常壓冷電漿對蔗渣水解液進行解毒生產細菌纖維素

Abstract

木質纖維素作為全球最大農業廢棄物成份來源，如何將其分解再利用一直以來都是循環經濟之重要課題。本篇擬透過農業廢棄資材甘蔗渣 (sugarcane bagasse, SB) 進行酸化水解以產生碳源，並透過常壓電漿(atmospheric cold plasma, ACP) 將酸水解過程中所產生毒性物質如甲酸、糠醛或羥甲基糠醛降解，並將電漿處理酸水解液應用於細菌性纖維 (bacterial cellulose, BC)生產，以期達到廢棄纖維素再生纖維素之目的。本研究首先以水萃、預處理和酸水解三階段處理SB，可從每1 g SB得到0.74 g可發酵糖、0.0096 g 甲酸、0.005 g 糠醛與0.013 g 羥甲基糠醛。優化ACP條件後，可發現當SB水解液以氬氣ACP於200 W下處理25分鐘可將毒性物質降解至最低抑制濃度。於BC生產實驗，可發現ACP處理前SB水解液之BC產量(1.88 g/L)較處理後組別(1.68 g/L)高，推測可能因SB水解液內含可促進BC生產之未知物質，然而此物質與毒性物質皆被ACP降解，導致BC產量不符合預期結果。由材料特性分析可知ACP處理與未處理SB水解液所生產BC，其化學鍵結、結構型態和結晶型態並不會與HS培養液生產BC有所差異，但ACP處理後組別發酵BC結晶度有下降的趨勢。於熱重分析結果發現模擬液組別會導致BC熱穩定性下降，而於SB組別皆不會受到影響，推測SB內可能含未知物質，其除了可增加BC產量外，亦可降低毒性物質對BC熱穩定性之影響。最後，透過電漿處理雖無法使SB酸水解液生產BC能力上升，但亦發現於電漿處理上，需針對微生物種類進行優化，未來擬透過不同氣體ACP處理酸解SB以找出適合BC生產之處理條件，以達廢棄纖維素再生纖維素之目標。

Lignocellulose is the major ingredient of global agricultural waste. Due to its availability and high sugar content, deconstruction of lignocellulosic material turns into most important issue in circular economy. In this study, sugarcane bagasse (SB) was hydrolyzed with sulfuric acid to obtain the carbon sources, and atmospheric cold plasma (ACP) was used to remove the toxic compounds produced from acid hydrolysis process including formic acid, furfural and 5-hydroxymethylfurfural (HMF). The detoxified acid hydrolysate was then applied in bacterial cellulose (BC) production to achieve the cellulosic waste recycle use. A three-step deconstruction strategy (water extraction, pretreatment, and acid hydrolysis) was carried out to increase fermented sugar recovery and decrease the toxic compounds formation. The result showed that 0.74 g of fermentable sugar, 0.0096 g of formic acid, 0.005 g of furfural, and 0.013 g of hydroxymethylfurfural were produced from one gram of SB. The toxic substances were then degraded to the lowest inhibitory concentration of BC production in the optimized ACP conditions (argon ACP at 200 W for 25 minute). In BC production, ACP treated SB hydrolysate group exhibited more higher BC production (1.88 g /L) compared to ACP untreated group (1.68 g/L). It may due to some unknown BC production enhancing ingredients are also be degraded during ACP process. In material property analysis, BCs produced from SB hydrolysate with/without ACP treatment presented the similar chemical composition, morphology and crystalline type compared to the BC produced from HS medium, but the crystallinity of BC fermented from the latter group decreased. In thermogravimetric analysis, the decreased thermostability of BC from mimic medium group showed that the toxic compounds may influence its network structure during BC production. However, this phenomenon did not appear in the ACP treated and untreated SB hydrolysate groups, which suggested that the existance of some ingradients in SB may offset the effect of toxic compoumds during BC production. It also needs more evidences to support the hypothesis. Last but not at least, although ACP treatment can be used to degrade the fermented inhibitors from SB hydrolysis, the treated SB hydrolysate did not improve BC production. In the future work, selection of different gas-based ACP system will be the other direction to find out the optimal detoxification for BC production and achieve the goal of cellulostic waste reuse to regenerate cellulose.