Effect on microbial growth and activity, Biology

Assignment Help:

Effect on Microbial Growth and Activity

Bacteria require higher aw for growth than fungi. Gram-negative bacteria have higher requirements than gram positives. Most spoilage bacteria do not grow below aw 0.91, while spoilage molds can grow as low as 0.80. Food-poisoning bacteria like Staphylococcus aureus can grow at aw as low as 0.86, while Clostridium botulinum does not grow below 0.94. Yeasts and molds can grow over a wider aw range than bacteria. The lowest aw values for bacteria is 0.75 for halophilic bacteria, while xerophilic molds and osmophilic yeasts can grow at aw values of 0.65 and 0.60, respectively. The limiting value of water activity for the growth of microorganisms is about 0.6 and below this value the spoilage of foods is not due to microorganisms but may be due to insect damage or chemical reaction such as oxidation. At a water activity of 0.6, corresponding to a water potential of -68MPa (Mega Pascals), the cytoplasm would need to contain very high concentrations of an appropriate compatible solute and it is probable that the macromolecules such as DNA would no longer function properly and active growth may stop.


Related Discussions:- Effect on microbial growth and activity

What is Inoculation and Culturing in Microbiology, What is Inoculation and ...

What is Inoculation and Culturing? In microbiology, inoculation is the process where a microbe of interest is introduced into a previously sterilized growth medium for the p

Enumerate about the mycotic infections, Enumerate about the Mycotic Infecti...

Enumerate about the Mycotic Infections Invasion of the nervous system by a fungus is known as a mycotic infection. A fungus is any member of a large group of lower plants (in s

What is the most probable inheritance pattern of a trait, What is the most ...

What is the most probable inheritance pattern of a trait with gaussian proportional distribution of phenotypical forms? If a trait statistically has a normal (bell-shaped curve

Explain disease jet lag, Jet Lag   Disturbance of body and environmental...

Jet Lag   Disturbance of body and environmental rhythms resulting from a rapid change in time zones gives rise to jet lag, which is characterized by insomnia, decreased quality

What is the functionality of lungs in human biology, What is the functional...

What is the functionality of Lungs in human biology? The right lung consists of three lobes, and the left lung, two lobes. Both lungs hold between 5 to 6 L of gas, called the t

Source of cells for regeneration, Source of Cells for Regeneration It...

Source of Cells for Regeneration It had been considered earlier that interstitial cells constitute a reserve of undifferentiated cells that provide the cellular material for

fat digestion requires two steps, Fat digestion requires two steps? What a...

Fat digestion requires two steps? What are the steps and what enzymes are used to accomplish each step?

What is a pipette and how is it used, What is a pipette and how is it used?...

What is a pipette and how is it used? There are lots of types of pipettes (or pipette), but most are basically a fancier version of a medicine dropper or eye dropper. They are

Explain insect resistance, In 2003 nearly 70 million hectares globally were...

In 2003 nearly 70 million hectares globally were planted in genetically modi?ed crops. Of these, 73%  were plants such as soybean, corn and cotton, which were modi?ed to be he

Measurement of species diversity, The measurement of species diversity prov...

The measurement of species diversity provides an important preliminary assessment of overall biodiversity. There are many ways by which species diversity is measured i.e. species r

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd