Campylobacter spp. bacteria are one of the leading causes of food borne illness worldwide and has the ability to form biofilms. These biofilms have been reported to confer resistance against antibiotics. In this study, the effect of five different antibiotics has been compared on the planktonic and biofilm forms of Campylobacter isolates by determining their minimum inhibitory concentration (MICs). A total of 55 isolates (11 Campylobacter jejuni and 41 Campylobacter coli) were subjected to flaA typing and cluster analysis. On the basis of flaA typing, 23 isolates, comprising 17 C. coli and 6 C. jejuni representing each cluster were chosen and analyzed for their biofilm forming potential at two different temperatures (37 degrees C and 42 degrees C) under both aerobic and microaerobic conditions. The biofilm production was higher at 37 degrees C in comparison to 42 degrees C, and it was enhanced under aerobic conditions compared to microaerobic conditions at both temperatures. MICs of gentamicin, kanamycin, tetracycline, erythromycin and carbenicillin were determined for both planktonic and biofilm forms of campylobacter bacteria grown in 96 well microtitre plates containing Muller Hinton (MH) broth. All the isolates in the planktonic form showed absolute resistance against carbenicillin. The MIC values of gentamicin, kanamycin, tetracycline and erythromycin for planktonic form were found to be 0.032 mu g/ml, 2 mu g/ml, 0.1 mu g/ml and 0.0125 mu g/ml, respectively; while, for biofilm forms the same were found to be 1.025 mu g/ml, 8 mu g/ml, 0.8 mu g/ml and 0.2 mu g/ml, respectively. The findings revealed 32, 16, 8 and 4 fold higher resistance by biofilm associated campylobacter bacteria against gentamicin, erythromycin, tetracycline and kanamycin, respectively.

A non interpenetrating supported carbon membrane was prepared using a resole-type phenol-formaldehyde resin as precursor. Amine groups were created on the carbon membrane through nitration using NO, and used to immobilize lipase enzyme by reacting with glutaraldehyde. To maintain high enzyme activity, surface carboxylic groups were modified and the immobilized enzyme on the membrane thus obtained was active even after 3 months of usage. The performance of the biphasic membrane reactor is studied in terms of amount of free fatty acid produced per unit time based on the volume of aqueous phase and the effect of operating variables (pH of aqueous phase solution, solvent used for olive oil, olive oil concentration, and aqueous phase circulation rate) were evaluated. Experiments show that the activity of lipase increases 1.42-fold upon immobilization. The maximum reaction rate was 3.6-fold higher, and the base case rate was 1.4-fold higher than the values reported in the literature for a similar enzyme membrane reactor but with a different membrane. (c) 2005 American Institute of Chemical Engineers.

Supported non-interpenetrating modified ultrafiltration carbon membrane has been prepared by gas phase nitration using NOx (mixture of NO and NO2) at 250°C and subsequently aminated in the second step using hydrazine hydrate at 60°C. Separation experiments on the chromic acid solution have been carried out using unmodified (giving 96% rejection), nitrated (giving 84% rejection) and aminated (giving 88% rejection) carbon membrane. The water flux of the modified membrane however, has been found to increase by two times compared to that for the unmodified membrane with only 12% loss in rejection. This work presents a transport mathematical model through cylindrical charged capillaries of the membrane based on two-dimensional space charge model consisting of Nernst–Planck equation for ion transport and non-linear Poisson–Boltzmann equation for the radial distribution of potential. The solutions of these non-linear equations are computationally intensive and the difficulty has been overcome by a series solution of the Poisson–Boltzmann equation for the charge distribution. The effective pore size and non-dimensional pore wall potential of the membranes have been determined using this model by fitting the experimental data of the separation. The effective pore radius of the unmodified, nitrated and aminated carbon membranes are found to be 2.0, 2.8 and 3.3nm respectively, which are less than the average pore size value determined from the molecular weight cut-off experiment and indicates the partial blocking of the pores by chromate ions.

We have synthesized carbon membranes by carbonizing a phenol–formaldehyde (PF) resin in the absence of air, and evaluated their physical properties and separation performance. Carbonization of the PF resin at 500 °C for 30 min resulted in around 20% mass reduction and produced a membrane material which exhibited a moderate BET surface area of 29.6 m2/g, with the majority of its porous structure confined to pores <15 nm. As observed by visible Raman spectroscopy, the carbon membrane seems to consist of a crystalline structure imbedded in an amorphous carbon matrix. The average grain size was found to be around 9.18 nm, which matches closely the results of Raman studies. The crystal structure is based on a hexagonal structure with a=7.8072 Å and c=7.066 Å with the latter length matching that of graphite. The difference in the former parameter was attributed to a motif consisting of a seven-membered plane benzene ring (one ring surrounded by six others) due to internal strain which was determined to be 3.22% by an XRD technique. The molecular weight cut-off (MWCO) of this membrane was found to be about 7500 Daltons. The performance of the membrane was studied by separating hexavalent chromium ions from an aqueous chromic acid solution. The apparent and intrinsic rejection of Cr6+ ions was of the order of 70 and 90%, respectively, and was found to increase with an increase in applied pressure.

Polyacrylamide (PAAm) hydrogels were synthesized by partial cross-linking of PAAm using p-formaldehyde as curing agent. The cross-linking reaction was studied using differential scanning calorimeter (DSC) and cure kinetics was determined. The dynamic DSC scans of freshly mixed reaction mixture that showed an endothermic peak corresponding to cure at 75 1 C, indicate multiple reactions. The FTIR studies of curing reactions indicated that alkaline hydrolysis of PAAm was also occurring during curing as evident by generation of carboxylic group in the cured PAAm or hydrogels. In the initial phase of cross-linking reaction and at lower temperature rapid hydrolysis occurred which was endothermic in nature, but at higher temperature curing reaction was favoured. Isothermal cure kinetics revealed that curing reaction was nth order type and followed third order kinetics. The study also indicates that with the degree of conversion 0.25-0.26, both curing and hydrolysis occurs simultaneously but at higher conversions curing reaction proceedes alone. The swelling studies also indicates that the swelling index of PAAm hydrogels increases with decreasing curing agent concentration; but increases with increasing swelling duration and curing time, and molecular weight of polymer.