Showing papers in "Journal of Chemical Technology & Biotechnology in 2008"

Advanced oxidation processes for water treatment: advances and trends for R & D

Abstract: Reference GGEC-ARTICLE-2008-057doi:10.1002/jctb.1873View record in Web of Science Record created on 2008-01-23, modified on 2016-08-08

An overview of the application of Fenton oxidation to industrial wastewaters treatment

Abstract: This review provides updated information on the application of the Fenton process as an advanced oxidation method for the treatment of industrial wastewaters. This technology has been used in recent decades as a chemical oxidation process addressed to meet a variety of objectives including final polishing, reduction of high percentages of organic load in terms of chemical oxygen demand or total organic carbon and removal of recalcitrant and toxic pollutants thus allowing for further conventional biological treatment. The efficiency and flexibility of this technology has been proven with a wide diversity of effluents from chemical and other related industries or activities, including pharmaceutical, pulp and paper, textile, food, cork processing, and landfilling among others.

Liquid–liquid extraction of biomolecules: an overview and update of the main techniques

Abstract: Two-phase systems can be exploited in separation science for the extraction/purification of desired biomolecules. This article reviews recent experimental work on the use of aqueous two-phase polymer systems, two-phase aqueous micellar systems and reversed micellar systems for the extraction/purification of biomolecules. The experimental partitioning behavior of different biomolecules is reviewed and new results with nisin and lipopolysaccharides are presented. An extensive description of each system is presented, based on the biomolecules behavior and the tools employed to improve their extraction and purification. Copyright © 2007 Society of Chemical Industry

Peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis: a continued work

Abstract: Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X-ray diffraction (XRD) analysis indicated that the crystallinity of PAA-treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers.

Protease production by Aspergillus oryzae in solid‐state fermentation using agroindustrial substrates

Abstract: BACKGROUND: An inexpensive and readily available agroindustrial substrate such as rice bran can be used to produce cheap commercial enzymes by solid-state fermentation. This work investigates the production of food-grade proteases by solid-state fermentation using readily available Thai rice bran. RESULTS: A local strain of Aspergillus oryzae (Ozykat-1) was used to produce proteases. Rice bran used alone proved to have poor substrate morphology (insufficient porosity) for satisfactory solid-state fermentation. A certain amount of wheat bran was necessary to improve the morphology of the substrate. The following variables affected protease production: substrate composition, initial moisture content and initial pH. A high protease activity (∼1200 U g−1 dry solids) was obtained on a substrate that had a wheat bran to rice bran ratio of 0.33 by dry weight, a moisture content of 50%, initial pH of 7.5, and incubation temperature of 30 °C. CONCLUSION: Nutritionally, rice bran used alone was as good a substrate as mixed bran for producing protease, but rice bran had poor morphological characteristics for consistent fermentation. A substrate that had a wheat bran to rice bran ratio of 0.33 by dry weight was best for producing protease. Copyright © 2008 Society of Chemical Industry

Practical experiences from the development of aqueous two‐phase processes for the recovery of high value biological products

Abstract: The development of recovery processes using aqueous two-phase systems (ATPS) has been limited by the extensive experimental work required to establish the optimal system parameters to ensure selective partitioning of the product of interest. Although using full factorial experiments has been demonstrated to be an effective strategy for the characterization of the partitioning behaviour of biological products in ATPS, this approach is characterized by its costly and time consuming nature. As an alternative, the use of a robotic-aided strategy has been proposed. However, the need for high cost equipment may limit the generic implementation of this strategy. Based on practical experience using ATPS, practical strategies for the predictive design of primary recovery processes using polymer–salt systems were derived. To evaluate the generic application of the proposed strategies, four experimental models (B-phycoerythrin, C-phycocyanin, double layered rotavirus-like particles and lutein) were selected. The application of these strategies resulted in the development of simplified recovery processes for the selected experimental models. The practical review presented is considered a relevant contribution that will provide general rules to facilitate the establishment of ATPS processes, particularly for new researchers in the field. Copyright © 2007 Society of Chemical Industry

Future directions for in‐situ product removal (ISPR)

