The irreversible thermal inactivation and the thermodynamics of calcium ion binding of Bacillus amyloliquefaciens alpha-amylase in the absence of substrates were studied. The enzyme inactivation on heating was apparently followed by first-order kinetics. The enzyme was stabilized with an increased concentration of calcium ion and thus the inactivation was highly dependent on the state of calciu...

X inactivation studies have been carried out on 22 pairs of female monozygotic twins, one set of female monozygotic triplets, and their mothers and singleton sisters, using the probe M27 beta. Forty-eight per cent of the twins, 55% of their mothers, and 42% of their singleton sisters showed skewed X inactivation. Two of the triplets and their mother had random X inactivation, while the third tr...

The serine proteinase isolated from Thermomonospora fusca YX shows considerable thermal stability up to 80 °C, and progressive inactivation occurs at higher temperatures. Lyotropic salts affected the thermal stability of the enzyme at 85 °C, suggesting that disruption of hydrophobic interactions play an important role in the decreased thermal stability of the enzyme above 80 'C. Thermal stabili...

Aqueous spore suspensions of Bacillus stearothermophilus ATCC 12980 were heated at different temperatures for various time intervals in a resistometer, spread plated on antibiotic assay medium supplemented with 0.1% soluble starch without (AAMS) or with (AAMS-S) 0.9% NaCl, and incubated at 55 degrees C unless otherwise indicated. Uninjured spores formed colonies on AAMS and AAMS-S; injured spor...

Dry heat was used to inactivate Salmonella newington, Salmonella typhimurium, Salmonella anatum, Salmonella kentucky, Salmonella cubana, Salmonella seftenberg, Salmonella thompson, and Salmonella tennessee in corn flour at 10 and 15% moisture. The flour was spray inoculated at 10(5) Salmonella cells per g and then stored at 49 degrees C (120 degrees F); viable Salmonella cells were counted on T...

Previously developed four-variable response surface models for describing the effects of temperature, pH/lactic acid, sodium chloride and sodium nitrite on the time to achieve a 4-log, non-thermal inactivation (t4D) of Listeria monocytogenes in aerobic, acidic environments were expanded to five-variable models that distinguish the effects of pH and acidulant concentration. A total of 18 new var...

The thermal inactivation kinetics of Salmonella enteritidis PT4 between 49 and 60 degrees C were investigated. Using procedures designed to eliminate methodological artifacts, we found that the death kinetics deviated from the accepted model of first-order inactivation. When we used high-density stationary-phase populations and sensitive enumeration, the survivor curves at 60 degrees C were rep...

A hot-air sterilizer capable of exposing airborne microorganisms to elevated temperatures with an almost instantaneous heating time was developed and evaluated. With this apparatus, aerosolized Bacillus subtilis var. niger spores were killed in about 0.02 sec when exposed to temperatures above 260 C. This is about 500 times faster than killing times reported by others. Extrapolation and compari...

The heat resistance of foot-and-mouth disease virus (FMDV) strains isolated from outbreaks in Thailand was investigated in phosphate-buffered saline (PBS) at 50, 60, 70, 80, 90, and 100 degrees C. The first-order kinetic model fitted most of the observed linear inactivation curves. The ranges of decimal-reduction time (D value) of FMDV strains at 50, 60, 70, 80, 90, and 100 degrees C were 732 t...

Decimal reduction time (time to inactivate 90% of the population) (D) values of Bacillus anthracis spores in milk ranged from 3.4 to 16.7 h at 72 degrees C and from 1.6 to 3.3 s at 112 degrees C. The calculated increase of temperature needed to reduce the D value by 90% varied from 8.7 to 11.0 degrees C, and the Arrhenius activation energies ranged from 227.4 to 291.3 kJ/mol. Six-log-unit viabi...