Showing papers in "Journal of Chemical Technology & Biotechnology in 2009"

Biosorption: critical review of scientific rationale, environmental importance and significance for pollution treatment

Abstract: Biosorption may be simply defined as the removal of substances from solution by biological material. Such substances can be organic and inorganic, and in gaseous, soluble or insoluble forms. Biosorption is a physico-chemical process and includes such mechanisms as absorption, adsorption, ion exchange, surface complexation and precipitation. Biosorption is a property of both living and dead organisms (and their components) and has been heralded as a promising biotechnology for pollutant removal from solution, and/or pollutant recovery, for a number of years, because of its efficiency, simplicity, analogous operation to conventional ion exchange technology, and availability of biomass. Most biosorption studies have carried out on microbial systems, chiefly bacteria, microalgae and fungi, and with toxic metals and radionuclides, including actinides like uranium and thorium. However, practically all biological material has an affinity for metal species and a considerable amount of other research exists with macroalgae (seaweeds) as well as plant and animal biomass, waste organic sludges, and many other wastes or derived bio-products. While most biosorption research concerns metals and related substances, including radionuclides, the term is now applied to particulates and all manner of organic substances as well. However, despite continuing dramatic increases in published research on biosorption, there has been little or no exploitation in an industrial context. This article critically reviews aspects of biosorption research regarding the benefits, disadvantages, and future potential of biosorption as an industrial process, the rationale, scope and scientific value of biosorption research, and the significance of biosorption in other waste treatment processes and in the environment. Copyright © 2008 Society of Chemical Industry

Plant-mediated synthesis of silver and gold nanoparticles and their applications

Abstract: Nanobiotechnology deals with the synthesis of nanostructures using living organisms. Among the use of living organisms for nanoparticle synthesis, plants have found application particularly in metal nanoparticle synthesis. Use of plants for synthesis of nanoparticles could be advantageous over other environmentally benign biological processes as this eliminates the elaborate process of maintaining cell cultures. Biosynthetic processes for nanoparticles would be more useful if nanoparticles were produced extracellularly using plants or their extracts and in a controlled manner according to their size, dispersity and shape. Plant use can also be suitably scaled up for large-scale synthesis of nanoparticles. In view of this, we have reviewed here the use of plants or their extracts in the synthesis of silver and gold nanoparticles for various human applications. Copyright © 2008 Society of Chemical Industry

Microalgal biomass as a fermentation feedstock for bioethanol production

Abstract: BACKGROUND: The increasing cost of fossil fuels as well as the escalating social and industrial awareness of the environmental impacts associated with the use of fossil fuels has created the need for more sustainable fuel options. Bioethanol, produced from renewable biomass such as sugar and starch materials, is believed to be one of these options, and it is currently being harnessed extensively. However, the utilization of sugar and starch materials as feedstocks for bioethanol production creates a major competition with the food market in terms of land for cultivation, and this makes bioethanol from these sources economically less attractive. RESULT: This study explores the suitability of microalgae (Chlorococum sp.) as a substrate for bioethanol production via yeast (Saccharomyces bayanus) under different fermentation conditions. Results show a maximum ethanol concentration of 3.83 g L−1 obtained from 10 g L−1 of lipid-extracted microalgae debris. CONCLUSION: This productivity level (∼38% w/w), which is in keeping with that of current production systems endorses microalgae as a promising substrate for bioethanol production. Copyright © 2009 Society of Chemical Industry

Contributions of electrochemical oxidation to waste-water treatment: fundamentals and review of applications

Abstract: OVERVIEW: This paper provides an overview of some fundamental aspects of electrochemical oxidation and gives updated information on the application of this technology to waste-water treatment. In recent years, electrochemical oxidation has gained increasing interest due to its outstanding technical characteristics for eliminating a wide variety of pollutants normally present in waste-waters such as refractory organic matter, nitrogen species and microorganisms. IMPACT: The strict disposal limits and health quality standards set by legislation may be met by applying electrochemical oxidation. However, treatment costs have to be cut down before full-scale application of this technology. Deployment of electrochemical oxidation in combination with other technologies and the use of renewable sources to power this process are two steps in this direction. APPLICATIONS: Effluents from landfill and a wide diversity of industrial effluents including the agro-industry, chemical, textile, tannery and food industry, have been effectively treated by this technology. Its high efficiency together with its disinfection capabilities makes electro-oxidation a suitable technology for water reuse programs. Copyright © 2009 Society of Chemical Industry

Dewatering of microalgal culture for biodiesel production: exploring polymer flocculation and tangential flow filtration

