Continuous Flow Thermal Processing For Viral Inactivation and Sterilization John Miles, Ph.D., President, MicroThermics, March 18, 2014.
What We Will Be Discussing Today Continues I. Nomenclature: HTST and UHT II. Introduction to MicroThermics III. Introduction to HTST Processing and UHT Sterilization. IV. Single Use Technology and HTST/UHT Processing
What We Will Be Discussing Today -Continued- V. Benefits of These Types of Processes VI. CIP of HTST and UHT Systems VII. Validation of HTST and UHT Processes VIII. Development and Research With These processes
Questions From Today s Discussion MicroThermics will be at Interphex Booth #3857 Contact us at MicroThermics. Details to follow.
I. HTST/UHT Nomenclature Pasteurization: Thermal treatment to inactivate pathogenic organisms. This is the applied result, not the method. For our purposes Pasteurization is specifically directed at viral inactivation. HTST: High Temperature Short Time HTST is the continuous version of pasteurization and it is considered High Temperature Short Time relative to batch methods. Caution: Googling HTST will bring a large collection of information most of which is not relevant to how we are using the HTST process for pasteurization.
HTST/UHT Nomenclature Sterilization: Inactivation of all organisms present in the media. This is the applied result. Sterilization can be accomplished many ways. Thermal sterilization can be by batch or continuous methods. Thermal sterilization is inactivation not removal. UHT Processing: Ultra High Temperature Processing This is a broad category that includes sterilization conditions but is not limited to it. For our purposes UHT Processing refers to sterilizing conditions. Caution: Googling UHT will bring a large collection of information most of which is not relevant to how we are using the UHT process for sterilization.
HTST/UHT Process Conditions General Comments on HTST and UHT Conditions These are continuous flow methods and they require shorter times than batch methods, usually total process times below 2 minutes. Temperatures, higher than those used for batch, are used to accomplish the proper microbial reduction in the times used for these processes. Process Condition Ranges: HTST conditions: 70-120 C for hold times of 60 to 2 seconds. UHT conditions: 138-150 C for hold times of 30 to 2 seconds.
II. Introduction To MicroThermics
MicroThermics Mission MicroThermics was established to provide tools supporting development and adoption of continuous-flow thermal processes and products. HTST Pasteurization/Viral Inactivation UHT Sterilization MicroThermics specializes in continuous flow thermal processes only. Equipment Services Support
MicroThermics History Established in 1989. Equipment spanning many industries. Pharma, biopharm, biotech, biofuel, food Installations in nearly 700 locations. 20 countries. Award winning.
MicroThermics HTST or UHT Processing System
MicroThermics HTST or UHT Processing System
III. Introduction to HTST and UHT Processing HTST and UHT methods rely on proper equipment design, precise control and documentation of the media/product exposure to high temperature over a specific time.
What Do We Pay Attention To? In pasteurization or sterilization process we are most concerned with two things. Assurance level and reliability Media quality Both are influenced by the thermal history or the Time- Temperature History (TTH) that is delivered. The TTH is actually the temperature of the media as it is processed.
Time-Temperature History (TTH) In batch type processes, the TTH is the cold-point temperature in the package or vessel, recorded over the time of the process. It is influenced by: Size of the package or vessel Loading pattern in an autoclave Agitation of the media
HTST & UHT Process Flow Diagram Preheat Final Heat Hold Tube Cooler 1 Cooler 2 Media Inlet Product Pump P1 P2 Back Pressure Valve Media Outlet Process Components Product Pump Generally a positive displacement pump to maintain positive control over residence time. Hear Exchangers Not plate and frame. Commonly tubular. Hold Tubes Designed to ensure that the product is maintained at the hold temperature for the hold time. Back-Pressure Valves Ensure that sufficient pressure is maintained to prevent boiling and control flow and temperature. Instrumentation Sufficient to monitor all critical control points.
How Are HTST & UHT Processes Physically Different From Batch Processes? These are Continuous-Flow Thermal Processes (CFTP) Think of the system like one long pipe. The media is pumped at constant flow rate through: Heaters Hold Tube (For specific hold time at temperature) Cooler(s) Back-pressure valve or device
The Significance Of The Hold Tube The pasteurization/sterilization process is defined as the hold time at the hold temperature. The hold tube is where the official pasteurization/sterilization process occurs. The hold tube ensures that the product is held at the hold temperature for a specific length of time (constant flow rate). For legal processes, the hold time and temperature are critical control points with legal implications.
