SCIENTIA IRANICA
Year:2001 | Volume:8 | Issue:3 (BIOTECHNOLOGY AND BIOENIRONMENTAL ENGINEERING)|Papers Count:12

In this paper, effects of pH, carbon and nitrogen sources, inducer, penicillin G, shaking and, aeration rate on penicillin G acylase (PGA, EC3.5.1.11) synthesis by Escherichia coli were studied and the optimum conditions for batch fermentation process were determined. The maximum activity of the enzyme and the biomass concentration were obtained at pH range of 8.0-9.0, with 250 rpm using 5 g.l-1 yeast extract as both carbon and nitrogen sources and 4 g. g.l-1 of phenyl acetic acid as the inducer. Addition of 0.2 g. g.l-1 penicillin G to the fermentation broth enhanced the enzyme production. The optimum aeration rate in the fermenter was obtained to be 0.85 wm. The growth kinetics of PGA production was analyzed using a second-order model applied to Leudeking-Piret kinetics. The analysis of Leudeking-Piret model demonstrates that PGA production by Escherichia coli obeys the growth-associated kinetics.

Anti-peptide antibodies against the N- and C-terminal regions of chimerical a-amylase, recombinant CD2 and insulin B- Shain were obtained by using synthesized peptides corresponding to the parts of target portions as immunogens. These anti-peptide antibodies, which should be obtained without the us of target proteins, adsorbed the target proteins and the antigen peptides; therefore, they could be used for detection and purification of those proteins. The adsorbed proteins were specifically eluted by the elands containing the antigen peptides under mild conditions.

Synthetic organic dyes are essential in satisfying the ever-growing demand, in terms of quality, variety and speed for coloration of a large number of substances. Due to the toxic nature, these materials present certain hazards and environmental problems. Toxicity of dyes varies with their structure. In this paper, a report is provided regarding a new Bacillus sp. Which decolorizes one of the triphenylmethane dyes, Crystal Violet, very efficiently? Efforts were made to assess the toxicity of Crystal Violet and its decolorized product through microbiological means. The test organisms used were various strains of Escherichia coli, Saccharomyces cerevisiae and Schizosaccharomyces pombe. Toxicity was measured in terms of inhibition of growth of test organisms. Various parameters like lag period, maximum cell mass concentration, specific growth rate (m) and inhibitive ability (n) were determined for the assessment of toxicity. In the presence of Crystal Violet (5 mg/ml), the specific growth rate (m) for E. coli DHSa, S. cerevisiae BJS418 and S. pombe ABP20 decreased from 1.25, 0.229 and 0.262 h-1 to 0.125, 0.125 and 0.044 h-1, respectively. The specific growth rates did not decrease in the presence of treated dye. The inhibitive ability of Crystal Violet was maximum (2.188) with S. cerevisiae BJS418, while it was minimum (0.688)for E. coli DHSa. Based on the results of the above parameters, it was found that Crystal Violet is toxic to all the organisms tested but when decolorized by Bacillus sp., it was found to be non-toxic.

In this paper, recovery of penicillin G from mycel-containing fermentation broth through physical extraction is investigated. The values of degree of extraction are evaluated as a function of media pH, partition coefficient between aqueous and organic phases for undissociated acid and the pKa of penicillin. The pH variations were measured during extraction operation and the optimum pH value for penicillin G recovery considering its decomposition was obtained. The mass transfer analysis of the extraction system was carried out using two-resistance mass transfer theory. The overall as well as aqueous and organic phase mass transfer coefficients were determined. The investigated mass transfer resistances for both phases are in the same order of magnitude, demonstrating that the mass transfer resistances for both phases have to be considered in equipment design and operation of penicillin G extraction systems.

A major challenge in membrane filtration of biomass is that flux declines quickly due to cake formation and membrane fouling, caused by internal or external deposition of the suspended solids. Considering that the key to successful application is flux maintenance or productivity, a possible procedure for flux stabilization, i.e., intermittency is discussed here. In intermittent operation, the microfiltration cycles from 'on' to 'off' periods provide relaxation and potential removal of cake solids in the 'off' period. The use of intermittency cans provide flux enhancement and modest improvement in productivity. Features that maximize the effect include higher frequency of intermittency, higher cross flow velocity, lower transmembrane pressure, smaller membrane pore size addition of salts and cleaning of the membrane surface. However, in all cases, the initial high fluxes are rapidly lost due to flux declines cake deposits on the membrane.

In this paper, a simple optimization methodology is applied for estimation of substrate mass transfer parameters including the overall external mass transfer coefficient, k1 and the effective diffusivity, De. Using experimental data for irreversible unireactant immobilized enzyme systems which follow Michaelis-Menten mechanism. The method utilizes a simple direct search optimization algorithm along with the numerical solution of the governing differential equation. The application of the method has been demonstrated through comparing the predicted values of k1 and De using the proposed method with experimental values reported in the literature for two different immobilized enzyme systems with irreversible reactions.

