Kluyveromyces marxianus | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Saccharomycetes |
Order: | Saccharomycetales |
Family: | Saccharomycetaceae |
Genus: | Kluyveromyces |
Species: | K. marxianus |
Binomial name | |
Kluyveromyces marxianus Van der Walt (1965) | |
Synonyms | |
|
Kluyveromyces marxianus in ascomycetous yeast and member of the genus, Kluyveromyces. It is the sexual stage of Atelosaccharomyces pseudotropicalis[ citation needed ] also known as Candida kefyr. [1] This species has a homothallic mating system and is often isolated from dairy products. [2]
This species was first described in the genus Saccharomyces as S. marxianus by the Danish mycologist, Emil Christian Hansen from beer wort. [3] He named the species for the zymologist, Louis Marx of Marseille who first isolated it from grape. [3] The species was transferred to the genus Kluyveromyces by van der Walt in 1956. [1] Since then, 45 species have been recognized in this genus. [1] The closest relative of Kluyveromyces marxianus is the yeast Kluyveromyces lactis , often used in the dairy industry. [4] Both Kluyveromyces and Saccharomyces are considered a part of the "Sacchromyces complex", subclade of the Saccharomycetes. [5] Using 18S rRNA gene sequencing, it was suggested that K. marxianus, K. aestuarii, K. dobzhanskii, K. lactic, K. wickerhamii, K. blattae, K. thermotolerans, and K. waltii collectively constituted a distinct clade of separate ancestry from the central clade in the genus Kluyveromyces. [2] Within this complex, two categories are defined based on the presence in certain taxa of a whole-genome duplication event: the two clades are referred to as pre-Whole Genome Duplication (WGD) and post-WGD. Kluyveromyces species are affiliated with the first of this clades while species of Saccharomyces belong to the latter. Separation of these clades based on the presence of the WGD event explains why, even though the two species are closely related, fundamental differences exist between them. [5]
Colonies of K. marxianus are cream to brown in colour with the occasional pink pigmentation due to production of the iron chelate pigment, pulcherrimin. [6] [7] When grown on Wickerham's Yeast-Mold (YM) agar, the yeast cells appear globose, ellipsoidal or cylindrical, 2–6 x 3–11 μm in size. [6] In a glucose-yeast extract broth, K. marxianus grows to produce a ring composed of sediment. A thin pellicle may be formed. In a Dalmau plate culture containing cornmeal agar and Polysorbate 80, K. marxianus forms a rudimentary to branched pseudomycelium with few blastospores. [8] K. marxianus is thermotolerant, exhibiting a high growth rate at 40 °C (104 °F). [9]
Kluyveromyces marxianus is an aerobic yeast capable of respiro-fermentative metabolism that consists of simultaneously generating energy from both respiration via the TCA cycle and ethanol fermentation. [2] The balance between respiration and fermentation metabolisms is strain specific. [5] This species also ferments inulin, glucose, raffinose, sucrose and lactose into ethanol. [5] [8] K. marxianus is widely used in industry because of its ability to use lactose. Two genes, LAC12 and LAC4, allow K. marxianus to absorb and use lactose as a carbon source. [5] This species is considered to be a "crabtree negative fungus", meaning it is unable to convert sugars into ethanol as effectively as crabtree positive taxa such as S. cerevisiae . [4] Studies, however, deem it to be crabtree positive which is likely due to strain differences since K. marxianus possesses the necessary genes to be crabtree positive. [5] K. marxianus is highly thermotolerant and able to withstand temperatures up to 45 °C (113 °F). [2] K. marxianus is also able to use multiple carbon substrata at the same time making it highly suited to industrial use. When glucose concentrations become depleted to 6 g/L, the lactose co-transport initiates. [10]
The formation of the ascospores occurs through the conjugation of the haploid cells preceding the formation of the ascus. [8] Alternatively, ascosporogensis can arise directly from diploid cells. [8] Each ascus contains 1–4 ascospores. [8] The ploidy of K. marxianus was originally thought to be a haploid but recent research has shown that many strains used in research and industry are diploid. [5] These conflicting findings suggest that K. marxianus can exist in vegetative form either as a haploid and a diploid.