Abstract: Background: Conventional biodiesel production relies on trans-esterification of lipids extracted from vegetable crops. However, the use of valuable vegetable food stocks as raw material for biodiesel production makes it an unfeasibly expensive process. Used cooking oil is a finite resource and requires extra downstream processing, which affects the amount of biodiesel that can be produced and the economics of the process. Lipids extracted from microalgae are considered an alternative raw material for biodiesel production. This is primarily due to the fast growth rate of these species in a simple aquaculture environment. However, the dilute nature of microalgae culture puts a huge economic burden on the dewatering process especially on an industrial scale. This current study explores the performance and economic viability of chemical flocculation and tangential flow filtration (TFF) for the dewatering of Tetraselmis suecicamicroalgae culture. Results: Results show that TFF concentrates the microalgae feedstock up to 148 times by consuming 2.06 kWh m-3 of energy while flocculation consumes 14.81 kWhm-3 to concentrate the microalgae up to 357 times. Economic evaluation demonstrates that even though TFF has higher initial capital investment than polymer flocculation, the payback period for TFF at the upper extreme ofmicroalgae revenue is ∼1.5 years while that of flocculation is ∼3 years. Conclusion: These results illustrate that improved dewatering levels can be achieved more economically by employing TFF. The performances of these two techniques are also compared with other dewatering techniques.

Bioprocesses for air pollution control

Abstract: Bioprocesses have been developed as relatively recent alternatives to conventional, non-biological technologies, for waste gas treatment and air pollution control in general. This paper reviews major biodegradation processes relevant in this field as well as both accepted and major innovative bioreactor configurations studied or used nowadays for the treatment of polluted air, i.e. biofilters, one- and two-liquid phase biotrickling filters, bioscrubbers, membrane bioreactors, rotating biodiscs and biodrums, one- and two-liquid phase suspended growth bioreactors, as well as hybrid reactor configurations. Some of these bioreactors are being used at full-scale for solving air pollution problems, while others are still at the research and development stage at laboratory- or pilot-scale.

Biodiesel production from Jerusalem artichoke (Helianthus Tuberosus L.) tuber by heterotrophic microalgae Chlorella protothecoides

Abstract: BACKGROUND: As a potential source of biomass, Jerusalem artichoke has been studied for bioethanol production; however, thus far it has not been investigated for the production of other liquid biofuels, such as biodiesel. This work aims to develop a novel approach for biodiesel production from Jerusalem artichoke tuber using heterotrophic microalgae. RESULTS: In this study, Chlorella protothecoides utilized hydrolysate of Jerusalem artichoke tuber as carbon source and accumulated lipid in vivo, with lipid content as high as 44% by dry mass, and a carbon source to lipid conversion ratio of about 25% in a 4-day scale cultivation. The lipids were extracted and then converted into biodiesel by transesterification. Cetane acid methyl ester, linoleic acid methyl ester and oleic acid methyl ester were the dominating components of the biodiesel produced. Unsaturated fatty acids methyl ester constituted over 82% of the total biodiesel content. CONCLUSION: This work suggests the feasibility of an alternative method of producing biodiesel from Jerusalem artichoke tuber using microalgae cultivation, and a cost reduction of carbon source feed in algal oil production can be expected. Copyright © 2009 Society of Chemical Industry

Valorisation of agro-industrial by-products, effluents and waste: concept, opportunities and the case of olive mill wastewaters

Abstract: Valorisation is a relatively new concept in the field of industrial residues management promoting the principle of sustainable development. One of the valorisation objectives regarding food processing by-products, waste and effluents is the recovery of fine chemicals and the production of precious metabolites via chemical and biotechnological processes. This paper identifies and discusses certain directions that seem to advance valorisation, as well as existing limitations that need to be overcome in the food processing sector. A valorisation strategy is exemplified for the wastewaters arising from the olive oil extraction process; the recovery of antioxidants by chemical methods and the fermentative production of enzymes of commercial interest have been reviewed. Copyright © 2009 Society of Chemical Industry

Exploiting olive oil mill effluents as a renewable resource for production of biodegradable polymers through a combined anaerobic-aerobic process