Abstract: This paper summarizes the main findings of a round-table discussion held to examine the key bottlenecks in the further application and industrial implementation of in-situ product removal (ISPR) techniques.** It is well established that ISPR can yield great benefits for processes limited by inhibitory or toxic products, as well as unstable products or reactions that are thermodynamically unfavorable. However, several issues for industrial implementation were revealed in the discussion. Most notably implementation will be dependent on (1) research into the appropriate process structure, (2) methods to achieve process robustness, (3) systematic selection methods for separation operations and (4) the nature of the product market. Here, these four issues will be discussed as a basis for future work in this area. Copyright © 2007 Society of Chemical Industry

Start‐up and enrichment of a granular anammox SBR to treat high nitrogen load wastewaters

Abstract: BACKGROUND: Landfill leachate is characterized by low biodegradable organic matter that presents difficulties for the complete biological nitrogen removal usually performed by conventional biological nitrification/denitrification processes. To achieve this, the anaerobic ammonium oxidation (anammox) process is a promising biological treatment. This paper presents an anammox start-up and enrichment methodology for treating high nitrogen load wastewaters using sequencing batch reactor (SBR) technology. RESULTS: The methodology is based on the gradual increase of the nitrite-to-ammonium molar ratio in the influent (from 0.76 to 1.32 mole NO2−-N mole−1NH4+-N) and on the exponential increase of the nitrogen loading rate (NLR, from 0.01 to 1.60 kg N m−3 d−1). 60 days after start-up, anammox organisms were identified by polymerase chain reaction (PCR) technique as Candidatus Brocadia anammoxidans. After one year of operation, NLR had reached a value of 1.60 kg N m−3 d−1 with a nitrogen (ammonium plus nitrite) removal efficiency of 99.7%. The anammox biomass activity was verified by nitrogen mass balances with 1.32 ± 0.05 mole of nitrite removed per mole of ammonium removed and 0.23 ± 0.05 mole of nitrate produced per mole of ammonium removed. Also, enrichment of anammox bacteria was quantified by fluorescence in situ hybridization (FISH) analysis as 85.0 ± 1.8%. CONCLUSIONS: This paper provides a methodology for the enrichment of the anammox biomass in a SBR to treat high nitrogen loaded wastewaters. Copyright © 2007 Society of Chemical Industry

Strategies of pH control and glucose‐fed batch fermentation for production of succinic acid by Actinobacillus succinogenes CGMCC1593

Abstract: BACKGROUND: Succinic acid is an important precursor of numerous products, including pharmaceuticals, feed additives, green solvents, and biodegradable polymers. In this work, strategies of pH control and glucose-fed batch fermentation for producing succinic acid using Actinobacillus succinogenes CGMCC1593 were carefully optimized. RESULTS: The production of succinic acid was stable within the pH range 6.0–7.2. Both cell growth and succinic acid production were inhibited by high concentrations of sodium and calcium ions, while there was no significant inhibition by magnesium ions. With an initial glucose concentration of 25 g L−1, and glucose concentration was maintained between 10 and 15 g L−1 during the course of fed batch fermentation, succinic acid concentration, productivity and yield were 60.2 g L−1, 1.3 g L−1 h−1 and 75.1%, respectively. CONCLUSION: Of all the neutralization reagents used for pH control of A. succinogenes CGMCC1593, solid MgCO3 was the most satisfactory. With increase of initial glucose concentration, the time course showed a longer growth lag period and the maximum biomass declined, while more carbon was diverted to succinate synthesis. The results obtained in this study should be helpful for the design of a highly efficient succinic acid production process. Copyright © 2008 Society of Chemical Industry

Continuous production of 1,2‐propanediol by the selective hydrogenolysis of solvent‐free glycerol under mild conditions

Abstract: BACKGROUND: The conversion of glycerol to value-added derivatives is now critical, owing to the large surplus of glycerol from biodiesel production. The main objective of this work is to develop a novel process for converting solvent-free glycerol to 1,2-propanediol. RESULTS: Several catalysts were screened for aqueous-phase hydrogenolysis of glycerol in an autoclave. The most effective catalysts (Ni/Al2O3, Cu/ZnO/Al2O3) were further tested for vapor phase hydrogenolysis in a fixed-bed. Ni/Al2O3 did not prove as effective for the production of 1,2-propanediol because of the high selectivity to CH4 and CO. Over Cu/ZnO/Al2O3, glycerol was mainly converted to the desired 1,2-propanediol and the reaction intermediate acetol. The production of 1,2-propanediol was favoured at higher hydrogen pressure. At 190 °C and 0.64 MPa, near complete conversion of glycerol was achieved with 1,2-propanediol selectivity up to 92%. In addition, a higher concentration (between 43.4% and 0.8%) of acetol was detected and an approximately stoichiometric relationship was found between acetol and 1,2-propanediol. CONCLUSION: 1,2-propanediol can be produced with high yields via the vapor phase hydrogenolysis of glycerol over Cu/ZnO/Al2O3. Furthermore, the mechanism of 1,2-propanediol formation is suggested to proceed mainly through an acetol route over Cu/ZnO/Al2O3. Copyright © 2008 Society of Chemical Industry