Microbiological analyses of soil chronically exposed to coal tar of an industrialized area in Iran resulted in isolation of some bacteria capable of degrading naphthalene, phenanthrene and anthracene in an aqueous solution. The initial PAH concentrations were at the water solubility level and degradation proceeded to a nondetectable level in some cases. The degradation rate decreased with an increase in the number of fused benzene rings. For PAHs with the same number of fused rings, however, fewer clustered molecules appeared to degrade faster. The kinetic parameters of hydrocarbon (substrates) degradation and microorganism growth rates were determined using the logistic mathematical model. The calculated data based on the proposed model were in good agreement with the experimental ones.

In this paper, effect of penicillin addition in enhancing the secretion of glutamic acid by Corynebacterium glutamicum was studied. The proper time of adding penicillin to maximize glutamic acid production was found to drift at repeated trials. In contrast, maximum acid productivity was obtained when penicillin was injected at a proper biomass concentration of about 7.7 gram dry weight per lit (gdw/l). Moreover, rate of consumption of sugar and ammonia through the course of glutamic acid fermentation was monitored. In production phase, these two rates were correlated properly with a ratio of 3.2:1 which is comparable to the theoretical stoichiometric value of 5:1. Therefore, through feeding a mixture of molasses and ammonia at the above mentioned ratio, an online double control of both sugar and pH in a fed-batch process based on single pH measurements becomes feasible.

In this paper, biopolymer flocculant-producing bacteria, strain As-101, isolated from activated sludge and identified as Bacillus species is considered. Study of the basic characteristics and comparison of the strain were carried out according to Bergey's manual of bacteriology and the bacterium was identified as Bacillus Coagulants. The activated sludge was treated by a commercial protease (trypsin) with an optimum concentration of 0.4 mg/ml for producing the maximum extent of deflocculation, which was near 16%. The production of bioflocculant by Bacillus As-101 was not parallel to the cell growth and a large amount of the bioflocculant was released into the culture at the end of the stationary phase, with the ability to make flocculation of kaolin clay suspension. The effect of cation concentration rate was also evaluated. The flocculating of bioflocculant was stimulated by the addition of Ca2+, with an optimum concentration of 0.068 mM. The cell flocs were deflocculated not only by trypsin, but also by EDTA which was after 10 hours by 1 mM EDTA.

In this paper, enzymatic saccharification of poplar wood has been studied. Poplar wood samples were subjected to chemical processing (acidic delignification and swelling by ammonium hydroxide) under selected operational conditions. By removal of lignin along with recovery of cellulose both at the level of 80% solid residues were obtained that were, then, used as the substrate for enzymatic hydrolysis using a mixture of the following two enzymes, cellulose and cellobiase. Increase in the swellingcapacity of the cellulose substrate along with decrease of the polymerization degree of lignocellulosicmaterials facilitates the action of celluloses enzymes. Considering selected operational conditions in the enzymatic saccharification of the wood residues, glucose was produced at the level of 30 g/l. The experimental results were fitted to the hyperbolic empirical model. There was a close relationship between the experimental and the calculated results in some of the enzymatic treatments.

In this paper, the production of lactic acid from deproteinized whey, using immobilized Lactobacillus casei on wood chips is investigated. The immobilization process was considered on various supports like wood chips, brick particle and porous glass by adsorption and on eggshell with glutaraldehyde by covalent bonding. Wood chips demonstrated the highest adsorption among all the supports and, therefore, was chosen as the best support for production. Batch production was studied at four temperatures and three different pH after five days. The highest concentration of lactic acid (16 g/l) was observed at T = 28°( and pH = 5.5. The optimum condition of temperature and pH for the continuous system was chosen as 32° (and 5, respectively, based on the results obtained in the batch system. The continuous reactor was designed as a packed-bed of L.casei immobilized on wood chips. The highest concentration of lactic acid produced in this system (14.8 g/l) was obtained with D = 0.2 h-1 after five days.

Combination of chemical and biological processes can be considered as a cheaper option for the treatment of toxic wastewater. Each process is influenced by its own parameters. Chemical treatment is affected by the reaction rate between the chemical agent and organic compounds as well as by environmental factors such as temperature. Biological processes are affected by pH organic load and sludge concentration. In this study, the treatment of formaldehyde by chemical and biological methods is investigated. The removal efficiency of formaldehyde in the chemical treatment reached 85% when temperature exceeded 60°C and the concentration of lime was 2000 mg/l. In the biological process. after acclimatization, the biodegradation of formaldehyde was well accomplished under both batch and continuous flow conditions. The maximum formaldehyde elimination was about 70%. Biomass and initial formaldehyde concentration have a significant influence on the degradation of formaldehyde.