Journal of Chemical Technology & Biotechnology

doi: 10.1002/jctb.799pmid: N/A

Jahanshahi, Mohsen; Pacek, Andrzej W; Nienow, Alvin W; Lyddiatt, Andrew

doi: 10.1002/jctb.907pmid: N/A

A novel dense pellicular adsorbent, custom‐designed for liquid fluidised bed adsorption of protein bioproducts, has been fabricated by coating zirconia–silica particles with agarose gel in a three‐phase emulsification process. A slurry feedstock comprising solid zirconia–silica particles (120 µm average diameter) suspended in an aqueous solution of agarose was emulsified in an oil–surfactant mixture in a stirred vessel to yield composite droplets. These were subsequently stabilised by cooling to form spherical pellicular particles characterised by a porous, pellicular coat cast upon a solid core. The impact of agitation speed, surfactant concentration, oil viscosity and slurry composition upon the pellicle depth and overall particle diameter was investigated. Pellicle depth decreased with increasing impeller speed and decreased oil viscosity, whilst increased slurry viscosity enhanced that parameter. Initial increases from low concentrations of Span 80 surfactant (0.1% w/v oil) reduced the depth of the agarose pellicle, but the highest values investigated (1.5% w/v oil) promoted particle aggregation. The fluidisation behaviour of particles fabricated under various conditions was characterised by the measurement of expansion coefficients and axial dispersion coefficients for the liquid phase when operated in a standard fluidised bed contactor. Both parameters were found to be comparable or superior to those reported for conventional, composite fluidised bed adsorbents. The controlled coating of porous agarose upon a solid core to yield specific pellicular geometries is discussed in the context of the fabrication of adsorbents customised for the recovery of a variety of bioproducts (macromolecules, nanoparticulates) from complex particulate feedstocks (whole broths, cell disruptates and unclarified bio‐extracts). Given the agreement between the size of the pellicular particles and the trends expected from theory, the large‐scale manufacture of such particles for customised industrial use is recommended. Copyright © 2003 Society of Chemical Industry

Martín Santos, MA; Fernández Bocanegra, JL; Martín Martín, A; García García, I

doi: 10.1002/jctb.908pmid: N/A

The production of ethanol by fermentation and subsequent distillation generates wastewater known as ‘vinasse’. This waste is highly polluting on account of its high organic load and antibacterial activity—which arises from the presence of phenolic compounds that reduce the efficiency of the detoxification treatments best suited to this type of waste (eg anaerobic digestion). This can be avoided by using a pre‐treatment based on a chemical oxidant (ozone) at an acid or alkaline pH. Ozonation in acid media provides more selective elimination of phenolic compounds and a more readily biodegradable waste (ie an increased BOD5/COD ratio). Copyright © 2003 Society of Chemical Industry

Wang, Hui‐Min; Wu, Jau‐Yann; Tsai, Shau‐Wei; Chen, Teh‐Liang

doi: 10.1002/jctb.916pmid: N/A

A novel separation process based on the hydrophobic adsorption at the n‐hexadecane–water interface was developed for the recovery of Acinetobacter radioresistens lipase from a pre‐treated fermentation broth. In a mixture containing water, lipase and n‐hexadecane, a water‐in‐oil emulsion was formed when the n‐hexadecane‐to‐water ratio (o/w ratio) was larger than 3, and a large amount of lipase was found to be adsorbed at the interface. Compared with the oil‐in‐water emulsion (occurring when o/w ratio < 3), the water‐in‐oil emulsion generated smaller droplets and larger interfacial area, and was more stable. The harvested emulsion phase could be centrifuged to give an aqueous, concentrated lipase solution. Adsorption of lipase at the interface could be described by the Langmuir isotherm. For lipase concentrations ranging from 8.4 to 87.2 U cm−3, a single‐stage adsorption resulted in a six‐ to four‐fold concentration and 16–45% activity recovery, where lipase concentration was the dominant factor. A method using data from a single‐stage adsorption to predict multiple‐stage operation was described, and the agreement between the experimental and the predicted results was good. To improve the enzyme recovery, a multiple‐run adsorption process was proposed. The use of salts enhanced the hydrophobic interaction between lipase and n‐hexadecane. Advantages of the proposed process include simple operation, low operational cost, environmentally friendly, no requirement for pre‐concentration of the enzyme solution, and negligible enzyme denaturation. Copyright © 2003 Society of Chemical Industry

