Growth of Sorbate-Resistant and -Sensitive Strains of Penicillium roqueforti in the Presence of Sorbate

Abstract

Growth of two strains of Penicillium roqueforti in different media foritified with sorbate was observed. The sorbic acid-sensitive strain grew in YES and mycological broths with sorbic acid concentrations up to 500 ppm, and in YM broth with sorbic acid concentrations up to 1000 ppm. The sorbic acid-resistant strain grew in YES and mycological broths with sorbic acid concentrations up to 6000 ppm, and in YM broth with sorbic acid concentrations up to 9000 ppm. Supplementing mycological broth with various ingredients affected growth of the resistant strain. Addition of 1% casein or 0.3% yeast, potato or malt extract increased the amount of mycelia produced in the absence of sorbate, but had little effect on mycelial growth in the presence of 3000 ppm sorbic acid. Substituting maltose for dextrose increased mycelial growth over that in the control medium in the presence of sorbate but had no effect in the absence of sorbate. Substituting sucrose, lactose or starch for dextrose decreased mycelial growth in the absence of sorbate, but had no statistically significant effect in the presence of sorbate. Sorbate had the smallest effect on mycelial growth in YM broth. The resistant strain caused a loss of sorbate from all media, but the sensitive strain did not. 1,3-Pentadiene was produced only by the resistant strain when growth occurred in the presence of sorbate. Uptake of sorbic acid by mycelia was considerably less for the resistant than the sensitive strain.