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Number of results: 5
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Abstract

A kinetic model to describe lovastatin biosynthesis by Aspergillus terreus ATCC 20542 in a batch culture with the simultaneous use of lactose and glycerol as carbon sources was developed. In order to do this the kinetics of the process was first studied. Then, the model consisting of five ordinary differential equations to balance lactose, glycerol, organic nitrogen, lovastatin and biomass was proposed. A set of batch experiments with a varying lactose to glycerol ratio was used to finally establish the form of this model and find its parameters. The parameters were either directly determined from the experimental data (maximum biomass specific growth rate, yield coefficients) or identified with the use of the optimisation software. In the next step the model was verified with the use of the independent sets of data obtained from the bioreactor cultivations. In the end the parameters of the model were thoroughly discussed with regard to their biological sense. The fit of the model to the experimental data proved to be satisfactory and gave a new insight to develop various strategies of cultivation of A. terreus with the use of two substrates.

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Authors and Affiliations

Marta Pawlak
Marcin Bizukojć
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Abstract

Biosynthesis of lovastatin (a polyketide metabolite of Aspergillus terreus) in bioreactors of different working volume was studied to indicate how the change of scale of the process influences the formation of this metabolite. The experiments conducted in shake flasks of 150 ml working volume allowed to obtain lovastatin titres at the level of 87.5 mg LOV l-1, when two carbon sources, namely lactose and glycerol were used. The application of the same components in a large stirred-tank bioreactor of 5.3-litre working volume caused a decrease of lovastatin production by 87% compared to the shake flask culture. The deficiency of nitrogen in this bioreactor did not favour the formation of lovastatin, in contrast to the small bioreactor of 1.95-litre working volume, in which lovastatin titres comparable to those in the shake flasks could be achieved, when organic nitrogen concentration was two-fold decreased. When the control of pH and/or pO2 was used simultaneously, an increase in lovastatin production was observed in the bioreactors. However, these results were still slightly lower than lovastatin titres obtained in the shake flasks.

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Authors and Affiliations

Marta Pawlak
Stanisław Ledakowicz
Marcin Bizukojć
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Abstract

Surfactants can interfere with the biological wastewater treatment processes. They contribute to the changes in activated sludge floes structure. In order to quantify the influence of surfactants on sludge floes morphology the series of experiments in the flow continuous system were conducted. Sodium dodccyl sulphate, which belongs to the most ubiquitous anionic surfactant in everyday use, was selected to be the object of investigations. The results of its biodegradation in continuous flow system at influent concentration of 250 mg -dm' are presented. It turned out that SDS diminished the mean projected area of floes from 50 OOO to 15 OOO μm' with the increase of dilution rate from 0.029 to 0.192 h·1• At the same time the obtained data confirmed that there was a correlation between the morphological parameters of floes and other biomass indicators. The linear relation between mean projected area of floes and volatile suspended solids was found.
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Authors and Affiliations

Ewa Liwarska--Bizukojc
Marcin Bizukojc
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Abstract

In this study the effect of anionic surfactants on the morphology of activated sludge floes and biomass activity is quantitatively described. Three anionic surfactants: sodium dodecyl sulphate, sodium alkylbenzene sulphonate and sodium alkyltrioxyethylene sulphate were tested. The batch experiments were performed for a wide range of initial concentrations of anionics in wastewater from 2.5 to 2500 mgdm3. In spite of different chemical structure the action of all tested anionic surfactants resulted in the decrease of activated sludge floes dimensions at the similar level. It occurred that in the range of anionics concentrations, which are typical for domestic wastewater (2.5-25 mgdm3), they contributed to the decrease of mean projected area of floes by about 30%, whereas at the concentrations of 250 and 2500 mg-dm3 mean projected area decreased usually by 50-60%. Sodium alkylbenzene sulphonate exerted the strongest inhibition effect on dehydrogenase activity of activated sludge biomass. This effect coincided with the decreased degrees of removal for this surfactant and its biodegradation products, especially at its lower initial concentrations in wastewater.
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Authors and Affiliations

Ewa Liwarska--Bizukojc
Marcin Bizukojc
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Abstract

This work aims at investigating the influence of the initial concentrations of carbon (glucose) and organic nitrogen (yeast extract) sources on Streptomyces rimosus ATCC10970 secondary metabolism in the stirred tank bioreactors. Additionally, glucose utilisation, biomass formation, pH, redox potential and dissolved oxygen levels, and the morphological development of S. rimosus pseudomycelium were studied. Eighteen secondary metabolites were detected by mass spectrometry and identified with the use of the authentic standard, or putatively with the use of literature and database of secondary metabolites. Varied initial yeast extract concentration acted much stronger on the formation of secondary metabolites than glucose did. For example, oxytetracycline was not biosynthesised at high yeast extract concentration while the formation of three other metabolites was enhanced under these conditions. In the case of glucose its increasing initial concentration led to higher secondary metabolite levels with the exception of an unnamed angucycline. High initial yeast extract concentration also drastically changed S. rimosus pseudomycelial morphology from the pelleted to the dispersed one. Ultimately, the cultivation media with the varied initial levels of carbon and nitrogen sources were proved to have the marked effect on S. rimosus secondary metabolism and to be the simplest way to either induce or block the formation of the selected secondary metabolites.
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Authors and Affiliations

Marcin Bizukojć
1
ORCID: ORCID
Anna Ścigaczewska
1
ORCID: ORCID
Tomasz Boruta
1
ORCID: ORCID
Agnieszka Ruda
1
Aleksandra Kawka
1

  1. Lodz University of Technology, Faculty of Process and Environmental Engineering,Department of Bioprocess Engineering, Wólczańska 213, 93-005 Łódź, Poland

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