High Pressure Inactivation Kinetics of Saccharomyces cerevisiae Ascospores in Orange and Apple Juices

High pressure inactivation kinetics (D and z values) of Saccharomyces cerevisiae ascospores were determined in fruit juices and a model juice buffer at pH 3.5 to 5.0. Approximately 0.5 to 1.0 × 10⁶ ascospores/mL were pressurized at 300 to 500 MPa in juice or buffer. D-values ranged from 8 sec to 10.8 min at 500 and 300 MPa, respectively. The range for z-values was 115 to 121 MPa. No differences (P≥0.05) in D (at constant pressure) or z-values among buffers or juices at any pH were determined, indicating little influence of pH in this range and absence of protective or detrimental effects of juice constituents.     

酿酒酵母子囊孢子形成条件的研究

对三株酿酒酵母在不同的产孢子培养基、不同的活化培养基和不同的培养温度下进行了子囊形成率的比较实验，结果表明，酿酒酵母在麦芽汁培养基上繁殖几代后，移接到产孢子培养基Ⅵ或Ⅴ上，在２５～３０℃进行培养，子囊形成率最高。     

Inactivation of Zygosaccharomyces Bailii in Fruit Juices by Heat, High Hydrostatic Pressure and Pulsed Electric Fields

Heat, high hydrostatic pressure (HHP) and high pulsed electric field (PEF) inactivations of Zygosaccharomyces bailii ascospores and vegetative cells suspended in apple, orange, pineapple, cranberry and grape juices were investigated. The ascospores exhibited a heat resistance that was more than 5–8 times greater than the vegetative cells. After 5 min of pressurization at 300 MPa, the population of vegetative cells decreased almost 5 log cycles, while the population of ascospores decreased between 0.5-1 log cycles. In each fruit juice studied, two pulses of 32–36.5 kV/cm decreased the population of vegetative cells or ascospores 3.5 to 5 log cycles.     

Heat Activation Characteristics of Talaromyces Ascospores

ABSTRACT: Heat activation of ascospores of 4 strains of Talaromyces was investigated. Dormancy of the ascospores was broken by heating in several buffer solutions. When the heating period was extended, emerged colonies increased at elevated temperatures and the number of colony-forming units (CFU) reached the population of the ascospores. A direct linear relationship was observed between the logarithm of CFU and the heating period at each temperature. Activation rates of the test strains were greater at higher temperatures. Activation energy values of the 4 strains, calculated on the basis of heat activation rates, ranged from 3.83 × 10⁴ to 1.39 × 10⁵ J/mol. The influence of medium on activation was studied by heating in different buffer solutions and fruit juices. The pH of buffer solutions had no effect on heat activation rates. However, activation rate was enhanced by heating in fruit juices.     

Metschnikowia: half tetrads,a regicide and the fountain of youth

The purpose of this review is to introduce Metschnikowia to the yeast researcher community and to convince readers that the genus is a worthwhile object of study in developmental biology, genetics, ecology and biotechnology. Metschnikowia sits at the foundation of modern immunology, having been instrumental in the discovery of animal phagocytosis. Some 81 species form a monophyletic group within the Metschnikowiaceae, which also include the smaller genus Clavispora and a few clades of Candida species. The family stands out by the habit of forming, by meiosis, only two ascospores, which in Metschnikowia are needle shaped. In some cases, the spores can reach enormous proportions, exceeding 200 µm in length; in others, ascus formation is preceded by the development of chlamydospores. The adaptive value of such features remains to be elucidated. Extensive genetic studies are lacking, but attempts to apply methods developed for model species have been successful. Some species are found at the plant–insect interface whereas others are pathogens of aquatic animals and have served as model organisms in the exploration of host‐parasite theory. Some species are globally distributed and others exhibit extreme endemism. Many species are remarkably easy to recover by sampling their known habitats. M. pulcherrima and close relatives may play an important role in wine quality and produce pulcherrimin, an iron‐dipeptide complex that can interfere with the growth of other microorganisms. Some symbiotic species incapable of growth in culture media have been assigned to the genus, but their kinship with the group remains to be demonstrated. Copyright © 2016 John Wiley & Sons, Ltd.