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Biochemical Engineering Journal (v.24, #3)
Effects of irrigation and water content of packings on alpha-pinene vapours biofiltration performance by Mohammad Bagher Bagherpour; Manouchehr Nikazar; Ulrika Welander; Babak Bonakdarpour; Mehri Sanati (pp. 185-193).
The main objective of this investigation is to determine the effect of different physical parameters on the performance of biofilters, treating hydrophobic compounds. In this respect, the effects of irrigation and water content of packings on the removal efficiency of bed in different pollutant loading rates, and gas phase flow rates, is studied. Alpha-pinene, which is produced from variety of industrial wood products, pulp and paper industries, and fragrance production units, has been selected as a model compound. Since the effectiveness of biofiltration depends strongly upon water solubility of compounds, in the case of alpha-pinene (2.5ppm, at 25°C), the process of waste gas treatment is faced with difficulties. In this paper, it is shown that performance of biofilters, treating hydrophobic contaminants, declines due to irrigation. This reduction is detected by an increase in the outlet concentration from 11% up to 22.5%. Its magnitude depends on the gas velocity inside the biofilter and outlet concentration of the bed. The result indicated that pore blocking along the bed has less effect on the performance reduction than diffusion coefficient. Also the inhibitory effects of velocity on biodegradation are considerably higher than the effects of concentration. In addition, this compost-based biofilter shows noteworthy higher elimination capacities in comparison with previous studied biofiltration systems. In this study, a maximum elimination capacity of 227gm−3 of packingh−1 is achieved by 95% of removal efficiency. The maximum concentration in the inlet gas was 650mgm−3.
Keywords: Biofilter; Irrigation; Water content; Hydrophobic; Waste gas treatment; Alpha-pinene
Influences of iron and humic acid on the growth of the cyanobacterium Anabaena circinalis by Bing-kun Sun; Yasunori Tanji; Hajime Unno (pp. 195-201).
Fe may play a key role in the growth of cyanobacteria, which sometimes cause water blooms in eutrophic water environments. Humic acid (HA) is also considered to be a controlling factor in algal growth, as HA is abundant around water basins and has a variety of chemical functions, including Fe-chelation and catalysis. To evaluate the influence of iron depletion and the presence of HA on the growth of Anabaena circinalis, a water bloom-forming cyanobacterium, ex situ cultivation experiments were performed using chemically defined media. The data were analyzed to characterize the effects of Fe and HA on cell growth. A Fe concentration of 10−8 to 10−7M was the threshold for growth of the cyanobacterium. HA may have toxic effects (at [HA]>0.01mgCl−1) and may reduce Fe bioavailability (at [HA]≥0.1mgCl−1), which delays and/or decreases the growth of the cyanobacterium.
Keywords: Water blooms; Cyanobacteria; Anabaena circinalis; Iron limitation; Humic acid
Repeated elicitation enhances phenylethanoid glycosides accumulation in cell suspension cultures of Cistanche deserticola by Xi-Yu Cheng; Bin Guo; Hua-Ying Zhou; Wen Ni; Chun-Zhao Liu (pp. 203-207).
Effect of yeast elicitor on growth and phenylethanoid glycosides (PeGs) accumulation in Cistanche deserticola cell suspension cultures was investigated. Both biomass and PeGs production were enhanced by the addition of yeast elicitor. The dry weight of 9.0gl−1 and PeGs production of 237.7mgl−1 in 21-day cell cultures treated with 106mg total sugar l−1 medium yeast elicitor for 3 days were achieved. Furthermore, a strategy of repeated addition of yeast elicitor was developed. Yeast elicitor repeatedly added on days 15, 17 and 19 at the dose of 106mg total sugar l−1 medium improved PeGs accumulation further and the final PeGs production in the cell cultures of C. deserticola reached 317.8mgl−1. The enhanced PeGs accumulation in C. deserticola cell suspension cultures was related to the increase of phenylalanine ammonium lyase activity stimulated by yeast elicitor.
Keywords: Cistanche deserticola; Phenylethanoid glycosides; Yeast elicitor; Repeated elicitation; Phenylalanine ammonia lyase
Determination of lumped kinetic parameters and their thermal dependence for the synthesis of cephalexin with immobilized penicillin acylase in organic medium by Andrés Illanes; Flavio Rodríguez; Carola Bahamondes; Claudia Altamirano (pp. 209-215).
