Fermentation Technology Basics

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Questions and Answers

What level of chloride content should be maintained in cooling water to prevent pollution?

Less than 200 ppm

Less than 50 ppm

Less than 100 ppm (correct)

Less than 150 ppm

What phenomenon may occur when chloride ions are above 150 ppm and the stainless steel exceeds 80ºC?

Stress corrosion cracking (correct)

Oxidation

Corrosion resistance

Temperature stability

What should be done if the dissolved solids in the cooling water become too high?

Increase the temperature

Stop the sterilization process

Add more salts

Discharge some water and add fresh water (correct)

Which method is NOT considered an acceptable solution for treating odors from fermentation processes?

Tall exhaust stacks Signup and view all the answers

Which parameter should be monitored in liquid waste before discharge into the sewer?

COD/BOD levels Signup and view all the answers

What is a common effect of sterilizing certain raw materials in fermentation processes?

Production of odor Signup and view all the answers

Which treatment method is effective for reducing odors but can result in discharging sodium and chlorine into waste systems?

Wet scrubbing towers Signup and view all the answers

Which noise control measure is considered essential for employees in fermentation facilities?

Hearing protection Signup and view all the answers

What is the primary reason for increasing the inoculum volume beyond one-tenth of the fermenter volume?

To shorten the growth phase of the culture Signup and view all the answers

Which of the following is NOT a function of nutrient feed tanks in a fermentation process?

Control fermentation temperature Signup and view all the answers

What type of filter material can be found in custom-designed sterile air filtration systems?

Carbon Signup and view all the answers

How does the design of air piping in nutrient feed tanks differ from high-volume airflow systems?

It is not designed for high volume air flow Signup and view all the answers

What is an important factor in the design of packed-bed filters for effective filtration?

Fine fiber diameter and bed depth of 10 to 18 inches Signup and view all the answers

Why is sufficient air pressure necessary in nutrient feed tanks?

To transfer the feed Signup and view all the answers

What type of nutrients typically do not require an anti-foam system in their agitation process?

Dissolvable nutrients Signup and view all the answers

What is a potential consequence of failing to kill a foreign organism or spore during sterilization?

Contamination of the fermenter Signup and view all the answers

Which of the following procedures should not be changed by individuals?

Operating procedures Signup and view all the answers

What can be used to confirm the presence of bacteriophages?

Phage plaque plates Signup and view all the answers

Which of the following is a common problem associated with lack of maintenance that can lead to contamination?

Worn-out mechanical seals Signup and view all the answers

Why is calibration of temperature and pressure gauges considered critical?

To ensure accurate sterilization temperatures Signup and view all the answers

What is a potential result of bacteriophage contamination in fermentation processes?

Reduction of cell mass Signup and view all the answers

What is the accuracy percentage of gas analyzers used for effluent gas analysis?

±1% Signup and view all the answers

Which method can be used to estimate liquid flow rates indirectly in a fermenter?

Load cell weight monitoring Signup and view all the answers

What component is used as a direct indicating gauge for measuring pressure?

Bourdon tube pressure gauge Signup and view all the answers

How does pressure affect a fermenter’s environment?

It contributes to maintenance of sterility. Signup and view all the answers

Which of the following is a characteristic of the Bourdon tube pressure gauge?

Changes cross-section from elliptical to circular with increased pressure. Signup and view all the answers

What is a major consideration when measuring flow rates of sterile liquids?

Presence of solid particles. Signup and view all the answers

Which measuring device is indicated for use under aseptic conditions?

Nested Diaphragm-Type pressure sensor Signup and view all the answers

What role does knowing the specific gravity of liquids play in flow rate measurement?

It allows for accurate estimation of flow rates. Signup and view all the answers

What is the primary reason for installing baffles with a gap between them and the vessel wall?

To minimize microbial growth Signup and view all the answers

Which type of sparger is primarily used in non-agitated laboratory scale vessels?

Porous sparger Signup and view all the answers

What is a characteristic feature of an orifice sparger?

It consists of a perforated pipe kept below the impeller Signup and view all the answers

Which sparger causes the least pressure loss among the different types?

Nozzle sparger Signup and view all the answers

What occurs when baffles are made narrower than the recommended size in a fermenter?

Agitation effect decreases sharply Signup and view all the answers

Why is the throughput of air low in porous spargers?

There is a pressure drop across the sparger Signup and view all the answers

In what applications has the orifice sparger been used despite its limitations?

In effluent treatment and yeast manufacture Signup and view all the answers

What size should the air holes be in the orifice sparger tubes?

At least 6mm in diameter Signup and view all the answers

Study Notes

Sterilization

A single foreign organism or spore not killed during sterilization can contaminate the fermenter.

Inoculum Volume

Larger cell masses from inoculum can shorten the growth phase.
Some companies make the inoculum volume larger than a tenth of the fermenter volume to reduce lag time.
This minimizes transfers from laboratory flask to the fermenter.

Nutrient Feed Tanks

Sterilizable tanks are essential for feeding nutrients in a productive fermentation department.
Multiproduct plants need different sized feed tanks for various nutrients.
Feed tanks are not designed for high volume air flow, but only enough pressure for transfer.

