Showing papers by "Kannan Pakshirajan published in 2015"

Simultaneous lipid production and dairy wastewater treatment using Rhodococcus opacus in a batch bioreactor for potential biodiesel application

Abstract: This study examined the valorization of dairy wastewater in the production of lipids by Rhodococcus opacus for biodiesel application. Using synthetic media based on dextrose and ammonium nitrate as the carbon and nitrogen source, respectively, the bacterium accumulated 71% (w/w) of lipids. Using only the raw dairy wastewater, the bacterium accumulated 14.28% w/w lipid and reduced the initial wastewater chemical oxygen demand (COD) by 30%. These values were, however, enhanced to 30–33% w/w and 62%, respectively, by supplementing the dairy wastewater with mineral salt media in the ratio 1:3. Bioreactor experiments were further performed using raw dairy wastewater and mineral salt medium in 1:3 ratio under both uncontrolled and controlled temperature and pH conditions. Interestingly biomass growth, lipid accumulation in the bioreactor experiments were found to be lower as compared to those in the shake flask experiments, whereas the wastewater COD removal was much higher in the bioreactor study. 1H nuclear magnetic resonance (NMR) spectroscopy of the fatty acids accumulated by the bacteria using dairy wastewater based media revealed that it contained more saturated fatty acids than unsaturated fatty acids. Gas chromatography (GC) analysis of the biodiesel produced by either ex-situ or in-situ transesterification of the bacterial lipids further revealed the presence of methyl palmitate (34.90%), methyl stearate (35.48%) methyl myristate (29.79%), methyl linoleate (27.87%), and methyl palmitate (25.85) as the main esters. The estimated properties of the transesterified product indicated its potential for biodiesel applications.

Heavy metal removal from multicomponent system by the cyanobacterium Nostoc muscorum: kinetics and interaction study.

Abstract: In this study, Nostoc muscorum, a native cyanobacterial species isolated from a coal mining site, was employed to remove Cu(II), Zn(II), Pb(II) and Cd(II) from aqueous solution containing these metals in the mixture. In this multicomponent study, carried out as per the statistically valid Plackett-Burman design of experiments, the results revealed a maximum removal of both Pb(II) (96.3 %) and Cu(II) (96.42 %) followed by Cd(II) (80.04 %) and Zn(II) (71.3 %) at the end of the 60-h culture period. Further, the removal of these metals was attributed to both passive biosorption and accumulation by the actively growing N. muscorum biomass. Besides, the specific removal rate of these metals by N. muscorum was negatively correlated to its specific growth rate. For a better understanding of the effect of these metals on each other’s removal by the cyanobacteria, the results were statistically analyzed in the form of analysis of variance (ANOVA) and Student’s t test. ANOVA of the metal bioremoval revealed that the main (individual) effect due to the metals was highly significant (P value <0.05) on each other’s removal. Student’s t test results revealed that both Zn(II) and Pb(II) strongly inhibited both Cu(II) removal (P value <0.01) and Cd(II) removal (P value <0.02). All these results not only demonstrated a very good potential of the cyanobacteria in the bioremoval of these metals but also the effect of individual metals on each other’s removal in the multicomponent system.

Bioremoval of Cu(II), Zn(II), Pb(II) and Cd(II) by Nostoc muscorum isolated from a coal mining site

Abstract: This study evaluated the potential of the cyanobacterium Nostoc muscorum isolated from a mining environment for the removal of the heavy metals Cu(II), Zn(II), Pb(II) and Cd(II) from a constituent aqueous solution of different initial concentrations (5 to 50 mg L−1). Prior to the metal bioremoval experiments, the effect of three main culture parameters, i.e. inoculum volume, inoculum age and pH, on N. muscorum growth was assessed and their levels optimized employing the Taguchi experimental design technique. The batch metal removal kinetics showed a maximum removal of Pb(II) (98 %) and Cu(II) (87.8 %), followed by Cd(II) (82 %) and Zn(II) (67.2 %) at 5 mg L−1 initial metal concentration. Furthermore, estimation of protein, carbohydrate and biomass contents of the metal-exposed N. muscorum revealed that Zn(II) and Cd(II) are more toxic compared to Cu(II) at all initial metal concentrations, whereas it was more tolerant towards Pb(II).

Effect of process variables on the sulfate reduction process in bioreactors treating metal-containing wastewaters: factorial design and response surface analyses

Abstract: The individual and combined effect of the pH, chemical oxygen demand (COD) and SO4 2− concentration, metal to sulfide (M/S2−) ratio and hydraulic retention time (HRT) on the biological sulfate reduction (SR) process was evaluated in an inverse fluidized bed reactor by factorial design analysis (FDA) and response surface analysis (RSA). The regression-based model of the FDA described the experimental results well and revealed that the most significant variable affecting the process was the pH. The combined effect of the pH and HRT was barely observable, while the pH and COD concentration positive effect (up to 7 and 3 gCOD/L, respectively) enhanced the SR process. Contrary, the individual COD concentration effect only enhanced the COD removal efficiency, suggesting changes in the microbial pathway. The RSA showed that the M/S2− ratio determined whether the inhibition mechanism to the SR process was due to the presence of free metals or precipitated metal sulfides.

Zn(II) and Cu(II) removal by Nostoc muscorum: a cyanobacterium isolated from a coal mining pit in Chiehruphi, Meghalaya, India.

