PECTIC ENZYME PRODUCTION BY 2 STRAINS OF PSEUDOMONAS FLUORESCENS ASSOCIATED WITH PINKEYE DISEASE OF POTATO TUBERS

A bacterium identified as Pseudomonas fluorescens was isolated from pinkeye lesions of infected Kennebec potato tubers. Two isolates which rapidly macerated tuber slices were selected for further study. Supernatants from macerated potato tuber slices inoculated previously with either isolate 13 or 31 of P. fluorescens contained pectic enzyme activity. Trace amounts of pectin methylesterase activity were observed in the supernatants. Optimum viscosity reduction of sodium polypectate (NaPP) or pectin substrates by the enzyme complexes occurred at pH 8.6 and 7.2 respectively. Paper chromatography of hydrolysis products indicated that substrates were hydrolyzed terminally as well as randomly when the reaction mixtures were buffered from pH 7.1 to 7.5 NaPP was degraded more rapidly than pectin by both enzyme complexes. Reducing group data indicated the greatest hydrolysis of both substrates occurred near pH 8.6 and that both enzyme complexes hydrolyzed NaPP preferentially. Trans-eliminase activity was found in both enzyme complexes. Optimum activity occurred between pH 8.0 and 9.0 using a NaPP substrate and between pH 7.0 and 8.0 using pectin. The addition of calcium to the reaction mixture increased hydrolysis suggesting the importance of calcium as a co-factor for trans-eliminase activity. Both enzyme complexes macerated potato tuber slices rapidly. Data suggested a relationship between viscosity reduction of NaPP, transelimination of NaPP, and loss of coherence of tuber tissue slices by enzyme complexes of both isolates. © 1969 Springer.