Development of Antimicrobial Membranes via the Surface Tethering of Chitosan

To render the surface of ultrafiltration membranes biocidal, cellulose membranes were modified with chitosan, a naturally occurring polycationic biocide. Through the use of chitosans of different molecular weights and membranes with different pore sizes, the alteration of the morphological structure of tethered chitosan layers was achieved. The importance of such structural differences in the antimicrobial activity of the prepared membranes against gram-positive Staphylococcus aureus and gram-negative Escherichia coli was studied. The antimicrobial efficiency improved with the use of chitosans with higher molecular weights and membranes with smaller pore sizes. This suggested that the surface location of the grafted chitosan chains was more preferential for a higher antimicrobial activity of the surface. Membranes modified with chitosan showed higher antimicrobial efficiency against gram-positive S. aureus than against gramnegative E. coli.Міжнародний благодійний фонд відродження Києво-Могилянської академі

Immobilization of antibacterial agents on the surface of cellulose membranes modified with polyglycedylmethacrylate

A new method of glycidylmethacrylate (GMA) radical copolymerization on the surface of commercial cellulose membranes followed by immobilization of synthetic antibiotics on grafted poly(GMA) chains has been developed. Transport and antimicrobial properties of modified membranes have been studied. It has been shown that decreasing of samples permeability is caused by grafting of GMA, and it depends on initiator concentration, duration of reaction and process temperature. Infrared spectrometry and capillary electrophoresis were used to analyze modified samples. Antibacterial properties of membranes modified by nalidixic acid and levofloxacin were studied against gram-negative bacteria E. coli and gram-positive bacteria S. aureus. Higher antibacterial activity of membranes modified by levofloxacin in comparison to those modified by nalidixic acid was shown. Thus, antibacterial activity of membranes modified by 0,5% solutions of antibiotics was 90% for samples with nalidixic acid and 100% for samples with levofloxacin. All samples showed lower antibacterial activity against gram-negative bacteria. The antibacterial activity remained stable for 36 days of membrane operation

Spatial sequencing of microbial reduction of chromate and nitrate in membrane bioreactor

Sequential reduction of chromate and nitrate, two competitive electron acceptors, has been demonstrated for strains of Pseudomonas genus for both planktonic cells and cells immobilised in agar layers on the surface of synthetic membrane. Denitrification occurs practically after chromate depletion. This order of reduction process is consistent with redox potentials of the respective reactions. In a membrane bioreactor, competitive inhibition results in nitrate transfer through the membrane without transformation. Thus the receiving phase is contaminated with nitrate. To address this problem, a membrane has been used for spatial sequencing of chromate and nitrate reduction. Bacterial cells were immobilised in two layers with each layer placed on opposing sides of the membrane. By this means, chromate reduction is localised into the layer contacting the feed phase while nitrate reduction occurs in the layer facing the receiving phase. As a result, only traces of the pollutants are detected in the receiving phase.Міжнародний благодійний фонд відродження Києво-Могилянської академі