香草醛(Vanillin)，為我們熟悉之香草的主要香氣來源，香草為世界最受廣泛應用以及最受歡迎的香料之一。香草的主要供應來源分別為天然香草與人工合成香草，天然香草取自香莢蘭的豆莢，由於香莢蘭培植時間長，豆莢採收後又須經過多道程序方可使用，導致量少而昂貴，無法滿足市場需求；人工合成香草雖然價格便宜、能滿足市場需求，但生產過程中會對環境產生嚴重汙染，因此近年來開始積極研究利用微生物生產香草醛，以滿足對天然香草醛的需求。阿魏酸為Amycolatopsis thermoflava生產香草醛的前驅物，A. thermoflava會CoA依賴性逆向羥醛反應轉化阿魏酸產生香草醛及其他下游產物。玉米芯中含有豐富的阿魏酸，既可以做為發酵之前驅物來源，又可以解決玉米加工後產生廢棄物的問題，兼具環境保護以及商業化的前景，更擁有使農業廢棄物增值化的效果。 本研究嘗試利用Amycolatopsis thermoflava將玉米芯中的阿魏酸藉由轉化生產香草醛。研究結果顯示，經預處理之玉米芯萃取液，藉由巴氏滅菌過程菌種得以生長，以固液比1:10 (w/v) 對玉米芯作萃取，其萃取液經75℃之巴氏滅菌後，菌種可將其阿魏酸轉化，產生17.01 mg/L香草醛與341.81 mg/L香草酸。高濃度之對-香豆酸會抑制菌種生長，兩階段發酵可使菌種順利生長於2 g/L阿魏酸與4 g/L對-香豆酸之環境中。使用超音波輔助搭配鹼萃取，於固液比1:30 (w/v)、氫氧化鈉濃度0.5 M以及操作功率60%的條件下萃取30分鐘，可獲得最大阿魏酸萃取率。 ;Vanillin is considered as one of the most important flavors worldwide and it is used extensively in food, beverage, cosmetic, and pharmaceutical industries. Vanillin production by microbial conversions of natural precursors has gained a lot of attention because it is accepted as ‘‘natural’’ vanillin. The biotechnological process to produce vanillin from various agro by-products had been investigated using different microorganisms. Corn cob is a potential feedstock containing a high concentration of ferulic acid as a precursor to be used for vanillin bio-production. In this study, trying to convert ferulic acid in corncobs to produce vanillin by Amycolatopsis thermoflava. The results show that the corncob extract within pretreatment and A. thermoflava can be grown after pasteurization. The corncob is extracted with solid- liquid ratio of 1:10 (w/v). The extract is sterilized within temperature of 75℃ for 30 minutes by pasteurization, and A. thermoflava can convert the ferulic acid and produce 17.01 mg/L of vanillin and 341.81 mg/L of vanillic acid. The high concentration of p-coumaric acid will inhibit the growth of the bacteria, and the two-stage fermentation can make the bacteria grow in the concentration of 2 g/L ferulic acid and 4 g/L p-coumaric acid. Using ultrasonic assisted with alkaline extraction, extracting for 30 minutes under the conditions of solid-liquid ratio of 1:30 (w/v), sodium hydroxide concentration of 0.5 M, and operating power of 60%, the maximum ferulic acid extraction rate can be obtained.
