Bioremediation of toluene‐contaminated air using an external loop airlift bioreactor

An external loop airlift bioreactor (ELAB) has been used to capture and degrade toluene from a contaminated air stream. Using a spinning sparger, the toluene could be transferred from small, uniform bubbles into the aqueous culture media with an overall mass transfer coefficient as high as 1.1 h^?1. Due to the very volatile nature of toluene, Pseudomonas putida (ATCC 23973) was cultured and maintained on benzyl alcohol, the first intermediate compound in the metabolic degradation pathway for toluene. Consequently, before successful continuous operation of the ELAB with toluene‐contaminated air, Pseudomonas putida was acclimatized to toluene by using 30 min intermittent sparging of contaminated air into the bioreactor. Continuous sparging of toluene‐contaminated air could then be successfully carried out with 100% capture and biodegradation efficiency at a contaminated air concentration of 15 mg dm^?3 and a loading rate of 35 mg dm^?3 h^?1. Higher concentrations and loading rates were only partially degraded. Although this capture matches only the low rates reported earlier using biofilters to remediate toluene, the ELAB operates using submerged culture and requires no packing which can plug during biofilter operation. In this study, Pseudomonas putida grew on toluene at a maximum specific growth rate of only 0.05 h^?1. © 2003 Society of Chemical Industry     

Optimum operating conditions for the removal of volatile organic compounds in a compost-packed biofilter

Biofiltration was performed for 101 days in a compost-packed biofilter (I.D. 5.0 cmxheight 62 cm) for the removal of nine volatile organic compounds (benzene, toluene,m-xylene,o-xylene, styrene, chloroform, trichloroethylene, isoprene, and dimethyl sulfide). Removal efficiency of the volatile organic compounds (VOCs) was dependent upon the column temperature, gas flow rate, and incoming concentrations of VOCs. At an empty bed residence time (EBRT) of 3 min and the incoming gas concentration of 66 g m^-3 overall removal and efficiency increased up to 92.1 and 86.4% at 25 °C and 45 °C, respectively. Upon further increase of the incoming gas concentration to 83 g m⁻³, the removal efficiency was 93.7% at 25 °C, but dropped to 73.1% at 45 °C. At incoming gas concentration of 92 g m^-3 and EBRT of 1.5 min, the removal efficiency at 25 °C (91.6%) was comparable to 32 °C (95.5%). However, for 1 min of EBRT removal efficiency was better (86.6%) at 32 °C as compared to at 25 °C (73.6%). The maximum removal rates of VOCs were 3,561, 4,196, and 1,150 g m^-3 h^-1 at 25, 32, and 45 °C, respectively. At an EBRT of 1.5 min and 32 °C the removal efficiency of individual component was highest for toluene (98.9%) andm-xylene (97.6%), and lowest for TCE (86.1%) and chloroform (89.4%). Aromatic compounds (benzene, toluene, and xylene) were removed by 97.1–98.9%. After 101 days of operation profiles of pH and moisture content from the top to the bottom of the column were 7.2–6.3 and 53.8–67.2%, respectively, at 32 °C column, and 67% of the incoming VOCs was removed in the first quarter of the column. After 36 days of operation the cell concentration increased 108-fold from its initial value at 25 °C, and reached a maximum of 1.08x108 cells·(g of dry compost)^-1.     

Biobased thermosetting resins composed of terpene and bismaleimide

Prepolymers prepared by reactions of 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) with myrcene (Myr) and limonene (Lim) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 150°C were compressed at 250°C to produce crosslinked Myr/BMI [molar ratio = 2:2–2:5 (MB22–MB25)] and Lim/BMI [molar ratio = 1:1 (LB11)] resins. The ¹H‐NMR analysis of the model reaction products of Lim and Myr with N‐phenyl maleimide (PMI) in DMI at 150°C revealed that a Diels–Alder reaction for Myr/PMI and a vinyl copolymerization for Lim/PMI preferentially proceeded in addition to the occurrence of the ene reaction to some extent. The Fourier transform infrared data of the cured resins were consistent with the results of the model reactions. All of the cured resins, except for MB22, showed tan δ peak values and 10% weight loss temperatures that were higher than 330 and 440°C, respectively. The flexural strength and modulus values of the MBs were higher than those of LB11. Field emission scanning electron microscopy analysis revealed that MB22–MB24 were homogeneous, whereas some combined particles appeared in LB11. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Studies on the biosorption of Pb(II) ions using Pseudomonas putida