Abstract: BACKGROUND: The performance of a three-stage process for polyhydroxyalkanoate (PHA) bioproduction from olive oil mill effluents (OME) has been investigated. In the first anaerobic stage OME were fermented in a packed bed biofilm reactor into volatile fatty acids (VFAs). This VFA-rich effluent was fed to the second stage, operated in an aerobic sequencing batch reactor (SBR), to enrich mixed cultures able to store PHAs. Finally, the storage response of the selected consortia was exploited in the third aerobic stage, operated in batch conditions. RESULTS: The anaerobic stage increased the VFA percentage in the OME from 18% to ∼32% of the overall chemical oxygen demand (COD). A biomass with high storage response was successfully enriched in the SBR fed with the fermented OME at an organic load rate of 8.5 gCOD L−1 d−1, with maximum storage rate and yield (146 mgCOD gCOD−1 h−1 and 0.36 COD COD−1, respectively) very similar to those obtained with a synthetic VFA mixture. By means of denaturing gradient gel electrophoresis (DGGE) analysis, different bacterial strains were identified during the two SBR runs: Lampropedia hyalina and Candidatus Meganema perideroedes, with the synthetic feed or the fermented OMEs, respectively. In the third stage, operated at increasing loads, the maximum concentration of the PHA produced increased linearly with the substrate fed. Moreover, about half of the stored PHAs were produced from substrates other than VFAs, mostly alcohols. CONCLUSION: The results obtained indicate that the process is effective for simultaneous treatment of OME and their valorization as a renewable resource for PHA production. Copyright © 2009 Society of Chemical Industry

Defluoridation performance and mechanism of nano‐scale aluminum oxide hydroxide in aqueous solution

Abstract: BACKGROUND: The present study has concentrated on investigating the fluoride removal potential of nano-scale aluminum oxide hydroxide (nano-AlOOH). A series of batch adsorption experiments were carried out to assess parameters that influence the adsorption process. The different parameters investigated include the effect of contact time, initial fluoride concentration, adsorbent dose, pH of the solution and co-existing anions. RESULTS: Most of the adsorption took place during the first 30 min and kinetic and equilibrium adsorption data show that the process obeys a pseudo-second-order kinetic equation and the Langmuir adsorption model. The fluoride removal efficiency is greater than 90% between pH 6 and 8 and decreases as pH values increase to 11. The presence of SO42− or PO43− in aqueous solution was found to reduce the fluoride uptake. Desorption studies showed that the fluoride can easily be desorbed at pH 13. CONCLUSION: Nano-AlOOH possesses a maximum fluoride capacity of 3259 mg F− kg−1, which is comparable with that of activated alumina. Maximum adsorption occurred at around pH 7, which makes nano-AlOOH a potential adsorbent for drinking water treatment. Copyright © 2009 Society of Chemical Industry

Cleaner water using bimetallic nanoparticle catalysts

Abstract: Groundwater contaminated by hazardous chlorinated compounds, especially chlorinated ethenes, continues to be a significant environmental problem in industrialized nations. The conventional treatment methods of activated carbon adsorption and air-stripping successfully remove these compounds by way of transferring them from the water phase into the solid or gas phase. Catalysis is a promising approach to remove chlorinated compounds completely from the environment, by converting them into safer, non-chlorinated compounds. Palladium-based materials have been shown to be very effective as hydrodechlorination catalysts for the removal of chlorinated ethenes and other related compounds. However, relatively low catalytic activity and a propensity for deactivation are significant issues that prevent their widespread use in groundwater remediation. Palladiumon-gold bimetallic nanoparticles, in contrast, were recently discovered to exhibit superior catalyst activity and improved deactivation resistance. This new type of material is a significant next-step in the development of a viable hydrodechlorination catalysis technology. c � 2008 Society of Chemical Industry

Simultaneous removal of sulfide and organics with vanadium(V) reduction in microbial fuel cells

Abstract: BACKGROUND: Sulfide-containing wastewater (also containing organics) and vanadium(V)-containing wastewater exist widely and can be treated in microbial fuel cells (MFCs) based on their chemical conditions. A novel process has been investigated using MFC technologies by employing sulfide, organics and V(V) as electron donors and acceptor, respectively. RESULTS: Electrons produced by oxidation of sulfide and organics in the anode compartment were transferred to the anode surface, then flowed to the cathode through an external circuit, where they were consumed to reduce V(V). Sulfide and total organics removal approached 84.7 ± 2.8% and 20.7 ± 2.1%, with a V(V) reduction rate of 25.3 ± 1.1%. The maximum power output obtained was 572.4 ± 18.2 mW m−2. The effects of the microbes on electricity generation as well as the products of sulfide oxidation and V(V) reduction were also evaluated and analyzed. CONCLUSION: This process achieves both sulfide and V(V) removal with electricity generation simultaneously, providing an economical route for treating these kinds of wastewaters. Copyright © 2009 Society of Chemical Industry