Sterile Filters

Sterile air filtration today is simple with commercial units readily available.
Companies may still design their own filters using various materials like carbon, cotton, and glass.
Packed-bed and cartridge filters are used to obtain sterile air and reduce humidity.
Filter material should remain dry to maximize filter lifetime.
Careful selection of the cartridge design or packed-bed filters can extend the filter lifetime to over 3 years.
Fine fiber diameter in packed-bed filters improves filtration efficiency.
Bed depth of filters is 10 to 18 inches and 10 microns.

Corrosion

Chloride ions above 150 ppm in water used during sterilization, along with stainless steel at above 80°C can cause stress corrosion cracking in the fermenter.
A conductivity probe in the cooling water line can indicate high salt levels, which may require discharging and replacing water.
Discharging water from the sterilization process to a stream or river may require pollution control agency permits and special monitoring.
The chloride content in the cooling water should be determined analytically every two weeks to keep levels below 100 ppm.
The dischargeable level of chloride content in cooling water is below 100 ppm.

Environmental Control

Odor

Certain materials smell when sterilized.
Each fermentation process has a unique odor ranging from mild to strong, pleasant to foul.
High volume air discharge from large fermenter houses can cause unavoidable odors.
Wet scrubbing towers with sodium hypochlorite can remove odors, but are expensive and discharge sodium and chlorine, making them unsuitable.
Tall exhaust stacks can dilute released gas with the atmosphere, but pollution control boards may not consider it acceptable.
Ozone treatment can be effective.

Organic Pollution

Fermentation departments should monitor and control the COD/BOD of liquid waste before discharging into the sewer.
Spill cleanup and reporting procedures should be a standard operating procedure.
Primary aeration basins can reduce the COD to 80-90 ppm.
Secondary aeration lagoons can reduce the BOD to acceptable levels.

Noise

Noise levels are difficult to reduce to standard levels.
Hearing protection for employees is essential.

Baffles

Baffles are metal strips attached to the wall, approximately one-tenth the vessel diameter.
Wider baffles slightly increase the agitation effect, but narrower baffles sharply decrease it.
Baffles should have a gap between them and the vessel wall for scouring action to minimize microbial growth.
Extra cooling coils attached to baffles improve cooling capacity of a fermenter without affecting geometry.

Aeration System (Sparger)

A sparger introduces air into the liquid in a fermenter.
Three basic types of spargers are used: porous, orifice, and nozzle.
Combined sparger-agitators are used in laboratory fermenters.

Porous Sparger

Used primarily on a laboratory scale in non-agitated vessels.
Bubble size is 10-100 times larger than the aerator block pore size.
Air throughput is low due to pressure drop and holes can become blocked by microbial growth.

Orifice Sparger

Used in small stirred fermenters.
It is a perforated pipe below the impeller in the form of crosses or rings.
Size should be ¾ of the impeller diameter.
Air holes are drilled on the under surfaces of the tubes and should be at least 6mm in diameter.
Orifice spargers without agitation are used in yeast manufacturing, effluent treatment, and single-cell protein production.

Nozzle Sparger

Point or nozzle spargers are used in agitated fermenters from laboratory to production scale.
They consist of a single open or partially closed pipe providing a point-source stream of air bubbles.
Single-nozzle spargers have lower pressure loss than other spargers and don't usually get blocked.

Gas Flow Measurement

Oxygen and carbon dioxide gas analyzers require accurate gas-flow measurement for effective analysis.
Instruments have ±1% full-scale accuracy and work on the principle of measuring a temperature difference across a heating device in the gas path.

Liquid Flow Measurement

Measuring flow rates of sterile liquids poses challenges.
Laboratory scale flow can be measured manually using a sterile burette.
Rotameters and electrical flow transducers can also be used.
Load cells attached to the fermenter and ancillary reservoirs can measure flow rates indirectly by monitoring weight changes.
Specific gravity allows accurate estimation of flow rates in different feed pipes.

Pressure Measurement and Control

Pressure is a crucial measurement for operating processes and media sterilization.
Pressure influences gas solubility and maintains sterility in the presence of positive pressure.
A Bourdon tube pressure gauge is a direct indicating gauge for pressure measurement.
Nested Diaphragm-Type pressure sensors are used for aseptic conditions.

Operating Procedures

Proper training for new operators explaining the importance of each operation is essential.
No individual changes to procedures are allowed.
A basic operating manual should be available.
Regular safety and technical meetings with operators should be scheduled to update them on technical and procedural changes.
Operators should be encouraged to provide feedback on observations, ideas, and errors without fear.

Sources of Contamination

Lack of maintenance can lead to contamination.
Braided packing on agitator shafts is a common problem, but germicidal solutions help.
Mechanical seals on agitator shafts have a sterilizing liquid circulating as a lubricant.
Accurate sterilizing temperatures are critical.
Flanged sterile piping should be checked for leaks.

Bacteriophage Contamination

Bacteriophages affecting bacterial and fungal fermentations can be found in soils, water, air, and raw materials.
They cause cell lysis, reducing cell mass, product formation, oxygen uptake, and heat generation.
Phage plaque plates, ultra-filters, and isolation of the specific virus can confirm phage presence.

Online Chemical Analysis

Online analysis of chemical factors is important for process control and optimization.
Techniques include sensors for pH, dissolved oxygen, and specific nutrients.
The data collected helps adjust process parameters to achieve desired results.

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Description

This quiz covers essential concepts in fermentation technology, including sterilization, inoculum volume, nutrient feed tanks, and sterile filtration. Understand the critical factors that influence the effectiveness and efficiency of fermentation processes in biotechnology.