Zymomonas mobilis ATCC 29191轉化葡萄糖成生質乙醇之培養基開發與固定化發酵策略探討

Development of optimal medium of Zymomonas mobilis ATCC29191 to production of bioethanol by catabolism of glucose and immobilization fermentation strategy

林志明(Chih-Ming Lin)

指導教授 ： 蘇文達

國立臺北科技大學/工程學院/化學工程研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00023

摘要

Zymomonas mobilis為格蘭氏陰性兼性厭氧菌，在無氧條件下將利用Entner- Doudoroff pathway代謝醣類並轉化成乙醇。Zymomonas mobilis轉化葡萄糖成乙醇，具高理論產率及轉化率等優點，非常適合於乙醇工業化大量生產。本研究主要目的，係開發Zymomonas mobilis轉化葡萄糖成乙醇之最適化培養基。研究證實Z. mobilis ATCC 29191在以葡萄糖(150 g/L)為碳源、(NH4)2SO4 (1 g/L)為氮源之培養基，經四十小時培養，可得最高乙醇濃度、產率及理論轉化率，分別達64.70 g/L、1.61 g/L/h與84.39 %。進一步研究顯示，以(NH4)2HPO4 (1 g/L) 取代(NH4)2SO4 (1 g/L)，不僅大幅提升產物乙醇之產率達2.69 g/L/h，同時可維持乙醇之高轉化率84.44 %。其次，本研究利用回應曲面實驗設計法(Response surface methodology, RSM)進行培養基最適化設計，研究證實Zymomonas mobilis轉化葡萄糖成乙醇之最適化培養基組成為：Glucose (166.5 g/L)、Yeast extract (6.1 g/L)、KH2PO4 (1 g/L)、(NH4)2HPO4 (1 g/L)、MgSO4•7H2O (0.5 g/L)。Zymomonas mobilis利用上述最適化培養基，可得最高之乙醇濃度、產率及理論轉化率，分別達 77.75 g/L、3.24 g/L/h與91.36 %。在重複批次發酵策略上，利用固定化的系統優於懸浮系統，固定化的載體以藻酸鈣為主，藻珠的體積為工作體積的10%，接菌量以工作體積的5%所顯示的效果最佳，其產率達到3.58g/L/h。在發酵液的回收與重覆使用的實驗上顯示了可以省下70.12%的水資源。利用減壓濃縮儀從發酵液當中萃取酒精的條件測試，以80mbar/45℃所顯示的效率最好，其中回收率為89.77%，萃取出的酒精濃度為38.36%，再利用減壓濃縮機處理數次之後也可得77.71%(V%)之酒精。由實驗結果顯示Zymomonas mobilis確係適合於乙醇工業化大量生產之菌株。未來冀望以此最適化培養基為基礎，進行不同發酵策略之探討，進而獲得較佳的乙醇產率。

關鍵字

Zymomonas mobilis ； 培養基最適化 ； 回應曲面法 ； 葡萄糖轉化 ； 生質乙醇

並列摘要

Zymomonas mobilis is a gram-negative and facultative anaerobic bacterium. It uses the Entner-Doudoroff pathway to synthesize ethanol by catabolism of carbohydrates. While using glucose as the principle substrate, Z. mobilis offer the higher specific rates of sugar uptake and ethanol production. Thus Z. mobilis acts as a suitable candidate for industrial production of bioethanol. The aim of our study is to develop an optimal medium for Z. mobilis ATCC 29191 that could biotransfer glucose to ethanol. Interestingly after 40 hour fermentation when glucose (150g/L) and (NH4)2SO4 (1g/L) as the carbon and nitrogen sources the ethanol concentration, productivity, and theoretical yield is 64.70 g/L,1.61 g/L/h and 84.39 % respectively for 40h fermentation. The further research demonstrated that the (NH4)2SO4 (1g/L) was replaced by (NH4)2HPO4 (1g/L) not only promotes the ethanol productivity to 2.69 g/L/h but also maintain the high theoretical yield to 84.44%. Additionally, this research carries on the optimal culture medium using the response surface methodology. These results demonstrated that the optimal medium for Z. mobilis ATCC 29191 to produce ethanol were glucose (166.5g/L), yeast extract (6.1g/L), KH2PO4 (1g/L), (NH4)2HO4 (1g/L), MgSO4 (0.5g/L). Using optimal culture medium, the highest ethanol concentration, productivity, theoretical yield is 77.75g/L, 3.24g/L/h and 91.36%. The immobilization is better than suspension system in the repeat batch fermentation strategy. The immobilized carrier is calcium alginate beads, that volume of beads is 10% of working volume and the inoculated concentration is 5% of working volume. Using this condition to produce ethanol, the ethanol productivity could reach to 3.58g/L/h. There is no difference in ethanol production when Z. mobilis ferment with fresh medium or the recycling disused fermentation fluid, and further could save about used 70.12% water. The rotary evaporator can separate out 38.36%(v%) ethanol and recycling percentage 89.77% from the fermentation broth when the operation condition condition is set in 80mbar/45℃. It will gain the 77.71%(v%) ethanol after deal with repeatedly.
Our results, newly showed that Zymomonas mobilis is a suitable strain for the ethanol industrialization production. The future work, we hope to use this optimal culture medium to find out the great productivity of ethanol with different fermentation strategy.

並列關鍵字

Zymomonas mobilis ； optimal medium ； Response Surface Methodology ； glucose catabolism ； bioethanol

參考文獻

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