Carbon Neutral Electricity Production from Municipal Solid Waste Landfill Leachate Using Algal-Assisted Microbial Fuel Cell.

We demonstrate the feasibility of algal lipid production and bioelectricity generation with concurrent treatment of municipal solid waste (MSW) leachate in a double-chamber algal-assisted microbial fuel cell (AAMFC). The cathode chamber was loaded with Synechococcus sp. and MSW leachate whereas anode chamber was loaded with anaerobic microflora. While treating 50% MSW leachate, highest power density (95.63 mW/m2), current density (2.48 A/m2), and biomass concentration (2.54 g/l) were observed. The algal growth in the cathode chamber increased the oxygen concentration from 5.5 to 8.6 mg/l. Secondly, we studied the influence of salinity in AAMFC performance. The addition of 30 mM NaCl with 50% leachate increased the power and current density to 110.92 mW/m2 and 5.169 A/m2, respectively. It also increased the biomass concentration, protein, and lipid content. The analysis of fatty acid profile of algae confirmed the presence of palmitic acid, stearic acid, and linoleic acid. The proposed technique is effective for concurrent treatment of MSW leachate and power generation besides algal lipid production without external aeration.

Ultrasound assisted green synthesis of silver nanoparticles using weed plant.

This study presents the facile, green and eco-friendly synthesis of silver nanoparticles (AgNPs) using weed plant Lantana camara L. leaf extract. The incorporation of ultrasound into this reduced the time and increased the reaction rate. The results showed that the AgNPs were spherical in shape with the average size of 33.8 nm. The EDAX pattern indicated the presence of abundant silver and XRD indicated that the (111) crystallographic plane more predominant than other planes. The possible functional groups responsible for the reduction and stabilization of AgNPs were identified using Fourier transform infrared spectroscope. The XPS results concluded that the nanoparticles were presented in its reduced metallic state. The antioxidant activity of AgNPs was assayed using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) test. The increase in the concentration of AgNPs increased the DPPH scavenging activity. The AgNPs revealed superior antibacterial activity against Gram positive and Gram negative organisms.

Mechanistic study on ultrasound assisted pretreatment of sugarcane bagasse using metal salt with hydrogen peroxide for bioethanol production.

This study presents the ultrasound assisted pretreatment of sugarcane bagasse (SCB) using metal salt with hydrogen peroxide for bioethanol production. Among the different metal salts used, maximum holocellulose recovery and delignification were achieved with ultrasound assisted titanium dioxide (TiO2) pretreatment (UATP) system. At optimum conditions (1% H2O2, 4 g SCB dosage, 60 min sonication time, 2:100 M ratio of metal salt and H2O2, 75°C, 50% ultrasound amplitude and 70% ultrasound duty cycle), 94.98 ± 1.11% holocellulose recovery and 78.72 ± 0.86% delignification were observed. The pretreated SCB was subjected to dilute acid hydrolysis using 0.25% H2SO4 and maximum xylose, glucose and arabinose concentration obtained were 10.94 ± 0.35 g/L, 14.86 ± 0.12 g/L and 2.52 ± 0.27 g/L, respectively. The inhibitors production was found to be very less (0.93 ± 0.11 g/L furfural and 0.76 ± 0.62 g/L acetic acid) and the maximum theoretical yield of glucose and hemicellulose conversion attained were 85.8% and 77%, respectively. The fermentation was carried out using Saccharomyces cerevisiae and at the end of 72 h, 0.468 g bioethanol/g holocellulose was achieved. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of pretreated SCB was made and its morphology was studied using scanning electron microscopy (SEM). The compounds formed during the pretreatment were identified using gas chromatography-mass spectrometry (GC-MS) analysis.

Utilization of coconut oil cake for the production of lipase using Bacillus coagulans VKL1.

