A study of factors influencing 2-methoxy-3-isopropylpyrazine production by Pseudomonas perolens using acid trap and UV spectroscopy

A method employing acid-trapping of air-purged volatiles followed by UV absorption was used to determine factors influencing the production of 2-methoxy-3-isopropylpyrazine (MIPP) by Pseudomonas perolens. MIPP in 6 abetm HCl was found to have absorption maxima at 220 nm (A + 9290 cm^-1m^-1) and 307 nm (A = 9370 cm^-1m^-1). In liquid media, the amount of recoverable MIPP was dependent on the pH of the buffer system. It varied from 50% recovery at pH 6.0 to 83% recovery at pH 9.0. From solid media, about 54% of the MIPP added was recovered by the air purge and acid trap device. Exogenous addition of valine, glycine, and methionine did not increase MIPP production suggesting that precursors are endogenous to the cell. The amount of MIPP production was influenced by the initial cell density. The highest amount of MIPP was observed at a cell density of 10⁶ cfu/ml or less. Higher cell densities resulted in lower production.