ABSTRACT

The complete removal of Pb(II) was achieved by intact Pseudomonas putida cells. The biosorption isotherm exhibited Langmuirian behaviour and followed pseudo-second-order rate kinetics. The standard Gibbs free energy change (?G°) for the biosorption of Pb(II) ions was found to be ?26.4 kJ mol^?1, attesting to a chemisorption process. Thermolysis of P. putida cells improved the Pb(II) binding capacity by around 27%. All the four components tested, namely DNA, protein, polysaccharide and lipid, were found to contribute to the uptake of Pb(II) ions. The possible mechanisms of Pb(II) binding by P. putida have been delineated.     

Treatment of mixed solvent vapors with hybrid system composed of biofilter and photo-catalytic reactor

The transient behavior of a hybrid system composed of biofilter and photo-catalytic reactor was observed at the height of each sampling port to treat waste-air containing ethanol. The biofilter packed with mixed media (of granular activated carbon and compost) was inoculated with a pure culture ofBurkholderia cepacia G4 andPseudomonas putida, while a photo-catalytic reactor was composed of 15W UV-A lamps and annular pyrex tubes packed with glass beads coated with sol type of TiO₂ before calcination. The maximum elimination capacities of toluene and ethanol turned out to be 130 g/m³/h and 230 g/m³/h, respectively, which were greater by 40 g/m³/h and 130 g/m³/h, respectively, than those from the experiments performed with a biofilter only. Thus, the maximum elimination capacities for toluene and ethanol increased by 44% and 130%, respectively, by use of a hybrid system. The photo-catalytic process contributed to the maximum elimination capacities of hybrid system on toluene and ethanol by 30.8% and 56.5%, respectively, which contributions for the elimination capacities on toluene and ethanol were allocated indirectly by 25.4% and 44.3% as well as directly by 5.4% and 12.2%, respectively. Direct contributions of photo-catalytic process were 17.5% and 21.5% to the increments of the elimination capacities on toluene and ethanol, respectively, while its indirect contributions were 82.5% and 78.5% to those on toluene and ethanol, respectively.     

A trickling fibrous-bed bioreactor for biofiltration of benzene in air

A novel trickling fibrous-bed bioreactor was developed for biofiltration to remove pollutants present in contaminated air. Air containing benzene as the sole carbon source was effectively treated with a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in the trickling biofilter, which was wetted with a liquid medium containing only inorganic mineral salts. When the inlet benzene concentration (C_gi) was 0·37 g m⁻³, the benzene removal efficiency in the biofilter was greater than 90% at an empty bed retention time (EBRT) of 8 min or a superficial air flow rate of 1·8 m³ m⁻² h⁻¹. In general, the removal efficiency decreased but the elimination capacity of the biofilter increased with increasing the inlet benzene concentration and the air (feed) flow rate. It was also found that the removal efficiency decreased but the elimination capacity increased with an increase in the loading capacity, which is equal to the inlet concentration divided by EBRT. The maximum elimination capacity achieved in this study was ∽11·5 g m⁻³ h⁻¹ when the inlet benzene concentration was 1·7 g m⁻³ and the superficial air flow rate was 3·62 m³ m⁻² h⁻¹. A simple mathematical model based on the first-order reaction kinetics was developed to simulate the biofiltration performance. The apparent first order parameter K_l in this model was found to be linearly related to the inlet benzene concentration (K_l=4·64−1·38 C_gi). The model can be used to predict the benzene removal efficiency and elimination capacity of the biofilter for benzene loading capacity up to ∽30 g m⁻³ h⁻¹. Using this model, the maximum elimination capacity for the biofilter was estimated to be 12·3 g m⁻³ h⁻¹, and the critical loading capacity was found to be 14 g m⁻³ h⁻¹. The biofilter had a fast response to process condition changes and was stable for long-term operation; no degeneration or clogging of the biofilter was encountered during the 3-month period studied. The biofilter also had a relatively low pressure drop of 750 Pa m⁻¹ at a high superficial air flow rate of 7·21 m³ m⁻² h⁻¹, indicating a good potential for further scale up for industrial applications. © 1998 Society of Chemical Industry     