Cell removal with supercritical carbon dioxide for acellular artificial tissue

Abstract: BACKGROUND: The objective of this work was to decellularize artificial tissue without using surfactant solutions. For this purpose, supercritical carbon dioxide was used as the extraction medium. RESULTS: Supercritical carbon dioxide containing a small amount of entrainer was a suitable medium to extract both cell nuclei and cell membranes from artificial tissue. Under gentle extraction conditions (15 MPa, 37 °C), cell nuclei were satisfactorily extracted from tissue within 1 h. In contrast, the efficiency of phospholipid removal depended strongly on the transfer rate of carbon dioxide in the interior of the tissue. Mechanical strength of tissue was not decreased even with prolonged treatment. CONCLUSION: Acellular artificial tissues could be prepared quickly by treatment with a carbon dioxide/entrainer system. The prepared acellular tissue could be obtained in absolutely dry condition. This is advantageous from the viewpoint of long-term preservation without putrefaction and contamination. Copyright © 2008 Society of Chemical Industry

Adhesive biomaterials for tissue reconstruction

Abstract: Tissue reconstruction and wound closure rely on sutures, staples and clips in current surgical procedures. These traditional devices are nonetheless unable to prevent leakage of fluids from a variety of tissue including blood vessels and dura mater. Furthermore, sutures are usually difficult to apply during minimal invasive surgery and often induce detrimental scarring that may impair healing. To overcome these disadvantages, biocompatible and biodegradable glues based on fibrin, polyethylene glycol (PEG) and cyanoacrylate have recently been used in patients to seal and repair tissue wounds. Cyanoacrylate glues create typically very strong tissue bonds but have mostly been applied externally for skin wound closure because of their residual cytotoxicity. Other adhesive biomaterials are also emerging; these glues and adhesives are usually based on proteins such as albumin and collagen or polysaccharides like chitosan; these are irradiated with coherent or non-coherent light to trigger their adhesion to tissue. These biomaterial based devices offer significant advantages over sutures, such as their sealing or repairing ability, easy application modality and delivery in situ of compounds for accelerating wound healing. This paper reviews different tissue reconstruction strategies employing adhesive biomaterials currently used in surgical and experimental procedures.

Design strategies for integrated protein purification processes: challenges, progress and outlook

Abstract: The key to successful and efficient protein purification is the selection of the most appropriate purification techniques and their combination in a logical way to obtain the desired purification in the minimum number of steps. However, the rationalization of protein purification process development is faced with a number of challenges. In this paper, the challenges in protein purification process development are captured. The state-of-the-art in protein purification process synthesis and design is reviewed and the strengths and weaknesses of the current strategies highlighted. Finally, views on the future directions of protein purification process development are presented.

Preparation of Ag‐doped TiO2 nanoparticles for photocatalytic degradation of acetamiprid in water

Abstract: BACKGROUND: Surface modification by doping with metal ions and organic polymers has been proven to be an efficient route to improve the photocatalytic activity of TiO2. Pesticide photocatalysis has been conducted with fine TiO2 particles suspended in an aqueous phase. RESULTS: It has been found that the Ag dopant accelerates TiO2 anatase to rutile transformation. At relatively low Ag concentrations (2‐6%), anatase grain sizes decreased and specific surface areas of the TiO2 powders increased. The presence of Ag in crystalline TiO2 was found to increase the photocatalytic activity of TiO2 in the photocatalytic degradation of acetamiprid at 25 ◦ C. CONCLUSION: All photocatalytic degradations of acetamiprid followed pseudo-first-order degradation kinetics (Ct = C0e −kt ) and parameters like the concentration of doped Ag appeared to play an important role affecting the reaction rate. The photocatalytic degradation velocity constant (k) was found to increase quickly with the Ag content, increasing from n = 0.02 to 0.06, and decreased slowly from n = 0.08 to 0.12. The half-lives of degradation (t1/2) were 18.8, 11.3, 16.2, 10.0, 6.9, 8.4 and 14.7min at n = 0, 0.02, 0.04, 0.06, 0.08 and 0.12, respectively. The optimal mole percentage of Ag in TiO2 should be between 4% and 8%.  2008 Society of Chemical Industry

Use of ionic liquids for the efficient utilization of lignocellulosic materials.

