Purified PHA Decolorization Using Sequential Oxidizing Agents
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Solution Overview
Problem
Conventional purification methods for polyhydroxyalkanoates (PHAs) fail to effectively reduce impurity content, particularly in flexible and tacky PHAs, leading to high b* values and hindering commercialization due to difficulties in solid-liquid separation and washing, especially in amorphous PHAs with low or no crystallinity.
Innovation Solution
A two-step decolorization process using sodium chlorite and hydrogen peroxide as oxidizing agents, followed by deproteinization, to improve color and purity of PHAs, with specific pH and temperature conditions for each step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification methods are used for flexible and tacky PHAs, then the purification process can be completed, but the impurities attached to PHA particles are not removed effectively and the b* value increases to 15 or higher
Solution Approach 1:
The patent changes the chemical environment parameters by adjusting pH to specific ranges (pH 2-7 for first decolorization, pH 8-13 for second decolorization) and controlling temperature (0-50°C) to optimize the decolorization process. These parameter changes enable effective impurity removal while maintaining PHA particle integrity, resolving the contradiction between color quality improvement and manufacturing ease.
Solution Approach 2:
The patent employs strong oxidizing agents (sodium chlorite in first decolorization, hydrogen peroxide in second decolorization) to accelerate the oxidation of impurities attached to PHA particles. This strong oxidation capability effectively removes colored impurities and reduces b* value to below 15, overcoming the limitation of conventional mild purification methods.
2Manufacturing precision
If conventional single-step decolorization is used, then the process is simple, but the color improvement is insufficient and b* value remains 15 or higher
Solution Approach 1:
The patent divides the decolorization process into two sequential steps: first decolorization using sodium chlorite at pH 2-7, followed by second decolorization using hydrogen peroxide at pH 8-13. This segmentation allows each step to target different types of impurities and achieve synergistic color improvement, reducing b* value to below 15 while maintaining manageable process complexity.
Solution Approach 2:
The patent uses different oxidizing agents as intermediaries for different decolorization steps. Sodium chlorite serves as the first intermediary to remove certain impurities, and hydrogen peroxide serves as the second intermediary to remove remaining colored impurities. This intermediary approach enables comprehensive color improvement that cannot be achieved by a single agent.
3Manufacturing precision
If extensive purification is performed to reduce impurities, then color quality improves, but production cost increases due to increased enzyme use
Solution Approach 1:
The patent uses strong oxidizing agents (sodium chlorite and hydrogen peroxide) that can effectively remove colored impurities without requiring extensive enzymatic treatment. This chemical oxidation approach achieves b* value reduction to below 15 with minimal enzyme consumption, resolving the contradiction between color quality improvement and production cost.
Solution Approach 2:
By optimizing pH and temperature parameters for the decolorization steps (pH 2-7 then pH 8-13, temperature 0-50°C), the patent maximizes the efficiency of oxidizing agents. This parameter optimization reduces the need for additional purification steps and enzyme use, maintaining cost-effectiveness while achieving excellent color quality.
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 process significantly reduces the b* value to less than 15, maintaining molecular weight and reducing production costs by minimizing enzyme use, effectively addressing color and purity issues in PHAs.
Implementation Method 1
first decolorization is carried out with a first oxidizing agent comprising sodium chlorite (NaClO2)
Implementation Method 2
second decolorization may be carried out with a second oxidizing agent comprising hydrogen peroxide (H2O2)
Implementation Method 3
the process may further comprise deproteinizing the second product using a protease
Data Source
AI summary
A method for preparing purified polyhydroxyalkanoate of the present invention may lower the b* value of a final product more than the conventional value by means of a decolorization step using two types of oxidizing agents sequentially. In addition, in the present invention, by using sodium chlorite (NaClO2), as a primary oxidizing agent, the effect of improving color is significant, and there is almost no decrease in molecular weight.