Pseudomonas perolens synthesis

Because the potential for producing "natural" 2-methoxy-3-alkyl pyrazines via fermentation might be improved by optimizing media composition, we studied the influence of media components on the synthesis 2-methoxy-3-isopropyl pyrazine by cultures of Pseudomonas perolens and selected mutant strains. 

Effect of Carbon Source. The growth of Pseudomonas perolens as well as culture levels of 2-methoxy-3-isopropyl pyrazine in minimal salts plus 1% pyruvate are shown in Figure 1. High cell density was obtained but the presence of 2-methoxy-3-isopropyl pyrazine was not detected until after cell numbers were no longer increasing. At this point, the amount of pyrazine increased rapidly reaching a maximum on the fifth day. The growth and pyrazine synthesis with other carbon sources showed similar behavior. The results are presented in Table I, and plotted for selected carbon sources at 1%... 

Further investigation found that synthesis of tetramethyl pyrazine was not limited to the Pseudomonas perolens with the multiple auxotrophy. Any one of the high producing strains that was incubated with lactate or pyruvate at 2% concentration was capable of producing tetramethyl pyrazine. This compound appeared after the methoxy pyrazine levels had stopped increasing (Fig 3). This would suggest that a precursor for the methoxy pyrazines must first be depleted before the excess pyruvate would be directed to tetramethyl pyrazine synthesis. 

Although this work has shown how various media constituents and pathway manipulations can influence the synthesis of substituted pyrazines by Pseudomonas perolens, elucidation of the individual biosynthetic steps is needed to understand fully the controls and explore the possibility that other substituted pyrazines could be made. 

Mclver, R.C., Factors Influencing the Synthesis of Methoxy Alkyl Pyrazines by Pseudomonas Perolens, Ph.D. thesis, University of Minnesota, St. Paul, p. 88, 1986. Kuila, R.K., B. Ranganathan, Ultraviolet light-induced mutants of Streptococcus lactis subspecies diacetylactis with enhanced acid- or flavor-producing ahihties, J. Dairy ScL, 61, 4, p. 379, 1978. 

D Kilkast. Sensory evaluation of taints and off-flavours. In MJ Saxby, ed. Food Taints and Off-Flavours. Glasgow Chapman Hall, 1993, pp. 1-32. RC Mclver, GA Reineccius. Synthesis of 2-methoxy-3-alkylpyrazines by Pseudomonas perolens. In C Parliament, R Croteau, ed. Bioformation of Flavours, ACS Symposium Series 1989, pp 266-274. 

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