Abstract
The aim of the long-term preservation of cells, tissues and organs is to maintain their cellular structures and biological functions for as long as possible. Cryopreservation is a process where biological material is stored and preserved at very low temperatures. However, freezing and thawing processes can cause irreversible cell damage, which is related to formation of ice crystals, osmotic stress, accumulation of reactive forms of oxygen, etc. Therefore the cell viability depends mainly on the freezing rate, the composition of the cryoprotective medium as well as on the thawing rate. Using a suitable cryoprotective medium can increase the viability rate of the yeasts after “revitalization“. Appropriate pre-cultivation before freezing also plays an important role. These facts show that cell freezing and thawing processes must be controlled to avoid cell damage.
Highlights
It is essential that even after a long-term storage, brewer's yeasts maintain their original properties which constitute one of the main requirements for their use in brewing.The preservation process should ensure high viability of the cells, and the preservation of their physiological as well as technological properties
Various techniques can be used for preservation of yeasts, for example regular re-inoculation on a suitable medium, drying methods, freeze-drying, freezing in liquid nitrogen, vitrification, etc. (Kumar et al, 2013; Day and Stacey, 2007; Kirsop and Doyle, 1991)
I addition, it offers a brief overview of other preservation techniques to enable a comparison of their particular advantages and disadvantages
Summary
It is essential that even after a long-term storage, brewer's yeasts maintain their original properties which constitute one of the main requirements for their use in brewing. The preservation process should ensure high viability of the cells, and the preservation of their physiological as well as technological properties. Various techniques can be used for preservation of yeasts, for example regular re-inoculation on a suitable medium (a liquid or solidified soil), drying methods, freeze-drying (lyophilization), freezing in liquid nitrogen (cryopreservation), vitrification, etc. (Kumar et al, 2013; Day and Stacey, 2007; Kirsop and Doyle, 1991). This paper is focused mainly on the long-term storage of brewing yeast using the cryopreservation technique. I addition, it offers a brief overview of other preservation techniques to enable a comparison of their particular advantages and disadvantages
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