Development of a Novel Cultivation Method for Molds and Its Characterization

本研究将新开发的膜表面液体培养（简称MSLC）应用于霉菌生产有用物质。我们不仅要优化培养条件，而且要澄清与摇瓶培养相比，MSLC获得更高产量的原因。我们研究了三种发酵体系，即1)米曲霉发酵曲酸，2)红曲霉生产红色素，3)重组米曲霉在不同培养条件下生产α-葡萄糖苷酶，培养基pH和c、n源浓度等因素均不同。在MSLC中，我们首先考察了各种多孔膜对培养行为的影响。最合适的膜是孔径约为0.2μm且具有亲水性的膜。MSLC在所有三种培养系统中都比摇瓶培养具有更高的生产力。我们研究了摇瓶培养中供氧的影响，以寻求MSLC生产率较高的原因。发现MSLC高产的原因不在于高供氧量。结果表明，基因表达、相关酶在细胞内产生的量以及产物通过细胞膜的通透性等方面的差异可能影响MSLC的高产率。

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.