Kinetics of catalase inactivation induced by ultrasonic cavitation

Kinetic patterns of sonication-induced inactivation of bovine liver catalase (CAT) were studied in buffer solutions (pH 4-11) within the temperature range from 36 to 55 degrees C. Solutions of CAT were exposed to low-frequency (20.8 kHz) ultrasound (specific power, 48-62 W/cm2). The kinetics of CAT inactivation was characterized by effective first-order rate constants (s-1) of total inactivation (kin), thermal inactivation (*kin), and ultrasonic inactivation (kin(us)). In all cases, the following inequality was valid: kin > *kin. The value of kin(us) increased with the ultrasound power (range, 48-62 W/cm2) and exhibited a strong dependence on pH of the medium. On increasing the initial concentration of CAT (0.4-4.0 nM), kin(us) decreased. The three rate constants were minimum within the range of pH 6.5-8; their values increased considerably at pH < 6 and pH > 9. At 36-55 degrees C, temperature dependence of kin(us) was characterized by an activation energy (Eact) of 19.7 kcal/mol, whereas the value of Eact for CAT thermoinactivation was equal to 44.2 kcal/mol. Bovine serum and human serum albumins (BSA and HSA, respectively) inhibited sonication-induced CAT inactivation; complete prevention was observed at concentrations above 2.5 micrograms/ml. Dimethyl formamide (DMFA), a scavenger of hydroxyl radicals (HO.), prevented sonication-induced CAT inactivation at 10% (kin and *kin increased with the content of DMFA at concentrations in excess of 3%). The results obtained indicate that free radicals generated in the field of ultrasonic cavitation play a decisive role in the inactivation of CAT, which takes place when its solutions are exposed to low-frequency ultrasound. However, the efficiency of CAT inactivation by the radicals is determined by (1) the degree of association between the enzyme molecules in the reaction medium and (2) the composition thereof.     

The ultrasonic degradation of biological macromolecules under conditions of stable cavitation. II. Degradation of deoxyribonucleic acid

Solutions of T7 bacteriophage or calf thymus DNA arc degraded in solution by ultrasonic fields of low intensity in the presence of vibrating air bubbles but are not degraded at these low intensities when such bubbles are absent. Evidence is presented for the hydrodynamic nature of the observed degradation and theoretical simulation of a plausible degradation mechanism is compared with experimental degradation studies. It is concluded that degradation of such linear macromolecules as DNA may occur as a result of stresses induced in the macromolecule; these stresses are the result of a relative movement of solvent molecules and the macromolecules in the time-independent flow of solvent near the vibrating bubbles.     

The susceptibility to ultrasonic disintegration ofKlebsiella pneumoniae NCTC 418

Summary The resistance to ultrasonic disintegration of cells ofKlebsiella pneumoniae grown at various dilution rates in continuous culture decreased with increasing cell size. Whilst this effect could be related to the cell wall content of the specimens, no direct relationship between the cell wall strength and the rigidity-conferring peptidoglycan was observed.     

Mechanism of cell disintegration in a high pressure homogenizer

The disintegration of baker's yeast (Saccharomyces cerevisiae) by a high pressure homogenizer, to a pressure of 25,000 psi. (172.37 MNm^?2) is described, together with details of the methods of measurement used to obtain information on the valve movement and pressure transients. The theory of the mechanism of cell disintegration is discussed.     

The inactivation of enzymes by ultrasonic cavitation at 20 kHz

Alcohol dehydrogenase, lysozyme, and catalase were assayed after exposure to cavitating 20 kHz ultrasound for varying times. Catalase was little affected, but alcohol dehydrogenase and lysozyme were both inactivated at an exponential rate. The rate of enzyme inactivation decreased with increasing protein concentration and was inhibited by the presence of 2-mercaptoethanol. The presence of stainless steel in the sonication vessel accelerated enzyme inactivation. On the basis of the results obtained, it is suggested that the mechanism of inactivation is chemical rather than mechanical, and a comparison is made between the rate of inactivation and the yield of free radicals as measured with a radiochemical dosimeter. Suggestions are offered to minimize the sonochemical effects on proteins isolated from cells with an ultrasonic disintegrator.     

Detection of ultrasonic cavitation based on low-frequency analysis of acoustic signal

The acoustic cavitation phenomenon constitutes a potential hazard in ultrasound diagnostics and therapy so that early and effective detection of cavitation is of great interest. However, cavitation might even bring a higher risk especially when an echocontrast agent based on microbubbles is used. The major goal of the present work was to develop a cavitation detection method based on increased level of cavitation noise in the range of low frequencies (about 1 Hz). This method was applied in vitro using a model of body fluid containing a model echocontrast agent, such as 5% solution of lyophilized egg albumin, which was sonicated by ultrasound disintegrator. Ultrasound signal evokes cavitation in microbubble suspension accompanied by a certain level of cavitation acoustic noise. The level of noise voltage increased in the frequency range of 0.1 to 2 Hz in the presence of cavitation. Hence, this method makes it possible to determine the value of cavitation threshold. In addition, we examined how the cavitation threshold is affected by temperature and viscosity. It was found that the cavitation threshold decreased with growing temperature while it increased with growing viscosity.     

