Search

In the effort to overcome the increase in antimicrobial resistance of different pathogens, natural products from microbial sources appear to be the most favorable alternative to current antibiotics. Production of antimicrobial compounds is highly dependent on the nutritional conditions. Hence, in order to achieve high product yields, selection of the media constituents and optimization of their concentrations are required. In this research, the possibility of antimicrobial substances production using Bacillus subtilis ATCC 6633 was investigated. Also, optimization of the cultivation medium composition in terms of contents of glycerol, sodium nitrite and phosphates was done. Response surface methodology and the method of desirability function were applied for determination of optimal values of the examined factors. The developed model predicts that the maximum inhibition zone diameters for Bacillus cereus ATCC 10876 (33.50 mm) and Pseudomonas aeruginosa ATCC 27853 (12.00 mm) are achieved when the initial contents of glycerol, sodium nitrite and phosphates were 43.72 g/L, 1.93 g/L and 5.64 g/L, respectively. The results of these experiments suggest that further research should include the utilization of crude glycerol as a carbon source and optimization of composition of such media and cultivation conditions in order to improve production of antimicrobial substances using Bacillus subtilis ATCC 6633.

Kombucha beverage was produced using effluent from clarifying the grape must. Substrate for fermentation was prepared by diluting sterilized winery effluent to 70, 50, and 30 g/L of total sugars. Fermentation lasted for nine days at 20, 25, and 30 °C. A pleasant taste kombucha was produced. The beverage was ready to drink after three days of fermentation. From 300 mL fermentation volume, more than 40 g/L of biomass was produced at maximum temperature and sugar content. Acetic acid was the acid, with a peak concentration of 14.63 g/L after nine days at 30 °C and 70 g/L. Tartaric acid originated from the grape. Oxalic acid content was higher at the lower fermentation temperature. Produced kombucha had good antimicrobial properties. Higher temperature and sugar content promote antimicrobial activity against both Gram-positive and Gram-negative bacteria. No activity against yeast was observed. Antimicrobial properties against bacteria and acetic, tartaric, and oxalic acids content were modelled using RSM. Correlation analysis showed a positive relationship between acetic and tartaric acid content and antimicrobial activity. • The winery effluent was successfully used for kombucha fermentation. • The novel kombucha product had good antimicrobial properties. • A wide variety of organic acids was determined in the obtained products. • Antimicrobial properties and organic acids content were modelled using RSM. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Agregation behavior of two newly synthesized thiazolium salts are studied. • Introduction of –CH 3 on thiazolium ring increase thermal stability and decrease CMC. • Micelle formation reduces the toxicity of salts. • Additional methylation also reduces toxicity. Abstract Two new thiazolium-based surfactants namely N -dodecylthiazolium bromide, [NddTz][Br] and N -dodecyl-4-methylthiazolium bromide, [4mNddTz][Br], were synthesized and investigated as new surface active and antimicrobial agents. Their thermal stability is determined by TG/DSC measurements, and the self-assembly behaviour in aqueous solutions systematically studied applying experimental and molecular dynamics (MD) approach. Obtained results of surface tension and electrical conductivity showed that both newly synthesized salts possess a similar surface activity in aqueous solutions compared to imidazolium-based surface active N -dodecyl-3-methylimidazolium bromide, [NddmIm][Br], ionic liquid. Also, thermodynamic parameters of micellization are calculated and compared with the results obtained by volumetric measurements. Antimicrobial activity of these salts is tested by microdilution method on Gram-positive and Gram-negative bacteria and yeasts. In vitro cytotoxicity study has been performed using human fetal lung fibroblasts (MRC-5) and colon adenocarcinoma (HT-29) cell line. [ABSTRACT FROM AUTHOR]