Correction to: pH control and the production of extracellular dextransucrase by Leuconostoc mesenteroides.

Unfortunately, M. M. Vrvic name has been published incorrectly in the original publication as M. M. Vrivic, corrected name appears in this erratum.

Ultrasound-assisted adsorption of copper(II) ions on hazelnut shell activated carbon.

The present study was aimed to removal of Cu(II) ions from aqueous solution by ultrasound-assisted adsorption onto the granular activated carbon obtained from hazelnut shells. The attention was focused on modeling the equilibrium and kinetics of Cu(II) adsorption onto the granular activated carbon. The granular activated carbon was prepared from ground dried hazelnut shells by simultaneous carbonization and activation by water steam at 950 degrees C for 2h. Adsorption isotherm data were better fitted by the Langmuir model than the Freundlich model in both the absence and the presence of ultrasound. The maximum adsorption capacity of the adsorbent for Cu(II), calculated from the Langmuir isotherms, in the presence of ultrasound (3.77 mmol/g) is greater than that in the absence of ultrasound (3.14 mmol/g). The adsorption process in the absence and the presence of ultrasound obeyed to the pseudo second-order kinetics. The removal of Cu(II) ions was higher in the presence of ultrasound than in its absence, but ultrasound reduced the rate constant. The intraparticular diffusion model indicated that adsorption of Cu(II) ions on the granular activated carbon was diffusion controlled as well as that ultrasound promoted intraparticular diffusion.

Ultrasonic extraction of oil from tobacco (Nicotiana tabacum L.) seeds.

The ultrasonic extraction (UE) of oil from the seeds of a semi-oriental tobacco (Nicotiana tabacum L.) plant strain by using n-hexane and petroleum ether was studied at different temperatures and seeds-to-solvent ratios. The oil yield depended on the seed comminution, the extraction temperature, the seeds-to-solvent ratio and the type of solvent. The oil yield was much higher if the seeds were ground before extraction. The oil yield increased with increasing the extraction temperature and with decreasing the seeds-to-solvent ratio. n-Hexane was somewhat more efficient in the oil extraction than petroleum ether. In recovering the tobacco seed oil (TSO), the UE was less efficient than the Soxhlet extraction. The advantage of the UE was a relatively high oil yield at 25 degrees C in a shorter time. The kinetics of UE of TSO was described using the model of unsteady diffusion through plant material.

The effect of agitation intensity on alkali-catalyzed methanolysis of sunflower oil.

The sunflower oil methanolysis was studied in a stirred reactor at different agitation speeds. The measurements of drop size, drop size distribution and the conversion degree demonstrate the effects of the agitation speed in both non-reaction (methanol/sunflower oil) and reaction (methanol/KOH/sunflower oil) systems. Drop size distributions were found to become narrower and shift to smaller sizes with increasing agitation speed as well as with the progress of the methanolysis reaction at a constant agitation speed. During the methanolysis reaction, the Sauter-mean drop diameter stays constant in the initial slow reaction region, rapidly decreases during the fast reaction period and finally reaches the equilibrium level. Due to the fact that the interfacial area increases, one can conclude that the rate of reaction occurring at the interface will also be enhanced progressively. The "autocatalytic" behavior of the methanolysis reaction is explained by this "self-enhancement" of the interfacial area, due to intensive drop breakage process.

Kinetics of ultrasonic extraction of extractive substances from garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage.

The kinetics of ultrasonic extraction of extractive substances (ES) from dry herbs of garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage using petroleum ether, 70% ethanol or water at 40 degrees C, as well as the composition of dry extracts, were studied. The mechanism of ultrasonic extraction is confirmed to occur in two steps: first, dissolution of the ES near the particle surface (washing) and, second, diffusion from the solid particles to the bulk of the liquid extract (slow extraction). The process is described mathematically using three concepts of the unsteady diffusion through plant material, the film theory and the empirical equation of Ponomaryov. The yield of ES increases with increasing solvent polarity, and nearly the maximum concentration of ES in liquid extracts is achieved for about 20 min. The composition of extracts depends on both the extraction conditions applied and the plant material.

Ultrasound-assisted adsorption of 4-dodecylbenzene sulfonate from aqueous solutions by corn cob activated carbon.

This study was aimed at removal of 4-dodecylbenzene sulfonate (DBS) ions from aqueous solutions by ultrasound-assisted adsorption onto the carbonized corn cob (AC). The main attention was focused on modeling the equilibrium and kinetics of adsorption of DBS onto the AC. The AC was prepared from ground dried corn cob by carbonization and activation by carbon dioxide at 880°C for 2h in a rotary furnace. The adsorption isotherm data were fitted by the Langmuir model in both the absence and the presence of ultrasound (US). The maximum adsorption capacities of the adsorbent for DBS, calculated from the Langmuir isotherms, were 29.41mg/g and 27.78mg/g in the presence of US and its absence, respectively. The adsorption process in the absence and the presence of US obeyed the pseudo second-order kinetics. The intraparticular diffusion model indicated that the adsorption of DBS ions on the AC was diffusion controlled as well as that US promoted intraparticular diffusion. The ΔG° values, -24.03kJ/mol, -25.78kJ/mol and -27.78kJ/mol, were negative at all operating temperatures, verifying that the adsorption of DBS ions was spontaneous and thermodynamically favorable. The positive value of ΔS°=187J/molK indicated the increased randomness at the adsorbent-adsorbate interface during the adsorption of DBS ions by the AC.

[Characterization and antimicrobial activity of the bioactive metabolites in streptomycete isolates].

Twenty different streptomycete isolates were obtained from soils of southeast Serbia. Five isolates identified as Streptomyces hygroscopicus (SH100, SH101, SH102, SH103, and SH104) showed strong activity against Botrytis cinerea, a parasite found in domestic vines. These isolates were extensively studied for their in vitro antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, yeasts and fungi, and also antiviral activity against Herpes simplex. The results indicated that the obtained isolates were highly active against Botrytis cinerea, Candida albicans, and Herpes simplex, with an inhibition zone of approximately 31 mm. The structure of the bioactive components was determined using elemental analysis, as well as UV/VIS, FTIR, and TLC.

pH control and the production of extracellular dextransucrase byLeuconostoc mesenteroides.

The specific growth rate, the maximum specific dextransucrase production rate and the maximum dextransucrase yield during the dextransucrase fermentation byLeuconostoc mesenteroides were all unaffected by both the pH of the culture medium, maintained at 5.5 or 6.7, and the mode of pH control, by adding NaOH or K2HPO4.