Abstract: Lignocellulosic materials are the most abundant renewable resource in the world and their efficient utilization provides a practical route to maintain social sustainable development. Application of ionic liquids has opened new avenues for the efficient utilization of lignocellulosic materials in such areas as fractionation, preparation of cellulose composites and derivatives, analysis, and removal of pollutants. However, there are still many challenges in putting these potential applications into practical use, for example, the high price of ionic liquids and lack of basic physico-chemical and toxicological data. Further research and financial support are required to address such challenges. Copyright © 2008 Society of Chemical Industry

Design of bioreactors for mesenchymal stem cell tissue engineering

Abstract: There is a growing need for efficient mesenchymal stem cell (MSC) production processes for a wide spectrum of clinical conditions ranging from the treatment of life-threatening graft-versus-host disease to cartilage repair. Development of cell and tissue engineered products derived from MSCs will be enabled by scalable production processes with standards of safety and efficacy similar to those established for the pharmaceutical industry. Many of the bioreactor design principles established for production of biopharmaceuticals can be applied to production of MSC products; however, specific control of the microenvironment is required for MSC expansion and differentiation. We review how porous scaffolds and bioreactor technologies are applied to the study of the MSC microenvironment. Current methods for MSC production are based on growth in tissue culture flasks, which is labour-intensive and expensive. We suggest that stirred, perfusion or microfluidic bioreactor technologies can more efficiently address the clinical need for large-scale MSC production. Soft lithography and microfluidic design offer extreme geometric precision to study MSC function as well as defining the microenvironment for tissue engineering at the micron scale. Copyright © 2008 Society of Chemical Industry

Hydrothermal catalytic conversion of biomass for lactic acid production

Abstract: The production of lactic acid has increased owing to growing polymer markets, increased demand in the chemical sector and many applications in the food industry. Biomass hydrothermal decomposition is potentially a method for lactic acid production. To obtain a higher yield of lactic acid, the influence of metal ions (Zn(II), Ni(II),Co(II) and Cr(III)) on biomass decomposition in sub-critical water (T = 300 °C) was investigated and the catalyst function in the complex reaction network of biomass degradation was discussed. In comparison with a non-catalytic process, the addition of 400 ppm Ni(II) catalyst increased the yield of lactic acid from 3.25% to 6.62% at 300 °C and 120 s for microcrystalline cellulose. The lactic acid yield for glucose was 9.51% for 400 ppm Co(II) catalyst at 300 °C and 120 s. In the case of Cr(III) and Ni(II), the conversion of maize straw, sawdust and rice husk first increased, and then decreased from 0 to 800 ppm. For catalyst Cr(III), Zn(II) and Ni(II), the conversion of wheat bran indicated a decreasing trend. Transition metal ions have a great influence on raw materials conversion to lactic acid. In the conversion of pyruvaldehyde to lactic acid, the ionic catalyzed Cannizzaro-type reaction would take place. Copyright © 2007 Society of Chemical Industry

Pre‐treatment and utilization of raw glycerol from sunflower oil biodiesel for growth and 1,3‐propanediol production by Clostridium butyricum

Abstract: BACKGROUND: The objective of the present work is to report an efficient pre-treatment process for sunflower oil biodiesel raw glycerol (SOB-RG) and its fermentation to 1,3-propanediol. RESULTS: The growth inhibition percentages of Clostridium butyricum DSM 5431 on grade A (pH 4.0) and grade B (pH 5.0) phosphoric acid-treated SOB-RG were similar to those of pure glycerol at 20 g glycerol L−1; i.e., 18.5 ± 0.707% to 20.5 ± 0.7% inhibition. In grade A, growth inhibition was reduced from 85.25 ± 0.35% to 32 ± 1.4% (a 53.25% reduction) at 40 g glycerol L−1 by washing grade A raw glycerol twice with n-hexanol (grade A-2). The kinetic parameters for product formation and substrate consumption in anaerobic batch cultures gave almost similar values at 20 g glycerol L−1, while at 50 g glycerol L−1 volumetric productivity (Qp) and specific rate of 1,3-propanediol formation (qp) were improved from 1.13 to 1.85 g L−1 h−1 and 1.60 to 2.65 g g−1 h−1, respectively, by employing grade A-2 raw glycerol, while the yields were similar (0.5–0.52 g g−1). CONCLUSION: The results are important as the pre-treatment of SOB-RG is necessary to develop bioprocess technologies for conversion of SOB-RG to 1,3-propanediol. Copyright © 2008 Society of Chemical Industry