Kluyveromyces marxianus has been isolated in dairy products, sisal leaves, and sewage from sugar manufacturing factories. [3] It is also a naturally occurring colonist of plants, including corn. [8]
Kluyveromyces marxianus is not usually an agent of human disease, although infection in humans can occur in immunocompromised individuals. [11] This species has been associated with candidemia [12] and has been recovered from catheters. [13] It has also found in biofilms on other indwelling devices such as pacemakers and prosthetic heart valves. [11] Between 1–3 % of cases involving K. marxianus that have been reported oncology patients, surgical wards, female genital infections and upper respiratory infections.[ citation needed ] Treatment with amphotericin B have been effective against K. marxianus in one case report. [11]
Industrial use of K. marxianus is chiefly in the conversion of lactose to ethanol as a precursor for the production of biofuel. [4] The ability for K. marxianus to reduce lactose is useful because of the potential to transform industrial whey waste, a problematic waste product for disposal, into useful biomass for animal feed, food additives or fuel. [5] Certain strains of the fungus can also be used to convert whey to ethyl acetate, an alternative fuel source. [14] K. marxianus is also used to produce the industrial enzymes: inulinase, β-galactosidase, and pectinase. [5] Due to the heat tolerance of K. marxianus, high heat fermentations are feasible, reducing the costs normally expended for cooling as well as the potential for contamination by other fungi or bacteria. In addition, fermentations at higher temperatures occur more rapidly, making production much more efficient. [9] Due to the ability of K. marxianus to simultaneously utilize lactose and glucose, the prevalence of K. marxianus in industrial settings is high as it decreases production time and increases productivity. [10] Recent efforts have attempted to use K. marxianus in the production of food flavourings from waste products tomato and pepper pomaces as substrata. [15]
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.
Saccharomyces cerevisiae is a species of yeast. The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium. It is the microorganism behind the most common type of fermentation. S. cerevisiae cells are round to ovoid, 5–10 μm in diameter. It reproduces by budding.
Kilju is the Finnish word for home made alcoholic beverage typically made of sugar, yeast, and water.
Komagataella is a methylotrophic yeast within the order Saccharomycetales. It was found in the 1960s as Pichia pastoris, with its feature of using methanol as a source of carbon and energy. In 1995, P. pastoris was reassigned into the sole representative of genus Komagataella, becoming Komagataella phaffii. Later studies have further distinguished new species in this genus, resulting in a total of 7 recognized species. It is not uncommon to see the old name still in use in the context of protein production, as of 2023; in less formal use, the yeast may confusingly be referred to as pichia.
Torulaspora delbrueckii is a ubiquitous yeast species with both wild and anthropic habitats. The type strain of T. delbrueckii is CBS 1146T, equivalent to CLIB 230 or ATCC 10662, etc.. The type strain of T. delbrueckii CBS 1146 T was sequenced in 2009, and is composed of 8 chromosomes in addition to a mitochondrial genome.
Saccharomycotina is a subdivision (subphylum) of the division (phylum) Ascomycota in the kingdom Fungi. It comprises most of the ascomycete yeasts. The members of Saccharomycotina reproduce by budding and they do not produce ascocarps.
Fermentation is a metabolic process that produces chemical changes in organic substances through the action of enzymes. In biochemistry, it is broadly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.
Zymomonas mobilis is a Gram negative, facultative anaerobic, non-sporulating, polarly-flagellated, rod-shaped bacterium. It is the only species found in the genus Zymomonas. It has notable bioethanol-producing capabilities, which surpass yeast in some aspects. It was originally isolated from alcoholic beverages like the African palm wine, the Mexican pulque, and also as a contaminant of cider and beer in European countries.
Kluyveromyces is a genus of ascomycetous yeasts in the family Saccharomycetaceae. Some of the species, such as K. marxianus, are the teleomorphs of Candida species.
