Yeast is a unicellular or a single cell organism that belongs to the broader group of organisms known as ‘fungi.’ They sometimes appear as multi cellular structures although these are false or pseudohyphaes in contrast to true hyphaes seen among other fungi.
Characteristics of yeasts:
There are about 1500 yeast species identified by scientists although 99% of the same species remains undiscovered. Among the identified species, some require oxygen to perform cellular breathing whereas others can even sustain in environments deprived of oxygen as they have the ability to perform anaerobic cellular respiration. Yeast derives its energy requirements from organic compounds, which are most likely to be sugar based. Due to this phenomenon, these organisms do not depend on sun light for its energy requirements and is often isolated naturally from sugar rich mediums.
Among many factors that affect the growth of yeast, some are manipulative through various mechanisms. However, not all yeasts thrive on same environmental states and therefore needs individualized attention according to the type of species when cultured in the lab.
Factors affecting yeast growth:
Following is a brief description of factors controlling how yeasts grow.
Temperature
Yeasts can tolerate extreme temperatures although it may lose its viability with time. Some yeast live in freezing conditions but many will grow in normal environmental temperatures existing in many places. Therefore, refrigeration or deep freezing may not be a full proof method to prevent yeast formation.
Acidity
Many species of yeast grow in media with a neutral PH or slightly acidic PH. Thus, yeast extracts or foods derived from yeasts are more likely to be acidic. When it comes to culture medium, scientists use the same characteristic in organic acids for its use as an effective culture medium.
Sugar concentration
As described earlier, yeasts require organic compounds such as sugar derivatives to obtain energy and therefore its concentration in the culture medium or in the environment will affect the rate of its growth.
Type of strain
Certain strains or species of yeasts will grow rapidly whereas some may be relatively slow. However, further research is required to link type of strain and its growth to understand its correlation better.
Oxygen
As described earlier, although anaerobic respiration is possible, many yeast strains will require oxygen enriched medium for its metabolic functions. Thus, when yeasts grow in a lab, they receive an aerobic environment for effective growth.
Minerals
Minerals such as magnesium, potassium and several other trace elements are essential for yeast growth and therefore should encourage growth when provided externally.
Phosphorus
When considering its part as an element in the nucleic acids and phospholipids, provision of phosphorus is important for effective yeast growth.
Sulphur
It is an essential element of certain amino acids and when added to a culture medium, it will encourage yeast growth.
Growth factors
Scientists have learn that, yeasts require certain vitamins, purines, pyrimidines, amino acids, fatty acids…etc for catalyzing the biosynthesis although they do not act as energy sources for yeasts. Therefore, such factors are named as ‘growth factors’ and should be available in trace quantities in the culture medium for optimal growth.
Apart from the above, there can be many other factors contributing to the growth of yeast and require further research to determine how extensively they affect in their growth..
