Хранителна химия, микробиология, биотехнология и безопасност

Секция „Хранителна химия и хранителна микробиология”

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

Секция „Хранителни биотехнологии и нанотехнологии”

Investigation of the antimicrobial activity of selected strains Lactobacillus delbrueckii subsp. bulgaricus
Изследване на антимикробната активност на селектирани щамове Lactobacillus delbrueckii subsp. bulgaricus
It is known that the probiotic potential of the traditional Bulgarian yoghurt is due to the antimicrobial activity of Lactobacillus delbrueckii ssp. bulgaricus. Therefore, the antimicrobial activity of 4 strains of Lactobacillus bulgaricus has been investigated - Lactobacillus delbrueckii ssp. bulgaricus MG1, Lactobacillus delbrueckii ssp. bulgaricus MG2, Lactobacillus delbrueckii ssp. bulgaricus MG3 and Lactobacillus delbrueckii ssp. bulgaricus MG4, isolated from naturally fermented dairy products, against pathogenic microorganisms: Escherichia coli ATCC 25922, Listeria monocytogenes ATCC 11994 and Salmonella sp. The antimicrobial activity was determined by the agar well diffusion method with both biomass and cell-free supernatant.
Автори: Марин Георгиев, Мария Балтаджиева, Алберт Кръстанов, Богдан Горанов, 1-Универститет по хранителни технологии – Пловдив, 2- Изследователска лаборатория за мляко и млечни продукти ЛБ-Лакт

Секция „Анализ и контрол на хранителните продукти”

Секция „Безопасност на храните”

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

Risk from Staphylococcus aureus in informally marketed raw cow milk
Риск от Staphylococcus aureus в сурово краве мляко, обект на нерегламентирана търговия
This study aimed to investigate the presence of Staphylococcus spp. and Staphylococcus aureus in raw cow milk samples taken from peddlers of five regions in Bulgaria. The results showed that all 44 samples tested were positive for Staphylococcus spp. All isolates were tested for coagulase production and subjected to PCR analysis. PCR amplification of 16S rRNA and nuc genes found the presence of Staphylococcus aureus in 23 (52.3%) of a total of 44 raw milk samples. The number of Staphylococcus spp. ranged from 3x102 to 1.08x106 cfu/ml, and that of Staphylococcus aureus from 1.5x102 to 3.19x105 cfu/ml. It is concluded that control over the hygiene of handling and processing raw milk is essential for its safety.
Автори: Desislava Bangieva, Valentin Rusev

Empirical determination of conversion factor for phycotoxin concentration depicting in whole mussel Mytilus galloprovincialis meat
Опитно определяне на коефициент за преизчисляване концентрацията на фикотоксини в цяло мидено месо на Mytilus galloprovincialis
Mussels accumulate marine biotoxins (phycotoxins) produced by certain phytoplankton species. In EU are set limits for toxin concentration (e.g. domoic acid, okadaic acid, yessotoxins etc.) beyond that mussels are safe for consumption. Marine biotoxins tend to accumulate in the digestive gland (hepatopancreas) of the mussel. Consequently, this tissue is preferred for toxin concentration determination. Normally the whole shellfish is consumed and therefore the occurrence data for phycotoxins need to be expressed in terms of whole shellfish meat. A theoretical factor of 5 is used to convert the value to whole shellfish meat. The aim of this study was to determine an empirical factor in order to convert phycotoxin concentrations from hepatopancreas to whole shellfish meat of main marine aquaculture in Bulgaria- mussels Mytilus galloprovincialis. Wild and cultivated mussels were collected from the north Black Sea coast of Bulgaria in summer 2017. In total 13 mussel samples were studied whereas in each sample subsamples of hepatopancreas only and whole mussel meat are prepared. Phycotoxins were extracted for all types of phycotoxins by means of liquid-liquid extraction and their concentration was determined via LC/MS. Yessotoxins appeared in most of the samples and therefore seemed most suitable for empirical conversion factor determination. It is calculated as ratio between determined concentration in hepatopancreas and whole shellfish meat. Mean defined value was 5.36. Determination and application of empirical conversion factor is important when establishing very low concentration for chronic exposure assessment. It will be advantageous when taking into account interspecies differences and to avoid phycotoxin omission if preparing whole shellfish sample.
Автори: Zlatina Peteva, M. Stancheva, St. Georgieva, A.Gerasimova, L. Makedonmski

Секция „Екология и токсикология на ХВП и биотехнологичната промишленост”

Bioenergy potential of potato peels hydrolysates
Биоенергиен потенциал на хидролизати от картофени обелки
Potato peels are solid organic waste which is released in large quantities and is a major environmental problem. In the present work potato peels are subjected to acidic (0.5M HCl) and enzymatic hydrolysis. The reducing sugars in the resulting hydrolysates have a concentration respectively of 26.5 mg/ml and 14.98 mg/ml. Their energy potential as substrate for ethanol fermentation and methanisation is then explored (production of bioethanol and biomethane that can be used as biofuel, bioenergy or heat). The tested hydrolysate has a high content of organic matter - 35.74 gO2/l, expressed as COD. The resulting potato hydrolysates demonstrated a good potential as a raw material to produce biofuels and valuable organic chemicals. Acknowledgements: This work was supported by scientific project N: 11755 with UCTM - Sofia, Bulgaria
Автори: Polina Velichkova, Shaaban Omar, Todor Ivanov, Ivo Lalov