Removal of Anionic Surfactants from Wastewater Using a Constructed Wetland

Removal of anionic surfactants from municipal wastewater using a constructed wetland with a horizontal subsurface flow was studied in 2007 and 2008. Extraction spectrophotometry with methylene blue served to determine the analyte concentrations in individual samples. The anionic surfactant‐removal efficiency depended on actual conditions, mostly the treated water flow intensity, its temperature, and a redox‐potential gradient in the longitudinal profile of the wetland bed. It increased with decreasing inflow and increasing temperature. The average efficiency was 83.7% in 2007 and 81.7% in 2008; however, values higher than 85% were often determined during the summer period. On the other hand, the efficiencies were usually lower than 80% in winter, especially in periods with intensive precipitation and inflows. The average concentration of anionic surfactants in water taken at the outflow was lower than 0.65 mg/l (expressed as sodium dodecyl sulfate). The most significant fraction of anionic surfactants (almost 50%) was degraded at the beginning (1 m from the inflow zone) of the wetland bed. The rhizosphere aeration via the vegetation roots strongly supported the anionic‐surfactant removal.     

Remediation of PCBs in soil by surfactant washing and biodegradation in the wash by Pseudomonas sp. LB400

Solutions from the washing of polychlorinated biphenyl (PCB)-contaminated soil with a variety of commercial nonionic or anionic surfactants were incubated with Pseudomonas sp. LB400 in an attempt to remediate the soil and destroy the PCBs. Nonionic surfactants washed more PCBs from the soil (up to 89%) but inhibited their biodegradation. Anionic surfactants washed less PCBs from the soil but were more effective in biodegradation tests, removing up to 67% of total PCBs.     

Effectiveness of surfactants in the microbial degradation of oil

Nonionic surfactants increase the rate of selective hydrocarbon utilization by Acinetobacter SL1. Within an homologus series of nonionic surfactants, growth on and utilization of a model oil by Acinetobacter SL1 is dependent upon the surfactant hydrophile‐lipophile balance (HLB). Biological effectiveness of the surfactants apparently is related to the degree of micelle formation by the surfactant in the aqueous phase. A simple algebraic expression describing the response of Acinetobacter SL1 to surfactant concentration gives a measure of the biological effectiveness of an individual surfactant. A cationic and an anionic surfactant inhibited the growth of Acinetobacter SL1 and Pseudomonas SL6 on hydrocarbon substrates. These results are discussed in relation to the selection of suitable detergents for increasing the effective biodegradation of pollutant oil in aquatic habitats.     

ENHANCEMENT OF ETHANOL PRODUCTION BY SIMULTANEOUS SACCHARIFICATION AND FERMENTATION (SSF) OF RICE STRAW USING ETHOXYLATED SPAN 20

In this work, four nonionic surfactants based on sorbitan monolaurate (Span 20) were synthesized by introducing ethylene oxide gas (n = 20, 40, 60, 80 ethylene oxide units) into Span 20 to give four new surfactants with different hydrophilic–lipophilic balance (HLB), namely, E(20), E(40), E(60), and E(80). The structures of the prepared nonionic surfactants were elucidated using Fourier-transform infrared (FT-IR) and ¹H-nuclear magnetic resonance (NMR) spectroscopy. The surface-tension measurements were recorded. The effects of the prepared nonionic surfactants on the simultaneous saccharification and fermentation (SSF) of microwave/alkali-pretreated rice straw to produce ethanol were investigated. From the obtained data, it was found that the addition of the nonionic surfactants at 2.5 g/L had a positive effect on SSF. The maximum ethanol yield (76 and 55%) was obtained after 72 hr for rice straw using Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively. Also, it was found that the ethanol yield increases with increasing HLB of the prepared nonionic surfactants by increasing ethylene oxide units. The adsorption of nonionic surfactants on lignocelluloses is proposed to be due to hydrophobic and hydrogen bonding interactions between nonionic surfactants and the lignin part in the lignocelulose. It can be concluded that additions of surface-active compounds, such as nonionic surfactants, increase enzymatic conversion of rice straw for bioethanol purposes.     

