A new cleaner technology for extracting pyruvic acid (PA) from fermentative broth was explored. This process involves recycling waste residue combined with small amount of dispersant added to extract PA. Limited amount of dispersant in the process of rectification under vacuum (1.5 kPa) was found to inhibit the polymerization of PA and to enhance the extraction rate of PA from 20.5 to 92.3% when the volume of dispersant was 0.20 times that of preliminary extract liquid (PEL). Experimental results indicate that a cleaner extraction of PA might be achieved by circulation. The purity of PA still exceeded 96% after the waste liquid was used up to 30 times when the added amount of dispersant was 5% of the PEL. A mathematic model was developed to describe the relationship of purity of PA (P), the repetition times of waste residue (N) and the added amount of dispersant (M) during the first-round of waste liquid usage: .
Key words: Pyruvic acid, extract, dispersant, rectification under vacuum, waste residue, circulation.
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