PHA Production with Low Initial Sulfur and Dynamic Feeding
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Solution Overview
Problem
Existing PHA production methods face limitations in sulfur source concentration at the start of culture, with little understanding of its impact on productivity, leading to inhibited PHA production.
Innovation Solution
Culturing PHA-producing microorganisms with a sulfur concentration of 0.0001 to 13 mM at the start and adding a sulfur source during the culture, maintaining a C/S ratio of 500 to 10,000, to enhance productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high sulfur concentration (10-40 mM) is used at the start of culture, then nutrient requirements are met for microbial growth, but PHA production is inhibited
Solution Approach 1:
The patent applies preliminary action by setting the initial sulfur concentration to a low level (0.0001 to 13 mM) before PHA production begins, preventing inhibition from the start. This preliminary condition setup ensures that sulfur does not interfere with PHA accumulation while still providing necessary nutrients for microbial growth.
Solution Approach 2:
The patent implements dynamics by transitioning from a static high sulfur concentration regime to a dynamic approach where sulfur concentration is initially kept low and then gradually increased during the culture process. This dynamic adjustment allows the system to avoid initial inhibition while meeting nutrient requirements as culture progresses.
2Quantity of substance
If batch culture is used with high nutrient components, then product concentration can be increased, but cytotoxicity from high concentration nutrients occurs
Solution Approach 1:
The patent applies preliminary action by pre-setting the sulfur concentration within a safe range (0.0001 to 13 mM) before culture begins, preventing cytotoxic effects from high sulfur levels while still providing sufficient nutrients for microbial growth and subsequent PHA production.
3Object-affected harmful factors
If fed-batch culture is used to reduce initial carbon source concentration, then cytotoxicity is reduced, but process complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the sulfur concentration parameter throughout the culture process - initially setting it low (0.0001 to 13 mM) to prevent inhibition, then gradually increasing it during fed-batch operation. This parameter adjustment strategy enables the use of fed-batch culture to reduce initial cytotoxicity while maintaining manageable process complexity through systematic control.
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
Enhances PHA productivity and reduces sulfur use, lowering wastewater treatment costs and improving efficiency in fermenter use.
Implementation Method 1
PHAs are naturally occurring thermoplastic polyesters produced and accumulated as energy storage substances in the cells of many kinds of microorganisms
Implementation Method 2
in an environment containing an abundance of carbon source, the microorganisms undergo a metabolic change induced by phosphorus source depletion and/or nitrogen source depletion and thus accumulate PHAs
Data Source
AI summary
A polyhydroxyalkanoate production method includes culturing a polyhydroxyalkanoate-producing microorganism in a culture medium to obtain microbial cells accumulating a polyhydroxyalkanoate. At start of the culturing of the polyhydroxyalkanoate-producing microorganism, the culture medium contains a sulfur source at a sulfur concentration of 0.0001 to 13 mM. The polyhydroxyalkanoate production method includes the step of adding a carbon source and a sulfur source to the culture medium during the culturing of the polyhydroxyalkanoate-producing microorganism, and an average ratio (C/S ratio) of a carbon weight (C) in the carbon source added per hour to a sulfur weight (S) in the sulfur source added per hour, as calculated for a period in which the sulfur source is added, is in a range of 500 to 10,000.