A metal‐chelate affinity reverse micellar system for protein extraction

A new nonionic reverse micellar system is developed by blending two nonionic surfactants, Triton X‐45 and Span 80. At total surfactant concentrations lower than 60 mmol/L and molar fractions of Triton X‐45 less than 0.6, thermodynamically stable reverse micelles of water content (W₀) up to 30 are formed. Di(2‐ethylhexyl) phosphoric acid (HDEHP; 1–2 mmol/L) is introduced into the system for chelating transition metal ions that have binding affinity for histidine‐rich proteins. HDEHP exists in a dimeric form in organic solvents and a dimer associated with one transition metal ion, including copper, zinc, and nickel. The copper‐chelate reverse micelles (Cu‐RM) are characterized for their W₀, hydrodynamic radius (R_h), and aggregation number (N_ag). Similar with reverse micelles of bis‐2‐ethylhexyl sodium sulfosuccinate (AOT), R_h of the Cu‐RM is also linearly related to W₀. However, N_ag is determined to be 30–90 at W₀ of 5–30, only quarter to half of the AOT reverse micelles. Then, selective metal‐chelate extraction of histidine‐rich protein (myoglobin) by the Cu‐RM is successfully performed with pure and mixed protein systems (myoglobin and lysozyme). The solubilized protein can be recovered by stripping with imidazole or ethylinediaminetetraacetic acid (EDTA) solution. Because various transition metal ions can be chelated to the reverse micelles, it is convinced that the system would be useful for application in protein purification as well as simultaneous isolation and refolding of recombinant histidine‐tagged proteins expressed as inclusion bodies. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

In Situ emulsification and mobilization of gasoline range hydrocarbons using surfactants

In this article the conditions that govern surfactant‐enhanced emulsification and mobilization of petroleum hydrocarbons in soil are reviewed. The effect of soil properties, groundwater constituents, and differing surfactant solutions on the emulsification process is discussed. A constant head soil flushing apparatus used to characterize surfactant‐enhanced mobilization of m‐xylene is described. Data showing the effect of surfactant‐enhanced mobilization on m‐xylene removal efficiency in washed sand is presented. Flushing solutions were used at concentrations from below to well above the critical micelle concentration (CMC) of the surfactants used. Removal efficiencies are shown to vary with surfactant concentration and with surfactant type. Flushing solutions of anionic, nonionic, and anionic/nonionic surfactant mixtures were evaluated.     

Influence of nonionic surfactants and hydroxypropyl-β-cyclodextrin on the biodegradation of nitrobenzene

This paper investigates the effect of two nonionic surfactants (Tween 80 and Triton X-100) and hydroxypropyl--cyclodextrin (HP--CD) on the biodegradation of nitrobenzene (NB) by Acinetobacter sp. in liquid cultures at different dosages as well as the fate of both surfactants. When the initial concentration of NB was about 400 mg/l, neither Tween 80 nor HP--CD had any effect on the degradation of NB. However, Triton X-100 retarded the full removal of NB and the bacterial growth entering the stationary phase. While the initial concentration of NB was increased to about 850 mg/l, they all significantly enhanced the extent and rate of biodegradation if they were added at concentrations above 2000 mg/l. HP--CD could not be utilized by Acinetobacter sp. as the sole carbon source whereas both surfactants could, but no surfactant depletion was observed during the biodegradation of NB. So the rapid bacterial growth observed in the presence of each additive should be attributed to the rapid metabolism of NB. Both surfactants would promote the degradation of NB more than HP--CD would do if their dosages were increased properly.     

Biohydrogen production from wheat straw hydrolysate by dark fermentation using extreme thermophilic mixed culture

