Solvent extraction penicillin

Antibiotics. Solvent extraction is an important step in the recovery of many antibiotics (qv) such as penicillin [1406-05-9] streptomycin [57-92-17, novobiocin [303-81-1J, bacitracin [1405-87-4] erythromycin, and the cephalosporins. A good example is in the manufacture of penicillin (242) by a batchwise fermentation. Amyl acetate [628-63-7] or -butyl acetate [123-86-4] is used as the extraction solvent for the filtered fermentation broth. The penicillin is first extracted into the solvent from the broth at pH 2.0 to 2.5 and the extract treated with a buffet solution (pH 6) to obtain a penicillin-rich solution. Then the pH is again lowered and the penicillin is re-extracted into the solvent to yield a pure concentrated solution. Because penicillin degrades rapidly at low pH, it is necessary to perform the initial extraction as rapidly as possible for this reason centrifugal extractors are generally used. 

Isolation. Isolation procedures rely primarily on solubiHty, adsorption, and ionic characteristics of the P-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins ate monobasic catboxyHc acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stabiHty over other penicillins, can be precipitated dkecdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes dkect extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). 

Weatherley (1998) has discussed all the relevant aspects of the separation of low molecular weight biologically produced molecules by solvent extraction. A high degree of selectivity can be realized by careful selection of the solvent. Problems associated with the rheology of the broth, the presence of surfactants and solid materials needs to be recognized. There is a scope to consider intensified electrostatic contact for broth dispersion and separation. Examples covered in this treatise include penicillin G and cA-dihydrodiols. 

The fermentation broth typically contains 20-30 mg/L of antibiotics, which is to say 30 parts per billion, and must be extracted into concentrated form using solvent extraction. The solvent extraction method was developed by Shell Oil and by Podbielniack and is based on the principle that penicillin is hydrolyzed in aqueous medium to H+ and RCOO ions. Thus, equilibrium in an acidic medium (i.e., one with low pH or high H+ concentration) is favored by the neutral RCOOH form, whereas equilibrium in an alkaline medium (i.e., one with high pH or low H+ concentration) is favored by the RCOO ionic form. The neutral form is more soluble in an organic medium, and the ionic form is more soluble in an aqueous medium. Thus, with amyl acetate as the organic solvent the partition coefficient of penicillin between solvent and water is about 100 at pH 3 and about 1 at pH 6. In the industrial process, the aqueous broth was acidified to pH 3 for the extraction into the organic solvent, and alkalized to a pH 6 for reverse extraction back into an aqueous medium. 

One attempt to improve the situation has been successful for small to moderate scale operations where high purity is required—namely, the Podbielniak centrifugal counter-current contactor and separator, which dominates the solvent extraction phase of penicillin manufacture. 

Erythromycin is, like penicillin, isolated by solvent-extraction methods. It is an organic base, and extractable with amyl acetate or other organic solvents under basic conditions rather than the acidic ones that favor penicillin extraction. 

The current viable process for the production of penicillin is large-scale fermentation. Large tanks of 5000 to 30,000-gal capacity are used. The penicillin is separated by solvent extraction. The mold grows best at 23 to 25°C, pH 4.5 to 5.0. The fermentation broth is made from corn steep liquor with lactose and inorganic materials added. Sterile air permits growth of the mold over a 50- to 90-hour period. 

Solvent extraction of penicillin from fermentation broths has been well documented in the literature. Penicillin G and penicillin V can be efficiently extracted with amyl acetate or butyl acetate at pH 2.5-3.0 and at 0° to 3°C.33 Schiigerl1 systematically reviewed solvent extraction of different forms of penicillin from fermentation broths. Figure 1 shows an integrated process for the extraction of penicillin G from clarified broth of Penicillium chryso-genurn fermentation.1 Penicillin G is converted to 6-amino penicillanic acid and phenylacetic acid at pH 8 in a 10 L Kiihni extractor by penicillin G-amidase immobilized in an emulsion liquid membrane. The 6-amino penicillanic acid is subsequently converted to ampicillin at pH 6 and the enzyme is recycled. 

Another excellent example is given by penicillin recovery, a weak acid. Penicillin can be recovered by solvent extraction and its partitioning coefficient into solvent can be steered by the pH value. In the dissociated form it is more hydrophilic, whereas in the protonated form it is more hydrophobic. Thus, at low pH, penicillin partitions into the solvent phase. 

Liquid extraction is utilized by a wide variety of industries. Applications include the recovery of aromatics, decaffeination of coffee, recovery of homogeneous catalysts, manufacture of penicillin, recovery of uranium and plutonium, lubricating oil extraction, phenol removal from aqueous wastewater, and extraction of acids from aqueous streams. New applications or refinements of solvent extraction processes continue to be developed. 

Phenoxymethyl penicillin in fermentation liquids may be determined selectively by measuring at 268 and 275 nm, after preliminary purification by solvent extraction and decomposition in base. Background ultraviolet absorbance is corrected by measurements made without basic decomposition 86. Beer1s law was valid for 0 to 280 units per ml. 

Penicillin V may be nitrated by 10% potassium nitrate in concentrated sulfuric acid 72, HO. The yellow derivative in ammonia solution can be determined colorimetrically. Birner s 72 method estimates both penicillin V and phenoxyacetic acid in fermentation broths. Selectivity is achieved by solvent extraction techniques. 

Antibiotics (e.g., penicillin G) 10-30 Filtration, solvent extraction, crystallization, centrifugation, drying [F2]... 

FIGURE 7.8-10 Typical solvent extraction process for penicillin recovery. 

Some solvent-extraction techniques are relatively difficult to effect using conventional laboratory apparatus. For example, the classical penicillin G extraction in which acidified broth is contacted with a water-immiscible solvent can only be operated effectively using continuous-flow methods because of the poor stability of the product at low pH values. This extraction can be reproduced on the bench scale using the AKUFVE apparatus, which was designed for extraction studies in the nuclear industry (12,13). Selective extraction may involve the use of a solvent in which the product has a poor partition coefficient. Countercurrent extractors are mostly process scale devices but the smallest four-stage extractor produced by Robatel could be considered a bench scale. It has a throughput of 50-100 mL/min. 

OTHER COMMENTS used as a solvent of lacquers and paints used to extract penicillin from fermentation broth during production of antibiotics used in the manufacture of photographic film used in pre-spotting and spotting operations in the dry cleaning industry. 

Complicated organic con x>unds, e.g. penicillin, can be labelled through biosynthesis. For example, if penicillin is grown in a substrate containing a simple compound, is incorporated into the p cillin mold. Since other S-containing products may be formed also, the penicillin must be purified, e.g. through solvent extraction or paper chromatography ( 9.2.6). 

M. Matsumoto, Y. Inomoto, K. Kondo, Comparison of solvent extraction and supported liquid membrane permeation using an ionic liquid for concentrating penicillin G. J. Membr Sci. 289 (2007) 92-96. 

Stoddard solvent 1,1,2,2-Tetrachloroethane extraction, penicillin Amyl acetate... 

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