Immobilization of Pycnoporus sanguineus laccase by metal affinity adsorption on magnetic chelator particles

Abstract: BACKGROUND: Immobilized enzymes provide many advantages over free enzymes including repeated or continuous reuse, easy separation of the product from reaction media, easy recovery of the enzyme, and improvement in enzyme stability. In order to improve catalytic activity of laccase and increase its industrial application, there is great interest in developing novel technologies on laccase immobilization. RESULTS: Magnetic Cu2+-chelated particles, prepared by cerium-initiated graft polymerization of tentacle-type polymer chains with iminodiacetic acid (IDA) as chelating ligand, were employed for Pycnoporus sanguineus laccase immobilization. The particles showed an obvious high adsorption capacity of laccase (94.1 mg g(-1) support) with an activity recovery of 68.0% after immobilization. The laccase exhibited improved stability in reaction conditions over a broad temperature range between 45 degrees C and 70 degrees C and an optimal pH value of 3.0 after being adsorbed on the magnetic metal-chelated particles. The value of the Michaelis constant (K-m) of the immobilized laccase (1.597 mmol L-1) was higher than that of the free one (0.761 mmol L-1), whereas the maximum velocity (V-max) was lower for the adsorbed laccase. Storage stability and temperature endurance of the immobilized laccase were found to increase greatly, and the immobilized laccase retained 87.8% of its initial activity after 10 successive batch reactions. CONCLUSION: The immobilized laccase not only can be operated magnetically, but also exhibits remarkably improved catalytic capacity and stability properties for various parameters, such as pH, temperature, reuse, and storage time, which can provide economic advantages for large-scale biotechnological applications of laccase. (c) 2007 Society of Chemical Industry.

Application of the Stover–Kincannon kinetic model to nitrogen removal by Chlorella vulgaris in a continuously operated immobilized photobioreactor system

Abstract: BACKGROUND: The aim of this study was to evaluate the ammonium nitrogen removal performance of algae culture Chlorella vulgaris in a novel immobilized photobioreactor system under different operating conditions and to determine the biokinetic coefficients using the Stover–Kincannon model. RESULTS: The photobioreactor was continuously operated at different initial ammonium nitrogen concentrations (NH4-N0 = 10–48 mg L−1), hydraulic retention times (HRT = 1.7–5.5 days) and nitrogen/phosphorus ratios (N/P = 4/1–13/1). Effluent NH4-N concentrations varied between 2.1 ± 0.5 mg L−1 and 26 ± 1.2 mg L−1 with increasing initial NH4-N concentrations from 10 ± 0.6 mg L−1 to 48 ± 1.8 mg L−1 at θH = 2.7 days. The maximum removal efficiency was obtained as 79 ± 4.5% at 10 mg L−1 NH4-N concentration. Operating the system for longer HRT improved the effluent quality, and the percentage removal increased from 35 ± 2.4% to 93 ± 0.2% for 20 mg L−1 initial NH4-N concentration. The N/P ratio had a substantial effect on removal and the optimum ratio was determined as N/P = 8/1. Saturation value constant, and maximum substrate utilization rate constant of the Stover–Kincannon model for ammonium nitrogen removal by C. vulgaris were determined as KB = 10.3 mg L−1 d−1, Umax = 13.0 mg L−1 day−1, respectively. CONCLUSION: Results indicated that the algae-immobilized photobioreactor system had an effective nitrogen removal capacity when the operating conditions were optimized. The optimal conditions for the immobilized photobioreactor system used in this study can be summarized as HRT = 5.5 days, N/P = 8 and NH4-N0 = 20 mg L−1 initial nitrogen concentration to obtain removal efficiency greater than 90%. Copyright © 2008 Society of Chemical Industry

