Temperature-Sensitive Bacillus subtilis natto Mutant Strain for Low Spore Natto
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Solution Overview
Problem
Current methods for producing natto with Bacillus subtilis natto struggle to reduce spore content while maintaining fermentation quality and preventing microbial contamination, as existing strains either fail to form spores adequately or require heat sterilization that compromises natto's texture and flavor.
Innovation Solution
A temperature-sensitive Bacillus subtilis natto mutant strain is developed, which has normal spore-forming ability in liquid culture but reduced spore-forming ability in fermentation conditions, allowing for natto production with low spore content and effective heat sterilization without compromising quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If heat sterilization is performed to reduce spore content in natto, then spore count is reduced, but natto's texture and flavor are compromised
Solution Approach 1:
The patent applies parameter changes by developing a temperature-sensitive mutant strain where spore formation is controlled by temperature parameters. The mutant forms spores at lower temperatures (20-37°C) but not at higher temperatures (40-53°C), allowing natural sterilization during the fermentation process itself without requiring additional heat sterilization that would damage product quality
Solution Approach 2:
The mutant strain performs self-service sterilization by naturally suppressing spore formation during the high-temperature fermentation process (40-53°C). The fermentation conditions themselves serve to reduce spore content, eliminating the need for separate heat sterilization steps that would compromise texture and flavor
2Quantity of substance
If a B. subtilis natto strain with low spore-forming ability is used, then spore content is reduced, but fermentation quality deteriorates
Solution Approach 1:
The patent applies dynamics by creating a temperature-sensitive mutant where spore-forming ability dynamically changes with temperature. The mutant maintains normal spore formation at low temperatures during starter culture preparation but dynamically suppresses spore formation at high temperatures during fermentation, ensuring both adequate spore content for inoculation and low spore content in final product while maintaining fermentation quality
Solution Approach 2:
The patent applies local quality by creating different functional characteristics in different stages of the process. The mutant strain exhibits high spore-forming ability (local quality for inoculation) during starter culture preparation at low temperatures, and low spore-forming ability (local quality for product quality) during fermentation at high temperatures, allowing both requirements to be satisfied
3Reliability
If spore-forming ability is enhanced for inoculation, then heat resistance is improved, but spore content in final product increases causing contamination risk
Solution Approach 1:
The patent applies periodic action through temperature cycling during the production process. The mutant strain is first cultured at low temperatures (20-37°C) to induce spore formation and heat resistance for robust inoculation, then the temperature is raised to high levels (40-53°C) during fermentation to suppress further spore formation, creating a periodic pattern that achieves both heat resistance and low final spore content
Solution Approach 2:
The patent applies preliminary action by pre-forming spores during the starter culture preparation phase at low temperatures before the fermentation process. This preliminary spore formation ensures adequate heat resistance for inoculation, while the subsequent high-temperature fermentation naturally suppresses additional spore formation, preventing contamination risk in the final product
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 mutant strain enables natto production with a low spore count, preventing contamination and allowing for heat sterilization that maintains natto's quality and texture, making it suitable for various processed food products.
Implementation Method 1
a Bacillus subtilis natto mutant strain which has a normal spore-forming ability in a temperature zone that is generally used in a liquid culture for obtaining a Bacillus subtilis natto starter for inoculation, but has a reduced spore-forming ability in a temperature zone that is generally used in natto fermentation
Implementation Method 2
if heat sterilization is performed at 100° C. or lower, the spores of Bacillus subtilis natto remain in the product
Data Source
AI summary
A method of producing natto includes inoculating a mutant strain of Bacillus subtilis var. natto onto steamed or boiled soybeans, and fermenting the soybeans inoculated with the mutant strain by maintaining a temperature of the soybeans at 40° C. to 53° C. The number of the mutant strain spores after fermenting the soybeans is 5×105 or less spores per gram of the fermented soybeans. A single colony of the mutant strain cultured in a selective solid medium supplemented with biotin at a gas phase temperature of 49° C. for 48 hours has a region having a hue of yellow (Y), a value of 9 or more, and a chroma of 2 or less, as defined by the Munsell Color System, and a surface area of the region is 20% or less of the total surface area of the single colony.