Publisher Summary This chapter outlines the breakdown of sugars by yeasts. To continue biosynthetic processes necessary for growth, yeasts obtain energy from sugars by breaking them down. The energy set free is stored as the “high energy” phosphate derivative adenosine 5’-triphosphate (ATP) that is synthesized as the sugar is catabolized. In catabolism, glycosidic bonds are hydrolyzed to yield component monosaccharides. A low concentration of oxygen is often important for obtaining a high yield of ethanol from certain sugars. Particularly in initial and terminal reactions, differences are found among different yeasts, and such relatively minor biochemical differences are often of considerable practical importance. The information provided in this chapter is based chiefly on studies yeast such as, Saccharomyces cerevisiae , Saccharomyces uvarum , Candida utilis , and Kluyveromyces fragilis . However, the ability of yeasts to utilize sugars is not only of potential value, it can also be a nuisance. Yeasts are notorious as spoilers of foods that contain a high concentration of one or more sugars, such as honey, maple syrup, sugar cane, and confectionery.

The utilization of sugars by yeasts.

https://mmbr.asm.org/content/mmbr/42/1/161.full.pdf

Genome comparison in yeast systematics: delimitation of species within the genera Schwanniomyces, Saccharomyces, Debaryomyces, and Pichia.

Deoxyribonucleic acid reassociation studies of 24 different wine and beer-associated strains of Saccharomyces confirmed the presence of three separate species. S. cerevisiae and S. bayanus strains had only 22% of their genomes in common. S. pastorianus, with intermediate hybridization values between S. cerevisiae and S. bayanus (52 and 72%, respectively) could possibly be a natural hybrid of the two species. S. pastorianus replaces S. carlsbergensis with which it is homologous for 93% of its genome, since the former species was described first by Hansen in 1904. These data do not agree with the results of traditional physiological tests.

Three newly delimited species of Saccharomyces sensu stricto.

Yeasts are ubiquitous in their distribution and populations mainly depend on the type and concentration of organic materials. The distribution of species, as well as their numbers and metabolic characteristics were found to be governed by existing environmental conditions. Marine yeasts were first discovered from the Atlantic Ocean and following this discovery, yeasts were isolated from different sources, viz. seawater, marine deposits, seaweeds, fish, marine mammals and sea birds. Near-shore environments are usually inhabited by tens to thousands of cells per litre of water, whereas low organic surface to deep-sea oceanic regions contain 10 or fewer cells/litre. Aerobic forms are found more in clean waters and fermentative forms in polluted waters. Yeasts are more abundant in silty muds than in sandy sediments. The isolation frequency of yeasts fell as the depth of the sampling site is increased. Major genera isolated in this study were Candida, Cryptococcus, Debaryomyces and Rhodotorula. For biomass estimation ergosterol method was used. Classification and identification of yeasts were performed using different criteria, i.e. morphology, sexual reproduction and physiological/biochemical characteristics. Fatty acid profiling or molecular sequencing of the IGS and ITS regions and 28S gene rDNA ensured accurate identification.

https://dyuthi.cusat.ac.in/xmlui/bitstream/handle/purl/2035/Marine%20yeasts-a%20rewiew.pdf;sequence=1

Marine yeasts — a review

Publisher Summary The chapter discusses the importance of proton magnetic resonance spectroscopy as an aid in identification and chemotaxonomy of yeasts. The term “yeast” refers to ascomycetes of the subclass hemiascomycetidae, order endomycetales, family saccharomycetaceae, which possess a predominantly unicellular thallus. They reproduce asexually by budding, transverse division or both and produce ascospores in a naked ascus, originating either from a zygote or parthenogenetically from a single somatic cell. Forms not known to produce ascospores are not obviously related to other groups of fungi. The chapter describes the chemotaxonomy of yeasts according to their mannose-containing polysaccharides. It discusses the application of the proton magnetic resonance spectroscopic method to yeast polysaccharides, isolation of mannose-containing polysaccharides of yeasts and preparation of pmr spectra, and methods used in determination of chemical structure of yeast mannose-containing poly saccharides. Finally, the chapter presents an overview of the classification of yeasts according to the pmr spectra of their mannose-containing polysaccharides.

Proton Magnetic Resonance Spectroscopy–An Aid in Identification and Chemotaxonomy of Yeasts1

Stock cultures of yeast strains which have acquired the ability to ferment and assimilate various sugars often represent a mixed population in regard to these features. Usually de-adaptation was not found after cultivation in glucose medium, indicating that the saltations are stable in this medium. The lyophilized cultures revived in glucose medium have the original characteristics of the strains. When single-cell colonies of various strains unable to utilize the appropriate sugar were grown in a liquid medium containing either galactose, sucrose or maltose, cells fermenting the sugar offered were found in the cultures. The acquisition of maltose-fermenting ability and the simultaneous acquisition of ability to utilize either galactose and raffinose, sucrose and raffinose, maltose and sucrose, or maltose, sucrose and α-methyl-d-glucoside were observed. By an identification according to the acquired features the yeasts concerned have to be classified in other species than the original strain.

The instability of physiological properties used as criteria in the taxonomy of yeasts

Selected yeasts classified as Candida sake van Uden et Buckley were examined for their physiological, morphological and immunological properties and their DNA relatedness. Candida maltosa Komagata, Nakase et Katsuya is herein recognized as a species separate from C. sake. Candida maltosa was distinguished from C. sake and from C. tropicalis by insignificant DNA reassociation. In addition, C. maltosa was distinguished from C. sake by its higher maximal growth temperature and lower guanine plus cytosine content of its DNA and from C. tropicalis by its failure to utilize soluble starch for growth and its resistance to cycloheximide. The species C. cloacae and C. subtropicalis are placed in synonymy with C. maltosa.

Physiological and DNA characterization of Candida maltosa, a hydrocarbon-utilizing yeast.

The acquisition of the ability to ferment galactose, maltose, sucrose, raffinose and melibiose by yeast strains of the genus Saccharomyces was investigated During cultivation in selective media 11 strains belonging to 5 species gained the ability to ferment one or several of these sugars De-adaptation was not usually observed after cultivation in glucose medium, indicating that the saltants are stable in this medium

D. Yarrow

Papers

The instability of physiological properties used as criteria in the taxonomy of yeasts

Physiological and DNA characterization of Candida maltosa, a hydrocarbon-utilizing yeast.

Variation in the fermentative pattern of some Saccharomyces species.