Membrane‐assisted vapor stripping: energy efficient hybrid distillation–vapor permeation process for alcohol–water separation

Abstract: BACKGROUND: Energy efficient alternatives to distillation for alcohol recovery from dilute solution are needed to improve biofuel sustainability. A process integrating steam stripping with a vapor compression step and a vapor permeation membrane separation step is proposed. The objective of this work is to estimate the energy and process costs required to make a fuel grade ethanol (0.5 wt% water) from 1 and 5 wt% ethanol aqueous streams using the proposed process. RESULTS: Using process simulation and spreadsheeting software, the proposed membrane-assisted vapor stripping process was estimated to require as little as 8.9 MJ of fuel-equivalent energy per kg of fuel grade ethanol recovered from a 1 wt% ethanol feed stream, 2.5 MJ kg−1 for a 5 wt% ethanol solution. This represents an energy saving of at least 43% relative to standard distillation producing azeotropic ethanol (6 wt% water). Process costs were also found to be lower than for distillation at the 3.0 × 106 kg-ethanol year−1 scale modeled. CONCLUSION: In this hybrid system, the stripping column provides high ethanol recoveries and low effluent concentrations while the vapor compression-membrane component enables the efficient recovery of latent and sensible heat from both the retentate and permeate streams from the membrane system. Published in 2008 by John Wiley & Sons, Ltd.

Influence of light quality and intensity in the cultivation of Spirulina platensis from Toliara (Madagascar) in a closed system

Abstract: BACKROUND: Spirulina platensis (Toliara, Madagascar) provides a food supplement which can fight against malnutrition and food insufficiency in Madagascar. In this country, the current production from three open basins does not cover the need and presents drawbacks, such as low productivity and possible contamination. So cultivation of S. platensis in a closed photobioreactor opens the possibility of extending this microalgae production. In this study, the influence of colour and intensity of the light on S. platensis growth and protein content was investigated in a bubble column. RESULTS: Growth kinetics were obtained for four colours (green, white, red and blue) and four intensities (400, 800, 1000 and 1200 lux) of light. The influence of light colour on Spirulina growth was discussed. The highest productivity (183.6 mg L-1d-1) and concentration (2643 mg L-1) were obtained for green light at 1200 lux. The protein content was 58 %. CONCLUSION: Using green light allows to improve S. platensis growth. The performances obtained with the closed system are higher than those reported in the literature.

Effects of organic matter and initial carbon–nitrogen ratio on the bioconversion of volatile fatty acids from sewage sludge

Abstract: BACKGROUND: The biodegradable organic matter and the initial carbon–nitrogen ratio can be substantially different in different batches of sewage sludge, which results in a difference in the acidification efficiency of sludge. Using sewage sludge from three different sources, batch tests were performed to analyze the relationship between volatile fatty acids (VFAs) and consumed organic matter, and to investigate the effects of initial carbon–nitrogen (C/N) ratio on the acidification efficiency of sludge. RESULTS: Maximum yields of 152.1 ± 3.5 mg total VFAs-COD per gram volatile solid (VS) added and 22.4 ± 1. 2m g butyric acid-COD g −1 VS added were obtained from the sludge with the highest initial C/N ratio. Statistical analysis indicated that protein was the major substrate for the produced VFAs. The sludge with the least initial C/N ratio (5.01) had the least yield, and only acetic acid, which was also mainly related to protein, was detected. CONCLUSION: The initial carbon–nitrogen ratio was one of the most important factors influencing the distribution patterns of VFAs and the yield of total VFAs produced from sewage sludge. A high C/N ratio could not only improve the yield of total VFAs but also enhance the yield of butyric acid.  2008 Society of Chemical Industry

Hydrothermal processing of rice husks: effects of severity on product distribution

