The aim of this work was to study the biosorption capacity of metals copper, lead and zinc by Geobacillus thermodenitrificans and Geobacillus thermocatenulatus. Solution of each metal was mixed with dry biomass and incubated at room temperature. The supernatant was taken and used for complexometric titration. The sorption capacity for Cu2+ was highest when using 0.5 g·l−1 Geobacillus thermodenitrificans (57 ± 4 mg·g−1). The sorption capacity rapidly decreases with increased concentrations. Similarly for Zn2+ ions, the highest sorption capacity was for biomass concentration 0.5 g·l−1 (18 ± 3 mg·g−1) and slowly decreases. For Pb2+ ions, the decrease is almost linear to the biomass concentration 2 g·l−1, i.e. from 117 ± 13 mg·g−1 to 53 ± 3 mg·g−1.The sorption capacity of Cu2+ ions was highest at the lowest biomass concentration of Geobacillus thermocatenulatus (65 ± 3 mg·g−1), then it sharply decreased and at concentration of biomass of 1 g·l−1 did not changed. In the case of Zn2+ ions, we could seen a moderate drop with the increasing concentration with the range of 24 ± 3 to 12.3 ± 0.4 mg·g−1. For Pb2+ ions was the decrease slow, from 119 ± 8 mg·g−1 to 54 ± 4 mg·g−1.Affinity of metals to bacteria was determined in the order Pb2+ > Cu2+ > Zn2+. The results show, that Geobacillus thermocatenulatus has better sorption capabilities than Geobacillus thermodenitrificans.

Finding of optimal hydrolysis conditions is important for increasing the yield of saccharides. The higher yield of saccharides is usable for increase of the following fermentation effectivity. In this study optimal conditions (pH and temperature) for amylolytic enzymes were searched. As raw material was used waste bread. Two analytical methods for analysis were used. Efficiency and process of hydrolysis was analysed spectrophotometrically by Somogyi-Nelson method. Final yields of glucose were analysed by HPLC. As raw material was used waste bread from local cafe. Waste bread was pretreated by grinding into small particles. Hydrolysis was performed in 100 mL of 15 % (w/v) waste bread particles in the form of water suspension. Waste bread was hydrolysed by two commercial enzymes. For the liquefaction was used α-amylase (BAN 240 L). The saccharification was performed by glucoamylase (AMG 300 L). Optimal conditions for α-amylase (pH 6; 80 °C) were found. The yield of total sugars was 67.08 g•L -1 (calculated to maltose). As optimal conditions for glucoamylase (pH 4.2; 60 °C) were found. Amount of glucose was 70.28 g•L 1 . The time of waste bread liquefaction was 180 minutes. The time of saccharification was 90 minutes. The results were presented at the conference CECE Junior 2014.

Solid-phase microextraction coupled with gas chromatography was used for the analysis of volatile aroma compounds in Niva cheese. The extraction conditions were very mild, which minimises thermal, mechanical, or chemical modification of the sample; the method is rapid, simple, and cheap. In total, 54 compounds were identified in Niva cheese using this method: 3 hydrocarbons, 5 aldehydes, 11 ketones, 18 alcohols, 3 esters, 10 fatty acids, and 4 sulphur compounds. These aroma compounds were quantified and subsequently the changes in the concentrations of them were studied throughout the ripening period. Most of the volatile compounds identified were present at all stages of the cheese ripening, their amounts changing significantly, however, in most cases the final concentration in the ripe cheeses was similar to the initial concentration in the unripe cheese.  

No abstract

BABÁK, L., ŠUPINOVÁ, P., BURDYCHOVÁ, R.: Growth models of Thermus aquaticus and Thermus scotoductus. Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 5, pp. 19-26 Members of the genus Thermus family are signifi ant producers of secondary metabolites, which are very commonly used in industry. Beside the productivity, it is also important to study the growth curve of each strain. The mathematical models which are commonly used to describe behavior of microbial strains under diff erent physical and chemical conditions can reduce measured data. In this study, the mathematical models which describe only the microbial count were used. For analysis, Verhulst model, von Bertalanff y model and Richards model were chosen. During the cultivation of Thermus aquaticus and Thermus scotoductus strains, optical density (OD) and concentration of microorganisms were measured. The mathematical models were fi tted to experimental data. The fi tting was made in program MATLAB. The coeffi cients of models and statistical evaluation of goodness of fi t of models were identifi ed from mathematical analyses. Graphs of individual models were plotted with prediction bounds. 95% confi dence levels were used to statistical evaluation of goodness of fi t of models and prediction bounds. Richards model was evaluted as the most corresponding with experimental data. Similar results were reached using Verhulst model. Von Bertalanff y model was not coresponded with experimental data. growth models, bacterial growth, Thermus aquaticus, Thermus scotoductusThe fi rst discovery of representatives of the genus Thermus have been a stimulus for a detailed study of physiology of thermophilic bacteria. Its discovery was very simple, because the cultivation is very easy. It was used salt synthetic medium that proved suitable for the growth of algae found in hot springs (BROCK, 1978). Representatives of the genus Thermus are Gram-negative aerobic bacteria, however some newly isolated species grow in anaerobic environments where nitrates used as the fi nal electron acceptors. This genus does not form endospores (BALKWILL et al., 2004). The morphology of the organism is largely infl uenced by temperature and growth phase. The organism is usually present in fi bers when the temperature is above 75 °C. The fi bers are formed only in the stationary growth phase culture at 65 to 70 °C (BROCK, 1978).Members of the genus Thermus family are used to produce thermophilic compounds, especially enzymes, such as Taq polymerase (DNA polymerase), serine proteases, glucosidases, pullulanase (ČEJKOVÁ, 2009). Because are these products mostly secondary metabolites, it is necessary to know the growth characteristics of microorganisms that can also be described by mathematical models. Taq is frequently used in polymerase chain reaction (PCR).Mathematical models are used to describe the behavior of microorganisms under diff erent physical or chemical conditions such as temperature, pH and water activity. In order to build these models, growth has to be measur...

