The growth of Gibberella fujikzlroi in stirred culture was studied. Media were designed in which the initial concentrations of glucose (G), nitrogen (N), phosphorus (P), and magnesium (M) were varied so that the first nutrient was exhausted a t a selected dry weight, and the remaining nutrients in all available sequences thereafter. Distinct phases of growth, related to the changing nutritional status of the mold, have been defined.The balanced phase was a period of proliferation in the presence of all nutrients, during which a unit increase in dry mycelium was accompanied by constant uptakes of G, N, P, M, and potassium (I<). The morphology remained virtually unchanged, and the d r y mycelium contained ca. 6 % fat, ca. 16% carbohydrate, and ca. 13% phosphorus-containing compounds, and the fractions of each remained constant. This phase continued until the first nutrient was exhausted. I'roliferation, indicated by increases in fat-and carbohydrate-free dry weight, then ceased in N-and G-limited fermentations. I n P-and M-limited fermentations, proliferation continued until the subsequent exhaustion of either G o r N, and during this transition phase the carbohydrate content of the mycelium increased, while in M-limited fermentations the fat content also increased. I n P-limited fermentations the uptake of both M and I< ceased, and reserves of metaphosphate were used.At the exhaustion of N in N-, P-, or M-limited fermentations, proliferation ceased but the dry weight continued to increase due t o increases in carbohydrate and triglyceride. In the presence of sufficient glucose, maximum amounts of 45% fat, visible as oil globules, and 32y0 carbohydrate were formed, but in the presence of less G these ceased t o increase when G was exhausted before these maxima were reached. In either case the nzaintenance phase followed, during which all mycelial components remained constant except the triglycerides, which decreased when exhaustion of G had initiated the maintenance phase; otherwise they also remained constant until G was subsequently exhausted, and then decreased. T h e terntinal phase began when the triglycerides were exhausted, and also when G was exhausted in G-limited fermentations, or in P-and M-limited fermentations in which G was exhausted before N. This phase was characterized by hyphal breakdown, a decrease in dry weight, and the liberation of mycelial components into the medium. 'Manuscript Can. J. Microbiol. Downloaded from www.nrcresearchpress.com by NC STATE UNIVERSITY on 09/21/13For personal use only.
80-1. FermenterThis was of conventional design, made of stainless steel, 20 in. diameter and 29 in. deep (Fig. 4). T h e two-paddle stirrer was driven a t 425 r.p.m. T h e supply of cooling water was automatically regulated to provide temperature control t o &0.15O C. Air was humidified and sterilized by passage through larger models of the apparatus already described. 2Model 0307, series WA, product of Hoover Ltd., Regent Street, London, W.1. Can. J. Microbiol. Downloaded from www.nrcresearchpress.com ...