Hydrolysate was tested as substrate for hydrogen production by extreme thermophilic mixed culture (70°C) in both batch and continuously fed reactors. Hydrogen was produced at hydrolysate concentrations up to 25% (v/v), while no hydrogen was produced at hydrolysate concentration of 30% (v/v), indicating that hydrolysate at high concentrations was inhibiting the hydrogen fermentation process. In addition, the lag phase for hydrogen production was strongly influenced by the hydrolysate concentration, and was prolonged from approximately 11 h at the hydrolysate concentrations below 20% (v/v) to 38 h at the hydrolysate concentration of 25% (v/v). The maximum hydrogen yield as determined in batch assays was 318.4 ± 5.2 mL‐H₂/g‐sugars (14.2 ± 0.2 mmol‐H₂/g‐sugars) at the hydrolysate concentration of 5% (v/v). Continuously fed, and the continuously stirred tank reactor (CSTR), operating at 3 day hydraulic retention time (HRT) and fed with 20% (v/v) hydrolysate could successfully produce hydrogen. The hydrogen yield and production rate were 178.0 ± 10.1 mL‐H₂/g‐sugars (7.9 ± 0.4 mmol H₂/g‐sugars) and 184.0 ± 10.7 mL‐H₂/day L_reactor (8.2 ± 0.5 mmol‐H₂/day L_reactor), respectively, corresponding to 12% of the chemical oxygen demand (COD) from sugars. Additionally, it was found that toxic compounds, furfural and hydroxymethylfurfural (HMF), contained in the hydrolysate were effectively degraded in the CSTR, and their concentrations were reduced from 50 and 28 mg/L, respectively, to undetectable concentrations in the effluent. Phylogenetic analysis of the mixed culture revealed that members involved hydrogen producers in both batch and CSTR reactors were phylogenetically related to the Caldanaerobacter subteraneus, Thermoanaerobacter subteraneus, and Thermoanaerobacterium thermosaccharolyticum. Biotechnol. Bioeng. 2010;105: 899–908. © 2009 Wiley Periodicals, Inc.     

Regioselective hydroxylation of daidzein using P450 (CYP105D7) from Streptomyces avermitilis MA4680

Regiospecific 3′‐hydroxylation reaction of daidzein was performed with CYP105D7 from Streptomyces avermitilis MA4680 expressed in Escherichia coli. The apparent K_m and k_cat values of CYP105D7 for daidzein were 21.83 ± 6.3 µM and 15.01 ± 0.6 min^?1 in the presence of 1 µM of CYP105D7, putidaredoxin (CamB) and putidaredoxin reductase (CamA), respectively. When CYP105D7 was expressed in S. avermitilis MA4680, its cytochrome P450 activity was confirmed by the CO‐difference spectra at 450 nm using the whole cell extract. When the whole‐cell reaction for the 3′‐hydroxylation reaction of daidzein was carried out with 100 µM of daidzein in 100 mM of phosphate buffer (pH 7.5), the recombinant S. avermitilis grown in R2YE media overexpressing CYP105D7 and ferredoxin FdxH (SAV7470) showed a 3.6‐fold higher conversion yield (24%) than the corresponding wild type cell (6.7%). In a 7 L (working volume 3 L) jar fermentor, the recombinants S. avermitilis grown in R2YE media produced 112.5 mg of 7,3′,4′‐trihydroxyisoflavone (i.e., 29.5% conversion yield) from 381 mg of daidzein in 15 h. Biotechnol. Bioeng. 2010. 105: 697–704. © 2009 Wiley Periodicals.     

Effect of detergents on antibody-antigen interaction.

The effect of the different detergent mixtures on immunodiffusion and immunoprecipitation was studied. The anionic detergent sodium dodecyl sulfate at concentrations above 0.2% ($\text{w}\text{v}$) inhibits the reaction between antigen and antibody by more than 90%. Nonionic detergents at a concentration of 1% ($\text{w}\text{v}$) have little or no detectable effect. In contrast, when we used mixtures of various concentrations of ionic and nonionic detergents the inhibitory effect of the ionic detergent decreased.     

Inhibition of Aflatoxin Production by Surfactants

The effect of 12 surfactants on aflatoxin production, growth, and conidial germination by the fungus Aspergillus flavus is reported. Five nonionic surfactants, Triton X-100, Tergitol NP-7, Tergitol NP-10, polyoxyethylene (POE) 10 lauryl ether, and Latron AG-98, reduced aflatoxin production by 96 to 99% at 1% (wt/vol). Colony growth was restricted by the five nonionic surfactants at this concentration. Aflatoxin production was inhibited 31 to 53% by lower concentrations of Triton X-100 (0.001 to 0.0001%) at which colony growth was not affected. Triton X-301, a POE-derived anionic surfactant, had an effect on colony growth and aflatoxin production similar to that of the five POE-derived nonionic surfactants. Sodium dodecyl sulfate (SDS), an anionic surfactant, and dodecyltrimethylammonium bromide, a cationic surfactant, suppressed conidial germination at 1% (wt/vol). SDS had no effect on aflatoxin production or colony growth at 0.001%. The degree of aflatoxin inhibition by a surfactant appears to be a function of the length of the hydrophobic and hydrophilic chains of POE-derived surfactants.     

