提升酵母菌之葡萄糖利用率以應用於高溫醱酵生產酒精之研究

Study on increasing yeast glucose consumption for fuel ethanol production at high temperature

黃常恩(Chang-en Huang)

指導教授 ： 段國仁

大同大學/工程學院/生物工程學系所/碩士(2011年)

摘要

在高溫進行酒精發酵可降低發酵槽的冷卻成本。凝絮性良好的酵母菌，並有利於酵母細胞的迴流再利用，有利於高密度細胞的酒精發酵。
本研究首先使用一株耐熱性酵母菌Kluyveromyces marxianus K21進行培養基配方測試，希望能提高其耐熱能力，結果發現添加鎂離子(Mg2+)、鈣離子(Ca2+)或海藻糖(Trehalose)的實驗無顯著提升葡萄糖利用率或對溫度的耐受性，但提高酵母萃取物的濃度能提升菌體的葡萄糖利用率。本研究發現使用酵母菌 K21菌株在45℃含有2% (w/v)酵母萃取物的環境下能將10% (w/v)葡萄糖完全發酵成酒精，其酒精濃度為47.31 g/L，超過10% 的葡萄糖濃度則無法被代謝掉。
本研究另外使用的凝絮性酵母(Saccharomyces cerevisiae)代號為 Wp002、1968及1335菌株，分別以不同濃度之酵母萃取物以及10%葡萄糖於28℃和38℃進行搖瓶培養。結果顯示2.0% 酵母萃取物可以促進酵母菌Wp002、1968及1335的生長，並提升葡萄糖的利用率，於28℃實驗中，其最高酒精濃度分別為每公升46.97、48.60及48.76克，酒精轉化率達理論轉化率的92.2、95.3及90.4%。於38℃實驗中，最高酒精濃度分別為每公升43.36、46.50及49.01克，酒精轉化率達理論轉化率的85.1、85.3及96.1%，結果顯示酵母菌1335 有最好的耐熱能力。
進一步使用酵母菌1335於醱酵槽進行批次醱酵，採用2.0 %酵母萃取物並以25.0 % (w/v)葡萄糖作為基質於28℃及38℃進行厭氧醱酵，實驗結果顯示，採用高濃度的酵母萃取物作為氮源，最後酒精濃度分別為105及98 gL-1，相較於低溫28℃醱酵，於高溫38℃下，無法完全利用25%葡萄糖，仍然有54.9 gL-1的葡萄糖殘留。

關鍵字

溫度耐受性酵母 ； 高溫酒精醱酵 ； 啤酒酵母 ； 馬克斯克魯維酵母 ； 酵母抽出物

並列摘要

Ethanol fermentation at high temperature can reduce cooling cost of the fermenter. Highly flocculating yeast is easy to precipate in the beer, and is possible to recirculate the yeast to achieve high cell density ethanol fermentation.

A thermotolerant yeast, Kluyveromyces marxianus K21, was employed to investigate the medium formulation to improve the thermotolerant ability. The result indicated that, when supplement with magnesium(Mg2+)、calcium(Ca2+) or trehalose , there is no significantly improvement on glucose consumption rate or thermotolerance. But the glucose consumption rate can be improved by increasing concentration of yeast extract at high temperature. Ethanol concentration of 47.31 g/L was achieved for the K. marxianus K21 in the medium containing 10% (w/v) glucose and 2 % (w/v) yeast extract at 45C. Glucose concentration more than 10 % (w/v) could not be consumed by the K. marxianus K21.

The cell growth and glucose consumption rate of flocculating yeast strains were improved by 2.0% (w/v) YE at 28 C. The maximum ethanol concentration of WP002, 1968 and 1335 strains was reached at 46.97, 48.60 and 48.76 g/L, respectively, in the 10 % (g/L) glucose concentration. The theoretical ethanol conversion rate from glucose was 92.2, 95.3, and 90.4%, respectively. Moreover, increase the fermentation temperature to 38 C, the growth and glucose consumption rate of WP002, 1968 and 1335 strains were improved by 2.0% (w/v) YE, and the maximum ethanol concentration was at 43.36, 46.50 and 49.01 (g/L), respectively, in the 10 % (g/L) glucose concentration. The theoretical ethanol conversion rate from glucose was 85.1, 85.3, and 96.1%, respectively. The results indicate that yeast 1335 was the most thermotolerant.

Yeast 1335 strain was applied in batch-fermentation using a medium containing 2.0% (w/v) yeast extract and 25.0% (w/v) glucose, and achieved 105 and 98 gL-1 at 28 and 38C respectively. Glucose was completely consumed at 28C after, while 54.9 gL-1 glucose remained unfermented in the beer at 38C.

並列關鍵字

thermotolerant yeast ； high temperature ethanol fermentation ； Saccharomyces cerevisiae ； Kluyveromyces marxianus ； yeast extract

參考文獻

陳文恆、郭家倫、黃文松、王嘉寶。2007。纖維酒精技術之發展。農業生技產業季刊 9:62-69。

周霖宏。2008。以葡萄糖為原料生生產酒精之醱酵策略。大同大學生物工程學研究所碩士論文。

簡萬山。2009。微量通氣對高濃度酒精醱酵之影響。大同大學生物工程學研究所碩士論文。

D'Amore, T., and G. G. Stewart, "Ethanol tolerance of yeast," Enzyme Microb Technol., vol. 9, pp. 322-330, 1987.

of thermotolerant yeast strains Saccharomyces cerevisiae for bioethanol