The Effect of Temperature Changes

The optimal temperatures reported for maximum production of penicillin by Penicillium chrysogenum have varied between 23 C and 28 C (Peterson, 1946; Johnson, 1946; Calam et al., 1951). These temperatures were established by comparing the yields obtained when the mold was held at various temperatures for the entire fermentation. Calam et al. (1951) obtained best yields at about 25 C. The work reported here is an attempt to determine the effect of variations in temperature during fermentation on penicillin yield. It is well known that maximum penicillin production by a culture occurs only when well defined conditions exist for the myecelium-producing phase and equally well defined, but different, conditions exist for the penicillin-producing phase. That these two phases should have the same temperature optimum seems unlikely. There have been relatively few published reports of the effects (on the yield of cells and cell by-products) of variations of temperature during a fermentation. Davis and Dedrick (1953) have shown that increased cell yields result when Chlorella cultures are grown at 25 C during the day and placed at lower temperatures during the night. Kovats (1946) found that maximum citric acid yields were obtained in sucrose surface fermentations when the temperature was held at 28 C for the first 3 days and then reduced to 20 C.