Naslov
Antibacterial activity of zinc containing clinoptilolite in different water media

Autori
Hrenović, Jasna ; Rajić, Nevenka ; Milenković, Jelena ; Ivanković, Tomislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, ostalo

Izvornik
Book of abstracts, 4th International Conference on Environmental, Industrial and Applied Microbiology / Mendez-Vilas, A. - Torremolinos, 2011, 628-628

Skup
4th International Conference on Environmental, Industrial and Applied Microbiology

Mjesto i datum
Torremolinos, Španjolska, 14.09.2011. - 16.09.2011

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Escherichia coli; Staphylococcus aureus; toxicity; zeolite; zinc

Sažetak
Natural zeolitized tuffs (NZ) rich in clinoptilolite are good adsorbents of heavy metals due to their high cation exchange capacity. The NZ containing 70 wt. % of clinoptilolite was obtained from the sedimentary deposit Zlatokop, Serbia. The particle size of the sample was in the range 0.063-0.1 mm. The NZ was firstly converted into the Na-form by treating the NZ with 2M of NaCl solution, in order to improve the clinoptilolite exchange capacity without affecting the crystallinity of NZ. The experiments on Zn2+ removal from water were performed at 30C during 24h using the batch method and ZnCl2 solution in concentration of 400 mg Zn/L with mass concentration of NZ of 1g/100mL. On this way NZ containing Zn2+ ions (named ClZn2+) was obtained. The ClZn2+ was than completely dehydrated at 550ºC under air. The dehydration led to a generation of ZnO nano-particles (about 5 nm) widespread over the surface of NZ. This material was assigned as ClZnO. The leaching test of ClZn2+ and ClZnO was performed using the 0.05M NaCl solution of pH 7.0 at 37C during 24h. The resulting leached concentration of Zn2+ in water was 0.67 mg/L for ClZn2+ whereas no leached Zn2+ was found for ClZnO. After the use of clinoptilolite for zinc removal from wastewater, we looked for future application of the used material, one of which can be removal of pathogenic bacteria in the tertiary stage of wastewater treatment. The antibacterial activity of ClZn2+ and ClZnO was tested against representative pathogenic Gram-negative (Escherichia coli, DSM 498) and Gram-positive (Staphylococcus aureus, clinical isolate at Institute of Public Health, Zagreb) bacteria. The antibacterial assay was carried out whit mass concentration of material of 1g/100mL in three different water media: Luria Bertani or LB medium, synthetic wastewater and real effluent water from the secondary stage of the biological wastewater treatment. The initial pH of used media was 7.0 and the chemical composition was as follows (in mg/L): LB medium (bacto-tryptone 10, 000 ; bacto-yeast extract 5, 000 ; NaCl 10, 000 ; COD 14, 000), synthetic wastewater (Na-propionate 1, 000 ; peptone 100 ; MgSO4 10 ; CaCl2 6 ; KCl 30 ; yeast extract 10 ; KH2PO4 20 ; COD 1, 206), effluent water (T-N 28.3 ; T-P 2.27 ; COD 31.4). All media and materials were autoclaved before the experiments were to commence. The experiments were carried out at 37C. The CFUs of bacteria were measured on LB agar at the start and after 24h of experiment. The antibacterial activity of material was expressed as percentage of log CFU reduction when compared to control where no material was added (Table 1). The percentage of inhibition of bacteria in the presence of ClZn2+ and ClZnO showed significantly negative correlation with the COD of water media used in assay (R = -0.987 and -0.949, respectively). The ClZn2+ showed better antibacterial activity than ClZnO, which is ascribed to the difference in leaching of Zn2+ ions from materials. The E. coli seems to be more resistant to Zn2+ ions than S. aureus. The difference in final pH among control and experimental reactors was not higher than 0.59 units. No significant antibacterial activity of materials was observed after 1h of contact with bacteria. Table 1. Antibacterial activity of ClZn2+ and ClZnO against E. coli and S. aureus after 24h of incubation in different water media when compared to control. c0 E. coli (106 CFU/mL) = 3.85±0.89 ; c0 S. aureus (107 CFU/mL) = 1.42±0.24 ; significantly different when compared to A-LB medium, B-synthetic wastewater, C-ClZn2+. The antibacterial activity of zinc containing clinoptilolite (mass concentration 1g/100mL, 24h of contact) was depended on the following factors in decreasing order: COD of the water medium, type of material and species of bacteria. The antibacterial activity of certain compound tested in the synthetic medium can be significantly different from those in real water medium.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

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