Bhattacharjee, Chiranjib; Datta, Siddhartha

doi: 10.1002/jctb.912pmid: N/A

A mass transfer model based on unsteady state mass balance over the concentration boundary layer, coupled with back transport resulting from the stirring action, opposing ultrafiltrate flux, has been developed in the present study. This model uses semi‐infinite consideration to solve the governing partial differential equation by the Laplace transformation method, which gives the analytical solution of the concentration profile. During the solution procedure, pseudo‐steady state assumption has been used, as a consequence of which volumetric flux and turbulent back transport flux have been taken as constants. Once the analytical expression for the concentration profile has been found, an iterative technique has been developed for simulating flux and rejection under any specified operating condition. The prediction from this model is found to be in good agreement with experimental results obtained during continuous stirred ultrafiltration of PEG‐6000 solution using a cellulose acetate membrane of 5000 Da molecular weight cut‐off. The average absolute deviation in the prediction of permeate flux has been found to be 5.6% and that for the prediction of rejection was 6.4%. Copyright © 2003 Society of Chemical Industry

An, Taicheng; Gu, Haofei; Xiong, Ya; Chen, Weiguo; Zhu, Xihai; Sheng, Guoying; Fu, Jiamo

doi: 10.1002/jctb.915pmid: N/A

Decolourization and COD removal from synthetic wastewater containing Reactive Brilliant Orange K‐R (RBOKR) dye using sonophotocatalytic technology was investigated. Experimental results showed that this hybrid technology could efficiently remove the colour and reduce COD from the synthetic dye‐containing wastewater, and that both processes followed pseudo first‐order kinetics. At the condition of 0.1 m3 h−1 airflow, 0.75 g dm−3 titanium dioxide and 0.5 mmol dm−3 RBOKR solution, the rate constants of decolourization and COD removal were 0.0750 and 0.0143 min−1 respectively for the sonophotocatalytic process; 0.0197 and 0.0046 min−1 respectively for the photocatalytic process and 0.0005 and 0.0001 min−1 respectively for the sonochemical process. The rate constants of sonophotocatalysis were greater than that of both the photocatalytic and sonochemical processes either in isolation or as a sum of the individual process, indicating an apparent synergetic effect between the photo‐ and sono‐processes. Copyright © 2003 Society of Chemical Industry

Libra, Judy A; Sosath, Frank

doi: 10.1002/jctb.904pmid: N/A

The treatment of a segregated textile wastewater containing reactive dyes was investigated in two continuous‐flow process trains using ozonation and biological processes. The degree of decolorization and dissolved organic carbon (DOC) removal achieved by ozonation followed by aerobic treatment (two‐stage) was compared with that found when an anaerobic and aerobic pretreatment was added (four‐stage). Although the biological pretreatment reduced color by ∼70%, similar amounts of ozone were required in both trains to achieve high degrees of overall removal of color and DOC. In both trains, ozonation increased biodegradability in the following aerobic reactor, however, in order to reach ∼80% overall DOC removal, a specific ozone absorption (A*) of ∼6 gO3 gDOCo−1 was required and >50% of the DOC was mineralized in the ozone reactor. A comparison of cost estimates based on investment and operating costs for the process alternatives showed that a four‐stage train would reduce costs only if it enabled a decrease in A* to less than 2 gO3 gDOCo−1. Difficulties in comparing treatment processes for segregated vs full‐stream wastewaters are discussed. Copyright © 2003 Society of Chemical Industry