This work deals with the problem of flavour of Edam cheeses, i.e. natural hard cheese with low heat curd. The cheese samples were produced in dairy MILTRA B, Ltd., Městečko Trnávka.A number of volatile substances contribute to flavour of cheese including alcohols, aldehydes, ketones, fatty acids, esters, lactones, terpenes etc. The development of these components during production was monitored in chosen Edam cheese (fat 30% w/w) using headspace-SPME-GC method. The samples were taken from cheesemilk up to technologically ripe cheese. In total 37 various organic compounds belonging to five chemical groups were identified in milk and cheese samples. Their total content increased during production. The first increase was observed after pressing and then especially in last part of ripening. Ethanol (185.8 ± 15.85 mg.kg−1), acetoin (97.7 ± 3.78 mg.kg−1), 2-methylpropanol (71.2 ± 5.23 mg.kg−1), acetic acid (54.4 ± 1.70 mg.kg−1) and acetaldehyde (36.4 ± 10.17 mg.kg−1) were the most abundant in ripened cheeses. The flavour and other organoleptic properties (appearance, texture) of Edam cheese samples were also sensorially evaluated during ripening. The five point ordinal scale and profile tests were used for evaluation. The sensory quality was improved during ripening, until the final marked flavour characteristic for these cheese types.

The aim of this work was to identify and quantify several sensory active compounds in various types of yogurts using gas chromatography and simultaneously to judge their influence on flavour of yogurts using sensory analysis. In total 4 types of white and 10 types of flavoured yogurts (creamy and low-fat) with various flavourings, produced in Dairy Valašské Meziříčí, Ltd., were analysed. The highest content of sensory active compounds (P < 0.05) was found in strawberry yogurts, with high amount of ethyl butyrate. Excepting ethanol no significant differences (P < 0.05) were found between low-fat and creamy varieties. The total content of sensory active compounds in white yogurts was significantly (P < 0.05) lower than in flavoured fruit types. The highest content was in low-fat and lowest in white bio yoghurts. Flavour of yogurts was evaluated sensorially using scale and ranking test. All creamy yogurt varieties were evaluated as significantly (P < 0.05) more tasty than low-fat ones. Similarly in case of white yogurts creamy yogurts were evaluated as the most tasty and low-fat ones as the worst. Bio yogurts were evaluated equally tasty as classic yogurts with the same fat content.

The aim of this work was to fi nd the best composition for fruit drink based on elderberries with optimal fl avour characteristics. For this purpose elderberry juice was mixed with various fruit juices (grape, black currant, apple, orange, carrot) in various ratios, fl avour was evaluated sensorially and instrumentally as the content of aroma compounds. Five fl avour characteristics (sweet, acid/sour, bitter, astringent, characteristic elderberry), offfl avour, odour, texture (mouth-feel), colour and overall acceptability were evaluated sensorially using scale. Aroma compounds were extracted by solid phase microextraction and assessed by gas chromatography with fl ame ionization detection and gas chromatography-mass spectrometry. The signifi cant diff erences (P < 0.05) in fl avour were found between samples, which could be explained by diff erences in their volatile profi les. In total 57 compounds were identifi ed in fruit juices and included 20 alcohols, 10 aldehydes, 8 ketones, 7 acids, 7 esters and 5 other compounds. Alcohols were quantitatively the most important group of all juices. The grape-elderberry juice, in optimum ratio 7:3 (70% v/v of elderberry), was proposed for practical use owing to the pleasant sweetish, elderberry fl avour, and excellent other sensory characteristics.