Development of a Novel Cultivation Method for Molds and Its Characterization

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In this, study we applied a newly-developed membrane-surface liquid culture (abbreviated as MSLC) to production of useful substances using molds. We not only intended to optimize the cultivation conditions but also clarify the reasons for the higher productivity obtained in MSLC in comparison with the results obtained in shaking flask cultures. We studied three fermentation systems, i.e., 1) kojic acid fermentation using Aspergillus oryzae, 2) red pigment production using Monascus pilosus, and 3) production of α-glucosidase using recombinant Aspergillus oryzae under various cultivation conditions, different in factors such as pH of the medium and C-and N-source concentrations. In MSLC, we first examined the effect of kinds of porous membranes on the cultivation behaviors. The most suitable membrane was found to be such a membrane that have a pore diameter of around 0.2μm and hydrophilic property. MSLC gave a higher productivity in the all three cultivation systems examined than those with shaking flask cultures. We examined the effect of oxygen supply in the shaking flask cultures to seek the reasons for the higher productivity in MSLC.The reasons for the higher productivity in MSLC were found not to be in the higher oxygen supply. It was suggested that differences in gene expression, the amount of relating enzyme produced in the cells, and permeability of the product through the cell membrane may affect the higher productivity in MSLC.