In this paper the bioethanol production in batch culture by free Saccharomyces cerevisiae cells from thick juice as intermediate product of sugar beet processing was examined. The obtained results suggest that it is possible to decrease fermentation time for the cultivation medium based on thick juice with starting sugar content of 5-15 g kg-1. For the fermentation of cultivation medium based on thick juice with starting sugar content of 20 and 25 g kg-1 significant increase in ethanol content was attained during the whole fermentation process, resulting in 12.51 and 10.95 dm3 m-3 ethanol contents after 48 h, respectively. Other goals of this work were to investigate the possibilities for experimental results prediction using artificial neural networks (ANNs) and to find its optimal topology. A feed-forward back-propagation artificial neural network was used to test the hypothesis. As input variables fermentation time and starting sugar content were used. Neural networks had one output value, ethanol content, yeast cell number or sugar content. There was one hidden layer and the optimal number of neurons was found to be nine for all selected network outputs. In this study transfer function was tansig and the selected learning rule was Levenberg-Marquardt. Results suggest that artificial neural networks are good prediction tool for selected network outputs. It was found that experimental results are in very good agreement with computed ones. The coefficient of determination (the R-squared) was found to be 0.9997, 0.9997 and 0.9999 for ethanol content, yeast cell number and sugar content, respectively

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.

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]

The polypropylene fibers have been used in bed coalescers for separation of micro-sized oil droplets from water for a long time. Possibilities of applying different forms of polypropylene as filter beds are still being in the focus of many researches. The possibility of applying waste polypropylene bags used for packing vegetables (PPDJ) was investigated in this paper. The results are compared with results obtained by applying waste polypropylene fibers from carpet production (PP). It is well known that there are difficulties to separate the oils of low viscosity by polymer fiber beds. Due to the above mentioned, the presented research refers to separation of low viscosity mineral oil from water. The obtained experimental results confirm that the material PPDJ could be efficiently used as a bed material for coalescers. The critical velocity of 50 m h -1 could be reached at using both polypropylene forms that is from bags PPDJ and from the carpet industry PP, when the adequate bulk density of materials is used.

General trend of free trade in regional level as well as in the direction of European Union has motivated sugar factories located in Serbia to invest into technologies that are more efficient in order to make their products more competitive at the markets in Europe. The aim of this work was to evaluate effects of falling film plate evaporators on the energy consumption of evaporation plant, as well as to validate performance of this type of evaporators. It was found that this type of evaporator decreased energy requirements and in the same time evaporation process was more effective due to high values of heat transfer coefficients. .