Polyphenolic antioxidants efficiently protect urease from inactivation by ultrasonic cavitation

Inactivation of urease (25 nM) in aqueous solutions (pH 5.0-6.0) treated with low-frequency ultrasound (LFUS; 27 kHz, 60 Wt/cm2, 36-56 degrees C) or high-frequency ultrasound (HFUS; 2.64 MHz, 1 Wt/cm2, 36 or 56 degrees C) has been characterized quantitatively, using first-order rate constants: kin, aggregate inactivation; kin*, thermal inactivation; and kin* (US), ultrasonic inactivation. Within the range from 1 nM to 10 microM, propyl gallate (PG) decreases approximately threefold the rate of LFUS-induced inactivation of urease (56 degrees C), whereas resorcinol poly-2-disulfide prevents this process at 1 nM or higher concentrations. PG completely inhibits HFUS-induced inactivation of urease at 1 nM (36 degrees C) or 10 nM (56 degrees C). At 0.2-10 microM, human serum albumin (HSA) increases the resistance of urease (at 56 degrees C) treated with HFUS to temperature- and cavitation-induced inactivation. Complexes of gallic acid polydisulfide (GAPDS) with HSA (GAPDS-HSA), formed by conjugation of 1.0 nM PGDS with 0.33 nM HSA, prevent HFUS-induced urease inactivation (56 degrees C).     

Incorporation of ultrasonic cell disintegration into a membrane bioreactor for zero sludge production

For the prevention of excess sludge production from a membrane bioreactor (MBR), an ultrasonic cell disintegration process was incorporated. The results of this study showed that excess sludge production could be prevented using an ultrasound hybrid (MBR-US) system at an organic loading of around 0.91 kg BOD₅/m³ per day. Under the same organic loading rate, the mixed liquor suspended solid (MLSS) of MBR-US system was maintained at 7000–8000 mg/l while the MLSS of a conventional MBR increased from 7000 to 13,700 mg/l during the experimental period. While sludge production was completely prevented, the effluent quality of the MBR-US system slightly deteriorated. The additional organic loading caused by disintegrated sludge return was considered to be a reason. With sonication the volume of the average particle size of the sludge in the aeration tank decreased from 132 to 95 μm. In the MBR-US system, around 25–30% of total phosphorus removal was achieved without sludge removal from the aeration tank.     

The ultrasonic degradation of biological macromolecules under conditions of stable cavitation. I. Theory,methods, and application to deoxyribonucleic acid

Solutions of calf thymus DNA have been degraded in the presence of vibrating air bubbles in ultrasonic fields of low power which would not normally induce ultrasonic cavitation. The DNA was degraded to a limiting intrinsic viscosity, after which further irradiation by ultrasound had little or no effect. This limiting intrinsic viscosity decreased with increase in the ultrasonic intensity. Previously developed theories have-been adapted to calculate the maximum velocity gradient associated with the streaming of the solution around such vibrating air bubbles. The tensile force which is induced and which acts on the DNA has been calculated on the basis of current theories of degradation by hydrodynamic shear. These calculations indicate that the degradation of the DNA by ultrasound under conditions of “stable cavitation” is mainly the result of the shearing forces engendered in the solution around the oscillating bubbles.     

Ultrasonic treatment of biological sludge: Floc disintegration, cell lysis and inactivation

The aim of this work was to study the effect of ultra sound treatment on the solid content of sludge and biological activity, and the increase in the soluble chemical oxygen demand (SCOD), proteins and nucleic acids concentrations during sonication. The results showed that sonication effectively degraded and inactivated the sludge. The sludge disintegration and cell lysis occurred continuously while sludge inactivation mainly occurred in the second stage (10-30 min) during sonication. The SCOD, supernatant proteins and nucleic acids concentrations, and sludge mass reduction and inactivation degrees increased with the sonication time and power density increases. Higher energy ultrasound was more efficient than lower energy ultrasound for the sludge treatment.     

Morphological disintegration of biological fluids and tissues and the imbalance of macro- and microelements

The contents of and interrelations between macro- and microelements were determined in human myometrial tissue and myomas. Benign growth of the myometrium was found to be associated with changes in its elemental composition. Especially illustrative are the changes in the correlation between zinc and copper (and, to a lesser degree, other elements).     

On criteria of optimal conditions at ballistic disintegration of microbial cells

Summary The present study examines the processes of ballistic disintegration carried out to release active biopolymers. The relationship between the activity of unit volume of homogenates and the time of disintegration has been obtained. Correctness of this relationship for any process of disintegration can serve as the criterion of optimal chemical composition of the medium in which this process occurs. Only two quantitative criteria have been found sufficient for comparison of any regimes of ballistic disintegration. The theoretical conclusions are proved by experiments in ballistic disintegrators of two types.Torulopsis candida cells were used to release the succinate oxidizing enzyme.