What is fermentation - Being able to grow anaerobically in the presence of a suitable organic
compound, such as a sugar.
Several reduced products are excreted by the cell as a way of disposing of the electrons derived from
oxidation.
Function and Types of hydrolytic enzymes - Hydrolytic enzymes...
MCB 2610 Lab Practical
What is fermentation - Being able to grow anaerobically in the presence of a suitable organic
compound, such as a sugar.
Several reduced products are excreted by the cell as a way of disposing of the electrons derived from
oxidation.
Function and Types of hydrolytic enzymes - Hydrolytic enzymes hydrolyze (break down) complex
molecules to get food that can be transported into the cell.
1. Amylase
2. Caseinase
3. Gelatinase
Amylase - catalyzes starch hydrolysis. Reacts readily with iodine to produce a dark blue color.
Clear zone indicates amylase production.
Iodine makes the starch blue.
Caseinase - Enzymes that hydrolyze milk protein (casein) into peptides and ultimately into amino
acids
Clear zone where caseinase is digested
Catalase - An enzyme which protects cells from hydrogen peroxide - a highly reactive and toxic
chemical produced as a byproduct of oxygen metabolism
H2O2 in the presence of catalase will produce water and oxygen as a byproduct
If catalase positive, bubbles of O2 will form when a drop of H2O2 is placed on the organism
Complex media - Exact chemical composition is not known
Most are made from inexpensive sources
Diverse mixture of proteins (peptides), sugars, vitamins, minerals
, Death phase - Occurs if conditions remain unchanged (no new medium or environment remains
stable). The cell death rate will eventually exceed any remaining cell division.
Defined media - Made up of a strict list of compounds
Allows scientists to characterize the versatility and limitations of an organism's metabolic capacity
Defined media can be used to help define the specific requirements for a particular organism
Differential media - Allows certain bacteria to be differentiated from others, typically by changing
of color, production of a zone of clearing etc.
Dye used for spore staining - 5% aqueous Malachite green dye
Gelatinase - An enzyme that hydrolyzes gelatin, a protein derived from collagen.
If gelatin is hydrolyzed, the media will become liquid
General purpose media - WIll support growth of a wide range of organism
Used to grow up dense cultures of bacteria, typically for experimentation
How does SF select for streptococci - Streptococci lack a respiratory system, so they use
fermentation. Brom cresol purple is an acid indicator that changes color when acid is produced,
indicating fermentation of the glucose.
Purple = negative for fermentation of glucose
Yellow = positive for fermentation of glucose
How is bacterial growth measured? - Using a spectrophotometer, you can measure the optical
density (absorbance) over a period of time
How is microbial growth defined? - Increase in population size
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