Comamonas testosteroni Strain TI as a Potential Base for a Microbial Sensor Detecting Surfactants

Strain Comamonas testosteroni TI, capable of degrading the nonionic surfactant (NIS) nonylphenolethoxylate (OP-10), was used for constructing a pilot cellular biosensor. The lower NIS detection limit for the biosensor was 0.25 mg/l. We studied the substrate specificity of the biosensor with respect to a wide range of organic compounds: surfactants, polyaromatic compounds (PAC), carbohydrates, alcohols, etc. It was shown that the biosensor based on Comamonas testosteroni TI did not respond to glucose, which was an advantage over the formerly described biosensor based on Pseudomonas rathonis T. The amplitude of the sensor response remained stable for 10 days.     

Pentachlorophenol degradation by Pseudomonas aeruginosa

Five Pseudomonas species were tested for ability to degrade pentachlorophenol (PCP). Pseudomonas aeruginosa completely degraded PCP up to 800 mg/l in 6 days with glucose as co-substrate. With 1000 mg PCP/l, 53% was degraded. NH₄ ⁺ salts were better at enhancing degradation than organic nitrogen sources and shake-cultures promoted PCP degradation compared with surface cultures. Degradation was maximal at pH 7.6 to 8.0 and at 30 to 37°C. Only PCP induced enzymes that degraded PCP and chloramphenicol inhibited this process. The PCP was degraded to CO₂, with release of Cl^-.The authors are with the Bacteriology Laboratory, Central Leather Research Institute, Madras-600 020, India.     

Human Leptin Stimulates Systemic Nitric Oxide Production in the Rat

Objective: Apart from having an effect on energy balance, leptin is also involved in cardiovascular regulation and in the pathogenesis of obesity‐associated hypertension. We investigated the effect of leptin on nitric oxide (NO) production. Research Methods and Procedures: Wistar rats were placed in metabolic cages, and urine was collected in 2‐hour periods. After the control period, leptin (1 mg/kg intraperitoneal) was administered, and urine collection was continued for up to 6 hours. Blood was obtained 0.5, 1, 2, 4, and 6 hours after hormone injection. Results: Leptin increased plasma concentrations of NO metabolites (nitrates + nitrites, NO_x) by 32.5%, 58.0%, and 29.7% at 1, 2, and 4 hours, respectively. Urinary NO_x excretion increased by 28.8% in the first and by 20.1% in the second 2‐hour period after injection. The plasma concentration of the NO second messenger, cyclic guanosine 3′,5′‐monophosphate (cGMP), increased by 83% and 50.6% at 2 and 4 hours after leptin administration, respectively. Urinary excretion of cyclic GMP increased by 36.1% in the first and by 43.1% in the second 2‐hour period. Leptin had no effect on the plasma concentration of atrial natriuretic peptide (ANP). The effect of leptin on plasma and urinary NO_x was abolished by the NO synthase inhibitor, N^G‐nitro‐l ‐arginine methyl ester (l ‐NAME) (30 mg/kg intraperitoneal) administered 15 minutes before leptin injection. l ‐NAME alone caused a 32.2% increase in systolic blood pressure, but this increase was not observed in rats receiving l ‐NAME and leptin. Discussion: The results indicate that leptin stimulates systemic NO production; leptin prevents blood pressure elevation induced by acute NO blockade, suggesting that leptin also triggers additional hypotensive mechanisms; and ANP is not involved in renal and vascular effects of leptin.     