HTST & UHT Flow Diagrams Preheat Final Heat Hold Tube Cooler 1 Cooler 2 Media Inlet P1 P2 Back Pressure Valve Product Pump Media Outlet Time-Temperature History 160 Temperature ( C) 140 120 100 80 60 40 HTST Viral Inactivation UHT Sterilization 20 0 0 20 40 60 80 100 120 Residence Time (Sec.)
How Do Time Temperature Histories Compare Between Batch and Continuous Methods? -Viral Inactivation- 120 100 Temperature ( C) 80 60 40 HTST Viral Inactivation Small Bottle Viral Inactivation 20 0 0 500 1000 1500 2000 2500 3000 Time (Sec)
How Do Time Temperature Histories Compare Between Batch and Continuous Methods? -Sterilization- 160 140 120 Temperature ( C) 100 80 60 UHT Sterilization Small Bottle "Reactor" 40 20 0 0 1000 2000 3000 4000 5000 6000 7000 8000 Time (Sec)
Process Assurance and HTST & UHT Technology HTST and UHT processing systems include measures to ensure: The integrity of the process Accuracy and integrity of the data Adequacy of the data Integrity of the product and its assurance levels
IV. HTST and UHT Processing Supports Single Use Technology Fermentation vessels that withstand the pressures and temperatures of steam sterilization are not needed. HTST/UHT processes can be used and pump through filters to fill aseptically into Single Use Fermentation Vessels/Bags. Occupies less floor space Occupies less capital Enhances flexibility
HTST and UHT Processes Support Adoption of Continuous Processing Methods Supports this major industrial trend Enables more cost effective and stable operation Enables more flexibility Can be directly connected to a continuous process. Continuously fill smaller fermentation vessels that are used to supply a continuous process.
V. Benefits of HTST and UHT Processing
Treatment Uniformity In Batch and Continuous Processes
Classic Benefits of HTST and UHT Processing Process temperature is monitored and recorded in real time. Uniform treatment within a process. No variation due to package size or location in an autoclave. No variation due to vessel size. Media quality is independent of batch size.
Classic Benefits of HTST and UHT Processing Greatly simplified scale-up. For larger batches, just process for longer periods. Operating conditions are validated. Note: Operating conditions can be optimized for assurance and quality. Less capital is occupied with an individual media batch.
Benefits Due to The Different Time-Temperature Exposure of HTST and UHT Processes Higher temperature and shorter times cause less damage to media or product components. As temperature of a process is increased, the speed of reactions increases exponentially. The speed of reactions that inactivate viruses and bacterial spores increases much more than the reactions that impact media quality. HTST and UHT processes operate at higher temperatures to take advantage of this. Media can be treated so briefly that there is little time for degradation of the media from heat.
Reason: Reaction Kinetics Two General Models: General Method (usu. Microbiological) Arrhenius Kinetics
Using The General Method Back To Basics: This equation describes the relationship between temperature and sterilization time. D is the time needed to reduce a population by one log cycle. This is analogous to the time needed to sterilize a product and differs only by a constant. z is the change in temperature that will cause a log change in the D value. z values for microbial destruction are generally lower than those for qualitative changes in the media. This means that, as temperature is increased, the rate of microbial destruction increases faster than that of qualitative destruction.
Reason: Reaction Kinetics Back To Basics: When we are at the reference temperature T, the D value will be Dr because the temperature T matches the reference temperature Tr and the exponent is zero. Using a z value of 10 as an example, if the temperature, T, is 10 C above Tr, then the exponent is -1 which causes the D to be 1/10 th of the Dr value. Taken further, if T is 20 C above Tr, then D is 1/100 th of the Dr value. So for every 10 C rise in temperature, we reduce the time to sterilize a product by 10 fold.
The Impact On Sterilization (Or Pasteurization) Sterilization Temperature Sterilization Time* (Minutes) 121.1 C/250 F 35 131.1 C/268 F 3.5 141.1 C/286 F 151.1 C/304 F 0.35 (21 Seconds) 0.035 (2.1 Seconds) Assumes z=10 C
The Key Is The Difference In z Value z values for microbial destruction are generally lower than those for qualitative changes in the media. This means that, as temperature is increased, the rate of microbial destruction increases faster than that of qualitative destruction.
Comparison Of Decimal Reduction Times (D) For Quality and Microbiological Content 4.0 3.0 2.0 1.0 Log (D) 0.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 4.0 Log (D M) Log (D Q) -1.0 3.0 2.0-2.0 D(Q)/D(M) 0.18 0.32 0.56 1.00 1.78 3.15 5.59 9.93 17.62 31.28 55.52 Log (D) 1.0 0.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0-1.0-2.0-3.0 Log (D M) Log (D Q) -3.0-4.0 Temperature ( C) l Reduction Times -4.0 Temperature ( C) D=Time needed to reduce concentration by 90% or one log cycle M=Microbiological Content, Q=Media Quality. Note: As temperature increases, deterioration of quality does not accelerate as much as inactivating microorganisms.
