Inactivation of microorganisms using electrostatic fields

This research investigated whether electrostatic fields can be used to inactivate surface-borne and airborne microorganisms. Vegetative cells of Pseudomonas fluorescens and Bacillus subtilis var. niger were deposited on filters and subjected to electrostatic fields of different strengths and polarities for controlled time periods. In addition, P. fluorescens bacteria, which represent sensitive species, were aerosolized and exposed to electrostatic fields of up to +/- 10 kV/cm. The results have shown that more than 90% of the P. fluorescens cells deposited on the surface of nonconductive filters are inactivated when fields of 15 kV/cm are applied for 30 min or longer. Similar effects were observed when P. fluorescens were exposed to fields of 5 and 10 kV/cm for 2 h. In contrast, the culturability of B. subtilisvar. niger cells exposed under the same conditions did not substantially decrease. Exposure of airborne P. fluorescens to +/- 10 kV/cm for 30 s also did not result in a significant reduction of culturability. This research has shown that specific combinations of electrostatic field strength and exposure time can be used to effectively inactivate certain bacterial cells deposited on nonconductive surfaces. For the investigated conditions, the treatment was not effective for bacteria in the airborne state.     

Inactivation of microorganisms in milk and apple cider treated with ultrasound

Nonthermal technologies are emerging as promising alternatives to heat treatment for food processing. Ultrasound, defined as sound waves with a frequency greater than 20 kHz, has proven bactericidal effects, especially when combined with other microbial-reduction strategies such as mild heating. In this study, ultrasound treatment (sonifier probe at 20 kHz, 100% power level, 150 W acoustic power, 118 W/cm2 acoustic intensity) with or without the effect of mild heat (57 degrees C) was effective at reducing microbial levels in raw milk, Listeria monocytogenes levels inoculated in ultrahigh-temperature milk, and Escherichia coli O157:H7 in apple cider. Continuous flow ultrasound treatment combined with mild heat (57 degrees C) for 18 min resulted in a 5-log reduction of L. monocytogenes in ultrahigh-temperature milk, a 5-log reduction in total aerobic bacteria in raw milk, and a 6-log reduction in E. coli O157:H7 in pasteurized apple cider. Inactivation regressions were second-order polynomials, showing an initial period of rapid inactivation, eventually tailing off. Results indicate that ultrasound technology is a promising processing alternative for the reduction of microorganisms in liquid foods.     

Whole-cell bioconversion using non-Leloir transglycosylation reactions: a review

Food Science and Biotechnology - Microbial biocatalysts are evolving technological tools for glycosylation research in food, feed and pharmaceuticals. Advances in bioengineered Leloir and...     

Inactivation of food-borne viruses using natural biochemical substances

Food-borne viruses such as human Noroviruses (NoVs), hepatitis A virus (HAV), Rotaviruses (RoVs) are a public health concern worldwide. Biochemical substances, which occur naturally in plants, animals or microorganisms, might possess considerable antimicrobial properties. In this study, the reported effects of biochemical substances on food-borne viruses are reviewed. The biochemical substances are grouped into several categories including (i) polyphenols and proanthocyanins, (ii) saponin, (iii) polysaccharides, (iv) organic acids, (v) proteins and polypeptides, (vi) essential oils. Although not fully understood, the mechanism of action for the antiviral activity of the natural compounds is presented. Generally, it is thought to be the prevention of the viral attachment to host cells, either by causing damage on the viral capsids or change of the receptors on the cell membranes. It is recommended that further studies are undertaken not only on the wide-range screening for novel antiviral substances, but also on the mechanism in-depth as well as the exploration for their potential application in controlling virus contamination in foods or food processing.     

Inactivation of biological agents using neutral oxone-chloride solutions

Bleach solutions containing the active ingredient hypochlorite (OCl-) serve as powerful biological disinfectants but are highly caustic and present a significant compatibility issue when applied to contaminated equipment or terrain. A neutral, bicarbonate-buffered aqueous solution of Oxone (2K2HSO5.KHSO4.K2SO4) and sodium chloride that rapidly generates hypochlorite and hypochlorous acid (HOCl) in situ was evaluated as a new alternative to bleach for the inactivation of biological agents. The solution produced a free chlorine (HOCl + OCl-) concentration of 3.3 g/L and achieved > or =5.8-log inactivation of spores of Bacillus atrophaeus, Bacillus thuringiensis, Aspergillus niger, and Escherichia coli vegetative cells in 1 min at 22 degrees C. Seawaterwas an effective substitute for solid sodium chloride and inactivated 5 to 8 logs of each organism in 10 min over temperatures ranging from -5 degrees C to 55 degrees C. Sporicidal effectiveness increased as free chlorine concentrations shifted from OCl- to HOCl. Neutrally buffered Oxone-chloride and Oxone-seawater solutions are mitigation alternatives for biologically contaminated equipment and environments that would otherwise be decontaminated using caustic bleach solutions.     

Research Watch: Disturbed microbes

Soil.     

Research Watch: Biofilter microbes

Biotreatment.     

Research Watch: Engineered microbes

Bioremediation.