High-Density Fermentation of Recombinant Bacillus subtilis for Psicose 3-Epimerase
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Solution Overview
Problem
Current methods for producing psicose 3-epimerase by fermentation suffer from low expression levels, low purity, and high production costs, with a need for improved high-density fermentation techniques to enhance cell density and enzyme production efficiency.
Innovation Solution
A method involving high-density fermentation of a recombinant Bacillus subtilis strain, utilizing specific fermentation media and controlled feed rates, temperature adjustments, and manganese chloride to optimize enzyme activity and cell density, resulting in increased psicose 3-epimerase expression and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fermentation methods are used, then the fermentation process is simple to operate, but the cell density remains low and enzyme expression level is insufficient
Solution Approach 1:
The patent implements dynamic fermentation control by adjusting aeration rate, agitation speed, and feed rate based on dissolved oxygen levels and cell density measurements. The aeration rate varies from 0.5-2 vvm in exponential phase to 2-5 vvm in stationary phase, while agitation speed adjusts from 200-400 rpm to 400-600 rpm, enabling high cell density achievement while maintaining process controllability
Solution Approach 2:
The patent employs feedback control mechanisms where dissolved oxygen levels (maintained at 20-40% saturation) and optical density measurements guide feed medium addition rates and aeration adjustments. This closed-loop control enables precise management of fermentation parameters to optimize both cell density and enzyme expression
2Productivity
If feed medium is added at high flow rates to increase cell density, then productivity improves, but dissolved oxygen levels drop and metabolic control becomes difficult
Solution Approach 1:
The patent dynamically adjusts aeration rate in response to feed medium addition and cell growth. During exponential growth phase, aeration is maintained at 0.5-2 vvm, while in stationary phase it increases to 2-5 vvm. This dynamic adjustment ensures dissolved oxygen remains at 20-40% saturation even during high-rate feed addition, preventing oxygen limitation
Solution Approach 2:
The fermentation process is divided into distinct phases (exponential growth and stationary phases) with periodic adjustments to feed rate, aeration, and agitation. This phased approach allows controlled nutrient addition while maintaining oxygen supply, enabling sustained high cell density without metabolic失控
3Productivity
If fermentation temperature is kept constant to maintain stable conditions, then process control is simple, but enzyme secretion efficiency is limited
Solution Approach 1:
The patent implements dynamic temperature control where the fermentation temperature is adjusted based on fermentation stage. During exponential growth phase, temperature is maintained at 37°C for optimal cell growth, while in stationary phase it is lowered to 25-30°C to enhance enzyme secretion efficiency. This staged temperature profile optimizes both growth and product formation
Solution Approach 2:
The patent performs preliminary strain optimization through gene expression vector construction and strain screening before fermentation. The recombinant Bacillus subtilis strain is pre-engineered with optimized psdE gene expression sequences and growth conditions, enabling high-level enzyme production without requiring complex real-time genetic manipulation during fermentation
4Productivity
If high cell density is achieved through extended fermentation time, then enzyme production increases, but production period becomes too long and cost increases
Solution Approach 1:
The patent uses dynamic parameter optimization where aeration (0.5-5 vvm), agitation (200-600 rpm), and feed rates are continuously adjusted based on cell density and metabolic state. This enables rapid achievement of high cell density (OD600 > 100) within 24-48 hours, significantly reducing fermentation time compared to static conditions
Solution Approach 2:
The patent optimizes multiple fermentation parameters simultaneously including initial glucose concentration (20-50 g/L), nitrogen source composition (peptone 5-15 g/L, yeast extract 5-15 g/L), and pH control (6.5-7.5). These parameter optimizations accelerate cell growth rate and enzyme production kinetics, reducing overall fermentation duration while maximizing yield
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
The method significantly increases psicose 3-epimerase activity to 4783 U/mL, improves enzyme purity, and reduces production costs by enhancing cell density and metabolic efficiency during fermentation.
Implementation Method 1
fermentation culture: adding 1-10% by volume of the activated seed cell suspension cultured in Step (1) to a fermentation medium and fermenting
Data Source
AI summary
The present invention relates to the technical field of microbial fermentation engineering, and specifically to a method for producing psicose 3-epimerase by high-density fermentation. In view of the low expression level of psicose 3-epimerase and other problems existing in the current fermentation, by controlling the feeding rate in the fermentation process, improving the culture temperature in the middle and late stages of fermentation and other measures in the present invention, the OD value during the fermentation with recombinant Bacillus subtilis and the total enzyme activity of psicose 3-epimerase in the fermentation broth are significantly increased, the expression of psicose 3-epimerase is markedly improved, and the production cost of allulose is reduced. Therefore, the present invention has a very broad prospect of application in industry.