The overproduction of enzymes was performed by manipulating the medium components. In our study, solvent-tolerant thermophilic lipase-producing Bacillus coagulans was isolated from soil samples and a stepwise optimization strategy was employed to increase the lipase production using coconut oil cake basal medium. In the first step, the influence of pH, temperature, carbon source, nitrogen source and inducers on lipase activity was investigated by the One-Factor-At-A-Time (OFAT) method. In the second step, the three significant factors resulted from OFAT were optimized by the statistical approach (CCD).The optimum values of olive oil (0.5%), Tween 80 (0.6%) and FeSO4 (0.05%) was found to be responsible for a 3.2-fold increase in the lipase production identified by Central Composite Design.

Improved biodegradation of textile dye effluent by coculture.

The present study demonstrates the de-colorization and degradation of textile effluent by coculture consisting of three bacterial species isolated from textile effluent contaminated environment with an aim to reduce the treatment time. The isolates were identified as Ochrobactrum sp., Pseudomonas aeruginosa and Providencia vermicola by 16S rRNA analysis. Their secondary structure was predicted and GC content of the sequence was found to be 54.39, 52.10, and 52.53%. The co-culture showed a prominent increase in the degradation activity due to the action of oxidoreductase enzymatic mechanism of laccase, NADH-DCIP reductase and azoreductase activity. The biodegradability index of 0.75 was achieved with 95% chemical oxygen demand (COD) reduction in 16 h and 78 and 85% reduction in total organic carbon (TOC) and total solids was observed. Bioaccumulation of metals was identified by X-ray diffraction (XRD) analysis. The effective decolorization was confirmed from the results of UV-vis spectroscopy, high performance liquid chromatography and Fourier transformed infrared spectrometer analyzes. The possible degradation pathway was obtained from the analysis of liquid chromatography-mass spectroscopy analysis and the metabolites such as 2-amino naphthalene and N-phenyl-1.3,5 triazine were observed. The toxic nature of the effluent was analyzed using phyto-toxicity, cell-death assay and geno-toxicity tests.

Biodegradation of malachite green by Ochrobactrum sp.

This study presents the biodegradation of malachite green (MG), a triphenylmethane dye, using a novel microorganism isolated from textile effluent contaminated environment. The organism responsible for degradation was identified as Ochrobactrum sp JN214485 by 16S rRNA analysis. The effect of operating parameters such as temperature, pH, immobilized bead loading, and initial dye concentration on % degradation was studied, and their optimal values were found to be 30 °C, 6, 20 g/L and 100 mg/L, respectively. The analysis showed that the extracellular enzymes were responsible for the degradation. The biodegradation of MG was confirmed by UV-visible spectroscopic and FTIR analysis. The phytotoxicity test concluded that the degradation products were less toxic compared to MG. The kinetics of biodegradation was studied and the activation energy was found to be 10.65 kcal/mol.

Direct transesterification of Oedogonium sp. oil be using immobilized isolated novel Bacillus sp. lipase.

This work emphasizes the potential of the isolated Bacillus sp. lipase for the production of fatty acid methyl ester by the direct transesterification of Oedogonium sp. of macroalgae. Dimethyl carbonate was used as the extraction solvent and also as the reactant. The effect of solvent/algae ratio, water addition, catalyst, temperature, stirring and time on the direct transesterification was studied. The highest fatty acid methyl ester yield obtained under optimum conditions (5 g Oedogonium sp. powder, 7.5 ml of solvent (dimethyl carbonate)/g of algae, 8% catalyst (%wt/wt of oil), distilled water 1% (wt/wt of algae), 36 h, 55°C and 180 rpm) was 82%. Final product was subjected to thermogravimetric analysis and (1)H NMR analysis. The results showed that the isolated enzyme has good potential in catalyzing the direct transesterification of algae, and the dimethyl carbonate did not affect the activity of the isolated lipase.

Simultaneous Cr(VI) reduction and phenol degradation using Stenotrophomonas sp. isolated from tannery effluent contaminated soil.