Techniques for oxygen transfer measurement in bioreactors: a review

Abstract: Oxygen is the most essential requirement for aerobic bioprocesses. The microbial growth in a bioreactor depends upon the oxygen transfer rate (OTR). The OTR is widely used to study the growth behavior of microbial and plant cell cultures. The mass transfercoefficient(kLa)determinesthemagnitudeoftheOTR.Therearemanytechniquesformeasuringoxygenconcentration andOTRinbioreactors.Zirconia,electrochemical,infrared,ultrasonicandlasercellsareusedtomeasureoxygenconcentration in the liquid medium. Optical sensors are better alternatives to measure oxygen concentration in small bioreactors. Sulfite oxidation and gassing-out methods with a Clark-type electrode have been used for OTR measurements in bioreactors. Many new novel techniques have evolved recently for intermittent and continuous online measurement of OTR/kLa in various types ofbioreactors.Thepresentpapergivesanoverviewofvariousmeasurementtechniquesandtheirlimitationsand/orsuitability for measurementof OTR/kLa in various kinds of bioreactors, especially small bioreactors. c � 2009 Society of Chemical Industry

Biostimulation strategies for fresh and chronically polluted marine environments with petroleum hydrocarbons

Abstract: Stimulation of indigenous degraders with suitable nutrients can significantly enhance bioremediation rates of marine environments polluted with petroleum hydrocarbons. Biostimulation is emerging as the best strategy for combating oil spills following first response actions. This mini review is focused on the conditions under which biostimulation leads to increased effectiveness and strategies for successful biostimulation to fresh and chronically polluted sites are suggested. c � 2009 Society of Chemical Industry

Separation and recovery of cellulose and lignin using ionic liquids: a process for recovery from paper‐based waste

Abstract: BACKGROUND: The production of paper makes use of cellulose and lignin as a raw material, and almost all cellulose and lignin production comes from raw wood materials, contributing to deforestation and resulting in potential environmental harm. It is therefore beneficial to develop technologies for cellulose and lignin recovery for re-use and sustainability of resources. RESULTS: Three imidazolium based ionic liquids (ILs), 1-(2-cyanoethyl)-3-methylimidazolium bromide (cyanoMIMBr), 1-propyl-3-methylimidazolium bromide (propylMIMBr) and 1-butyl-3-methylimidazolium chloride (butylMIMCl), were synthesised by microwave technology and fully characterised by mass spectrometry, thermogravimetric differential scanning calorimetry, thin layer chromatography, nuclear magnetic resonance and Fourier transform infrared spectroscopies. Cellulose and lignin were soluble in all three ILs with solubility being greatest in cyanoMIMBr. Regeneration of cellulose and lignin was achieved from saturated solutions of cellulose in IL and lignin in IL for all three ILs. The ILs propylMIMBr and butylMIMBr have been used for the first time in the separation and recovery of cellulose and lignin and regeneration of the IL from a mixture of cellulose and lignin in IL. FTIR analysis confirms successful recovery. CONCLUSIONS: This work demonstrates the ability of ILs to separate and recover cellulose and lignin from a mixed system. Copyright © 2009 Society of Chemical Industry

Supercritical CO2 extraction of pigment components with pharmaceutical importance from Chlorella vulgaris

Abstract: BACKGROUND: Chlorella vulgaris is a green microalgae that contains various pigment components of carotenoids and chlorophylls. Supercritical CO2 is widely used for extraction of pharmaceutical compounds because it is non-oxic and easily separated from extracted material by simply depressurizing. In this work, pharmaceutical compounds from Chlorella vulgaris have been extracted using supercritical CO2 with or without entrainerat various extraction conditions. RESULTS: Based on high performance liquid chromatography (HPLC) analysis, the extracts contained pigment components, such as lutein, β-carotene, chlorophyll a andb. Higher extraction pressure and temperature promoted higher lutein extraction by supercritical CO2. The optimum pressure and temperature for extraction were obtained as 50 MPa and 80 ◦ C. Ethanol as an entrainer was more effective than acetone for the extraction of pigment components. Pigment components in the extract obtainedbysupercriticalCO2 withandwithoutentrainerwerecomparedwiththeextractobtainedbyaconventionalextraction method. CONCLUSION:SupercriticalCO2 hasbeensuccessfullyappliedfortheextractionofpigmentcomponentsfromChlorellavulgaris. Supercritical CO2 enabled high selectivity for lutein extraction; however, the lutein yield was lower than that obtained by extraction using supercritical CO2 with ethanol and soxhlet. c � 2008 Society of Chemical Industry

Production of α-amylase under solid-state fermentation utilizing coffee waste.