Abstract: BACKGROUND: Treatment in aqueous media (hydrothermal or autohydrolysis reactions) is an environmentally friendly technology for fractionating lignocellulosic materials. Rice husks were subjected to hydrothermal processing under a variety of operational conditions to cause the selective breakdown of xylan chains, in order to assess the effects of reaction severity on the distribution of reaction products. RESULTS: The effects of severity (measured by the severity factor, R0) on the concentrations of the major autohydrolysis products (monosaccharides, xylo- and glucooligosaccharides, xylooligosaccharide substituents, acetic acid, acid-soluble lignin and elemental nitrogen) were assessed. The interrelationship between the severity of treatment and molecular weight distribution was established by high-performance size-exclusion chromatography. Selected samples were subjected to refining treatments as ethyl acetate extraction and ion exchange for refining purposes, and the concentrates were assayed by high-performance anion-exchange chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. CONCLUSIONS The protein equivalent of the products present in liquors accounted for 43 to 51% of the protein present in the raw rice husks. The concentrations of glucose (derived from starchy material) and arabinose (split from the xylan backbone) were fairly constant with severity. Even in treatments at low severity, high molecular weight compounds derived from xylan accounted for a limited part of the stoichiometric amount. Operating under harsh conditions, about 50% of the total xylan-derived compounds corresponded to fractions with a degree of polymerization (DP) <9. After refining, saccharides accounted for more than 90% of the non-volatile components of the sample. The refined products showed a series of xylose oligomers up to about DP 13, and a series of acetylated xylose oligomers up to about DP 15.

Fuel cell power generation from marine sediments: investigation of cathode materials.

Abstract: BACKGROUND: Marine sediment microbial fuel cells (MFC) utilise oxidisable carbon compounds and other components present in sediments on ocean floors and similar environments to produce power in conjunction with, principally, oxygen reduction at the cathode in the overlying water. The aim of the work was to investigate a range of cathode materials for sediment MFC, to achieve relatively high levels of power. RESULTS: Cell potential and power density performance data are reported for sediment MFC using cathodes of: carbon sponge, cloth and paper, graphite and reticulated vitreous carbon (RVC), Co and Fe-Co tetramethoxyphenyl porphyrin (FeCoTMPP) and platinised carbon and titanium. The anode was graphite cloth. After a period of stabilisation, open circuit voltages of 700 mV and maximum power densities of 62 mW m−2 were obtained, using FeCoTMPP. Relatively low cost carbon cathodes gave power densities of around 30 mW m−2. CONCLUSIONS: The study has shown that low level power can be produced from marine sediments using MFC without separators between the fuel and seawater containing dissolved oxygen. Cathode performance was an important factor determining the power output. Electrocatalyst at the cathode improved performance: FeCoTMMP gave power densities of 60 mW m−2 which was twice that achieved with the best un-modified carbon. Copyright © 2008 Society of Chemical Industry

CO2 absorption into amine solutions: a novel strategy for intensification based on the addition of ferrofluids

Abstract: BACKGROUND: In this paper a novel approach for increasing the mass transfer coefficient in gas/liquid mass transfer is reported and applied to the industrially important system of CO2 absorption. The approach makes use of a ferrofluid additive to the liquid phase. To demonstrate this strategy, a wetted wall column has been built and experiments have been conducted on the CO2/methyl diethanolamine (MDEA) system. This reaction system allows the absorption to be carried out in the transition regime between slow and fast regimes, so that the mass transfer coefficient (kL) and interfacial area (ai) can be measured independently, in the presence and absence of ferrofluids. A surfactant-coated aqueous magnetic fluid was prepared and shown to be stable in MDEA solutions. RESULTS: The experimental results, with this fluid, show that there is an enhancement in mass transfer in the presence of ferrofluids, the extent of which depends on the amount of ferrofluid added. The enhancement in mass transfer coefficient was 92.8% for a volume fraction of the fluid of about 50% (solid magnetite volume fraction of about 0.39%). Experiments were also carried out to further enhance the mass transfer rates by employing a periodic oscillating magnetic field. Under the conditions employed, there was no further impact of magnetic field on mass transfer rates. CONCLUSIONS: Magnetic nanoparticles are able to significantly enhance gas/liquid mass transfer rates when added to the liquid phase. The reasons for this striking effect are under investigation. It is possible for significantly higher enhancements to be produced by the action of an external field, but this requires special fluids to be formulated which are not affected by the chemical solvent used. These results have significance for the absorption of CO2 in industrial absorbers using amine solutions.  2008 Society of Chemical Industry

Effect of sludge retention time in sludge holding tank on excess sludge production in the oxic-settling-anoxic (OSA) activated sludge process