Effect of nutrients on optimal production of biosurfactants by <Emphasis Type="Italic">Pseudomonas putida</Emphasis>—A gujarat oil field isolate

Nutritional requirements for maximal production of biosurfactant by an oil field bacterium Pseudomonas putida were determined. The optimal concentrations of nitrogen, phosphate, sulfur, magnesium, iron, potassium, sodium, calcium, and trace elements for maximal production of biosurfactants were ascertained, and a new “Pruthi and Cameotra” salt medium was formulated. Data show that maximal biomass (2.4 g L⁻¹) and biosurfactant production (6.28 g L⁻¹) takes place after 72 h of growth on 2% hexadecane. The biosurfactant was produced optimally over pH and temperature ranges of 6.4–7.2 and 30–40°C, respectively. That the highest biosurfactant yield was obtained during late log phase of growth indicates that the biosurfactant is a secondary metabolite.     

Antioxidant effects of flavonoids ofAnthriscus sylvestris in lard

Ethanol/water (7∶3) extracts of the plant speciesAnthriscus sylvestris possess antioxidant activity. Separation and identification of antioxidant components by thin-layer and column chromatography and spectral analysis demonstrated that quercetin and apigenin appeared to be the main flavonoid species inAnthriscus sylvestris. Rutin was one of the major quercetin glycosides. Structures of the isolated compounds were determined by infrared and¹H nuclear magnetic resonance spectroscopies. Ethanolic extract (70%) ofA. sylvestris showed concentration-dependent, strong antioxidant activity as determined by the Schaal Oven test of lard at 60°C. Rancimat analysis at 100°C showed that the antioxidant activity of 70% ethanolic extract ofA. sylvestris was superior to quercetin, apigenin, or a tocopherol mixture.     

Further improvements in the yield of monoglycerides during enzymatic glycerolysis of fats and oils

Three approaches were used in an effort to increase the yield of monoglycerides (MG) during the lipase catalyzed reaction of glycerol with triglyceride fats and oils: i) various commercially available lipases were screened for ability to catalyze MG synthesis; ii) mixtures of lipases were compared with single lipases; and iii) two-step temperature programming was applied during the reaction. Of these, temperature programming was found to be the most effective. With an initial temperature of 42°C for 8–16 hr followed by incubation at 5°C for up to 4 days, a yield of approximately 90 wt% MG was obtained from beef tallow, palm oil and palm stearin. When the second incubation temperature was greater than 5°C, the yield of MG was progressively lower with increasing temperature. In the case of screening of newly available commercial lipase preparations, lipases fromPseudomonas sp. were found to be most effective, giving a yield of approximately 70 wt% MG at 42°C from tallow. Lipases fromGeotrichum candidum, Penicillium camembertii (lipase G) andCandida rugosa were inactive. A mixture of lipases fromPenicillium camembertii andHumicola lanuginosa was found to be more effective than either enzyme alone, giving a yield of approximately 70 wt% MG using beef tallow or palm oil. A mixture ofPenicillium camembertii lipase with eitherPseudomonas fluorescens lipase orMucor miehei lipase was not more effective thanPseudomonas fluorescens orMucor miehei lipase alone.     

