1. MICROBIAL GROWTH KINETICS

2. INDEX INTRODUCTION GROWTH CURVE LAG PHASE EXPONENTIAL PHASE
STATIONARY PHASE
DECLINE PHASE

3. BATCH CULTURE
A closed culture system which contains initial and limited amount of nutrients.
The inoculated culture undergoes 4 phases i.e
i) Lag phase
ii) log/Exponential phase
iii) Stationary phase
iv) Decline phase
Growth curve is sigmoidal in batch cultures .

4. GROWTH CURVE

5. Lag phase
cell biomass concentration i.e x= 0 because the cells are adapting to the environment so no growth occurs.
Specific growth rate is also zero i.e µ= 0
In commercial process lag phase should be reduced as much as possible .

6. Exponential phase
During log/exponential phase cell growth rate increases gradually which is maximum and constant .
so µ = µmax.
dX/dt =µ.X where X=conc. of cell biomass
t= time, in hours
µ= specific growth rate
on integration between the limits X₀ at the time t=0 and X at time t Xt = X₀. eµt
on taking natural log
ln X = ln X₀+µt
where X₀=original biomass conc.
Xt=biomass after time ‘t’ hours
e=base of natural logarithm

7. In fungi we need to consider the length of hyphae as well as number of apex tips.
dH/dt = µh
dA/dt= µA where H= hyphal length
A = no. of apical tips
In submerged culture a myecial organism may grow as pellets. Growth of pellets is exponential until diffusion limitation . Growth of pellet proceeds from outer shell of biomass which is actively growing zone.
M⅓= kt + M₀⅓
where M₀ and M is myecial mass at time 0 and t respectively.

8. STATIONARY PHASE

9. In the region A to B, an increase in the substrate conc
In the region A to B, an increase in the substrate conc. gives an proportional inc. in biomass.
x= Y(Sr-s) where Y= yield factor
Sr = initial substrate conc.
s= residual substrate conc.
Yield factor is a measure of efficiency of conversion of any 1 substrate into biomass.
In the region B to C utilization of substrate affected either due to toxic accumulation or availability of another substrate.
Over the zone C to D an increase in the initial substrate conc. does not give proportional inc. in biomass.

10. DECLINE PHASE
Decrease in the growth rate and cessation of the growth due to depletion of substrate is described by eqn
µ= µmax s/ (Ks+s)
where s = residual substrate conc.
Ks= substrate utilization constant
Decrease in growth of cells is also due to accumulation of toxic byproducts produced by cells.

11. THANK YOU