1. Lecture 1 Biochemical Engineering
Material Balances
Lecture 1
Biochemical Engineering

2. Review of Thermodynamics
System – any matter identified for investigation
Surroundings – the remainder of the universe
Boundary – separates system from surroundings
May be real and tangible or virtual and nominal

3. Types of System

4. Process – causes changes in the system or surroundings
Batch process – operates in a closed system
Semi-batch process – allows either input or output of mass
Fed-batch process – allows input of material to the system but not output
Continuous processs – allows matter to flow in and out of the system
Batch process – all materials are provided at the start, and the products are removed only when the process is complete
Semi batch – all other process that does not fit in the other three
If input and output rates of continuous process is equal, it can continue on indefinitely

5. Equilibrium vs Steady-state
Describes a process in which the properties of the system (T, p, V, …) doesn’t vary with time
Equilibrium
Describes a system in which all opposing forces are counter-balanced, leading to insignificant changes in the properties of the system

6. Law of Conservation of Mass
Mass in = Mass out
Given component A, what if Mass in ≠ Mass out?
Something is wrong with the measurements
The system has a leak
Component A is consumed/generated within the system
Component A accumulates in the system

7. General Mass Balance For component A Mass in Mass out Mass generated
Mass consumed
Mass accumulated

8. Sample Problem
A continuous process is set up for treatment of waste water. Each day, 105 kg cellulose and 103 kg bacteria enter the feed stream, while 104 kg cellulose and 1.5 x 104 kg bacteria leave the effluent. The rate of cellulose digestion by the bacteria is 7 x 104 kg/day. The rate of bacterial growth is 2 x 104 kg/day; the rate of bacterial lysis is 5 x 102 kg/day. Write balances for cellulose and bacteria in the system
Cellulose:
2x104 accumulation
Bacteria:
5.5x103 accumulation

9. Types of Material Balance
Differential Balance
Used for continuous processes
Based on flow rates
Integral Balance
Used for batch, semi-batch and fed-batch
Based on the quantity or mass, usualy over a specified time period

10. Simplified General Mass Balance: the Steady-state
Material
At steady-state, does mass in = mass out?
With reaction
Without reaction
Total mass
Yes
Total moles No
Mass of a molecular specie
Moles of a molecular specie
Mass of an atomic specie
Moles of an atomic specie
𝑚𝑎𝑠𝑠 𝑖𝑛+𝑚𝑎𝑠𝑠 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑒𝑑=𝑚𝑎𝑠𝑠 𝑜𝑢𝑡+𝑚𝑎𝑠𝑠 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑

11. Procedure for material balance calculation
Draw a clear process flow diagram
Select a set of units and state it clearly
Select a basis for calculation and state it clearly
State all assumptions applied to the problem
Identify which components of the system are involved in reaction

12. What percentage water is in the filter cake?
A fermentation slurry containing Streptomyces kanamyceticus cells is filtered using a continuous rotary vacuum filter. Slurry is fed to the filter at the rate of 120 kg/h; 1 kg slurry contains 60 g cell solids. To improve filtration rates, particles of diatomaceous aerth filter aid are added at a rate of 10 kg/h. the concentration of kanamycin in the slurry is 0.05% by weight. Liquid filtrate is collected at a rate of 112 kg/h; the concentration of the kanamycin in the filtrate is 0.045% (w/w). Filter cake containing cells and filter aid is removed continuously from the filter cloth.
What percentage water is in the filter cake?
If the concentration of kanamycin dissolved in the liquid within the filter cake is the same as that in the filtrate, how much kanamycin is absorbed per kg filter aid?
Draw a clear process flow diagram
Select a set of units and state it clearly
Select a basis for calculation and state it clearly
State all assumptions applied to the problem
Identify which components of the system are involved in reaction
4.4%
9.6x10-4 kg/kg

13. How much glucose and ammonia are required?
Xanthan gum is produced using Xanthomonas campestris in batch culture. Laboratory experiments have shown that for each gram of glucoses utilized by the bacteria 0.23 g of oxygen and 0.01 g ammonia are consumed, while 0.75 g gum, 0.09 g cells, and 0.27 g gaseous CO2 and 0.13 g H2O are formed. Other components of the system such as phosphate can be neglected. Medium containing glucose and ammonia dissolved in 20,000 L water is pumped into a stirred fermenter and innoculated with X. campestris. Air is sparged into the fermenter; the total amount of off- gas recovered during the entire batch culture is kg. because xanthan gum solutions have high viscosity and are difficult to handle, the final gum concentration should not be allowed to exceed 3.5% wt.
How much glucose and ammonia are required?
What percentage air is provided?
Draw a clear process flow diagram
Select a set of units and state it clearly
Select a basis for calculation and state it clearly
State all assumptions applied to the problem
Identify which components of the system are involved in reaction
980 kg glucose; 9.8 kg NH3
25% excess air

14. Material Balance w/ Recycle, Purge and Bypass