The Pasteur effect describes how available oxygen inhibits ethanol fermentation, driving yeast to switch toward aerobic respiration for increased generation of the energy carrier adenosine triphosphate (ATP). More generally, in the medical literature, the Pasteur effect refers to how the cellular presence of oxygen causes in cells a decrease in the rate of glycolysis and also a suppression of lactate accumulation. The effect occurs in animal tissues, as well as in microorganisms belonging to the fungal kingdom.
The Crabtree effect, named after the English biochemist Herbert Grace Crabtree, describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) in aerobic conditions at high external glucose concentrations rather than producing biomass via the tricarboxylic acid (TCA) cycle, the usual process occurring aerobically in most yeasts e.g. Kluyveromyces spp. This phenomenon is observed in most species of the Saccharomyces, Schizosaccharomyces, Debaryomyces, Brettanomyces, Torulopsis, Nematospora, and Nadsonia genera. Increasing concentrations of glucose accelerates glycolysis which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism around the time when the first fruits on Earth fell from the trees. The Crabtree effect works by repressing respiration by the fermentation pathway, dependent on the substrate.
Lachancea kluyveri is an ascomycetous yeast associated with fruit flies, slime fluxes, soils and foods.
A killer yeast is a yeast, such as Saccharomyces cerevisiae, which is able to secrete one of a number of toxic proteins which are lethal to susceptible cells. These "killer toxins" are polypeptides that kill sensitive cells of the same or related species, often functioning by creating pores in target cell membranes. These yeast cells are immune to the toxic effects of the protein due to an intrinsic immunity. Killer yeast strains can be a problem in commercial processing because they can kill desirable strains. The killer yeast system was first described in 1963. Study of killer toxins helped to better understand the secretion pathway of yeast, which is similar to those of more complex eukaryotes. It also can be used in treatment of some diseases, mainly those caused by fungi.
Mucor indicus is among the most important members of zygomycetes fungi. This dimorphic fungus is capable of production of several valuable products. Some strains of the fungus have been isolated from the traditional Indonesian food tempeh. M. indicus is nowadays used for production of several homemade food and beverages especially in Asia. This has also been successfully used as a safe nutritional source for fish and rat. The fungus is generally regarded as safe though there are few reports claiming that this is a pathogenic fungus.
Kefir is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. It is prepared by inoculating the milk of cows, goats, or sheep with kefir grains.
Candida blankii is a species of budding yeast (Saccharomycotina) in the family Saccharomycetaceae. The yeast may be a dangerous pathogen and resistant to treatment in human hosts. Research on the fungi has therapeutic, medical and industrial implications.
Aerobic fermentation or aerobic glycolysis is a metabolic process by which cells metabolize sugars via fermentation in the presence of oxygen and occurs through the repression of normal respiratory metabolism. Preference of aerobic fermentation over aerobic respiration is referred to as the Crabtree effect in yeast, and is part of the Warburg effect in tumor cells. While aerobic fermentation does not produce adenosine triphosphate (ATP) in high yield, it allows proliferating cells to convert nutrients such as glucose and glutamine more efficiently into biomass by avoiding unnecessary catabolic oxidation of such nutrients into carbon dioxide, preserving carbon-carbon bonds and promoting anabolism.
Metschnikowia pulcherrima is a ubiquitous species of yeast, with numerous strains, belonging to the family Metschnikowiaceae, and found on grapes, cherries, flowers, spoiled fruit and consequently carried by fruit flies. It is a non-Saccharomyces yeast and plays an important role in the vinification of wine when it is present on grapes or winery equipment, and has historically seen use in South Africa’s wine industry. It is also being studied at the University of Bath as a possible alternative to the use of Palm oil, and early results show promise. M. pulcherrima is ovoid to ellipsoidal in shape and reproduces by budding. Its cells are globose and thick-walled, holding a single, large oil droplet of high refractive index. As the result of incomplete budding where cells remain attached after division, pseudohyphae may form under anaerobic conditions.
Lachancea thermotolerans is a species of yeast.
Hanseniaspora osmophila is a species of yeast in the family Saccharomycetaceae. It is found in soil and among the bark, leaves, and fruits of plants, as well as fermented foods and beverages made from fruit.
{{cite book}}
: CS1 maint: multiple names: authors list (link){{cite book}}
: |first1=
has generic name (help)