Abstract: Coffee industry substrates such as coffee pulp, coffee cherry husk, silver skin, spent coffee and mixtures of these coffee wastes (MC) were evaluated for their efficacy as sole carbon source for the synthesis of α-amylase in solid-state fermentation (SSF) using a fungal strain of Neurospora crassa CFR 308. For SSF with coffee pulp and with MC, α-amylase activity of 3908 U g ―1 ds (units per gram of dry substrate) and 3870 U g ―1 ds, respectively, was observed. Parameters such as moisture (60%), pH (4.6), temperature (28 °C), particle size (1.0 mm), inoculum size (10 7 spores g ―1 ds), and fermentation time (5 days) were optimized for enzyme synthesis, wherein 4981 and 4324 U g ―1 U g ―1 ds of α-amylase activity was obtained in SSF with coffee pulp and MC, respectively. The enzyme production was further improved when the substrates were subjected to pre-treatment by steaming. Accordingly, maximum α-amylase activity of 7084 U g ―1 ds and 6342 U g ―1 ds was obtained with steam-pretreated coffee pulp and MC, respectively, demonstrating them to be excellent sole carbon sources for synthesis of α-amylase production. © 2009 Society of Chemical Industry.

Improvements in the production of bacterial synthesized biocellulose nanofibres using different culture methods

Abstract: This review summarizes previous work that was done to improve the production of bacterial cellulose nanofibres. Production of biocellulose nanofibres is a subject of interest owing to the wide range of unique properties that makes this product an attractive material for many applications. Bacterial cellulose is a natural nanomaterial that has a native dimension of less than 50 nm in diameter. It is produced in the form of nanofibres, yielding a very pure cellulose product with unique physical properties that distinguish it from plant-derived cellulose. Its high surface-to-volume ratio combined with its unique properties such as poly-functionality, hydrophilicity and biocompatibility makes it a potential material for applications in the biomedical field. The purpose of this review is to summarize the methods that might help in delivering microbial cellulose to the market at a competitive cost. Different feedstocks in addition to different bioreactor systems that have been previously used are reviewed. The main challenge that exists is the low yield of the cellulosic nanofibres, which can be produced in static and agitated cultures. The static culture method has been used for many years. However, the production cost of this nanomaterial in bioreactor systems is less expensive than the static culture method. Biosynthesis in bioreactors will also be less labour intensive when scaled up. This would improve developing intermediate fermentation scale-up so that the conversion to an efficient large-scale fermentation technology will be an easy task. Copyright © 2009 Society of Chemical Industry

Production of fuel ethanol from softwood by simultaneous saccharification and fermentation at high dry matter content.

Abstract: BACKGROUND: The production of bio-ethanol from softwood is considered a promising alternative to fossil fuels in Sweden. In order to make fuel ethanol economically competitive with fossil fuels, it is important to reduce the production cost, which can be done by increasing the dry matter content of the fermentation medium, thus reducing the energy demand in the final distillation of the fermentation broth. Running simultaneous saccharification and fermentation l at higher dry matter content has, however, been found to decrease the ethanol yield. RESULTS: The use of different stirrer types and stirring speeds in the present study has shown to have an influence on the final ethanol yield in SSF with 10% water-insoluble solids (WIS). Also, higher concentration of pretreatment hydrolysate, i.e., with increased inhibitor concentration, at the same WIS resulted in a decreased ethanol yield. However, despite stirring problems and high inhibitor concentration, ethanol was produced at 12% WIS with an ethanol yield in the SSF step of 81% of the theoretical based on the content of fermentable sugars in the fermentor. CONCLUSION: The decrease in ethanol yield in SSF at high dry matter content has been shown to be a combined effect of increased mass transfer resistance and increased inhibitor concentration in the fermentation broth. (c) 2008 Society of Chemical Industry (Less)

Optimization of alkaline transesterification of rice bran oil for biodiesel production using response surface methodology.

