Mechanism of morphological development of mycelia and its application on production of microbial product

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The intrastructure of mycelial pellets of Mortierella alpina and the morphological parameters, such as hyphal growth rate, tip formation rate, tip extension rate and branch formation rate of Mortierella alpina have been investigated in this research. The intrastructure of mycelial pellets were visualized following labeling with fluorescein isothiocyanate (FITC) and Nile red using fluorescence microscopy. The pellet was an ellipse shape, but its intrastructure was shaped as doughnut and a cave was present inside, which was clear by judging 3-D image of intrastructure of pellet. Using image analysis, the fatty acid production was shown on the verge of pellet, which was corresponded on the place of dense mycelia. The cavity ratio was calculated from area based on the fluorescent intensity and remained at 20% in a 50-L fermentor but finally increased to 35%. Mycelial pellet volume was paralleled to the cavity ratio.Using a flow-through chamber under 25 different combinations of carbon and nitrogen concentrations, morphological parameters were measured and found that they were influenced not by C/N ratio but by carbon concentration in medium. Specific rates of hyphal growth and tip formation remained at constant at lower carbon concentration of 5 g/l, respectively. Tip extension rate from one tip was 60 (μm/tip/h) in a carbon concentration below 15 g/l, and branching formation rate was independent upon carbon concentration. Tip extension rate was a function of specific hyphal growth rate, and the specific hyphal growth rate was linearly proportional to the specific tip formation rate, which demonstrated that tip extension rate was exponentially proportional to the specific tip formation rate. Branch formation rate per hyphal element remained unchanged even at lower tip extension rate than 60 (μm/tip/h) and at lower specific hyphal growth rate than 0.83 h^<-1>, respectively.