This study presents simultaneous hexavalent chromium (Cr(VI)) reduction and phenol degradation using Stenotrophomonas sp., isolated from tannery effluent contaminated soil. Phenol was used as the sole carbon and energy source for Cr(VI) reduction. The optimization of different operating parameters was done using Placket-Burman design (PBD) and Box-Behnken design (BBD). The significant operating variables identified by PBD were initial Cr(VI) and phenol concentration, pH, temperature, and reaction time. These variables were optimized by a three-level BBD and the optimum initial Cr(VI) concentration, initial phenol concentration, pH, temperature, and reaction time obtained were 16.59 mg/l, 200.05 mg/l, 7.38, 31.96 °C and 4.07 days, respectively. Under the optimum conditions, 81.27 % Cr(VI) reduction and 100 % phenol degradation were observed experimentally. The results concluded that the Stenotrophomonas sp. could be used to decontaminate the effluents containing Cr(VI) and phenol effectively.

Treatment of pharmaceutical effluent by ultrasound coupled with dual oxidant system.

In this study, sonolysis (US), a dual oxidant system (DOX), and ultrasound coupled with a dual oxidant system (US/DOX) were employed to degrade real pharmaceutical effluent. In a DOX system, two effective oxidizing agents such as hydrogen peroxide and activated persulphate were used simultaneously. In this work, for the first time, an easily available waste material, iron swarf, was used as an activator for persulphate oxidation. Iron swarf coupled with an ultrasound system showed better activation. High iron dosage, acidic pH and high temperature favoured degradation with both DOX and US/DOX. Sequential addition of iron swarf produced better results compared to single-step addition. The activation energy was found to be 47.25 and 23.47 kJ/mol for DOX and US/DOX, respectively. The biodegradability index of the effluent was enhanced from 0.13 to 0.81 after treatment with US/DOX.

Treatment of phenol-containing wastewater by photoelectro-Fenton method using supported nanoscale zero-valent iron.

This study presents the degradation of phenol by the photoelectro-Fenton method using nano zero-valent iron (nZVI) immobilized in polyvinyl alcohol-alginate beads. The effect of nZVI loading, H(2)O(2) concentration, pH, and initial phenol concentration on phenol degradation and chemical oxygen demand reduction was studied. The scanning electron microscope images of the nZVI beads were used to analyze their morphology, and their diameters were in the range of 500-600 µm. The concentration of nZVI in the beads was varied from 0.1 to 0.6 g/L. Fe(2+) leakage of 1 and 3 % was observed with 0.5 and 0.6 g/L of nZVI, respectively, and the observed beads' fracture frequency was 2 %, which confirmed the stability of the beads. The optimum operating conditions that arrived for better degradation were 0.5 g/L of nZVI, pH 6.2, and 400 mg H(2)O(2)/L. The treatment of effluent by this method increased the biodegradability index of the effluent, and the degradation data were found to follow pseudo first-order kinetics.

Ultrasound-assisted alkaline pretreatment of sugarcane bagasse for fermentable sugar production: optimization through response surface methodology.

Ultrasound-assisted alkaline pretreatment of sugarcane bagasse (SCB) for fermentable sugar production was carried out and the influence of particle size, liquid to solid ratio (LSR), NaOH concentration, temperature and sonication time on delignification and reducing sugar production was ascertained with Placket-Burman design. The best combination of each significant factor was determined by a central composite design (CCD) and optimum pretreatment conditions for maximum reducing sugar yield (96.27%) were particle size of 0.27 mm, LSR of 25 ml/g, NaOH concentration of 2.89% (w/v), temperature of 70.15°C and pretreatment time of 47.42 min. Under these conditions, 92.11% of theoretical reducing sugar yield was observed experimentally. The substantial reduction in pretreatment time and temperature with improved efficiency is the most attractive features of the ultrasound-assisted alkaline pretreatment.

Isolation of thermo-stable and solvent-tolerant Bacillus sp. lipase for the production of biodiesel.