Ratio of D Value For Quality Deterioration Vs Target Organism Inactivation D(Q)/D(MC) 60.00 50.00 Ratio Of Decimal Reduction Times 40.00 30.00 20.00 10.00 Ratio Of Decimal Reduction Times 60.00 50.00 40.00 30.00 20.00 10.00 0.00 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 Temperature ( C) 0.00 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 Temperature ( C) D(Q)/D(M) D=Time needed to reduce concentration by 90% or one log cycle The ratio increases because as temperature increases, the time needed to inactivate microorganisms decreases exponentially more than that leading to reduced quality.
What Does This Mean? As we increase temperature the speed of microbiological inactivation exceeds that of quality deterioration. The delivered result is that HTST and UHT processes retain more media/product quality than their corresponding batch methods with the same lethality. Higher assurance levels can be applied while retaining more quality.
Most Significantly Many media or products, that cannot be successfully pasteurized/sterilized using batch methods, may be quite successfully processed using HTST or UHT processes. The lower thermal impact on product quality provides the opportunity for new products that cannot be done with batch processes. HTST and UHT Technologies are enabling technologies.
HTST and UHT Processes Quick Summary Support Single Use Technology Retain more media/product quality (closer to unprocessed) Enable higher assurance levels Provide uniform treatment and simplified scale-up Enable pasteurization or sterilization of products that do not tolerate batch processing well.
VI. Cleaning of HTST and UHT Processing Systems -CIP-
CIP of HTST and UHT Systems HTST and UHT processing systems are built in compliance with the BPE for easy cleaning and draining. CIP procedures are developed and validated for specific media and lengths of processing times to minimize the need for exhaustive validation after each use and cleaning. CIP is often validated by visual inspection (boroscopy) and treatment with more aggressive reagents to test for removal of material.
CIP of HTST and UHT Systems CIP cleaning is accomplished in several automated steps. Media is rinsed from the system with water. A caustic solution is circulated at high velocity at approximately 65 C to react and strip deposits from critical surfaces for approximately 20 minutes, and then rinsed. An acid solution is circulated at high velocity at approximately 65 C to react and strip deposits from critical surfaces for approximately 20 minutes, and then rinsed.
VII.Validation of HTST and UHT Processes
Validation Of Batch Processes Validation of many batch methods of processing involves putting Biological Indicators (BIs) through the process along with the materials being treated. This provides a validation of the treatment based on its delivered affect on the BI.
Validation Of HTST and UHT Processes Continuous processes like HTST and UHT are not compatible with using a BI for a number of reasons. If a BI were to be placed in the media being processed, it would heat far more slowly than the media. This would be so significant that the thermal exposure experienced by the BI would be grossly less than that of the actual thermal process. Physically placing a BI into the process and harvesting it would be very difficult. Many BI s will not survive the physical conditions. These processes can be validated by processing a spore suspension and counting survivors. Cumbersome and technically challenging Produces useful results. Not to be done daily.
Validation Approach HTST and UHT processes operate at steady state conditions. Validation of these processes is validation of those specific operating conditions. Once the operating conditions and the TTH has been validated with an active organism, this condition (i.e. the TTH) has been demonstrated to deliver the proper lethality. Product is released parametrically based on data indicating the proper operation at those specific operating conditions.
Validation Background In HTST and UHT processes, the population of the indicator organism or spore is often virtually eliminated in the heating steps. This makes estimation of the hold tube impact difficult or impossible at the higher temperatures of the process. For this reason, validation of HTST and UHT processes often involves steps that determine the lower limit above which the process operates.
Validation Strategy The overall strategy is to operate the system and process a suspension of an organism to indicate the adequacy of the process. First, the hold time and temperature conditions are designed to thoroughly inactivate the target organism to the desired level or assurance level. Next, the entire process (heat, hold & cool)is modeled to estimate the reduction of the indicator organism. Then the hold temperature of the model is reduced to identify several temperatures that would begin to show survivors. A suspension of the indicator organism is processed at each of several conditions to provide data describing its performance and indicating the adequacy of the model.