Seawater desalination using PVDF-HFP membrane in DCMD process: assessment of operating condition by response surface method

Central composite design (CCD) was applied in this work to analyze the performance of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) flat sheet membrane in the seawater desalination using direct contact membrane distillation (DCMD) process. It is the most popular in response surface method (RSM). Development on Quadratic Regression model for membrane performance as a function of the operating conditions was studied. The ranges for each operating condition were selected as follows: feed temperature (T_f): 48–58?°C, feed flow rate (Q_f): 80–180?mL/min, permeate temperature (T_p):17–22?°C and permeate flow rate (Q_p): 80–180?mL/min. The model R-squared of 0.9759 (adjusted to degree-of-freedom), Lack-of-fit test (p?=?0.4764), predicted residual error sum of squared (PRESS) statistic of 10.3 suggest that the model is adequate to correlate the impact of operating conditions on permeates. ANOVA analysis showed that factors as feed flow rate, feed temperature, and permeate temperature have a valuable impact (p?≤?0.05) on the response variable. Additionally, the interaction among feed temperature-feed flow rate, feed flow rate-permeate flow rate, and the quadratic impact of feed temperature, permeate temperature, and permeate flow rate have shown an important impact (p?≤?0.05) on the permeate flux. Optimization of operating conditions to make the permeate flux and salt rejection high as possible was determined according to desirability function approach. A desirability of 0.969 was achieved at a feed temperature of 58?°C, feed flow rate of 180?mL/min, permeate temperature of 18.8?°C, and permeate flow rate of 145.3?mL/min in which a permeate flux of 12.56?kg/m²h and a salt rejection of 99.97% was obtained.     

Importance of lichen secondary products in food choice of two oribatid mites (Acari) in an alpine meadow ecosystem

In an alpine meadow ecosystem in the Swiss National Park, the lichensCetraria islandica andCladonia symphycarpa occur in small vegetation patches dominated byCarexfirma (Cyperaceae) andSesleria coerulea (Gramineae). Laboratory food-choice experiments with two oribatid mitesFuscozetes setosus andCarabodes intermedius show that the thallus structure and secondary products ofC. islandica are repellent factors against herbivorous mites. In contrast, secondary products ofC. symphycarpa may be an attractant for the mites.     

Mechanism by which noninhibitory concentrations of glucose increase inhibitory activity ofp-coumaric acid on morning-glory seedling biomass accumulation

Noninhibitory levels of glucose-C [ 72 µg carbon (C)/g soil] increased the inhibitory activity ofp-coumaric acid on morning-glory seedling biomass accumulation in Cecil B_t-horizon soil. The amount ofp-coumaric acid required for a given level of inhibition of shoot and seedling biomass accumulation decreased as the concentration of glucose increased. Soil extractions with neutral EDTA (0.25 M, pH 7) after addition of combinations ofp-coumaric acid and glucose (concentrations ranging from 0 to 1.25 µmol/g soil) to the soil showed that utilization ofp-coumaric acid by microbes decreased linearly as the concentration of glucose increased. The increased inhibitory activity of a given concentration ofp-coumaric acid in the presence of glucose was not due to a reduction in soil sorption ofp-coumaric acid or effects of nitrogen-limited microbial growth. Noninhibitory levels of phenylalanine andp-hydroxybenzoic acid slowed the utilization ofp-coumaric acid by microbes in a similar manner as glucose. The presence of methionine, however, did not affect the rate ofp-coumaric acid utilization by microbes. These observations suggest that differential utilization of individual molecules in organic mixtures by soil microbes can modify, and in this case increase, the effectiveness of a given concentration of an inhibitor such asp-coumaric acid on the inhibition of seedling growth such as morning-glory.The use of trade names in this publication does not imply endorsement by the United States government or the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.     

Free‐radical terpolymerization of n‐butyl acrylate/butyl methacrylate/d‐limonene

d ‐Limonene (Lim) is a renewable monoterpene derived from citrus fruit peels. We investigated it for use as part of a more sustainable polymer formulation. The bulk free‐radical terpolymerization of n‐butyl acrylate (BA)/butyl methacrylate (BMA)/Lim was carried out at 80°C with benzoyl peroxide as the initiator. The terpolymerization was studied at various initial BA/BMA/Lim molar ratios, and the products were characterized for conversion, terpolymer composition, molecular weight, and glass‐transition temperature. Lim was observed to undergo a significant degradative chain‐transfer reaction, which greatly influenced the polymerization kinetics. The rate of polymerization, final conversion, and polymer molecular weight were all significantly reduced because of the presence of Lim. Nonetheless, polymers with relatively high weight‐average molecular weights (20,000–120,000 Da) were produced. The terpolymer composition was well predicted with the reactivity ratios estimated for each of the three copolymer subsystems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42821.     

