Studies on the Nutrition of Penicillium roqueforti

Though Penicillium roqueforti is of great economic importance, its nutritional requirements and physiology have received scant attention.In physiological studies, a chemically defined medium capable of sup- porting the growth of large amounts of mycelium would be an obvious advantage.In a study of the esterase and protease of P. roqueforti, Naylor et al. (1930) modified the medium of Czapek by substituting ammonium chloride for sodium nitrate.They found that optimum growth, under their conditions, occurred at an initial pH of 4.5.Thibodeau and MIacy (1942) also concluded that ammonium and organic nitrogen were better nitrogen sources than salts of nitrate and the initial pH of the medium, when adjusted between 4.0 and 7.5, had no effect on the growth of the mold; they did not report the amount of growth quantitatively.Gottlieb (1946) found that P. roqueforti was able to use amino acids as the sole carbon source when incorporated into Richard's me- dium; but here, too, no quantitative data on mycelial yield were given.This paper describes the formulation of a chemically defined medium for the submerged growth of P. roque- forti.It was devised to obtain relatively large yields of mycelium for further physiological studies of this or- ganism. EXPERIMENTAL METHODSPenicillium roqueforti Minnesota strain P 108-2 was used throughout this study.Stock cultures were main- tained in soil at room temperature (Greene and Fred, 1934).The spore inoculum consisted of a thrice washed spore suspension prepared from 4-day-old V-8 agar slant cultures.The V-8 agar slants were prepared by mixing and slanting equal quantities of sterile V-8 vegetable juice and 3 per cent agar in sterile 6-oz pre- scription bottles.The suspensions were standardized by hemocytometer counts to provide 15 X 106 spores per ml.Then 0.5 ml of the standardized spore suspen- sion was inoculated into 50 ml of medium, contained in 300-ml Erlenmeyer flasks.Cultures were grown at 25 C in submerged culture on a rotary shaker (at 325 times per min and describing a radius of 12 in.).At the