| 摘要: | 細菌纖維素(Bacterial cellulose, BC)作為一種具有廣泛應用潛力的生物材料，其生產過程中存在成本高和環境影響大的問題，如高成本的氮源、生產過程中產生的廢液難以處理等。因此，探討了利用低成本複合胺基酸作為氮源以及回收自我發酵廢液再利用於培養木質醋酸菌的方法，以提高細菌纖維素產量並降低生產成本。
本研究利用了濃縮糖蜜醱酵後所殘留的廢液加以處理所產生的複合胺基酸作為氮源，首先探討複合胺基酸在培養基添加的濃度，其中為5%濃度生產細菌纖維素較佳，再來因為複合胺基酸中麩胺酸(Glutamic acid)佔的比例最高，所以測試了是否因為純麩胺酸的成分導致細菌纖維素產量增加，結果顯示並不是麩胺酸的原因，由此得知複合胺基酸裡面有其他胺基酸、蛋白質有利於細菌纖維素生產的生產。接著為了提高細菌纖維素產量直接添加Yeast extract和Peptone，結果顯示兩者差異並不明顯，所以利用低成本的複合胺基酸就能夠取代昂貴的Yeast extract和Peptone，在28oC靜態培養十天後獲得4.02g/L的BC膜，與Hestrin & Schramm(HS)培養基(3.36g/L)相比提升了19%。將BC進行材料分析，其FTIR官能基無改變且無新的官能基出現，TGA發現BC可達366-375oC之熱穩定性，XRD分析細菌纖維素計算出crystallinity (%)可達83-84%、crystal size(CrS)有5-8nm、crystallinity index(CrI)有0.8、 d-spacing有0.39-0.61 nm，DSC分析細菌纖維素之熔點介於82-114oC，以SEM觀察細菌纖維素呈現網狀且緊密結構。另外，因細胞膜上的Glucose dehydrogenase (GDH)反應，將部分葡萄糖轉化為葡萄糖酸，導致細菌利用葡萄糖生成纖維素產量較少，所以研究利用勒沙特列原理，在培養基裡先給予適量的葡萄糖酸(因為GDH的可逆反應)來提高利用葡萄糖生成纖維素的反應以提升BC產量。首先利用回收自我發酵廢液來做添加，並與HS培養基比較，其中以添加15%回收發酵液BC產量最佳，在28oC靜態培養十天後獲得5.614g/L的細菌纖維素，與HS培養基(4.945g/L)相比提升了13.56%。將BC進行材料分析，其FTIR官能基無改變且無新的官能基出現，TGA發現BC可達367-372oC之熱穩定性，XRD分析細菌纖維素計算出crystallinity (%)可達81-82%、crystal size(CrS)有5-8nm、crystallinity index(CrI)有0.78、 d-spacing有0.39-0.61 nm，DSC分析細菌纖維素之熔點介於104-112oC，以SEM觀察細菌纖維素呈現網狀且緊密結構。接著使用immobilized cell、free cell、membrane reactor做GDH反應製造葡萄糖和葡萄糖酸混合物進行培養，在28oC靜態培養十天後獲得5.74g/L，與HS培養基(5.15g/L)相比提升了11.45% ，實驗結果顯示利用勒沙特列原理，在培養基裡先給予適量的葡萄糖酸來提高葡萄糖的利用率是有效的方式。將BC進行材料分析，其FTIR官能基無改變且無新的官能基出現，TGA發現BC可達365-368oC之熱穩定性，XRD分析細菌纖維素計算出crystallinity (%)可達81-84%、crystal size(CrS)有5-8nm、crystallinity index(CrI)有0.7-0.8、 d-spacing有0.39-0.61 nm，DSC分析細菌纖維素之熔點介於94-120oC，以SEM觀察細菌纖維素呈現網狀且緊密結構。
Bacterial cellulose (BC) is a biomaterial with significant application potential, but its production faces high costs and environmental issues, such as the expensive nitrogen sources and the difficult-to-treat waste liquid generated during the production process. This study explores the use of low-cost complex amino acids as a nitrogen sources and reuse of self-fermentation wastewater to cultivate Komagataeibacter xylinus to enhance BC yield and reduce production costs.
In this research, complex amino acids derived from treated concentrated molasses fermentation waste liquid were used as the nitrogen source. Initially, the optimal concentration of composite amino acids in the medium was determined to be 5%. Since glutamic acid was the predominant component in the complex amino acids, it was tested to see if it alone increased BC production, but results showed that other amino acids and proteins in the complex amino acids contributed to the production. To further increase BC yield, yeast extract and peptone were directly added, but no significant differences were observed, indicating that the low-cost complex amino acids could replace the expensive yeast extract and peptone. After ten days of static culture at 28°C, a BC yield of 4.02 g/L was obtained, which was a 19% improvement compared to the Hestrin & Schramm (HS) medium (3.36 g/L). Material analysis of the BC showed FTIR has no change in functional groups and TGA found that BC can reach a thermal stability up to 366-375°C, XRD analysis of BC calculates that the crystallinity (%) was 83-84%, with a crystal size (CrS) of 5-8 nm, a crystallinity index (CrI) of 0.8, and d-spacing of 0.39-0.61 nm, DSC analysis of the melting point was between 82-114°C, and SEM revealed a network and dense structure. Due to the glucose dehydrogenase (GDH) reaction on the cell membrane converting part of the glucose to gluconic acid, reducing the BC yield, the study applied Le Chatelier's principle by adding an appropriate amount of gluconic acid to the medium to enhance BC production. Using recycled fermentation waste liquid, the best BC yield was achieved with 15% addition, obtaining 5.614 g/L of BC after ten days of static culture at 28°C, a 13.56% increase compared to the HS medium (4.945 g/L). Material analysis of the BC showed FTIR confirmed no change in functional groups, TGA found that BC can reach a thermal stability up to 367-372°C, XRD analysis of BC calculates that the crystallinity (%) of 81-82%, CrS of 5-8 nm, CrI of 0.78, and d-spacing of 0.39-0.61 nm, DSC analysis of the melting point ranged from 104-112°C, and SEM showed a network and dense structure. Finally, using immobilized cells, free cells, and membrane reactors to produce a glucose and gluconic acid mixture via GDH reaction, a BC yield of 5.74 g/L was obtained after ten days of static culture at 28°C, an 11.45% increase compared to the HS medium (5.15 g/L). The results demonstrated that using Le Chatelier's principle to enhance glucose utilization by adding gluconic acid is an effective approach. Material analysis of the BC showed FTIR indicated no change in functional groups, TGA found that BC can reach a thermal stability up to 365-368°C, XRD analysis of BC calculates that the crystallinity (%) of 81-84%, CrS of 5-8 nm, CrI of 0.7-0.8, and d-spacing of 0.39-0.61 nm, DSC analysis of the melting point ranged from 94-120°C, and SEM showed a network and dense structure. |
