Lecture 7 & 8 Microbial Growth

Question 1

Stages of microbial growth

Answer 1

1. lag phase
   - prepping
2. exponential (log)
   -using nutrients at maximum rate
3. stationary
   nutrients are depleting
4. death

Question 2

batch culture vs continuous

Answer 2

batch
-nutrients are finite
-follow lag, log, stationary, death

continuous
- nutrients are infinite, constantly replenished
cells are removed
remains in stationary phase

Question 3

Growth in a Chemostat cell yield

Answer 3

Cell yield = cell number / volume
this depends on nutrient availability

if nutrients are in excess, cell yield and growth rate will be at maximums and limited by natural metabolic processes.
meu maximum

Question 4

Growth in Chemostat D = f/v

Answer 4

Dilution rate = flow rate / reactor volume

the growth rate in a chemostat is controlled by and equal to the dilution rate

if D increases, growth rate increases, as nutrients added more quickly, but eventually, the cells cannot grow as fast as they are removed = washout

in chemostat, always in stationary phase because cells are exponentially growing but they are being removed. cell growth = cell removed

Cr = concentration of resevoir

carrying capacity
–> how many cells can be sustained via nutrient availability

Question 5

what is a washout?

Answer 5

if D increases, growth rate increases, as nutrients added more quickly, but eventually, the cells cannot grow as fast as they are removed = washout

Question 6

Measure microbial growth methods

Answer 6

1) direct count
- hemocytometer

2) Culture methods
- spread and streak plate

3)Biomass
-dry weight
-photospectrometer

4) microbial methods
PCR