Abstract: BACKGROUND: Response surface methodology (RSM), based on central composite rotatable design (CCRD), was used to optimize four transesterification reaction variables: methanol-to-oil molar ratio (3:1–12:1), catalyst (NaOCH3) concentration (0.5–1.25 wt% in relation to oil mass), reaction temperature (45–65 °C) and reaction time (30–90 min) at two levels (24 experimental design) to produce rice bran oil methyl esters (RBOME). RESULTS: The molar ratio of methanol to oil and reaction temperatures were the most significant (P < 0.01) factors affecting the yield of RBOME. A linear relationship was found between the observed and predicted values (R2 = 0.9520). Using multiple regression analysis a quadratic polynomial equation was established for methyl ester yield. The quadratic term of catalyst concentration showed a significant (P < 0.01) effect on esters yield. The interaction terms of methanol to oil molar ratio and catalyst concentration with reaction time exhibited a positive effect on the methyl esters yield (P < 0.05). The optimum reaction conditions for transesterification of rice bran oil were 7.5:1 methanol-to-oil ratio, 0.88% catalyst concentration, 55 °C reaction temperature and 60 min reaction time, resulting in a RBOME yield of 83.3%. Gas chromatographic analysis of RBOME produced in the present experiment revealed linoleic, oleic, palmitic and stearic acids to be the major fatty acid methyl esters (FAMEs). CONCLUSION: RSM was found to be a suitable technique for optimizing transesterification of rice bran oil. Fuel properties of RBOME as measured according to accepted methods were found to satisfy almost all prescribed ASTM (D 6751) and EN 14214 specifications. Copyright © 2009 Society of Chemical Industry

Review: Microscale methods for high-throughput chromatography development in the pharmaceutical industry

Abstract: Demands within the pharmaceutical sector to cut costs and improve process efficiencies have grown considerably in recent years. Major challenges exist for companies trying to establish financially viable and robust manufacturing processes for increasingly complex therapeutics. These issues have driven the investigation of miniaturised process-design techniques by which to identify suitable operating conditions using small volumes of feed material typical of that available in the early stages of bioprocess development. Such techniques are especially valuable for the optimisation of chromatographic separations, which often represent a significant percentage of manufacturing costs and hence for which there is a pressing need to determine the best operating policies. Several methods employing microlitre volumes of sample and resin have been explored recently, which are aimed at the high-throughput and cost-effective exploration of the design space for chromatographic separations. This methodology paper reviews these microscale approaches and describes how they work, gives examples of their application, discusses their advantages and disadvantages and provides a comparative assessment of the different methods, along with a summary of the challenges that remain to be overcome in relation to these techniques. Copyright © 2009 Society of Chemical Industry

Genome‐scale modeling of Synechocystis sp. PCC 6803 and prediction of pathway insertion

Abstract: BACKGROUND: Cyanobacterium Synechocystis sp. PCC 6803 has been used widely as a model system for the study of photosynthetic organisms and higher plants. The aim of this work was to integrate the genomic information, biochemistry and physiological information available for Synechocystis sp. PCC 6803 to reconstruct a metabolic network for system biology investigations. RESULTS: A genome-scale Synechocystis sp. PCC 6803 metabolic network, including 633 genes, 704 metabolites and 831 metabolic reactions, was reconstructed for the study of optimal Synechocystis growth, network capacity and functions. Heterotrophic, photoautotrophic and mixotrophic growth conditions were simulated. The Synechocystis model was used for in silico predictions for the insertion of ethanol fermentation pathway, which is a novel approach for bioenergy and biofuels production developed in the authors' laboratory. Simulations of Synechocystis cell growth and ethanol production were compared with actual metabolic measurements which showed a satisfactory agreement. CONCLUSION: The Synechocystis metabolic network developed in this study is the first genome-scale mathematical model for photosynthetic organisms. The model may be used not only in global understanding of cellular metabolism and photosynthesis, but also in designing metabolic engineering strategies for desirable bio-products. Copyright © 2008 Society of Chemical Industry

Degradation of C.I. Acid Red 88 aqueous solution by combination of Fenton's reagent and ultrasound irradiation

Abstract: BACKGROUND: Pollution caused by industrial wastewater has become a common problem for many countries. In particular, dye pollutions from industrial effluents disturb human health and ecological equilibrium. The discharge of highly colored synthetic dye effluents is aesthetically displeasing and can damage the receiving water body by impeding penetration of light. Azo dyes can be reduced to more hazardous intermediates on anaerobic conditions. Therefore, an effective and economic treatment of effluents containing a diversity of textile dyes has become a necessity for clean production technology for textile industries. Herein we wish to report the degradation of Acid Red 88 by the combination of Fenton's reagent and ultrasound irradiation. RESULTS: The results show that the combination of ultrasonic irradiation and Fenton's reagent is effective for the degradation of Acid Red 88 aqueous solution. Furthermore, it can achieve better results than either Fenton's reagent or ultrasound alone. The optimum conditions for the degradation of Acid Red 88 aqueous solution were 1.96 mmol L−1 H2O2, 0.108 mmol L−1 Fe2+, pH 3.0, and ultrasonic irradiation frequency of 40 kHz. A degradation efficiency of 98.6% was achieved within 135 min. CONCLUSION: We have provided an efficient and convenient procedure for the degradation of Acid Red 88 aqueous solution. In the present procedure, the azo linkage of Acid Red 88 is broken and some carbonyl compounds are formed, but the complete mineralization of dye cannot be achieved. Copyright © 2008 Society of Chemical Industry

