Performance Characteristics of Solvent Extraction of Penicillin using Butyl Acetate

Author : Pabale, Maximo Dennis Lateo
Major Adviser : Calibo, Ronnie L.
Committee Members : Acda, Reynaldo I.; Demafelis, Rex B. 
Year : 1993
Month : May
Type : Thesis
Degree: BS
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An experimental study on the performance characteristics of solvent extraction of penicillin was performed. Batch and continuous solvent extraction operations were done using prepared penicillin/water solution and filtered fermentation broth. The results of this study indicated that extraction time should be as brief as possible to achieve high recoveries. Solvent to solution ratio should be about 0.3 to 0.4 while extract to buffer ratio should be about 3 to 5.

Batch studies indicated that the best recovery was achieved using the ratio (0.3, 3.0) at 10 seconds contact time for the first extraction and 2 minutes contact time for the second extraction. Average recovery at these conditions was 36.5%.

In the continuous operation, using an improvised extraction set-up as described by Whitmore, the best recovery achieved for (0.3, 3.0) was at 20 second contact time for the first extraction with a recovery of 67.03 % and 2.5 minutes for the second extraction with a recovery of 52.43 %. The low recovery for the first extraction may be attributed to the shift in the effective distribution coefficient which is maximum at pH = 2.0. Sulfuric acid lowers the pH of the solution to 2.0 but contact with butyl acetate with pH = 5.0 shifts the pH to 3.0 (determined through actual pH determination) which lowers the distribution coefficient and the amount of penicillin that can transfer to the solvent. Material balance calculations showed as much as 18.25 % was untransferred from the spent solution. The same phenomenon was observed for the secondary extraction attributed to the shift in distribution coefficient wherein the distribution of penicillin will be biased towards the aqueous phase at pH greater than 6.0. Phosphate buffer used had a pH = 7.5 but the extract with a pH = 3.0 shifts the pH to about 5.0 (determined through actual pH determination) favoring penicillin to stay in the organic phase rather than transfer to the aqueous phase. Material balance calculations showed as much as 17.49 % untransferred penicillin from the spent solvent.

The best recovery obtained for filtered broth extraction was 45.30 % for primary extraction and 39.96 % for the secondary extraction. It was observed that some sort of emulsification evolved that may significantly decrease the transfer of penicillin to the solvent due to improper mixing or contact.

Arnyl acetate stands out as the better solvent from the standpoint of its satisfactory effective distribution coefficient and low solubility in water.

The efficiency of the extractor using the Underwood equation shows that the number of actual stages in the extractor is 0.20 or a stage efficiency equal to 15.87 %.

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