THE REPUBLIC OF CROATIA EMPLOYED POPULATION STATISTICAL METHODS ANALYSIS IN A PERIOD 2008 TO 2012

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Quadrupole mass spectrometry in the monitoring and control of fermentations

The application of quadrupole mass Spectrometry to the monitoring of fermentation processes allows continuous and simultaneous non-invasive measurement of gases and volatile substrates, intermediates or products. Components are directly and continuously sampled through a silicone rubber membrane either from solution in the culture medium and/or in the influent or effluent gas streams. Gases measured include H2, CH4, O2, CO2, H2S, N2, N2O and (as calibration standard) Ar: vapours include methanol, ethanol, propanol, acetone, n-butanol, acetic acid and butyric acid. This versatility of detection is enhanced by off-line determinations of non-volatiles after pH adjustment (e.g. total CO2−3 or NH+4) or derivativization (e.g. some carboxylic or keto acids). Appropriate automation allows multicomponent analysis at many sampling points (i.e. simultaneously in many different fermentors).Applications are described for aerobic processes (antibiotic production, yeast fermentation, growth on methanol) and anaerobic processes (acetone-butanol fermentation, anaerobic digestion of farm and domestic wastes, and fermentation in the rumen). Future developments include exploitation of the high sensitivity, long-term stability and high specificity of mass spectrometric measurements to process control and optimization

Identification of dissolved volatile metabolites in microbial cultures by membrane inlet tandem mass spectrometry

A membrane inlet tandem mass spectrometer is used for easy identification of volatile metabolites in microbial cultures. Filtrates of the cultures are without further purification placed into a measuring cell and introduced via a membrane inlet into a triple‐quadrupole mass spectrometer. The samples are analysed with electron impact and chemical ionization mass spectrometry and tandem mass spectrometry. An extra dimension of separation is obtained by utilizing differences in response time due to differences in transport rates through the membrane. The following examples are used to demonstrate the technique. (i) Filtrates from cultures of three parasitic protozoa (trichomonads); two different strains of Trichomonas vaginalis isolated from humans and from Tritrichomonas foetus isolated from cattle were analysed. Indole was found in all samples; dimethyl disulphide was also present in cultures of the two organisms isolated from humans. (ii) The yeast Brettanomyces was grown in the presence of coumaric acid, ferulic acid, vanillic acid or syringic acid and the filtrate analysed for volatile products. In all cases ethyl acetate was found; coumaric acid biotransformation also gave 4‐ethylphenol, whereas ferulic acid also gave 4‐ethyl‐2‐methoxyphenol

Identification of dissolved volatile metabolites in microbial cultures by membrane inlet tandem mass spectrometry

A membrane inlet tandem mass spectrometer is used for easy identification of volatile metabolites in microbial cultures. Filtrates of the cultures are without further purification placed into a measuring cell and introduced via a membrane inlet into a triple‐quadrupole mass spectrometer. The samples are analysed with electron impact and chemical ionization mass spectrometry and tandem mass spectrometry. An extra dimension of separation is obtained by utilizing differences in response time due to differences in transport rates through the membrane. The following examples are used to demonstrate the technique. (i) Filtrates from cultures of three parasitic protozoa (trichomonads); two different strains of Trichomonas vaginalis isolated from humans and from Tritrichomonas foetus isolated from cattle were analysed. Indole was found in all samples; dimethyl disulphide was also present in cultures of the two organisms isolated from humans. (ii) The yeast Brettanomyces was grown in the presence of coumaric acid, ferulic acid, vanillic acid or syringic acid and the filtrate analysed for volatile products. In all cases ethyl acetate was found; coumaric acid biotransformation also gave 4‐ethylphenol, whereas ferulic acid also gave 4‐ethyl‐2‐methoxyphenol