Comparison of soybean peroxidase with laccase in the removal of phenol from synthetic and refinery wastewater samples

Abstract: BACKGROUND: Several studies have demonstrated the feasibility of treating aqueous phenols and aromatic amines with oxidoreductases in synthetic wastewater samples. However, little work has been done on the effectiveness of enzymatic treatment on real wastewater. Here a comparison was made of the oxidative coupling of phenol catalyzed by laccase or soybean peroxidase (SBP) using synthetic and refinery wastewaters. RESULTS: Optimization of pH, enzyme concentration, effect of polyethylene glycol (PEG) addition, and reducing anions were examined for a 3 h reaction time. Laccase had an optimum pH of 5.6–6.0, while SBP had a broad optimum from 6.0 to 8.0. In synthetic samples in tap water to achieve ≥ 95% removal of 1.0 mmol L−1 phenol in 3 h required 0.12 and 1.5 U mL−1 of catalytic activity of laccase and SBP, respectively. In refinery samples comparable removals required 1.2- to 1.8-fold more enzyme than in synthetic tap water samples. Added PEG allowed for a small reduction in the SBP concentration for synthetic wastewater but was ineffective with either enzyme in treating refinery samples. Reducing ions increased the demand for oxidant but, with the exception of cyanide, phenol removal still occurred. CONCLUSION: Both laccase and SBP were effective in removing phenol from aqueous refinery samples, albeit at slightly higher concentrations than required for the corresponding synthetic samples. Copyright © 2008 Society of Chemical Industry

An overview of the mathematical modelling of liquid membrane separation processes in hollow fibre contactors

Abstract: Liquid membranes have traditionally been employed for liquid/liquid mass transfer and have found applications in industrial, biomedical and analytical fields as well as in hydrometallurgical processes, wastewater treatment and remediation of polluted groundwater. However, in spite of the known advantages of liquid membranes, there are few examples of industrial application. The development of reliable mathematical models and design parameters (mass transport coefficients and equilibrium or kinetic parameters associated with the interfacial reactions) is a necessary step for design, cost estimation, process optimisation and scale-up. This work reports an overview of the different approaches that have been proposed in the literature to the mathematical modelling of liquid membrane separation processes in hollow fibre contactors providing, at the same time, a useful guideline to characterise the mass transport phenomena and a tool for the optimal design and intensification of separation processes. Copyright © 2009 Society of Chemical Industry

Removal of selected pharmaceuticals in waters by photochemical processes

Abstract: BACKGROUND: Large amounts of pharmaceutical compounds are consumed throughout the world, and after being metabolized in humans are discharged into water streams. Some of them are not completely removed in wastewater treatment plants and, as a result, they are found in some effluents as well as in surface and ground waters. RESULTS: Four pharmaceutical compounds (metoprolol, naproxen, amoxicillin and phenacetin) frequently found in wastewaters were selected to be individually photo-oxidized in ultra-pure water by monochromatic UV radiation. The influence of independent variables (pH, temperature, and additional presence of hydrogen peroxide) was established, and first-order rate constants and quantum yields evaluated. The compounds were also oxidized using Fenton's reagent and, after establishing the influence of the operating conditions (ferrous ions and hydrogen peroxide concentrations, pH and additional presence of UV radiation), the rate constants for the radical reaction between each pharmaceutical and hydroxyl radicals were determined. Finally, the simultaneous photo-oxidation of mixtures of the selected pharmaceuticals in several types of water (commercial mineral water, groundwater and reservoir water) was performed by means of UV radiation alone and by the combination UV/H2O2. The influence of the independent variables in these processes was discussed, and the kinetic study allowed the determination of various rate constants for each compound. CONCLUSION: As the pharmaceutical concentrations theoretically calculated by the proposed kinetic model agree well with the experimental results obtained, this model constitutes an excellent tool to predict the elimination of these compounds when they are present in different natural waters. Copyright © 2009 Society of Chemical Industry

