Publications by authors named "Vlada B Veljkovic"

White mustard ( L.) seed oil is used for cooking, food preservation, body and hair revitalization, biodiesel production, and as a diesel fuel additive and alternative biofuel. This review focuses on biodiesel production from white mustard seed oil as a feedstock.

View Article and Find Full Text PDF

This study reports on the use of oil obtained from waste plum stones as a low-cost feedstock for biodiesel production. Because of high free fatty acid (FFA) level (15.8%), the oil was processed through the two-step process including esterification of FFA and methanolysis of the esterified oil catalyzed by H2SO4 and CaO, respectively.

View Article and Find Full Text PDF

In this paper, extraction of resinoid from the aerial parts of white lady's bedstraw (Galium mollugo L.) using an aqueous ethanol solution (50% by volume) was studied at different temperatures in the absence and the presence of ultrasound. This study indicated that ultrasound-assisted extraction was effective for extracting the resinoid and gave better resinoid yields at lower extraction temperature and in much shorter time than the maceration.

View Article and Find Full Text PDF

Yields of extracted substances, as well as total phenol and flavonoid compounds obtained by classical and ultrasonic extractions from dry leaves of two tobacco types (oriental and Virginia) by two different solvents (acetone and methanol) at two operating temperatures (25 and 40 degrees C) were compared. The yield of extractive, as well as total phenol and flavonoid compounds depended on the type of solvent, operational temperature and the tobacco type. The importance of these factors was assessed using 2(4) full factorial experiments without replication.

View Article and Find Full Text PDF

A media consisting of isatin-Schiff bases (isatin-3-thiosemicarbazone, isatin-3-semicarbazone, and isatin-3-phenylhydrazone) was developed to maximize the production of antibiotics Hexaene H-85 and Azalomycine B by Streptomyces hygroscopicus. The media isatin-3-thiosemicarbazone resulted in the maximum antibiotics concentration of 372 mug cm(-3) for Hexaene H-85 and 118 mug cm(-3) for Azalomycine B. The impact of modified media on soil morphology also was investigated.

View Article and Find Full Text PDF

The kinetics of Ca(OH)(2)-catalyzed methanolysis of sunflower oil was studied at a moderate temperature (60 degrees C), a methanol-to-oil molar ratio (6:1) and different catalyst amounts (from 1% to 10% based on oil weight). The methanolysis process was shown to involve the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter period. The TG mass transfer limitation was caused by the low available active specific catalyst surface due to the high adsorbed methanol concentration.

View Article and Find Full Text PDF

A chemically defined media consisting of carboxymethylcellulose (CMC) was developed to maximize the production of antibiotics, hexaene H-85 and azalomycine, by Streptomyces hygroscopicus CH-7. The production of antibiotics by filamentous organisms is often dependent on the morphology and size distribution of the pellet population within the culture. By adding the polymer to the fermentation medium, the growth was changed from a single large glob to small reproducible pellets, and wall growth was diminished to a minimum.

View Article and Find Full Text PDF

The kinetics of the sunflower oil methanolysis process was studied at lower temperatures (10-30 degrees C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the methanolysis reaction.

View Article and Find Full Text PDF