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以Candida subtropicalis進行二階段醱酵產製木糖醇之研究 曾昭維、張德明

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以Candida subtropicalis進行二階段醱酵產製木糖醇之研究 曾昭維、張德明

E-mail: [email protected]

摘 要

中文摘要 近年來食品的機能性已經廣為大眾所重視,包括均衡的營養需求,以及其他對人體有正面影響的功能。而木糖醇 具有類似薄荷的清涼口感、低熱量、與蔗糖相等的甜度、以及不需胰島素代謝及可被人體消化吸收等特性,因此在新ㄧ代 食品之要求中逐漸得到重視。而農林廢料中含有豐富纖維素、半纖維素,及木質素。將半纖維素以酸水解即可得豐富之木 糖、葡萄糖,及其他少量糖類(半乳糖、甘露糖、阿拉伯糖)。近年來許多研究皆利用半纖維素水解液作為醱酵基質生產 木糖醇,不僅可以降低成本更可以達到環保減費之目的。 本研究主要探討利用水解液中兩種主要糖類(木糖與葡萄糖)為 碳源時,由於菌體雙期生長特性與其所產生的兩階段醱酵過程,藉由在不同階段裡控制不同溶氧量,以期有效提升木糖醇 的產量及產率。研究結果顯示在雙碳源的環境下有利於提升木糖醇的產量及產率。以單一碳源溶氧量對菌體生長之影響,

在葡萄糖醱酵時溶氧量範圍為5 ~ 10%菌體的生長情況最佳(μ = 0.356 h-1);而在木糖醱酵產製木糖醇時,固定通氣量 0.25 vvm、轉速為130 rpm時有較佳的產量(0.649 g g-1)及產率(0.263 g L-1 hr-1)。綜合上述之結果,串聯饋料批次及批 次的兩個階段醱酵之操作,實驗證實以此方式之操作方式確實能有效地提升木糖醇的產率(0.246 g L-1 hr-1)。 關鍵字:

兩階段醱酵、木糖醇、溶氧、半纖維素水解液、雙期生長。

關鍵詞 : 木糖醇 ; 溶氧量 ; 雙期生長 ; 半纖維素水解液 ; 兩階段醱酵 目錄

目 錄 封面內頁 中文摘要………i 英文摘要………

………ii 目錄………iii 圖目錄………

………viii 表目錄………...x 第一章 研究目的

………..1 第二章 文獻回顧……….…….3 2.1 木糖醇的 介紹………...………..3 2.1.1 木糖醇的來源..………..………..…3 2.1.1.1 農業副產品 簡介………….………….…….…...3 2.1.1.2 半纖維素……….……..…..……….…..….6 2.1.1.3 木糖製備生產的過程…

…….………..…..9 2.1.1.3.1 水解液之製備….……..………...9 2.1.1.3.2 水解液之分離純化….………

…...11 2.1.2 木糖醇的性質….……….12 2.1.3 木糖醇於人體內的代謝………15 2.1.4 木糖醇之應用………15 2.1.4.1 預防齲齒……….………18 2.1.4.2 食品添加 劑…….………19 2.1.4.3 糖尿病患者之糖類補充劑……….…19 2.1.4.4 其他應用….………

………20 2.2 生產木糖醇方法……….20 2.2.1 傳統化學合成法………

…………..20 2.2.2 微生物醱酵法………..22 2.2.2.1 生產木糖醇之酵母菌種類………

…...22 2.2.2.2 酵母菌代謝木糖之途徑………...24 2.2.2.3 固定化生產木糖醇………...26 2.3 酵母菌的雙期生長……….27 2.4影響酵母菌轉化木糖醇的因子………..28 2.4.1 碳源………..28 2.4.1.1 單一碳源……….…….….…28 2.4.1.2 多碳源

…..……….….……….…….….…29 2.4.1.3 天然半纖維素水解液………..30 2.4.2 氮源………

………..31 2.4.3 pH值……….32 2.4.4 溫度………

………..33 2.4.5 鹽類………..34 2.4.6 溶氧量………

………..34 2.4.7 菌體量………..35 2.4.8 副產物乙醇………

………..36 第三章 材料與方法………38 3.1 菌株………

…………38 3.2 實驗藥品………38 3.3 實驗儀器設備………

……….38 3.4 菌株培養………39 3.4.1 培養基………

…..39 3.4.2 菌種保存………..41 3.4.3 菌種活化………41 3.4.4 前培養……….………..41 3.5 醱酵槽培養………..………..……….42 3.5.1 批次醱酵培養………..42 3.5.1.1 碳源的組成對於產製木糖醇的影響……..….…43 3.5.1.2 溶氧量 對於菌體生長之影響………..……..…43 3.5.1.3 通氣量對於產製木糖醇之影響……..……..…44 3.5.2 兩階段醱酵培養………

