利用米根黴液態醱酵生產L型乳酸的最適化

Optimized Production of L-Lactic Acid by Submerged Fermentation of Rhizopus oryzae

賴宜涵(Yi-Han Lai)

指導教授 ： 許垤棊

大同大學/工程學院/生物工程學系所/碩士(2006年)

摘要

利用米根黴(Rhizopus oryzae ATCC 9363)醱酵生產L型乳酸的實驗過程中，傳統上會以碳酸鈣控制pH值；但是在純化L型乳酸的過程中，會產生造成環境污染的硫酸鈣 (石膏)。由於，氨水會對米根黴造成化學性傷害，但是碳酸銨具有緩衝能力；因此，本研究以含銨．氨水溶液—添加2%(w/v)碳酸銨10%(w/v)氨水，取代碳酸鈣控制醱酵槽中培養基的pH值。另外，醱酵槽培養基中需添加每升1克的尿素；培養米根黴於具有尿素的培養基中時，其較容易抵抗氨水的毒性。因此，添加尿素可以增加乳酸產量。
米根黴於五公升生物反應器中進行醱酵時，並利用含銨．氨水溶液控制pH值為5.0，可以得到L型乳酸產量為每公升106.2克，產率為86%，生產速率平均每小時每公升為3.22克。此時，L型乳酸的醱酵實驗達到最適化。利用上述最適條件操作重覆批次醱酵實驗，可以成功進行四次，而其最大乳酸產量每公升亦超過100克。

關鍵字

含銨．氨水溶液、L型乳酸、米根黴

並列摘要

In conventional cultures of R. oryzae ATCC9363 for lactic acid production, calcium carbonate was used as a pH-controlling agent, causing a substantial amount of solid waste (gypsum) in the process of lactic acid purification. In the present study, instead of calcium carbonate, an ammoniacal solution consisting of 2% (w/v) ammonium carbonate and 10 % (w/v) ammonia was used to control the pH of culture medium. It was found that the damage of ammonia water on fungal cells decreased because of the buffering effect of ammonium carbonate. Therefore this ammoniacal solution was used as the pH-controlling agent throughout the experiments. Furthermore, addition of urea to the culture medium can increase the production of lactic acid suggested that R.oryzae cultured in the presence of urea is more resistant to the toxicity of ammonia.
As the fermentation of L-lactic acid operated around pH 5, maximal L-lactic acid at 106.2 g/L with a yield of 0.86 and a productivity of 3.22 g/L‧h were obtained. The followed repeated batch fermentation was successfully carried out for 4 cycles; maximal L-lactic acid concentration was more than 100g/L.

並列關鍵字

ammoniacal solution；L-lactic acid；Rhizopus ory

參考文獻

Anders, R. J. J. G. Cervency, and A. L. Milkowski, (Dec. 19, 1989). U.S. Patent 4,888,191, (to Oscar Mayer Foods Corp., U.S.A.).

Anders, R. J. J. G. Cervency, and A. L. Milkowski, (May. 21, 1991). U.S. Patent 5,017,391, (to Oscar Mayer Foods Corp., U.S.A.).

Bai, D., X., Zhao, X., Li, and S. Xu, 2004.Strain improvement of Rhizopus oryzae for over-production of L (+)-lactic acid and metabolic flux analysis of mutants. J. biosci. bioeng. 18: 41-48.

Bai, D., M. Jia, X. Zhao, R. Ban, F. Shen, X. Li and S. Xu, 2003. L(+)-lactic acid production by pellet-form Rhizopus oryzae R1021 in a stirred tank fermentor. Chem. eng. sci. 58: 785-791.

Benthin, S. and J. Villadsen, 1995. Production of optically pure D− lactate by Lactobacillus bulgaricus and purification by crystallization and