The present research investigates the use of ionic silver coated sand dust (ISSD) for the sunlight mediated degradation of diesel under saline conditions. Sand dust was used as a template for reduction of silver ions by effective removal of chloride ions. Diesel degradation was estimated in terms of degradation (%), chloride removal, volume reduction and nanoparticle synthesis, respectively. The process was optimized using a 7-level Box-Behnken design. Among several factors, time (B), Tween 80 (C), ISSD dosage (D) and silver(I) concentration (F) were found to be most significant. Maximum diesel degradation 99.8% was obtained in a period of 14 h which was analyzed by gas chromatography. XPS analysis confirmed silver reduction as the underlying phenomena. TEM analysis and albeit first approximation method confirmed that enhanced degradation occurred due to physical contact between diesel components and ISSD. First order kinetic model exhibited the best fit. Light microscopy results showed the various stages in diesel degradation by a reduction in bubble size. Ex situ application was carried out using ISSD impregnated thiourea modified chitosan/PVA membranes by surface floatation technique for the remediation of diesel contaminated sea water. Complete diesel degradation was noted after 48 h of sunlight exposure.

Nilanjana Mitra

Department of Bio-Medical Sciences

School of Bio Sciences and Technology

Vellore Campus

Das D

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Journal of Hazardous Materials

Five yeast species, namely Candida tropicalis, Cryptococcus laurentii, Trichosporon asahii, Rhodotorula mucilaginosa and Candida rugosa isolated from hydrocarbon-contaminated soil were found to be potent degraders of diesel oil. These microorganisms showed the presence of enzymes cytochrome P450, NADPH cytochrome c reductase, aminopyrine N demethylase, alcohol dehydrogenase, aldehyde dehydrogenase, naphthalene dioxygenase, catalase and glutathione S transferase when the cells were incubated for 48h in Bushnell Haas medium supplemented with 2{\%} diesel oil as the sole source of carbon. The cytochrome P450 monooxygenase enzyme system was found to play an important role in diesel oil degradation. A plasmid approximately 12kb in size was found to be harboured by all the yeast species. The role of the plasmid on diesel oil degradation was assessed by biomass inhibition studies, which confirmed that the metabolic machinery of yeast species for diesel oil degradation was plasmid coded. This is the first report establishing the involvement of a plasmid in diesel oil degradation by yeast species. {\textcopyright} 2012 Taylor {\&amp;} Francis.

Environmental Technology

Role of plasmid in diesel oil degradation by yeast species isolated from petroleum hydrocarbon-contaminated soil

The yeast Candida tropicalis, isolated from petroleumcontaminated soil in India, was found to be the potent producer of biosurfactant in mineral salt media containing diesel oil as the carbon source and found to be an efficient degrader of diesel oil (98{\%}) over a period of 10 days. The crude biosurfactant decreased the surface tension of cell-free broth, 78 to 30 mN/m, with a large oil displacement area and highly positive drop collapse test. The crude biosurfactant was purified using silica gel column chromatography followed by dialysis. With the use of Fourier transform infrared (FT-IR) spectroscopy, in combination with gas chromatography-mass spectrometry (GC-MS) analysis, chemical structures of the purified biosurfactant was identified as sophorolipid species. Involvement of biosurfactant in physiological mechanism of diesel adsorption on yeast cell surface was characterized based on zeta potential. When diesel oil was emulsified with biosurfactant, the surface charge of the diesel was modified, resulting in more adsorption of diesel on yeast cell surface. Biosurfactant production by yeast species was monitored using scanning electron microscopy (SEM) analysis and found that yeast species could form thick mat of mucilaginous biosurfactant that could interconnect the individual cells. Uptake of diesel oil by C. tropicalis was elucidated through transmission electron microscopy (TEM) analysis. Interestingly, it was observed that internalization of diesel oil droplet was taking place, suggesting a mechanism similar in appearance to active pinocytosis. {\textcopyright} 2012 Taylor and Francis Group, LLC.

Bioremediation Journal

Role of Sophorolipid Biosurfactant in Degradation of Diesel Oil byCandida tropicalis

The performance of diesel oil degradation by Candida tropicalis immobilized on various conventional matrices (sodium alginate, carboxyl methyl cellulose, chitosan) and biowaste materials (wheat bran, sawdust, peanut hull powder) was investigated using the method of entrapment and physical adsorption. The yeast species immobilized in wheat bran showed enhanced efficiency in degrading diesel oil (98%) compared to free cells culture (80%) over a period of 7 days. Copious amount of exopolysaccharides were also produced in the presence of diesel oil. The biofilm forming ability of C. tropicalis on PVC strips was evaluated using XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) reduction assay and monitored by scanning electron microscopy and atomic force microscopy. Yeast biofilm formed on gravels showed 97% degradation of diesel oil over a period of 10 days. The potential use of the biofilms for preparing trickling filters (gravel particles), for attenuating hydrocarbons in oily liquid wastes before their disposal in the open environment is suggested and discussed. This is the first successful attempt for 'artificially' establishing hydrocarbon degrading yeast biofilm on solid substrates.

Biodegradation

Degradation of diesel oil by immobilized Candida tropicalis and biofilm formed on gravels

Response surface methodology (RSM) employing the three-level Box-Behnken factorial design was used to optimize the biosorption of Ag(I) by the macrofungus Pleurotus platypus. The initial Ag(I) concentration (100-300mg/L), pH (3.0-9.0) and biomass dosage (1.0-5.0g/L) were chosen as the process variables for the optimization. A coefficient of determination (R2) value (0.99), model F value (234.18) and its low p-value (F{\textless}0.0001) along with the lower value of coefficient of variation (2.44{\%}) indicated the fitness of response surface quadratic model during the present study. At the optimum pH (6.0), initial metal concentration (220mg/L) and biomass dosage (3.0g/L), the model predicted 46.7mg/g Ag(I) uptake and an experimental 46.77mg/g Ag(I) uptake by P. platypus was obtained. This is the first report on Ag(I) sorption by P. platypus using statistical experimental design employing RSM which may be helpful towards the treatment of industrial effluent containing silver. The present study has confirmed the effectiveness of the macrofungus Pleurotus platypus as biosorbent of Ag(I) and thus, P. platypus can be exploited for the removal of silver from industrial effluents before their discharge into water bodies. {\textcopyright} 2011 WILEY-VCH Verlag GmbH {\&amp;} Co. KGaA, Weinheim.

CLEAN - Soil, Air, Water

Response Surface Approach for the Bisorption of Ag(I) by MacrofungusPleurotus platypus

International Biodeterioration & Biodegradation

Diesel degradation potential of endophytic bacteria isolated from Scirpus triqueter

Sunlight mediated diesel degradation under saline conditions using ionic silver coated sand via nanoreduction: Use of impregnated form of thiourea modified chitosan membranes for ex situ application

Journal	Data powered by TypesetJournal of Hazardous Materials
Publisher	Data powered by TypesetElsevier BV
ISSN	0304-3894
Open Access	0