Immobilization of a thermostable α‐amylase by covalent binding to an alginate matrix increases high temperature usability

Thermostable α‐amylase was covalently bound to calcium alginate matrix to be used for starch hydrolysis at liquefaction temperature of 95°C. 1‐ethyl‐3‐(3‐dimethylamino‐propyl) carbodiimide hydrochloride (EDAC) was used as crosslinker. EDAC reacts with the carboxylate groups on the calcium alginate matrix and the amine groups of the enzyme. Ethylenediamine tetraacetic acid (EDTA) treatment was applied to increase the number of available carboxylate groups on the calcium alginate matrix for EDAC binding. After the immobilization was completed, the beads were treated with 0.1 M calcium chloride solution to reinstate the bead mechanical strength. Enzyme loading efficiency, activity, and reusability of the immobilized α‐amylase were investigated. Covalently bound thermostable α‐amylase to calcium alginate produced a total of 53 g of starch degradation/mg of bound protein after seven consecutive starch hydrolysis cycles of 10 min each at 95°C in a stirred batch reactor. The free and covalently bound α‐amylase had maximum activity at pH 5.5 and 6.0, respectively. The Michaelis‐Menten constant (K_m) of the immobilized enzyme (0.98 mg/mL) was 2.5 times greater than that of the free enzyme (0.40 mg/mL). The maximum reaction rate (V_max) of immobilized and free enzyme were determined to be 10.4‐mg starch degraded/mL min mg bound protein and 25.7‐mg starch degraded/mL min mg protein, respectively. The high cumulative activity and seven successive reuses obtained at liquefaction temperature make the covalently bound thermostable α‐amylase to calcium alginate matrix, a promising candidate for use in industrial starch hydrolysis process. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Degradation of polycyclic aromatic hydrocarbons in the presence of synthetic surfactants.

The biodegradation of polycyclic aromatic hydrocarbons (PAH) often is limited by low water solubility and dissolution rate. Nonionic surfactants and sodium dodecyl sulfate increased the concentration of PAH in the water phase because of solubilization. The degradation of PAH was inhibited by sodium dodecyl sulfate because this surfactant was preferred as a growth substrate. Growth of mixed cultures with phenanthrene and fluoranthene solubilized by a nonionic surfactant prior to inoculation was exponential, indicating a high bioavailability of the solubilized hydrocarbons. Nonionic surfactants of the alkylethoxylate type and the alkylphenolethoxylate type with an average ethoxylate chain length of 9 to 12 monomers were toxic to a PAH-degrading Mycobacterium sp. and to several PAH-degrading mixed cultures. Toxicity of the surfactants decreased with increasing hydrophilicity, i.e., with increasing ethoxylate chain length. Nontoxic surfactants enhanced the degradation of fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.     

Mixed reverse micelles facilitated downstream processing of lipase involving water‐oil‐water liquid emulsion membrane

Our earlier work for the first time demonstrated that liquid emulsion membrane (LEM) containing reverse micelles could be successfully used for the downstream processing of lipase from Aspergillus niger. In the present work, we have attempted to increase the extraction and purification fold of lipase by using mixed reverse micelles (MRM) consisting of cationic and nonionic surfactants in LEM. It was basically prepared by addition of the internal aqueous phase solution to the organic phase followed by the redispersion of the emulsion in the feed phase containing enzyme, which resulted in globules of water‐oil‐water (WOW) emulsion for the extraction of lipase. The optimum conditions for maximum lipase recovery (100%) and purification fold (17.0‐fold) were CTAB concentration 0.075 M, Tween 80 concentration 0.012 M, at stirring speed of 500 rpm, contact time 15 min, internal aqueous phase pH 7, feed pH 9, KCl concentration 1 M, NaCl concentration 0.1 M, and ratio of membrane emulsion to feed volume 1:1. Incorporation of the nonionic surfactant (e.g., Tween 80) resulted in remarkable improvement in the purification fold (3.1–17.0) of the lipase. LEM containing a mixture of nonionic and cationic surfactants can be successfully used for the enhancement in the activity recovery and purification fold during downstream processing of enzymes/proteins. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1084–1092, 2014     