………..44 3.5.2.1 兩階段醱酵………..……….45 3.6 分析方法………

……….45 3.6.1 生質量之菌重測定………..45 3.6.1.1 菌體離心秤乾重測定………

………….46 3.6.1.2 菌體分光光度計測定………46 3.6.2 糖類、木糖醇、乙醇之分析………

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…47 3.6.3 酚硫酸法………....47 3.6.4 實驗數據整理………48 第四章 實驗結果與討論………50 4.1 搖瓶結果……….……50 4.2 醱酵槽批次實驗……….…………..53 4.2.1 消泡劑對菌體生長之影響………...……53 4.2.2 雙碳源 基質對產製木糖醇的影響…………...……53 4.3 兩階段醱酵條件探討………...…..56 4.3.1 兩階段醱酵 操作設計………...………..56 4.3.2 菌體代謝葡萄糖時溶氧量的影響……….59 4.3.2.1 葡萄糖的 消耗速率……….………..59 4.3.2.2 菌體量………..62 4.3.2.3 產物乙醇………

………..62 4.3.3 木糖產製木糖醇之條件探討………....64 4.3.3.1 轉速對於產製木糖醇的影響…

……….……..64 4.3.3.2 不同通氣量對木糖醇產量及產率的影響…..64 4.3.4 兩階段醱酵產製木糖醇……….……

….69 4.3.5高菌體濃度醱酵(第一階段葡萄糖代謝).……….72 第五章 結論與展望………

……..74 5.1 總結………...………..74 5.2 未來展望……….………

……76 參考文獻………78 圖 目 錄 圖2-1 以化學催化法生產木糖醇…...………

………...5 圖2-2 半纖維素之結構之ㄧ…...……..………...………..7 圖2-3 木糖醇於人體內代謝之途徑…

…………...………...17 圖2-4 傳統化學合成法製造木糖、木糖醇的流程圖…...………..21 圖2-5 酵母菌代謝木糖之途徑

…...………...………..25 圖4-1 單一碳源之搖瓶培養,菌體、木糖醇、乙醇對木糖之時間 曲線………

……….51 圖4-2 雙碳源之搖瓶培養,菌體、木糖醇、乙醇對木糖之時間曲 線………

………...………….52 圖4-3 葡萄糖單一碳源下,添加不同比例之消泡劑對於菌體生…. 長之影響……

………54 圖4-4 混合碳源與單一碳源對於生產木糖醇之影響………55 圖4-5 兩 階段醱酵...58 圖4-6 萄糖濃度70 g/L之醱酵情形………60 圖4-7 葡萄糖單一碳源下,不同溶氧量的環境下,菌體醱酵生. 長情形...61 圖4-8 葡萄糖單一碳源下,溶氧量對於產量、產率、比生長速率 的影響………

…...63 圖4-9 固定通氣量為1 vvm,轉速對於產製木糖醇的影響……65 圖4-10 葡萄糖及木糖雙碳源下,不 同通氣量對於醱酵產製木糖醇 的影響……...……….…66 圖4-11兩階段醱酵酵..…………

………....70 圖4-12高菌體濃度醱酵,不同氮源濃度對於菌體生長之影響………73 表 目 錄 表2.1 木糖醇於蔬果中之含量………...………4 表2.2 各類植物之纖維素組成及其含量…..……….8 表2.3 各種糖類甜度之比較………..………...13 表2.4 木糖醇之物理及化學性質...………...………...

……14 表2.5 各種五碳糖臨床代謝實驗..…………...………16 表2.6 微生物從木糖轉化成木糖醇結果一覽表……

……….23 表3.1 YMPX(G)營養培養基之組成………...……….40 表 3.2實驗係數之整理………

………49 表4.1雙碳源與單一碳源對產製木糖醇之影響...57 表4.2搖瓶培養與不同通氣量批次培 養對於產製木糖醇的影響..68 表4.3兩階段醱酵與批次醱酵對於產製木糖醇的影響…………71

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