This study presents the production of biodiesel from algae oil by transesterification using thermophilic microorganism. The microorganism used in this study was isolated from the soil sample obtained near the furnace. The organism was identified as Bacillus sp., and the lipase obtained was purified by ammonium sulfate precipitation and ion exchange chromatography leading to 8.6-fold purification and 13% recovery. Molecular weight of the enzyme was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and it was found to be 45 kDa. The effect of pH, temperature, and solvent addition on lipase activity was investigated. The enzyme showed maximum activity at 55 °C and at pH 7 and was also found to be highly active in the presence of organic solvents such as hexane and t-butanol. The isolated lipase was successfully used for the production of biodiesel. The transesterification activity of the isolated lipase showed 76% of fatty acid methyl esters yield in 40 h, which indicated that this enzyme can be used as a potential biocatalyst for the biodiesel production.

Utilization of sugarcane bagasse for bioethanol production: sono-assisted acid hydrolysis approach.

In this study, the production of sugar monomers from sugarcane bagasse (SCB) by sono-assisted acid hydrolysis was performed. The SCB was subjected to sono-assisted alkaline pretreatment. The cellulose and hemicellulose recovery observed in the solid content was 99% and 78.95%, respectively and lignin removal observed during the pretreatment was about 75.44%. The solid content obtained was subjected to sono-assisted acid hydrolysis. Under optimized conditions, the maximum hexose and pentose yield observed was 69.06% and 81.35% of theoretical yield, respectively. The hydrolysate obtained was found to contain very less inhibitors, which improved the bioethanol production and the ethanol yield observed was 0.17 g/g of pretreated SCB.

Treatment of petroleum refinery wastewater by ultrasound-dispersed nanoscale zero-valent iron particles.

Petroleum refineries release wastewater, which is rich in organic pollutants and cannot be treated easily. This study presents the treatment of petroleum refinery wastewater using nanoscale zero valent iron (NZVI) in the presence of ultrasonication. NZVI characteristics were analyzed using SEM and XRD. The influence of NZVI dosage and initial pH on % chemical oxygen demand (COD) reduction was studied. From the results, it can be inferred that a dosage of 0.15 g/l and an initial pH are optimum for the effective degradation of effluents. The degradation data were found to follow first order kinetics. The results indicate that using NZVI in combination with ultrasonication is an efficient method for the treatment of petroleum refinery wastewater.

Ultrasound mediated reduction of Cr(VI) using sludge obtained during electrocoagulation.

This study presents the ultrasound mediated reduction of toxic hexavalent chromium (Cr(VI)) into non-toxic trivalent chromium (Cr(III)) using sludge obtained during the electrocoagulation of pharmaceutical wastewater (EC sludge). Experiments were carried out with and without ultrasound to explore its influence. The effect of initial concentration of Cr(VI) (100-200 mg/l), pH (6-8) and EC sludge dosage (5-10 g/l) on Cr(VI) reduction was studied. The morphological and functional group changes of EC sludge due to Cr(VI) reduction were analysed with scanning electron microscopy and Fourier transform infrared, respectively. The reduction rates observed in the presence of ultrasound were found to be higher than the rates observed for without ultrasound. The results concluded that the EC sludge can be successfully used for reduction of Cr(VI) at lower cost.

Mass transfer studies on the reduction of Cr(VI) using calcium alginate immobilized Bacillus sp. in packed bed reactor.

This study presents the external mass transfer effects on the reduction of hexavalent chromium (Cr(VI)) using calcium alginate immobilized Bacillus sp. in a re-circulated packed bed batch reactor (RPBR). The effect of flow rate on the reduction Cr(VI) was studied. Theoretically calculated rate constants for various flow rates were analyzed using external film diffusion models and compared with experimental values. The external mass transfer coefficients for the bioconversion of Cr(VI) were also investigated. The external mass transfer effect was correlated with a model of the type J(D)=K Re(-(1-n). The model was tested with various K values and the mass transfer correlation J(D)=5.7 Re(-0.70) was found to predict the experimental data accurately. The proposed model would be useful for the design of industrial reactor and scale up.

Sonoassisted microbial reduction of chromium.

