用米根黴的菌絲團生產L型乳酸

Production of L-Lactic Acid Using Mycelia Flocs of Rhizopus oryzae.

吳靜怡(Ching-Yi Wu)

指導教授 ： 許垤棊

大同大學/工程學院/生物工程學系所/碩士(2005年)

摘要

在米根黴( Rhizopus oryzae BCRC 9363 )的傳統培養液中，菌絲會凝聚成菌塊，我們發現是因為培養液中的氮源耗盡的因素。因此在液態培養的過程定時補充氮源，可防止菌塊的產生，而形成棉絮狀的菌絲。因此，L型乳酸產量大大地提高。當在5公升攪拌式生物反應器中進行醱酵，用碳酸鈣乳液控制pH值在 4.3－4.5 之間，且每隔8小時補充少量的硫銨，以維持氨氮的濃度在每公升0.3－0.5公克之間。在此條件下，以每公升120克的葡萄糖為受質，L型乳酸產量為105公克，產率為0.88，生產速率為每小時每公升2.63公克。若沒有補充氮源，菌塊會纏繞在生物反應器內的裝置上面，而且L型乳酸產量顯著的下降。本研究展示一個簡單的方法使米根黴產生棉絮狀菌絲，而且L型乳酸的生產量達到最適化。

關鍵字

米根黴 ； 補充氮源 ； L型乳酸 ； 絮狀菌絲

並列摘要

The formation of mycelial clumps in conventional cultures of Rhizopus oryzae resulted mainly from the depletion of nitrogen source in the cultural medium. Based on this behavior, L(+)-lactic acid production could be enhanced in the submerged culture using mycelial flocs induced by replenishing ammonium-nitrogen in the cultural medium, thereby the formation of mycelial clumps or pellets which often occurred in conventional cultures of R. oryzae was prevented. When the fermentation was performed in a 5-L stirred tank bioreactor with the pH being controlled in the range of 4.3 – 4.5 by adding calcium carbonate slurry, and small amounts of ammonium sulfate was added at 8-h intervals to sustain ammonium level of the culture in the range of 0.3 – 0.5 g/L, lactic acid production was optimized. The lactic acid concentration produced was 105 g/L, with the yield of 0.88 and the productivity of 2.63 g/L-h, using 120 g/L of glucose as substrate. Without replenish of ammonium-nitrogen, mycelial clumps attached everywhere in the bioreactor and lactic acid production dramatically declined. This article demonstrates a simple way to obtain mycelial flocs of R. oryzae thereby an optimized lactic acid production can be achieved.

並列關鍵字

mycelial flocs ； replenish of nitrogen source ； L(

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