Role of surfactant on the proteolysis of aqueous bovine serum albumin

Nonionic and ionic surfactants diminish the initial rate of proteolysis of aqueous bovine serum albumin (BSA) by subtilisin Carlsberg. Surfactants studied include: nonionic tetraethylene glycol monododecyl ether (C12E4); anionic sodium dodecyl sulfate (SDS), anionic sodium dodecylbenzenesulfonate (SDBS), and cationic dodecyltrimethylamonium bromide (DTAB). Kinetic data are obtained using fluorescence emission. Special attention is given to enzyme kinetic specificity determined by fitting initial-rate data to the Michaelis-Menten model. All surfactants reduce the rate of proteolysis, most strongly at concentrations near and above the critical micelle concentration (CMC). Circular dichroism (CD), tryptophan/tyrosine fluorescence spectra, and tryptophan fluorescence thermograms indicate that BSA partially unfolds at ionic surfactant concentrations near and above the CMC. Changes in BSA conformation are less apparent at ionic surfactant concentrations below the CMC and for the nonionic surfactant C12E4. Subtilisin Carlsberg activity against the polypeptide, succinyl-Ala-Ala-Pro-Phe-p-nitroanilide, decreased due to enzyme-surfactant interaction. At the concentrations and time frames studied, there was no enzyme autolysis. Importantly, aqueous proteolysis rates are significantly reduced at high surfactant concentrations where protein-micellar-surfactant aggregates occur. To explain the negative effect of surfactant on subtilisin Carlsberg proteolytic activity against BSA, we propose that micelle/protein complexes hinder enzyme access.     

Effect of surfactants on separate hydrolysis fermentation and simultaneous saccharification fermentation of pretreated lodgepole pine

The effects of surfactants addition on enzymatic hydrolysis and subsequent fermentation of steam exploded lodgepole pine (SELP) and ethanol pretreated lodgepole pine (EPLP) were investigated in this study. Supplementing Tween 80 during cellulase hydrolysis of SELP resulted in a 32% increase in the cellulose‐to‐glucose yield. However, little improvement was obtained from hydrolyzing EPLP in the presence of the same amount of surfactant. The positive effect of surfactants on SELP hydrolysis led to an increase in final ethanol yield after the fermentation. It was found that the addition of surfactant led to a substantial increase in the amount of free enzymes in the 48 h hydrolysates derived from both substrates. The effect of surfactant addition on final ethanol yield of simultaneous saccharification and fermentation (SSF) was also investigated by using SELP in the presence of additional furfural and hydroxymethylfurfural (HMF). The results showed that the surfactants slightly increased the conversion rates of furfural and HMF during SSF process by Saccharomyces cerevisiae. The presence of furfural and HMF at the experimental concentrations did not affect the final ethanol concentration either. The strategy of applying surfactants in cellulase recycling to reduce enzyme cost is presented. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

New Methoxyflavone from Casimiroa sapota and the Biological Activities of Its Leaves Extract against Lead Acetate Induced Hepatotoxicity in Rats

Flavonoids are agents with strong antioxidant properties and ameliorate many diseases associated with oxidative stress. Leaves of Casimiroa sapota were investigated for components and antioxidant/anti‐inflammatory activities against lead acetate ((AcO)₂Pb) induced hepatotoxicity in rats. Three groups of male albino rats were administrated orally with vehicle or C. sapota (100 and 200 mg/kg b.w/day) for 28 days; other group was injected with sub‐acute dose (100 mg/kg b.w/day) of (AcO)₂Pb. Three protective groups were injected with (AcO)₂Pb (100 mg/kg b.w/day) for 7 days at day 22 after treatment with either C. sapota (100 or 200 mg/kg b.w/day) or silymarin (SILY) for 28 days. We isolated and identified, from C. sapota, a new compound for the 1st time in nature; 5,6,2′,3′‐tetramethoxyflavone in addition to the rare compound 5,6,3′‐trimethoxyflavone (second report of isolation from nature) and the known compound 5,6,2′,3′,4′‐pentamethoxyflavone. There is an improvement in all hemato‐biochemical parameters, antioxidant defense system and anti‐inflammatory cytokines of protective groups, which received C. sapota in dose dependent manner. The percentage of changes in all parameters measured in (AcO)₂Pb groups that received vehicle, CS100, CS200 or SILY were 109.2, 37.3, 12.5%, and 1.2% compared with the healthy control group. The C. sapota groups confer a better antioxidant activity by preventing oxidative stress and inflammation in (AcO)₂Pb treated rats. The compounds isolated are responsible at least in part for the observed protective effects.