Spray Drying Lactic Acid Bacteria Under Reduced Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional spray drying methods are not economically feasible for preserving lactic acid bacteria due to high outlet temperatures that typically exceed the survival limits of these microorganisms, leading to significant bacterial death.
Innovation Solution
The method involves reducing the pressure inside the spray dryer to lower the boiling point of water and using an inert gas, such as nitrogen or helium, to achieve outlet temperatures between 20°-60°C, while quickly cooling the dried powder to enhance bacterial survival and produce dry, stable powders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional spray drying is used with ambient atmospheric pressure, then drying efficiency is improved, but outlet temperature becomes too high (above 60°C) causing bacterial death
Solution Approach 1:
The patent changes the pressure parameter from ambient atmospheric pressure to reduced pressure (vacuum conditions). This parameter change lowers the boiling point of water, enabling the drying process to occur at lower outlet temperatures (20-60°C) that preserve bacterial viability while maintaining economical throughput rates.
Solution Approach 2:
The patent utilizes the phase transition of water at reduced pressure. By operating under vacuum, water evaporates at temperatures below its normal boiling point, allowing the drying process to proceed at temperatures suitable for heat-labile materials like lactic acid bacteria.
2Reliability
If drying pressure is reduced to lower outlet temperature, then bacterial survival is improved, but the boiling point of water decreases making it harder to achieve complete drying
Solution Approach 1:
The patent simultaneously optimizes multiple parameters: pressure is reduced to lower the drying temperature for bacterial survival, while residence time and air circulation are adjusted to ensure complete moisture removal despite the lower boiling point. The system achieves both low temperature drying and complete dehydration.
Solution Approach 2:
The patent employs continuous air circulation and extended residence time under vacuum conditions to maintain the drying process. This continuous action ensures that even though water evaporates at lower temperatures, the drying is completed thoroughly by sustaining the evaporative process throughout the drying chamber.
3Reliability
If outlet temperature is lowered below 60°C, then bacterial survival is improved, but drying time increases making the process economically unfeasible
Solution Approach 1:
The patent changes the pressure parameter to enable low-temperature drying to proceed at economical throughput rates. The vacuum condition accelerates the drying kinetics at low temperatures by maintaining a large vapor pressure gradient, thus reducing drying time while preserving bacteria.
4Device complexity
If conventional drying with air is used, then equipment complexity is low, but oxygen exposure reduces bacterial survival
Solution Approach 1:
The patent replaces atmospheric air with an inert gas atmosphere (nitrogen or other inert gases) in the drying chamber. This eliminates oxygen exposure that would otherwise harm the bacteria, while the inert atmosphere maintains the reduced pressure conditions necessary for low-temperature drying. The equipment complexity increase is justified by the significant improvement in bacterial survival.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in higher bacterial survival rates comparable to freeze-dried products, with improved powder dispersibility and stability, making spray drying a viable alternative for heat-labile materials like lactic acid bacteria.
Implementation Method 1
By lowering the drying chamber pressure to say 65 kPa the boiling point of water would be reduced from 100° C. to 88° C.
Implementation Method 2
the best result was obtained when the drying gas used in spray dryer was free of oxygen, and we therefore contemplate that the gas should preferably be an inert gas like Nitrogen or any noble gas like Helium, Argon and Neon etc.
Implementation Method 3
as soon as the spray dried powder is separated from the drying gas (eg by a cyclone separator) it should be cooled, such as to a temperature below 20° C., and/or by an inert conveying gas.
Data Source
AI summary
The present invention relates to an improved method for drying microorganisms, especially lactic acid bacteria, in a spray dryer.