The treatment of waste-air containing mixed solvent using a biofilter: 1. Transient behavior of biofilter to treat waste-air containing ethanol

Transient behavior of a biofilter packed with mixed media (of granular activated carbon and compost) inoculated with a pure culture ofPseudomonas putida was observed at the height of each sampling port to treat wasteair containing ethanol. In addition, flooding effects of an excess supply of buffer solution was observed at each sampling port of the biofilter until it recovered the status prior to the flooding. Unlike previous investigations, various process conditions were applied to successive biofilter runs in order to monitor the corresponding unsteady behavior of the biofilter in this work. In early stage of biofilter run the removal efficiency of ethanol maintained almost 100%. However, it began to decrease when inlet load surpassed 100 g/m³/h consistent with maximum elimination capacity. At the end of biofilter-run removal efficiency was decreased and maintained at 40%. The results of this work were compared to those of such biofiltration studies as the work of Christen et al. from the point of view that pure cultures of microorganism were used in both works. Except for the period of flooding effect of the 2nd stage, the inlet load and removal efficiency continued at 105.5 g/m³/h and 95%, respectively, while they were 93.7 g/m³/h and 95%, respectively, according to the result of Christine et al. Removal efficiency remained at 90% for the beginning period of 3 days of the 3rd stage, and it gradually decreased to 60% for remaining 5 days of the stage with an inlet load of 158.26 g/m³/h, which may be interpreted as better than the result of Christine et al. Their result was that the removal efficiency on the inlet load of 154 g/m³/h of ethanol was continued to be 60% for 6 days of a separate biofilter run and decreased to 40% later. Thus, with similar inlet loads of ethanol, removal efficiency of this work was equivalent to or higher than that of Christine et al.     

Synthesis and characterization of a terpolymer of limonene,styrene, and methyl methacrylate via a free‐radical route

The free‐radical terpolymerization of a monocyclic terpene, namely, limonene (Lim), with styrene (Sty) and methyl methacrylate (MMA) in xylene at 80 ± 0.1°C for 2 h, with benzoyl peroxide (BPO) as an initiator under an inert atmosphere of nitrogen was extensively studied. The kinetic expression was R_pα[BPO]^0.5[Sty]^1.0[MMA]^1.0[Lim]^?1.0, where R_p is the rate of polymerization. The overall energy of activation was calculated as 26 kJ/mol. R_p decreased as [Lim] increased. This was due to a penultimate unit effect. The Fourier transform infrared spectra of the terpolymer showed bands at 3025–3082, 1728, and 2851–2984 cm^?1 due to C? H stretching of phenyl (? C₆H₅) protons of Sty, ? OCH₃ of MMA, and trisubstituted olefinic protons of Lim, respectively. The ¹H‐NMR spectra showed peaks at 7.3–8.1, 3.9–4.4, and 5.0–5.5 δ due to the phenyl, methoxy, and trisubstituted olefinic protons of Sty, MMA and Lim, respectively. The values of the reactivity ratios r₁ (MMA; 0.33) and r₂ (Sty + Lim; 0.06) were calculated with the Kelen–T?udos method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2343–2347, 2004     

cis/trans isomerization of unsaturated fatty acids as possible control mechanism of membrane fluidity inPseudomonas putida P8

Exponentially growing cells ofPseudomonas putida had an increased ratio of saturated to unsaturated fatty acids in response to increased growth temperatures. Resting cells in which fatty acid biosynthesis was stopped reacted to a thermal increase by convertingcis-monounsaturated fatty acids totrans isomers.cis/trans isomerization of up to 60% of the unsaturated fatty acids was also activated by alcohols of different chain length. Their effective concentrations apparently depended on the lipophilic character of the alcohols. Also, a salt shock caused by the addition of NaCl resulted in the production oftrans fatty acids. However, cells that were adapted to growth media of high osmolarity synthesized cyclopropane fatty acids instead oftrans fatty acids. Activity ofcis/trans-isomerase was dependent on the growth phase and was significantly higher during logarithmic growth than during the stationary phase. The results of this study agree with the hypothesis that the isomerization ofcis intotrans unsaturated fatty acids is an emergency action of cells ofP. putida to adapt membrane fluidity to drastic changes of environmental conditions.     