Abstract: Nostoc muscorum was isolated from a coal mining pit in Chiehruphi, Meghalaya, India, and its potential to remove Zn(II) and Cu(II) from media and the various biochemical alterations it undergoes during metal stress were studied. Metal uptake measured as a function of the ions removed by N. muscorum from media supplemented independently with 20 μmol/L ZnSO4 and CuSO4 established the ability of this cyanobacterium to remove 66% of Zn(2+) and 71% of Cu(2+) within 24 h of contact time. Metal binding on the cell surface was found to be the primary mode of uptake, followed by internalization. Within 7 days of contact, Zn(2+) and Cu(2+) mediated dissimilar effects on the organism. For instance, although chlorophyll a synthesis was increased by 12% in Zn(2+)-treated cells, it was reduced by 26% in Cu(2+)-treated cells. Total protein content remained unaltered in Zn(2+)-supplemented medium; however, a 15% reduction was noticed upon Cu(2+) exposure. Copper enhanced both photosynthesis and respiration by 15% and 19%, respectively; in contrast, photosynthesis was unchanged and respiration dropped by 11% upon Zn(2+) treatment. Inoculum age also influenced metal removal ability. Experiments in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (a photosynthetic inhibitor), carbonyl cyanide m-chlorophenyl hydrazone (an uncoupler), and exogenous ATP established that metal uptake was energy dependent, and photosynthesis contributed significantly towards the energy pool required to mediate metal removals.

Cadmium removal by Anabaena doliolum Ind1 isolated from a coal mining area in Meghalaya, India: associated structural and physiological alterations

Abstract: The cyanobacterium Anabaena doliolum Ind1 isolated from a coal mining site was tested for removal of cadmium at optimum pH 7.0 and temperature 25˚C. The organism recorded high percentage of metal removal (92-69%) within seven days of exposure to 0.5-2.0 ppm cadmium. Biosorption onto the cell surface was the primary mode of metal removal. Fourier transform infrared spectroscopy (FTIR) established hydroxyl, amides, carboxyl, sulphate and carbonyl groups to be the major functional groups on the cell surface involved in cadmium binding. Cellular ultrastructure and a range of vital physiological processes (i.e., photosynthetic pigments, respiration, photosynthesis, heterocyst frequency and nitrogenase activity) remained unaffected upon 0.5 ppm treatment; higher concentrations of cadmium exerted visible adverse effects. Amongst the five photosynthetic pigments tested, phycocyanin was the most targeted pigment (inhibition was 15-89%). Both respiration and photosynthetic activities were inhibited by cadmium with more severe effect seen on respiration. 2.0 ppm cadmium exposure also had drastic negative effect on nitrogenase activity (87% decreased).

Evaluation of Cr(VI) Exposed and Unexposed Plant Parts of Tradescantia pallida (Rose) D. R. Hunt. for Cr Removal from Wastewater by Biosorption.

Abstract: Phytoremediation is an efficient method for the removal of heavy metals from contaminated systems A productive disposal of metal accumulating plants is a major concern in current scenario In this

Biotechnology in Environmental Monitoring and Pollution Abatement 2015.

Abstract: Rapid industrial growth has led to elevated discharges of toxic chemicals and nutrients in water bodies. The level of a particular pollutant discharged into water bodies depends on industrial activities in the vicinity. Industries such as textiles, mining, tanneries, metal plating, fertilizer and agroindustries, batteries, pesticides, ore refineries, petrochemicals, and paper manufacturing are amongst others that contribute greatly to soil, sediment, air, and water pollution problems. Some of the chemicals are not biodegradable and therefore tend to accumulate in tissues and bioaccumulate in the food chain. This results in health problems in human beings and death of aquatic organisms. In water bodies, the presence of nitrogen and phosphorus increases the production of biomass in aquatic systems, thereby impairing the water quality and threatening the natural balance of these ecosystems. Although stringent nitrogen and phosphorus discharge standards from wastewater have been set in many countries, industries often face problems in meeting these requirements. From the regulatory perspective of a particular country, it is necessary to develop new or optimize the existing wastewater treatment technologies for compliance with the latest discharge standards. The demand for the use of sustainable and ecofriendly environmental processes is rapidly growing subjected to economic, public, and legislation pressure. Biotechnology provides a plethora of opportunities for effectively addressing issues pertaining to the monitoring, assessment, modeling, and treatment of contaminated soil, sediment, air, and water streams. The different biotechnologies available nowadays represent both well-established and novel (bio)technologies, although several aspects of their performance remain to be tested, for instance, the use of novel biocatalysts and reactor designs, a fundamental understanding of microbial community dynamics and mechanisms occurring within a (bio)reactor, the assessment of the performance of (bio)reactors during long-term operation, and its modeling [1–6]. If these mechanisms are understood and the knowledge gap is bridged, novel biotechniques will potentially change the way users rebuild technologies for the sustainable use of different biological processes for soil, sediment, air, and wastewater treatment.

Treatment of refinery wastewater using Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor

Abstract: In this study, refinery wastewater collected from Guwahati, India, was treated in an upflow packed bed reactor (PBR) with immobilized Arthrobacter chlorophenolicus A6. The wastewater was initially characterized using standard methods. The toxicity of the wastewater was determined using aerobic mixed microbial consortia following the resazurin toxicity assay. As the chemical oxygen demand (COD) level in the raw refinery wastewater was very low (190 mg l−1), the raw wastewater was spiked with a mixture of substituted phenol at different concentrations. The batch shake flask experiment revealed that the COD removal efficiency was found to be less when the raw refinery wastewater was not spiked with nutrient. On the other hand, when supplemented with nutrients in the form of mineral salt medium, more than 98% COD removal was achieved. The PBR was operated by varying the influent phenolic concentration in the range of 250–350 mg l−1 and at a hydraulic retention time of 12.5 h. Results indicated that mo...