Abstract: The activated sludge process is a core technology in wastewater treatment plants. Excess sludge produced in the process must be treated and disposed of properly and may account for up to 60% of total plant operating cost. Therefore, it is necessary to develop new biological concepts to minimize excess sludge production. The oxic-settling-anoxic process (OSA process), a modified activated sludge process, may produce less excess sludge than the conventional activated sludge process. The effect of sludge retention time in the sludge holding tank of the OSA process on excess sludge yield has been studied. Four pilot-scale activated sludge systems were employed, one of which was a conventional activated sludge process, and was used as the control system. The other three were OSA systems operated with different sludge retention times (5.5 h, 7.6 h, and 11.5 h) in the sludge holding tank. All systems were operated with synthetic wastewater for 7 months. Results showed that the three OSA processes with 5.5 h, 7.6 h, and 11.5 h sludge retention time reduced the excess sludge by 33%, 23% and 14%, respectively. Compared to the control process, chemical oxygen demand (COD) removal efficiency and effluent NH3–N concentration were not significantly influenced, but total nitrogen (TN) removal efficiency decreased by 0–9%. Total phosphorus (TP) removal efficiency of OSA processes with 7.6 h and 11.5 h sludge retention time increased by 19%. Sludge settleability was excellent in the three OSA processes. No distinct shift in the diversity of the predominant species was found in microbial populations. We conclude that the OSA system could reduce excess sludge production. Results suggest 6–7 h sludge retention time would be optimal. Copyright © 2007 Society of Chemical Industry

Wastewater treatment for production of H2S‐free biogas

Abstract: BACKGROUND: In anaerobic wastewater treatment processes, the presence of sulfate-reducing bacteria (SRB) produces H2S. Many techniques are being used to remove H2S from biogas to obtain H2S-free biogas but none of those are cost effective or efficient enough to remove the H2S completely. The objective of the present study was to introduce some changes/modifications to the process parameters of the wastewater treatment operation to eliminate SRB from the system. RESULTS: The growth of SRB was found to be completely suppressed under thermophilic conditions (55 °C) but not at 37 °C. H2S-free biogas containing 56.5% methane was obtained at 55 °C after 180 days of treatment. The effect of higher concentrations of volatile fatty acids (VFAs) on the growth of SRB and methanogens at 37 °C and 55 °C were also studied. At higher VFA concentrations, SRB outgrew the methanogens at 37 °C but at 55 °C the situation was found to be reversed. For continuous operation at 55 °C and low dilution rate (0.0075 h−1), SRB was suppressed and biogas having 29% methane but free of H2S was obtained. CONCLUSION: Operating the reactor at high temperature (550C) and low hydraulic retention time (HRT) can result in the production of H2S-free biogas, with a high concentration of methane. Copyright © 2008 Society of Chemical Industry

Optimization of lipase production by Penicillium simplicissimum in soybean meal

Abstract: BACKGROUND: Lipase production by Penicillium simplicissimum using soybean meal as substrate has been investigated. A factorial design technique was used to evaluate the effects of incubation temperature, initial moisture of the meal and substrate supplementation with low cost supplements, on lipase production. Soybean oil and wastewater from a slaughterhouse, which is rich on oil and fat, corn steep liquor and yeast hydrolysate, were tested as supplementary carbon and nitrogen sources. RESULTS Cultivation conditions were optimized for the production of lipase by factorial design and response surface methodology. Results show that the microorganism produces very low protease activity (0.21 U gds−1 dry substrate), which helps to maximize lipase production. Soybean meal without supplements appears to be the best medium of those tested for lipase production by P. simplicissimum. CONCLUSION: This work showed that temperature and moisture are the factors that most strongly influence lipase production by P. simplicissimum using soybean meal as substrate. The growth conditions that optimize lipase production are 27.5 °C using substrate with 550 g kg−1 of initial moisture. In optimum conditions lipase activity of 30 U gds−1 dry substrate was obtained. Copyright © 2007 Society of Chemical Industry

Production of activated carbon from agricultural by‐products

Abstract: The production of activated carbon from agricultural by-products is a research field of increasing interest as it deals with the problem of the disposal of agro-residues, at the same time producing an added-value product that can be used in a number of environmental applications. The paper presents an overview of the latest developments in processes for the production of activated carbon from agricultural by-products, with emphasis on the methodology applied, the effect of critical process parameters such as retention time, temperature, chemical to material ratio, as well as the adsorbing capacity of the activated carbons produced in removing select compounds from synthetic and real wastewaters. Agricultural by-products can be a source for activated carbon production with high surface areas and high adsorption capacity. Copyright © 2008 Society of Chemical Industry