Identification and analysis of polyaromatic hydrocarbons (PAHs)—biodegrading bacterial strains from refinery soil of India

Polyaromatic hydrocarbons (PAHs) utilizing bacteria were isolated from soils of seven sites of Mathura refinery, India. Twenty-six bacterial strains with different morphotypes were isolated. These strains were acclimatized to utilize a mixture of four polycyclic aromatic hydrocarbons, i.e., anthracene, fluorene, phenanthrene, and pyrene, each at 50 mg/L concentration as sole carbon source. Out of total isolates, 15 potent isolates were subjected to 16S rDNA sequencing and identified as a member of diverse genera, i.e., Bacillus, Acinetobacter, Stenotrophomonas, Alcaligenes, Lysinibacillus, Brevibacterium, Serratia, and Streptomyces. Consortium of four promising isolates (Acinetobacter, Brevibacterium, Serratia, and Streptomyces) were also investigated for bioremediation of PAH mixture. This consortium was proved to be efficient PAH degrader resulting in 40–70 % degradation of PAH within 7 days. Results of this study indicated that these genera may play an active role in bioremediation of PAHs.     

Agro-waste biosorbents: Effect of physico-chemical properties on atrazine and imidacloprid sorption

Low cost agro-waste biosorbents namely eucalyptus bark (EB), corn cob (CC), bamboo chips (BC), rice straw (RS) and rice husk (RH) were characterized and used to study atrazine and imidacloprid sorption. Adsorption studies suggested that biosorbents greatly varied in their pesticide sorption behaviour. The EB was the best biosorbent to sorb both atrazine and imidacloprid with K_F values of 169.9 and 85.71, respectively. The adsorption isotherm were nonlinear in nature with slope (1/n) values <1. The Freundlich constant Correlating atrazine/imidacloprid sorption parameter [K_F.(1/n)] with the physicochemical properties of the biosorbents suggested that atrazine adsorption correlated significantly to the aromaticity, polarity, surface area, fractal dimension, lacunarity and relative C-O band intensity parameters of biosorbents. Probably, both physisorption and electrostatic interactions were responsible for the pesticide sorption. The eucalyptus bark can be exploited as low cost adsorbent for the removal of these pesticides as well as a component of on-farm biopurification systems.     

A laboratory study of auctions for reducing non-point source pollution

Non-point source pollution, such as nutrient runoff to waterways from agricultural production, is an environmental problem that typically involves asymmetric information. Land use changes to reduce pollution incur opportunity costs that are privately known to landholders, but these changes provide environmental benefits that may be more accurately estimated by regulators. This paper reports a testbed laboratory experiment in which landholder/sellers in sealed-offer auctions compete to obtain part of a fixed budget allocated by the regulator to subsidize abatement. In one treatment the regulator reveals to landholders the environmental benefits estimated for their projects, and in another treatment the regulator conceals the potential projects’ “environmental quality.” The results show that sellers’ offers misrepresent their costs more for high-quality projects when quality is revealed, so total abatement is lower and seller profits are higher when landholders know their projects’ environmental benefits. This suggests that concealing this information may improve regulatory efficiency.     

Survival of bio-inoculants on fungicides-treated seeds of wheat,pea and chickpea and subsequent effect on chickpea yield

Survival of Mesorhizobium ciceri (SP₄) and Azotobacter chroococcum (CBD-15 and M₄) was tested on chickpea (Cicer arietinum) seeds treated with fungicides bavistin [methyl N-(1H-benzimidazol-2yl) carbamate] and thiram (tetramethyl-thiuram disulfide), whereas survival of phosphate solubilizing bacteria (PSB), Pseudomonas striata (27) and Bacillus polymyxa (H₅) was examined on two cultivars (Arkel and BV) of pea (Pisum sativum) seeds treated with thiram. Viability of Azotobacter chroococcum (W₅) was also examined on wheat (Triticum aestivum) seeds treated with bavistin, captan (cis-N-trichloromethyl thio-4 cyclohexane-1, 2-dicarboximide) and thiram under laboratory conditions using standard dilution and the plate count technique. All the tested strains of diazotrophs and PSB showed decline in their viable population on prolonged contact with fungicides. However, PSB showed variation in their viable population even with the cultivar.

BV cultivar of pea seeds showed better recovery of viable P. striata (10.75 to 10.61 log no. of viable cells with in 0-24 hrs) in the presence of thiram, whereas the Arkel cultivar of pea resulted in better recovery of viable B. polymyxa. Azotobacter chroococcum (W₅), a potential strain for wheat, showed better survival in the presence of bavistin, compared to thiram and captan. Higher viable population of Mesorhizobium ciceri (SP₄) and Azotobacter chroococcum (M₄) was recovered from chickpea seeds treated with bavistin compared to thiram. However, thiram-treated seeds resulted in a greater number of extractable Azotobacter chroococcum (CBD-15). Under field conditions, adverse effect of thiram was reflected on the performance of Mesorhizobium ciceri (SP₄) and A. chroococcum (M₄) strains, resulting in reduced root and shoot biomass and grain yield, compared to bavistin treated and culture inoculated treatment. CBD-15 showed better performance in the presence of thiram compared to bavistin.     

Biodegradation of C.I. Acid Red 1 by indigenous bacteria <Emphasis Type="Italic">Stenotrophomonas</Emphasis> sp. BHUSSp X2 isolated from dye contaminated soil

A significant proportion of xenobiotic recalcitrant azo dyes are being released in environment during carpet dyeing. The bacterial strain Stenotrophomonas sp. BHUSSp X2 was isolated from dye contaminated soil of carpet industry, Bhadohi, India. The isolated bacterial strain was identified morphologically, biochemically, and on the basis of 16S rRNA gene sequence. The isolate decolorized 97 % of C.I. Acid Red 1 (Acid RED G) at the concentration of 200 mg/l within 6 h under optimum static conditions (temperature ?35 °C, pH 8, and initial cell concentration 7?×?10⁷ cell/ml). Drastic reduction in dye degradation rate was observed beyond initial dye concentration from 500 mg/l (90 %), and it reaches to 25 % at 1000 mg/l under same set of conditions. The analysis related to decolorization and degradation was done using UV-Vis spectrophotometer, HPLC, and FTIR, whereas the GC-MS technique was utilized for the identification of degradation products. Phytotoxicity analysis revealed that degradation products are less toxic as compared to the original dye.     

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of α and β endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 μg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan–degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.