This study presents sonoassisted microbial reduction of hexavalent chromium (Cr(VI)) using Bacillus sp. isolated from tannery effluent contaminated site. The experiments were carried out with free cells in the presence and absence of ultrasound. The optimum pH and temperature for the reduction of Cr(VI) by Bacillus sp. were found to be 7.0 and 37 degrees C, respectively. The Cr(VI) reduction was significantly influenced by the electron donors and among the various electron donors studied, glucose offered maximum reduction. The ultrasound-irradiated reduction of Cr(VI) with Bacillus sp. showed efficient Cr(VI) reduction. The percent reduction was found to increase with an increase in biomass concentration and decrease with an increase in initial concentration. The changes in the functional groups of Bacillus sp., before and after chromium reduction were observed with FTIR spectra. Microbial growth was described with Monod and Andrews model and best fit was observed with Andrews model.

Bacillus sp. mutant for improved biodegradation of Congo red: random mutagenesis approach.

This study presents the improved biodegradation of Congo red, a toxic azo dye, using mutant Bacillus sp. obtained by random mutagenesis of wild Bacillus sp. using UV and ethidium bromide. The mutants obtained were screened based on their decolorization performance and best mutants were selected for further studies. Better decolorization was observed in the initial Congo red concentration range 100-1000 mg/l for wild species whereas mutant strain was found to offer better decolorization up to 3000 mg/l. Mutant strain offered 12-30% reduction in time required for the complete decolorization by wild strain. The optimum pH and temperature were found to be 7.0 and 37 degrees C, respectively. Two efficient strains such as Bacillus sp. ACT 1 and Bacillus sp. ACT 2 were isolated from the various mutants obtained. Bacillus sp. ACT 2 showed improved enzymatic production and Bacillus sp. ACT 1 showed improved growth compared to wild strain. The enzyme responsible for the degradation was found to be azoreductase by SDS-PAGE and about 53% increased production of enzyme was achieved with mutant species. The experimental data were modeled using growth and substrate inhibition models.

Improved biodegradation of Congored by using Bacillus sp.

The biodegradation of Congored, a toxic azo dye, was studied by using a hybrid technique involving sonolysis as pretreatment followed by biological treatment. The experiments were carried out with and without pretreatment using dye solution as a sole source of nutrition with an isolated and acclimatized strain of Bacillus sp. obtained from tannery industry effluent. The pretreatment time was varied as 30, 60, 90, 120, 150 and 180 min and then the pretreated dye solution was subjected to biological treatment. The effectiveness of pretreatment was compared with the results of biological degradation of non pretreated Congored and the results showed that the pretreatment improved the efficiency of the biodegradation of Congored. During the biological degradation, the increase in initial dye concentration decreased the decolorization rate and at high concentrations (1500 and 2000 mg/l), the inhibition was observed. The optimum pH and temperature were determined to be 7.0 and 37 degrees C, respectively. The data obtained through biodegradation experiments were fitted with five different kinetic models and the results were analyzed.

An overview of enzymatic production of biodiesel.

Biodiesel production has received considerable attention in the recent past as a biodegradable and nonpolluting fuel. The production of biodiesel by transesterification process employing alkali catalyst has been industrially accepted for its high conversion and reaction rates. Recently, enzymatic transesterification has attracted much attention for biodiesel production as it produces high purity product and enables easy separation from the byproduct, glycerol. But the cost of enzyme remains a barrier for its industrial implementation. In order to increase the cost effectiveness of the process, the enzyme (both intracellular and extracellular) is reused by immobilizing in a suitable biomass support particle and that has resulted in considerable increase in efficiency. But the activity of immobilized enzyme is inhibited by methanol and glycerol which are present in the reacting mixture. The use of tert-butanol as solvent, continuous removal of glycerol, stepwise addition of methanol are found to reduce the inhibitory effects thereby increasing the cost effectiveness of the process. The present review analyzes these methods reported in literature and also suggests a suitable method for commercialization of the enzymatic process.