Batch - Mass and Kinetic Balances

Question 1

What are the two most important quantitative parameters for fermentation design?

Answer 1

Yield and Productivity

Question 2

What are the three main fermentation modes?

Answer 2

Batch, Continuous, and Fed-Batch

Question 3

What is the specific growth rate?

Answer 3

A rate parameter that measures how quickly a microorganism grows in it’s exponential phase

Question 4

What are the four phases of biomass growth (in a batch)?

Answer 4

1) Lag phase
2) Log or exponential growth phase
3) Deceleration phase
4) Stationary phase

Question 5

What generally causes the stationary phase?

Answer 5

There is no more substrate to be consumed and converted into biomass

Question 6

What is the growth rate formula for biomass?

Answer 6

dx/dt = u x [u is the specific growth rate]

Question 7

What is the integrated and log form of the growth rate formula for biomass at time t?

Answer 7

ln(xt) = ln(xo) u t [t is time, x is biomass concentration, and u is specific growth rate]

Question 8

How would a yield of biomass (x) from substrate (s) be written?

Answer 8

Ysx [ s -> x]

Question 9

What are the two types of productivities?

Answer 9

Volumetric productivity and Specific productivity

Question 10

What is volumetric productivity?

Answer 10

It is concentration of a species per unit of time. [mass per volume per time]

Question 11

What is specific productivity?

Answer 11

It is yield of a species per unit time [mass per mass per time]

Question 12

What is rs (r sub s)?

Answer 12

specific substrate consumption rate

Question 13

What is rx (r sub x)?

Answer 13

Specific growth rate or u

Question 14

What is rp (r sub p)?

Answer 14

Specific rate of product formation

Question 15

what is rco2 (r sub co2)?

Answer 15

Specific CO2 production rate (CER)

Question 16

What is ro2 (r sub 02)?

Answer 16

Specific oxygen consumption rate (OUR)

Question 17

Yields are typically normalized to what two components?

Answer 17

Substrate or biomass

Question 18

What is the substrate mass balance for a batch reactor?

Answer 18

dcs/dt = -rs x

Question 19

What is the product mass balance for a batch reactor?

Answer 19

dcp/dt = rp x

Question 20

What is the product biomass balance for a batch reactor?

Answer 20

dx/dt = u x

Question 21

What are the 7 characteristics of a batch reactor?

Answer 21

1) constant volume (no flow in or out)
2) All medium is in the fermenter at inoculation (no adding substrate)
3) Growth is not limited at the beginning of the fermentation (U = Umax)
4) Dynamic process (changes with time)
5) Low volumetric productivity at the beginning
6) Versatile
7) No issues with mutations or contaminations