Bacteria inactivation

Figure 4.9 Images of Micrococcus lyiae bacteria inactivation of the photocatalyst,...

Table 6.1 Efficiency of bacteria inactivation as a function of the treated percentage of the total water volume...

The trapping of photoelectrons (17.14) leaves photogenerated holes available for reaction with hydroxyl ions to form hydroxyl radicals. Decreased activity above the optimum metal ions concentration is possibly due to the oxidation of Fe2+ by hydroxyl radicals or holes. The competition of holes between Fe+2 and OH— means that less OH radicals would be generated for the bacteria inactivation. The reactivity... 

It was found that neither the type of web supports nor the nature of the Ti02 seemed to influence the bacteria inactivation kinetics (Gumy 2006). No enhancement was observed with fixed catalysis compared with light only (Fig. 17.4), for the... 

Drug-resistant bacteria inactivate /3-lactam antibiotics by hydrolyzing the amide linkage of the lactam ring. Augmentin consists of a /3-lactam antibiotic (amoxicillin) and potassium clavulanate, a compound that blocks the enzyme responsible for the hydrolysis. This combination enables the amoxicillin to avoid being deactivated by the enzyme. 

Heparinase Bacteria Inactivates heparin by sugar removal residutil heparin removal after extracorporeal blood circulation Yang et al. (1986) and Comfort et al. (1989)... 

Sharrer, M. and Summerfelt, S. (2007). Ozonation Eollowed by Ultraviolet Irradiation Provides Effective Bacteria Inactivation in a Freshwater Recirculating System, Aquacultural Eng., 37, pp. 180-191. 

Spibmbergo, S. and Bertucco, A. (2003) Non-thermal bacteria inactivation with dense CO2. Biotechnology and Bioen neering 84 (6), 627—638. 

Guo M-Z, Ling T-C, Poon C-S (2012) Ti02-based self-compacting glass mortar comparison of photocatalytic nitrogen oxide removal and bacteria inactivation. Build Environ 53 1-6... 

Modesto O, Hammer P, Nogueira REP (2013) Gas phase photocatalytic bacteria inactivation using metal modified Ti02 catalysts. J Photochem Photobiol A 253 38-44... 

Irradiation. Although no irradiation systems for pasteurization have been approved by the U.S. Food and Dmg Administration, milk can be pasteurized or sterilized by P tays produced by an electron accelerator or y-rays produced by cobalt-60. Bacteria and enzymes in milk are more resistant to irradiation than higher life forms. For pasteurization, 5000—7500 Gy (500,000—750,000 tad) are requited, and for inactivating enzymes at least 20,000 Gy (2,000,000 rad). Much lower radiation, about 70 Gy (7000 tad), causes an off-flavor. A combination of heat treatment and irradiation may prove to be the most acceptable approach. 

Bacteria produce chromosomady and R-plasmid (resistance factor) mediated P-lactamases. The plasmid-mediated enzymes can cross interspecific and intergeneric boundaries. This transfer of resistance via plasmid transfer between strains and even species has enhanced the problems of P-lactam antibiotic resistance. Many species previously controded by P-lactam antibiotics are now resistant. The chromosomal P-lactamases are species specific, but can be broadly classified by substrate profile, sensitivity to inhibitors, analytical isoelectric focusing, immunological studies, and molecular weight deterrnination. Individual enzymes may inactivate primarily penicillins, cephalosporins, or both, and the substrate specificity predeterrnines the antibiotic resistance of the producing strain. Some P-lactamases are produced only in the presence of the P-lactam antibiotic (inducible) and others are produced continuously (constitutive). 

The antibacterial effectiveness of penicillins cephalospotins and other P-lactam antibiotics depends upon selective acylation and consequentiy, iaactivation, of transpeptidases involved ia bacterial ceU wall synthesis. This acylating ability is a result of the reactivity of the P-lactam ring (1). Bacteria that are resistant to P-lactam antibiotics often produce enzymes called P-lactamases that inactivate the antibiotics by cataly2ing the hydrolytic opening of the P-lactam ring to give products (2) devoid of antibacterial activity. 

---