On-line monitoring of penicillin V during penicillin fermentations: a comparison of two different methods based on flow-injection analysis

Abstract

Two different flow-injection analysis (FIA) methods used for on-line monitoring of penicillin V during fed-batch penicillin fermentations are compared. The fermentations are carried out using a high yielding strain of Penicillium chrysogenum and both analyzers are used continuously for on-line monitoring during 200 h. Both methods are based on a reaction catalyzed by β-lactamase, which converts penicillin V to penicilloic acid. In analyzer 1 the sample is injected into a buffer stream and carried to a stirred measurement cell containing an enzyme electrode. The enzyme electrode consists of β-lactamase immobilized onto a sensitive pH glass electrode with a very low response time. No predilution of the sample is required in this analyzer. In analyzer 2 the sample is injected into an enzyme reactor containing immobilized β-lactamase. The formed penicilloic acid is detected by decolorization of an iodine-starch complex. By means of a second injection valve it is possible to have the sample by-pass the enzyme reactor and instead pass a dummy reactor in which no β-lactamase is immobilized. Thereby both the concentration of penicillin and penicilloic acid can be measured. On-line dilution of the sample is ensured by a gradient technique. Experimental results from on-line monitoring of penicillin V using the two methods are presented. The large amount of precise measurements enables a very good resolution of the penicillin production; something of extreme value for verification of mathematical models describing the fermentation kinetics.