Enzymatic depilation of animal hide: identification of elastase (LasB) from Pseudomonas aeruginosa MCM B-327 as a depilating protease

Conventional leather processing involving depilation of animal hide by lime and sulphide treatment generates considerable amounts of chemical waste causing severe environmental pollution. Enzymatic depilation is an environmentally friendly process and has been considered to be a viable alternative to the chemical depilation process. We isolated an extracellular protease from Pseudomonas aeruginosa strain MCM B-327 with high depilation activity using buffalo hide as a substrate. This 33 kDa protease generated a peptide mass fingerprint and de novo sequence that matched perfectly with LasB (elastase), of Pseudomonas aeruginosa. In support of this data a lasB mutant of MCM B-327 strain lacked depilatory activity and failed to produce LasB. LasB heterologously over-produced and purified from Escherichia coli also exhibited high depilating activity. Moreover, reintroduction of the lasB gene to the P. aeruginosa lasB mutant via a knock-in strategy also successfully restored depilation activity thus confirming the role of LasB as the depilating enzyme.     

Biodegradation of nitro-explosives

Environmental contamination by nitro compounds is associated principally with the explosives industry. However, global production and use of explosives is unavoidable. The presently widely used nitro-explosives are TNT (Trinitrotoluene), RDX (Royal Demolition Explosive) and HMX (High Melting Explosive). Nevertheless, the problems of these nitro-explosives are almost parallel due to their similarities of production processes, abundance of nitro-explosives and resembling chemical structures. The nitro-explosives per se as well as their environmental transformation products are toxic, showing symptoms as methaemoglobinaemia, kidney trouble, jaundice etc. Hence their removal/degradation from soil/water is essential. Aerobic and anaerobic degradation of TNT and RDX have been reported, while for HMX anaerobic or anoxic degradation have been described in many studies. A multisystem involvement using plants in remediation is gaining importance. Thus the information about degradation of nitro-explosives is available in jigsaw pieces which needs to be arranged and lacunae filled to get concrete degradative schemes so that environmental pollution from nitro-explosives can be dealt with more successfully at a macroscale. An overview of the reports on nitro-explosives degradation, future outlook and studies done by us are presented in this review.     

Plasmid-associated biodegradation of an organophosphorus pesticide, Monocrotophos, by Pseudomonas mendocina

Pseudomonas mendocina isolated from soil degraded an insecticide, Monocrotophos (MCP), by 67% and harbored a 7.4 kb plasmid, designated as pMCP424. On the basis of curing and transformation experiments, MCP degradation by Pseudomonas mendocinawas plasmid-borne and transferable to other bacteria.