Food chemistry, microbiology,biotechnology and safety

Section „Food Chemistry and Food Microbiology”

Characterization of antioxidant and antimicrobial activity of (Thymus vulgaris L.)
Характеристика на антиоксидантна и антимикробна активност на (Thymus vulgaris L.)
This work presented a critical review on thyroid antioxidant and antimicrobial activity (Thymus vulgaris L.) and the possibilities for its use in culinary technology. Essential oils and methanol extracts derived from Thymus vulgaris seeds have been found to show single and combined antibacterial activities against nine Gram-positive and Gram-negative pathogenic bacteria: Staphylococcus aureus, Bacillus Cereus, Escherichia coli, Proteus vulgaris, Proteus mirabilis, Salmonella typhi, Salmonella typhimurium, Klebsiella pneumoniae and Pseudomonas aeruginosa. The essential oils and methanol extracts of Thymus vulgaris L. have significant antibacterial properties, was found. Thyme essential oils were also tested for their inhibitory effects. Gas (GC) and Gas Chromatography / Mass Spectrometry (GC/MS) methods were used to identify aromatic components in thyme leaf extracts.
Автори: Albena B. Parhzanova1, Snezhana D. Ivanova1

A selective medium for the enumeration and differentiation of Lactobacillus delbrueckii ssp. bulgaricus
Селективна среда за изброяване и диференциране на Lactobacillus delbrueckii ssp. Bulgaricus
Lactobacillus delbrueckii subsp. bulgaricus is an important species of lactic acid bacteria used as a starter culture in the production of yogurt and some cheeses. Given the importance of this strain in dairy industry, it is necessary to have an efficient medium to be able to study this bacterium and isolate new strains. DeMan Rogosa and Sharpe (MRS) has been used for decades to enumerate lactic acid bacteria. However, the viability of lactic acid bacteria is restricted in MRS because of rapid nutrient depletion. In this study, we have developed Modified Reinforced Clostridial Medium Blue (mRCM-BLUE) based on specific nutritional and biochemical requirements of L. bulgaricus; in order to meet industry need for a more superior growth medium for the bacteria. Two strains of L. bulgaricus and three species of probiotic bacteria were used for the present study. MRS, Reinforced Clostridial Medium (RCM) and Lactic Agar (LA) media were prepared according to manufacturers’ instructions. mRCM-BLUE was developed by supplementing RCM with 0.025% CaCl2 , 0.2% Tween 80, 0.01% uracil and 0.01% aniline blue dye. Bacterial growth rate on the different media was monitored for 12 h at 42°C. Bacterial cells from pure strains and mixed cultures were enumerated using the cell count method. Colonies of L. bulgaricus that appeared on the different media plates were observed and compared based on colony morphology and appearance. Our results demonstrated that mRCM-BLUE (RCM supplemented with CaCl2, uracil, Tween 80 and aniline blue dye) significantly (P < 0.5) enhanced the growth and differentiate L. bulgaricus compared to MRS, LA and RCM in mixed lactic acid bacterial cultures. Therefore, mRCM-BLUE can be used in dairy industry to rapidly grow and isolate L. bulgaricus strains from natural sources to meet the high demand of this bacteria. mRCM-BLUE may also be used microbiologically for the analyses of new strains of L. bulgaricus.
Автори: Nwadiuto Nwamaioha, Rabin Gyawali, Tahl Zimmerman, Salam A. Ibrahim

Section „Food Biotechnology and Nanotechnology”

Section „Analysis and Control of Foodstuffs”

Section „Food Safety”

A dual choline/phosphocholine colorimetric method for measuring the relative strength of inhibitors of choline kinases of Gram-positive pathogens.
Двоен холинов/фосфохолинов колориметричен метод за измерване на относителната сила на холинкиназните инхибитори на Грам-положителни патогени
Outbreaks of food-borne illnesses become more common, however, consumers are becoming more concerned about the use of chemical and artificial food preservation methods. In order to face the problem of food-borne pathogens in a way that is acceptable for consumers, antimicrobials from natural sources need to be discovered and developed for use. The goal of this research is to discover natural antimicrobials that can inhibit choline kinase, an established drug target in Gram-positive bacteria. The objective of this project was to develop a simple, robust, and easy to implement screening system for natural inhibitors of choline kinase. The system presented here was based on a previously developed colorimetric method for assessing choline kinase activity and can be used to compare strength of inhibition by determining IC50 values. This is a dual choline/phosphocholine method that has 3 steps: (1) activated charcoal for filtration, (2) triiodide for choline detection, and (3) molybdenum blue dye (MBD) for phosphocholine detection. Whole cell extracts containing the choline kinase of Streptococcus pneumoniae (sChoK) are used in enzymatic reactions and three known inhibitors of human choline kinase (hChoK) are used as a model: Hemocholinium-3, RSM-928A, and MN58. The IC50 values of these drugs were >2700 µM, 0.54 µM, and 170-225 µM, respectively. Importantly, not all three steps of the colorimetric method could be used in the case of every inhibitor, since each had its own particular reactive profile with the dyes that could lead to confounded measurements with either the triiodide or MBD dyes. But in every case, the system was flexible enough to allow for measuring choline or phosphocholine, if not both metabolites. We establish here that this dual choline/phosphocholine system can be used with any possible inhibitor, no matter its reactive profile, to determine its strength of inhibition. This colorimetric method is an ideal benchtop method for screening for natural
Автори: Tahl Zimmerman, Juan Carlos Lacal, and Salam A. Ibrahim

Section „Ecology and Toxicology of Food and Biotech Industry”