Carini, D; Dunn, IJ; Morbidelli, M

doi: 10.1002/jctb.900pmid: N/A

The degradation of 3‐methylpyridine (3MEP), a model heterocyclic industrial molecule, was performed in a sequential batch ozonation–biofilm process. Four process steps (bubble‐column ozonation, heterotrophic biofilm degradation, biofilm nitrification, and biofilm denitrification) were combined in different sequences. Three packed‐bed biofilm reactors were started up so as to have separate, specific activities (heterotrophic, nitrification and denitrification). Batch experiments with acetate, ammonia, and nitrate proved that all reactors displayed degradation activity for all substances. Different batch sequences of these reactors were tested with the products of batch ozonation of 3MEP as the first step. The best results were obtained using a two‐step process, in which the ozonation was followed by a single fluidized‐bed, heterotrophic biofilm reactor. The high C/N ratio of 3MEP and the appreciable non‐specific activity of this reactor made it possible to achieve all the biodegradation in the one reactor. Establishing the optimal batch ozonation time (80 min) was determined by an ozone electrode and by stopping the process when the dissolved ozone concentration rose above an initial low level. The identifiable products of 3MEP ozonation were nitrate, acetate, formate, pyruvate, oxalate and ammonium. A C‐balance, compared with TOC measurement, indicated that about 50% of the carbon was in unidentified, but biogradable, ozonation products. Copyright © 2003 Society of Chemical Industry

Domínguez, Alberto; Deive, Francisco J; Sanromán, M Angeles; Longo, María A

doi: 10.1002/jctb.922pmid: N/A

The production of extracellular lipase in submerged cultures of Yarrowia lipolytica CECT 1240 has been investigated. Several compounds have been added to the culture medium, in order to assess their efficiency as inducers of lipase production. First, the effect of triglycerides (olive oil, sunflower oil, tributyrin) and fatty acids (oleic acid) has been studied. The highest activity level was obtained with sunflower oil (58 U cm−3), followed by olive oil (49 U cm−3). The cultures with tributyrin and oleic acid attained similar activities (33 U cm−3). Then, several surfactants (Tween 80, Triton X‐100, gum arabic, polyethylene glycol 200) were added to the cultures with sunflower oil, in an attempt to increase the levels of extracellular lipase activity. The obtained activities were slightly lower than those achieved without surfactants. The assay of a wide range of surfactant concentrations in the case of PEG‐200 (with which the highest activity levels had been attained) did not improve the results. This strain secreted lipase concentrations two‐fold higher and showed significantly different behaviour towards the presence of surfactants in the culture medium, compared with other wild‐type Yarrowia lipolytica strains. Copyright © 2003 Society of Chemical Industry

Vidal, L; Durany, O; Suau, T; Ferrer, P; Benaiges, MD; Caminal, G

doi: 10.1002/jctb.909pmid: N/A

An expression system based on Escherichia coli and the T5 promoter allowed the overproduction of a his‐tagged rhamnulose‐1‐phosphate aldolase (RhuA; EC 4.1.2.19), an enzyme with applications in the production of deoxyazasugars and deoxysugars compounds. Shake flask and bioreactor cultivation with E coli M15 (pQErham) were performed under different media and inducing conditions for RhuA expression. A Defined Medium (DM) with glucose as carbon source gave a high volumetric and enzyme productivity (3460 AU dm−3 and 288 AU dm−3 h−1 respectively) compared with Luria–Bertoni (LB) medium (2292 AU dm− 3 and 255 AU dm−3 h−1). The minimum quantity of (isopropyl‐β‐D‐thiogalactoside) IPTG for optimal induction was estimated in 18–20 µmol IPTG gDCW−1. The highest volumetric production of RhuA (8333 AU dm−3) was obtained when IPTG was added in the late log‐phase. No significant differences were found in specific RhuA activity for induction temperatures of 30 and 37 °C. An effective two‐step purification process comprising affinity chromatography and gel permeation has been developed (overall recovery 66.5%). These studies provide the basis for the further development of an integrated process for recombinant RhuA production suitable for biotransformation applications. Copyright © 2003 Society of Chemical Industry