The kinetically controlled synthesis of β-lactam antibiotics with penicillin acylase is favored at low temperatures and high cosolvent concentrations. The synthesis of cephalexin from 7-amino 3-desacetoxy cephalosporanic acid and phenylglycine methyl ester has been performed at varying temperatures below 20°C with glyoxyl agarose-immobilized penicillin acylase in ethylene glycol medium at previously optimized pH, cosolvent concentration and nucleophile to acyl donor ratio. An equation for batch reactor performance was derived considering the kinetic mechanism proposed for the kinetically controlled synthesis of β-lactam antibiotics. From the experimental data gathered at different temperatures and the model of batch reactor performance developed, lumped kinetic parameters were determined at each temperature by a numerical method and temperature explicit polynomial functions for each kinetic parameter were derived.
Keywords: Enzyme biocatalysis; Enzyme kinetics; Enzyme bioreactors; Kinetic parameters; Penicillin acylase; Cephalexin
Modified shrinking particle model for the rate of enzymatic hydrolysis of impure cellulosic waste materials with enzyme reuse by the substrate replacement by Kamyar Movagharnejad (pp. 217-223).
A model based on the shrinking particle theory is developed for the rate of enzymatic hydrolysis of natural impure cellulosic wastes with a product concentration present in the start of the reaction. The enzymatic hydrolysis of some waste materials (rice pollards) has been studied in a batch stirred reactor at 50°C. A comparison between the experimental data for diverse reaction systems and those predicted from the model, demonstrated the applicability of the latter. The average mean absolute deviation was about 10.0%.
Keywords: Cellulase; Cellulose; Enzyme biocatalysis; Hydrolysis; Modelling; Recycling
Comparative production of human interleukin-2 fused with green fluorescent protein in several recombinant expression systems by Hyung Joon Cha; Hwa Sung Shin; Hye Jung Lim; Hye Sook Cho; Nimish N. Dalal; Minh Q. Pham; William E. Bentley (pp. 225-233).
The selection of an optimal recombinant expression system is important for successful protein production. Here, we compared production of human interleukin-2 (hIL-2)-green fluorescent protein (GFP) fusion proteins in several expression systems such as bacteria Escherichia coli, yeast Pichia pastoris, insect Spodoptera frugiperda Sf-9 cells, insect Tricoplusia ni larvae, and insect Drosophila melanogaster S2 cells. Due to the highly hydrophobic nature of hIL-2, the GFP/hIL-2 fusion protein was expressed as an inclusion body in the E. coli system, resulting in minimal green fluorescence; however, Western blot analysis revealed the proper fusion band. In all other cases, the fusion proteins were expressed intracellularly or secreted as a functional form; green fluorescence was observed in each of these expression systems. We determined the linear relationships between GFP fluorescence and hIL-2 concentration in each case and used these correlations for comparison of the various expression systems in terms of production yield, productivity, product solubility (for intracellular expression systems), secretion efficiency (for secretion systems), and even functionality by simple measurement of GFP fluorescence. Even though the culture conditions were not optimized for each expression system, this comparison can be used as preliminary criteria for the selection of a proper expression system for recombinant protein production.
Keywords: Escherichia coli; Pichia pastoris; Spodoptera frugiperda; Sf-9 cells; Tricoplusia ni; larvae; Drosophila melanogaster; S2 cells; Green fluorescent protein fusion; Human interleukin-2
On the effectiveness factor calculation for a reaction – diffusion process in an immobilized biocatalyst pellet by Juan C. Gottifredi; Elio E. Gonzo (pp. 235-242).
This contribution deals with effectiveness factor ( η) and concentration profile of key component estimations when a single independent reaction takes place in a porous catalyst structure where enzymes are immobilized. The procedure is quite general since any kinetic expression can be handled and the case of catalytic activity distribution can also be taken into account. With the knowledge of kinetic parameters and effective diffusivity η and concentration profiles can be estimated through very simple algebraic equations. Thus, the numerical solution of a non linear second order boundary value differential equation, which usually needs some spline scheme, is avoided.The obtained approximate results are compared with numerical findings for the case of slab geometry where a very simple numerical procedure can be used to solve the resulting differential non linear equation. Approximate results are shown very accurate in the whole range of kinetic parameters, even in those cases where the reaction kinetics shows an apparent negative order of reaction and η values can be above unity. Tables are used to better compare approximate and numerical values. Concentration profile predictions are also very accurate in the region nearby the external surface of the catalyst particle.These approximate results are used to establish criteria to analyze experimental kinetic data in those cases where diffusional phenomena, that could affect chemical parameter estimations, must be avoided.
Keywords: Effectiveness factor prediction; Enzyme immobilization; Concentration profiles; Michaelis–Menten kinetic; Kinetic data analysis. Thiele modulus
The biodegradation of phenol at high initial concentration by the yeast Candida tropicalis by Jiang Yan; Wen Jianping; Li Hongmei; Yang Suliang; Hu Zongding (pp. 243-247).
