Tonka A. Vasileva

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The Colorado potato beetle is a pest damaging potato and eggplant crops. This insect adapts quickly to the most synthetic insecticides and requires more poisonous agents to decrease its population [1]. In spite of the resistance developed by Leptinotarsa decemlineata, chemical insecticides remains the main method to control it [2]. The search for natural(More)
Neo-clerodane diterpenoids have attracted interest for their varied biological activities. In continuation of our systematic studies on Scutellaria plants [1–3], we have now investigated S. galericulata L. The acetone extract of the aerial parts of S. galericulata was subjected to column chromatography to yield five compounds: 1–5. The IR spectrum of 3(More)
The present study was carried out in three seasons — spring, summer and autumn in Topolnitsa Dam Lake (Bulgaria) which has been subjected to continuous contamination with trace metals due to copper extraction in the area. We investigated the trace metal levels in surface water and liver samples of European perch (Perca fluviatilis L.). We also linked the(More)
Glycosyltransferase activity of 13 Leuconostoc mesenteroides strains isolated from Bulgarian fermented vegetables was investigated. All the strains displayed a mucoid phenotype on sucrose-containing agar media. Strains were characterized according to carbohydrate fermentation, species-specific multiple PCR using several primers, repetitive element-PCR(More)
A study of the influence of different plant terpenoids and amino sugar derivate acarbose on the activity of glycosyltransferase complex and purified dextransucrase from Leuconostoc mesenteroides URE 13 strain was carried out. All the tested terpenoids showed an inhibitory effect on glycosyltransferases from strain URE 13 at concentration 0.34 mmol. Out of(More)
A study on the production of soluble and cell wall-bound glucansucrases (GS) and fructansucrases (FS) by Leuconostoc mesenteroides URE13 and L. mesenteroides Lm17 during their growth on media containing sucrose, glucose or fructose as a main carbon source was carried out. The changes in the enzyme activity, the assimilation of sugars and the formation of(More)
Aqueous alkaline depolymerization of technical hydrolysis lignin (THL) was carried out with a 5% NaOH solution at a temperature of 180°C for 6 hours, the ratio between the biomass and depolymerizing agent being 1:8. The poplar wood sawdust was treated under the same conditions for 2 hours, where anthraquinone was added as a catalyst (0.5 wt %). The poplar(More)
Article info: Received: 22 February 2012 In revised form: 28 April 2012 Accepted: 30 April 2012 ABSTRACT Dextransucrases are enzymes that transfer the glucosyl moiety from sucrose to other acceptor molecules. In the present study, we have investigated the biosynthesis of dextransucrases by two strains of Leuconostoc mesenteroides isolated from Bulgarian(More)
In the present study our major aim was to evaluate the up-to-date contamination status of the Topolnitsa reservoir. It is located in a region with intensive copper mining, which has been constantly contaminated with metals in the last few decades. Thus, we measured As, Cd, Cu, Ni, Pb, and Zn concentrations in surface water samples, as well as, in liver of(More)