Octanol/water partition coefficients of ionic liquids

Abstract: BACKGROUND: Room temperature ionic liquids (ILs) are attractive alternatives to environmentally unfriendly volatile organic solvents. Partitioning is one of the most important and fundamental properties of a chemical, and the octanol/water partition coefficient is widely used to measure the tendency of a chemical to cross biological membranes. However, there is very limited information on the concentration dependence of the partition coefficients of ILs. This study investigated the octanol/water partitioning of 1-butyl-3-methylimidazolium ([bmim]) ILs containing either hexafluorophosphate ([PF6]) or bis[(trifluoromethyl)sulfonyl]amide ([Tf2N]) over a wide range of IL concentrations of three to five orders of magnitude. RESULTS: It was found that the apparent partition coefficients of the ILs increased with increasing IL concentration. A model based on the ionic nature of ILs was proposed to explain this behaviour, and the results showed a good fit with the experimental data. The intrinsic partition coefficients and dissociation constants of the ILs were determined using the equations from the proposed model. The differences in the intrinsic partition parameter values between the two ILs showed a good correlation with other physicochemical properties. CONCLUSIONS: The present study clearly shows that the octanol/water partition coefficients of ILs increase with increasing IL concentration owing to the formation of ion pairs. By using the proposed partition model, it was possible to determine the intrinsic partition coefficients of ILs, and it was found that the apparent partition coefficients of ILs converge to the intrinsic partition coefficients of the ionic species and ion pairs of ILs with decreasing and increasing IL concentration respectively. Copyright © 2008 Society of Chemical Industry

Strain isolation and optimization of process parameters for bioconversion of glycerol to lactic acid

Abstract: BACKGROUND: The crude glycerol from biodiesel production represents an abundant and inexpensive source which can be used as raw material for lactic acid production. The first aim of this investigation was to select a strain suitable for producing lactic acid from glycerol with a high concentration and productivity. The second aim was to obtain the optimum fermentation conditions, as a basis for large-scale lactate production in the future. RESULTS: Eight bacterial strains, which could aerobically convert glycerol to lactic acid, were screened from soil samples. One of the strains, AC-521, which synthesized lactic acid with a higher concentration, was identified based on its 16S rDNA sequences and physiological characteristics. These results indicated that this strain was a member of Escherichia coli. The optimal fermentation conditions for Escherichia coli AC-521 were 42 °C, pH 6.5, 0.85 min−1 (KLa). CONCLUSION:Escherichia coli AC-521 suitable for producing lactic acid from glycerol with high concentration and productivity was identified. After 88 h of fed-batch fermentation, both the lactic acid concentration and glycerol consumption reached maximum, giving 85.8 g L−1 of lactic acid with a productivity of 0.97 g L−1 h−1 and a yield of 0.9 mol mol−1 glycerol. Copyright © 2009 Society of Chemical Industry

Radiolabelling with short-lived PET (positron emission tomography) isotopes using microfluidic reactors

Abstract: This mini-review covers the issues concerning the application of microfluidics towards radiolabelling with short-lived isotopes used for PET (positron emission tomography), and surveys the literature in this area. The application of microfluidic reactors to radiolabelling reactions is currently receiving a great deal of interest because of the potential advantages they have over conventional labelling systems. The volume and variety of radiolabelling reactions for PET is expected to grow markedly over the coming years due to increased demands for PET scanning. High demands and expectations for radiolabelled compounds will have to be met by exploiting new types of chemistry and technologies, such as microfluidics, to improve the production and development of PET tracers.

Biological removal of 17α-ethinylestradiol (EE2) in an aerated nitrifying fixed bed reactor during ammonium starvation

Abstract: BACKGROUND: Conventional wastewater treatment plants (WWTPs) tend to partially remove recalcitrant chemicals, such as pharmaceuticals. Among these, the synthetic estrogen 17α-ethinylestradiol (EE2) is of great environmental concern. In this work a continuously aerated submerged fixed bed bioreactor was used for the biological removal of EE2 at µg L−1 levels. RESULTS: Removal efficiencies higher than 96% were obtained at a hydraulic retention time (HRT) of 4.3 days and a volumetric loading rate (Bv) of 11 µg EE2 L−1 d−1. Increasing the Bv up to 40 and 143 µg EE2 L−1 d−1 led to slightly lower removal efficiencies, 81 and 74%, respectively. Nitrification was confirmed to be the main biological mechanism involved in EE2 removal. Most interestingly, the elimination of EE2 was not affected by the absence of ammonium in the feed, suggesting that ammonia-oxidizing bacteria (AOB) were able to maintain their population density and their activity, even after several months of starvation. CONCLUSION: The concept of an aerated submerged fixed bed bioreactor, capable of removing estrogens in a sustainable and biological way, shows great potential as an effluent polishing step for existing WWTPs. Copyright © 2008 Society of Chemical Industry