Ozone Disinfection Efficiency for Indicator Microorganisms at Different pH Values and Temperatures

Disinfection efficiency of ozone was determined in various types of water at different pH (6, 7 and 8) values and temperatures (15, 25 and 35 ^°C) for E. coli and Salmonella. Three different applied ozone concentrations (1.5, 1.7, and 2 mg/L) in the gas phase were applied, and samples were taken at different time intervals to determine microbial survival using spread plate count (SPC) and ozone residual. Highest microbial inactivation was observed in distilled water with applied ozone concentration of 2 mg/L in the gas phase. Survival of E. coli was higher at pH 8 and 15 ^°C as compared to lower pH values and temperatures as depicted by the inactivation kinetics of the test microbes used in the study. Salmonella showed 5 and 6 log removal after contact time of 45 and 60 sec, respectively, at 2 mg/L. Disinfection of mixed culture showed relatively more survival of E. coli; as 3 and 4 log removal of E. coli and 4 and 5 log removal of Salmonella was observed after 45 and 60 sec.     

Improved modelling of the unsteady‐state behaviour of an immobilized‐cell,fluidized‐bed bioreactor for phenol biodegradation

The dynamic response of an immobilized‐cell, fluidized‐bed reactor (ICFBR) to step changes in phenol loading was investigated at 10°C for a pure culture of Pseudomonas putida Q5, a psychrotrophic bacterium. A novel dynamic model was developed and tested to simulate the response of all four key process variables: the bulk phenol concentration, the suspended biomass concentration, the concentration profile of the substrate in the biofilm and the biofilm thickness. Accurate model predictions required the use of kinetics, determined using cells which were not acclimated to the post‐shock reactor conditions (‘unacclimated’ cells) and the implementation of a specific‐growth‐rate suppression factor to account for the unbalanced growth situations experienced during the transient response periods.     

Characterization of thiosulfate-oxidizing Enterobacter hormaechei JH isolated from barnyard manure

In an effort to discover sulfur-oxidizing microorganisms, a new bacterium was screened from barnyard manure. This strain was identified as Enterobacter hormaechei JH by its morphological, physiological, and biochemical properties, as well as by 16S rRNA gene sequence analysis. E. hormaechei JH are Gram-negative rod, non-spore-forming, and aerobic. The pH range for E. hormaechei JH growth was 2.0–9.0, and the optimal pH was determined as pH 7.0. The optimal temperature for growth was 30°C. We compared the growth of this strain with Thiobacillus delicates KCTC2851, which is a well known thiosulfate oxidizing microorganism. E. hormaechei JH presented greater growth than T. delicates KCTC2851. Thus, the above results indicate this strain is a candidate for improving the removal efficiency of biological deodorizing systems. This work was presented at 13 ^th YABEC symposium held at Seoul, Korea, October 20–22, 2007.     

Optimisation and Evaluation of La0.6Sr0.4CoO3 – δ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

In this work, La_0.6Sr_0.4CoO_{3 – δ}/Ce_{1 – x}Gd_xO_{2 – δ} (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700 °C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (R_p) of 0.11 Ω cm² at 700 °C is obtained for the cathode containing 30 wt.‐% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950 °C; the corresponding R_p of 0.24 Ω cm² at 600 °C and 0.06 Ω cm² at 700 °C are achieved, respectively. An YSZ‐based anode‐supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950 °C. The cell with an active electrode area of 4 × 4 cm² exhibits the maximum power density of 0.42 W cm^–2 at 650 °C and 0.54 W cm^–2 at 700 °C. More than 300 h operating at 650 °C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application.