Example Operating Conditions For Validation* Study 140 120 138 /Zero Log Predicted Survivors Temperature ( C) 100 80 60 137 /1.1 Log Predicted Survivors 135 /3.3 Log Predicted Survivors 132 /4.4 Log Predicted Survivors 40 20 0 0 10 20 30 40 50 60 70 80 90 100 Time (Sec) Kinetic parameters for Geobacillus stearothermophilus from Bioprocess Biosyst Eng (2006) 28: 351 378
Example Operating Conditions For Validation* Study (Closer View) 150 140 130 Temperature ( C) 120 110 100 138 /Zero Log Predicted Survivors 137 /1.1 Log Predicted Survivors 135 /3.3 Log Predicted Survivors 132 /4.4 Log Predicted Survivors 90 80 0 10 20 30 40 50 60 70 80 90 100 Time (Sec) Kinetic parameters for Geobacillus stearothermophilus from Bioprocess Biosyst Eng (2006) 28: 351 378
Validation Comments This strategy tests the entire process, not just the hold time and temperature. Based on actual survivor counts at several temperatures, a model can be developed that predicts the assurance level of the process at the actual (higher) operating temperatures. The model can also be developed to estimate the contribution of the heaters and coolers. Operating conditions can then be adjusted to ensure that the contribution of the hold tube is what is needed.
Alternate Validation Methods Directly measure the impact of the hold tube. This strategy involves taking samples at start and end of the hold tube and provides data that specifically indicates the impact of the heating steps and the hold tube. Taking samples while cooling them simultaneously can be challenge but does provide very accurate results.
Example Operating Conditions For Validation Study (Closer View) 150 140 Sample Co Sample Cf 130 Temperature ( C) 120 110 100 138 /Zero Log Predicted Survivors 137 /1.1 Log Predicted Survivors 135 /3.3 Log Predicted Survivors 132 /4.4 Log Predicted Survivors 90 80 0 10 20 30 40 50 60 70 80 90 100 Time (Sec) * Kinetic parameters from Bioprocess Biosyst Eng (2006) 28: 351 378
VII. Conducting Development and Research with HTST and UHT Processes
Development Considerations When Working With HTST and UHT Processes The TTH from these processes are different from those in batch processes. In general, the media are closer to their unprocessed condition from HTST and UHT processes than batch processes. This can influence performance of the media. It is important to qualify media through the HTST or UHT process at small scale, before going to production scale. If the conditions of the HTST or UHT process is changed this becomes important again.
Time Temperature History Comparison of Batch and Continuous Methods -Sterilization- 160 140 120 Temperature ( C) 100 80 60 UHT Sterilization Small Bottle "Reactor" 40 20 0 0 1000 2000 3000 4000 5000 6000 7000 8000 Time (Sec)
Time Temperature History Comparison of Batch and Continuous Methods -Viral Inactivation- 120 100 Temperature ( C) 80 60 40 HTST Viral Inactivation Small Bottle Viral Inactivation 20 0 0 500 1000 1500 2000 2500 3000 Time (Sec)
Development Considerations When Working With HTST and UHT Processes Most of the time, more nutrients are retained in HTST and UHT processes when compared to batch processes. This is often true of other materials in the media. (Ex: Less agar is needed for solid media.) It is useful to consider that fewer compounds that interfere with yield may be generated in HTST and UHT processes. These may prompt modification of the formula and allow improvement and cost reduction. It is important to consider the performance of the media from HTST or UHT processes in down-line process operations like filtration.
Development Considerations When Working With HTST and UHT Processes It is important to use the same UHT or HTST process TTH at different locations/line/facilities, even though throughput may be different. It is also important to use a scaled down HTST or UHT for R&D that delivers the same TTH as your production facilities. It is useful to maintain similar flow regimes as well. Allows qualification of formulae before scale-up. Allows development of the formulae before scale-up. It is important to develop cleaning protocols for new media and for new processing conditions.
Research Considerations When Working With HTST and UHT Processes HTST and UHT processes provide opportunities to optimize the operating conditions because the process is independent of the batch size. This permits maximization of lethality and assurance levels, and simultaneous maximization of retention of media quality by modification of the time-temperature history. These efforts can be very beneficial especially for sensitive media.
Summary HTST and UHT Processing Supports Single Use Technology Systems Are Cleaned by CIP Produces Closer To Unprocessed Quality Enables Higher Assurance Levels Provides Uniform Treatment And Simplified Scale-up Enables Treatment Of Many Sensitive Media/Products TTH Is Validated And Release Is Parametric W/Testing Development Is Based On Less Process Impact On Quality And New TTH. Allows Duplication of TTH To Duplicate Quality. Lab-scale Systems With Proper TTH Are Critical To Development.
Thank You Further Questions Or Information: See us Interphex 2014 Booth #3857 Contact: MicroThermics John Miles, President: jmiles@microthermics.com Edgardo Vega, evega@microthermics.com Sandeep Rajan, srajan@microthermics.com E-mail: info@microthermics.com www.microthermics.com 919-878-8045