Strain Candida tropicalis was isolated from acclimated activated sludge, and was identified as a member of the genus Candida. Phenol biodegradation using a pure culture of C. tropicalis was studied. The results showed that C. tropicalis has pretty high phenol degradation potential, which could thoroughly degrade the phenol of 2000mgl−1 in the mineral salt medium within 66h. High inoculum volume lessened phenol toxic property for the cells and increased phenol biodegradation velocity. However, for a certain starting inoculum, with the step increase of phenol concentration, substrate inhibition was obviously enhanced, and more phenol consumption was not assimilated by cell for growth, but was used to counteract strong substrate inhibition. In addition, the cell growth and phenol degradation intrinsic kinetics of C. tropicalis in batch cultures were also investigated over a wide range of initial phenol concentrations (0–2000mgl−1) using Haldane model. The results received in these experiments demonstrated that the Haldane kinetic model adequately described the dynamic behavior of the phenol biodegradation by the strain of C. tropicalis.
Keywords: Candida tropicalis; Haldane's equation; High phenol concentration; Inoculum volume; Phenol degradation; Substrate inhibition
Decolorization of an azo dye, Reactive Black 5 and MnP production by yeast isolate: Debaryomyces polymorphus by Qingxiang Yang; Ayfer Yediler; Min Yang; Antonius Kettrup (pp. 249-253).
The optimum conditions for decolorization of an azo dye, C.I. Reactive Black 5 (RB5) and the kinetic characteristics of manganese-dependent peroxidase (MnP) production by yeast isolate, Debaryomyces polymorphus, were investigated. D. polymorphus could completely degrade 200mgl−1 of non-hydrolyzed and hydrolyzed C.I. Reactive Black 5 within 24h of cultivation at an inoculum size of 1.4gl−1 wet cells in 50ml medium consisting of 5gl−1 glucose and 0.5–1.0gl−1 ammonium sulphate (pH 5–7). In addition, the MnP activities during the cultivation were evaluated in the absence and presence of 200mgl−1 C.I. Reactive Black 5. Maximum activity of MnP (1555.6Ul−1) was detected at 24h cultivation in the presence of the dye, and a significant reduction of the enzyme activity was observed thereafter. The presence of C.I. Reactive Black 5 in the culture was found to be indispensable to the production of MnP by D. polymorphus. A good correlation was found between the dye degradation and the enzyme production.
Keywords: Decolorization; Yeast; Manganese-dependent peroxidase; Azo dye; C.I. Reactive Black 5
Modelling of anaerobic digestion in a fluidised bed with a view to control by J.F. Béteau; V. Otton; J.Y. Hihn; F. Delpech; A. Chéruy (pp. 255-267).
This paper deals with dynamical modelling of a complex wastewater treatment process with a view to design control laws. It consists of biological anaerobic digestion, which takes place on a porous medium in a fluidised bed reactor. Both hydrodynamic and biological models are studied separately. Their parameters are identified from experimental data, and the models are then validated. A stability analysis is carried out for both of them and the validity area is given. The obtained models are coupled in a global model of the whole process, which is experimentally validated. A stability analysis is then performed. Finally, local controllability and observability properties are given.
Keywords: Dynamic modelling; Fluidised bed bioreactors; Anaerobic processes; Axial dispersion; Wastewater treatment
How CTAB assists the refolding of native and recombinant lysozyme by Jun Wang; Diannan Lu; Ying Lin; Zheng Liu (pp. 269-277).
Refolding of native and recombinant lysozyme was accomplished by dilution with refolding buffer containing low-concentration cetyltrimethylammonium bromide (CTAB). In both cases, the use of β-cyclodextrin (β-CD) was unnecessary. Centered on the interaction between CTAB and the protein being refolded, experimental studies were conducted to investigate the effect of CTAB on the refolding yield, product distribution and the refolding kinetics. A comparative study of the artificial chaperone-assisted refolding of native and recombinant lysozyme was included to generate a more comprehensive understanding of the function of CTAB in assisting protein refolding. It was shown that the formation of CTAB–denatured lysozyme complex occurred at the beginning stage of refolding effectively inhibited the formation of aggregate, leading to an improved refolding. The dissociation of this complex occurred, when lysozyme started to fold into its native conformation catalyzed by GSSG/GSH. The use of β-CD facilitated the dissociation the CTAB–protein complex and thus increased the overall rate of lysozyme refolding. The results described by present study are also helpful for the design of surfactant and the optimization of refolding process for different proteins.
Keywords: Protein; Refolding; Lysozyme; Cetyltrimethylammonium bromide (CTAB); Recombinant human lysozyme; Artificial chaperone