This study is concerned with the effect of different initial glycerol
concentrations in the medium on xanthan production by Xanthomonas campestris
ATCC 13951. Xanthan biosynthesis was carried out in batch mode under aerobic
conditions at a temperature of 30oC and agitation rate of 150 rpm for 7 days.
The process efficiency was estimated based on the values of raw xanthan
yield, average molecular weight of the polymer and residual content of
glycerol, total nitrogen and phosphorus. Based on these results, the initial
concentration of glycerol as a carbon source in the production medium was
suggested. In the applied experimental conditions, high raw xanthan yield
(12.15 g/l) of good quality (Mw = 2.86?105 g/mol) and the lowest amount of
residual nutrients (glycerol 2.75 g/l, nitrogen 0.46 g/l and phosphorus 0.67
g/l) was achieved in the medium with the initial glycerol content of 20 g/l.
The obtained results are the basis for optimization of xanthan production on
glycerol containing media in order to increase the product yield and quality.
Optimization of the cultivation medium for production of antibiotic effective
against pathogenic bacteria Staphylococcus aureus using strain of
Streptomyces spp. isolated from the environment represents the aim of this
study. After the biosynthesis, the medium was analyzed by determining
residual sugar and nitrogen, and the antibiotic activity was determined using
diffusion-disc method. Experiments were carried out in accordance with the
Box-Behnken design, with three factors varied on three levels (glucose: 10.0,
30.0 and 50.0 g/L; soybean meal: 5.0, 15.0 and 25.0 g/L; phosphates: 0.5, 1.0
and 1.5 g/L) and for the optimization of selected parameters Response Surface
Methodology was used. The obtained model with the desirability function of
0.985 estimates that the lowest amounts of residual sugar (0.89 g/L) and
nitrogen (0.24 g/L) and the largest possible inhibition zone diameter (21.88
mm) that with its antibiotic activity against S. aureus creates the medium
containing 10.0 g/L glucose, 5.0 g/L soybean meal and 1.04 g/L phosphates.
Article Highlights • Optimization of xanthan production media based on the vegetable oil industry wastewaters • The response surface method was used for the optimization of xanthan production • The experimental values are in excellent agreement with the predicted values for modelled responses
The biocontrol agents are a very promising alternative to synthetic
pesticides that are presently used to control plant diseases caused by
phytopathogenic microorganisms. Members of the Bacillus genera are soil
bacteria that produce significant quantities of agriculturally important
bioactive compounds. Production of these compounds can be improved by
changing the nutritional and environmental conditions. The aim of this study
was the optimization of medium composition, using response surface
methodology, for the production of compounds effective against Xanthomonas
campestris ATCC 13951 by Bacillus subtilis ATCC 6633. To study the production
of antimicrobial compounds by selected Bacillus strain, the producing
microorganisms were cultivated on nutrient broth. The inhibition zone
diameter of 18.0 mm obtained by the diffusion-disc method indicated that the
used Bacillus subtilis strain produces compounds with antimicrobial activity
against Xanthomonas campestris ATCC 13951. To optimize the composition of the
cultivation medium in terms of glycerol, sodium nitrite and phosphates
content, experiments were carried out in accordance with Box-Behnken design,
and optimization of multiple responses was performed using the concept of
desirability function. The developed model predicted that the maximum
inhibition zone diameter (26.23 mm) against tested phytopathogen is achieved
when the initial content of glycerol, sodium nitrite and phosphate were 50.00
g/L, 2.85 g/L and 11.00 g/L, respectively. To minimize the consumption of
medium components and costs of effluents processing, additional optimization
set was made. The techno-economic analysis of the obtained results has to be
done to select optimal medium composition for industrial production of
antimicrobial compounds.
The aim of this study was formulation of medium for the production of bactericide effective against Staphylococcus aureus and Escherichia coli using Streptomyces sp. isolated from the soil. Biosynthesis of antibacterial compounds was performed on media prepared in accordance with Box-Behnken design with three factors on three levels and three repetitions in the central point where the contents of the carbon source (10.0-50.0 g/L), soybean meal (5.0-25.0 g/L) and phosphates (0.5-2.5 g/L) were varied. Fructose, lactose, sucrose, starch and glycerol were used as carbon sources. Since the cultivation broths showed activity only against Staphylococcus aureus, the values of inhibition zone diameters for this microorganism were statistically processed using response surface methodology and desirability function approach in order to optimize relations of varied nutrients. Media with glucose were not used in these experiments, but the mathematical model defined in previous research was applied for optimization. The developed models predict that optimal concentrations of carbon source, soybean meal and phosphates are about 10.0, 5.0 and 0.5 g/L, respectively, except in the lactose-containing medium, where the optimal phosphate content is 0.9 g/L. Performing the bioprocess in optimal media, the maximum inhibition zone diameter against Staphylococcus aureus was formed by the medium with fructose (34.5 mm). [Project of the Serbian Ministry of Education, Science and
Technological Development, Grant no. TR-31002]
Резиме: У тренутку припреме овог чланка, у Србији није започела градња ни једног ветро парка, мада је званично најављена изградња на више локација (Чибук, Ковин, Алибунар, Долово, Неготин). У грађевинском погледу, за пројектовање ветропарка је веома важно утврђивање геомеханичког склопа терена, који условљава начин фундирања (плитко или дубоко) ветрогенератора. Због велике висине стуба (90-120м) темељи су изложени врло великој хоризонталној сили од ветра и сеизмике, наспрам релативно мале тежине ветротурбине, кућишта и стуба. У овом раду су приказани резултати инжењерско-геолошких, геомеханичких и геофизичких истражних радова и геомеханичких лабораторијских испитивања, за изградњу ветро парка "Никине воде" на гребену планине Дели Јован у општини Неготин. Кључне речи: Ветропарк, геомеханичка испитивања, геофизичка испитивања
Article Highlights • Simulation software was used for the xanthan production process and cost model development • Simulation model was developed based on defined kinetic models • Results represent a basis for defining a general design for the suggested bioprocess
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