Biosynthesis of 2-methoxy-3-isopropylpyrazine by Pseudomonas perolens

The production of 2-methoxy-3-isopropylpyrazine (MIPP) was influenced by the initial cell density of the testing media. At cell densities of 1 {dollar}times{dollar} 10{dollar}sp6{dollar} cfu/ml or less, the highest amount of MIPP was observed. Production was decreased at higher cfu densities. This might be due to the pyruvate being used predominantly as bioenergy rather than for flavor production in the high cell density media. Exogenous addition of valine, glycine or methionine did not increase MIPP production.; Based on results of labeling experiments, endogenous valine, glycine, and methionine were likely to be the main donors to the structure of MIPP. That exogenously adding proposed precursors did not increase the production of MIPP is likely due to their allosteric inhibition effect. The alpha and beta carbon atoms of valine and the carboxyl carbon of glycine were labeled in the (2-{dollar}sp{lcub}13{rcub}{dollar}C) pyruvate feeding experiment. Similarly the two methyl groups of valine, alpha and carboxyl carbons of glycine, and the methyl group of methionine were labeled in the (3-{dollar}sp{lcub}13{rcub}{dollar}C) pyruvate feeding experiment. These data indicated that pyruvate is the main precursor of valine, and the glycine is from glyoxylate shunt after many turns of the Kreb Cycles. Labeled methionine is from the C-1 pool where the glyoxylic acid passes its labeled aldehyde carbon to the methyl group of methionine in the (3-{dollar}sp{lcub}13{rcub}{dollar}C) pyruvate feeding experiment.