The document discusses microbial growth kinetics, detailing phases such as lag, log (exponential), stationary, and death stages of cell growth. It explains factors affecting growth rates including cell characteristics, medium conditions, and nutrient sources, as well as equations describing growth and death kinetics. The content emphasizes the importance of environmental factors in cell mass and number variations throughout the growth process.

1. MICROBIAL GROWTH KINETICS
Dr. Vividha Raunekar

2. Dr. Vividha
Raunekar
CELL GROWTH
Cell growth is a process of orderly increase in cell number as well as cell mass
Orderly/ controlled
Uncontrolled growth
Phases of cell growth- Different growth rate variation

3. Dr. Vividha
Raunekar
BATCH CULTURE
Lag Phase- cell mass increases; no division; adaptation, such as change in medium,
environment,
Length of lag phase is dependent on – 1. cell characteristics- passage number, cell health,
2. media conditions- nutrients, differential media
3. multiple lag phase- different carbon sources (glucose, lactose, etc)- different
metabolism (according enzyme activation)
Diauxic growth- two nutrient sources; two growth curves

4. Dr. Vividha
Raunekar
LOG PHASE/ EXPONENTIAL GROWTH PHASE-
Highest cell growth rate
Exponential increase in cell mass and number
Exponential phase
Balanced growth- when environmental conditions does not affect biomass composition; where
growth rate is constant

5. Dr. Vividha
Raunekar
LOG PHASE KINETICS-
First order reactions
Rate of reaction is only dependent (directly proportional to) on conc. of reactants
Biomass synthesis- availability of biomass
C, N, O, nutrients, temp, pH
Rate of cell growth in log phase: rx=µ.x

6. Dr. Vividha
Raunekar
Rate of cell growth in log phase: rx=µ.x (unit: kg.m-3.h-1)
rx- volumetric rate of biomass production
X- number of mass of cells (unit: kg.m-3)
µ- specific growth rate (unit: h-1)
rx=µ.x =dx/dt
Integrating,
X=X0.eµt
X0= viable conc. at time 0
Straight line equation: y=mx+c

7. Dr. Vividha
Raunekar
STATIONARY PHASE/ DECELERATION PHASE
Starts at the end of acceleration phase
Net growth rate is 0
Growth rate = death rate
No of cells dividing= no of cells dying
dx/dt= 0

8. Dr. Vividha
Raunekar
DEATH PHASE
No of cells dying is more than no of cells diving or metabolizing
New media is not being added; nutrient deprivation; release of toxic products and
accumulation

9. Dr. Vividha
Raunekar
KINETICS OF DEATH PHASE
Exponential cell death rate
Death rate is slower than rate of growth
First order reaction
rd= kd. N
Rd- rate of cell death
Kd- specific death constant
N- no of viable cells

10. Dr. Vividha
Raunekar
rd= -dN/dt= kd.N
N=N0. e-kdN
After integration
LnN= LnNo. -kdt

11. Dr. Vividha
Raunekar
Thank you