以Gluconacetobacter xylinus連續生產細菌纖維素之反應器設計與操作

Abstract

細菌纖維素由於其獨特的物理、化學特性，使其在許多領域的應用上比植物纖維素具有更高的利用價值，例如食品工業、造紙工業、生醫領域甚至光電設備都可見到細菌纖維素的應用實例。傳統工業生產薄膜形態的細菌纖維素僅能以靜置批次培養的方式生產，此方法得到的纖維素薄膜大小受限於反應器規格，而且操作複雜度較高，培養過程中需反覆進行預活化和後處理的步驟，無形中提高了纖維素薄膜的生產成本且費時。如果改以連續式操作生產將可改善這些缺點。 本研究設計了一個適合以連續式操作生產細菌纖維素的反應器，包括圓木滾輪的設置以便收集纖維素薄膜；反應器中斜面的設置和連接角度的探討以利纖維素薄膜的連接；清洗槽的設計方便清洗甫生成的纖維素薄膜。 在反應器的操作方面，本實驗以4天為一週期以BSH培養基進行連續式操作，實驗結果顯示以每週期添加50ml培養基可得到最高纖維素產率(0.11g-BC/g-glucose)。並在每週期結束後殘留20ml的舊培養基作為下一週期的植菌來源再添加新鮮培養基可得到最高的纖維素總產量。在培養基葡萄糖濃度方面，以添加80g/L葡萄糖濃度的BSH培養基在28天的培養當中可得到最高的纖維素乾重(2.07g)，但在產率方面則隨葡萄糖濃度增加而遞減。 同時實驗中也觀察到連續式操作的前兩個週期的行為和第三週期後達穩定狀態時有所不同，原因包括兩者的初始細菌濃度不同以及培養基成分的差異，此結果造成無法利用批次操作的結果來預知連續式操作達穩定後的行為。因此本研究利用增加批次操作的初始細菌濃度以及在培養基中添加特定濃度葡萄糖酸的方式，可使批次操作的結果較接近於連續式操作達穩定後的結果，如此便可利用一次批次操作(4天)來預測連續式操作的結果。 利用連續式操作生產細菌纖維素，在每日平均產量方面是傳統批次培養的2~7倍，同時又省去了批次培養反覆的預活化及後處理等操作成本，因此可有效提升纖維素產量同時降低生產成本。

Traditional methods of producing bacterial cellulose (BC) membranes include batch, static cultivation, which require complex operating procedures because of the repeated preculture and cleaning steps. Also the size of cellulose membranes produced depends on the reactor. Continuous cultivation could improve these disadvantages. This study designed a continuous culture reactor with a roller to collect the produced cellulose membranes, a ramp to improve the connection beween two membranes and a holding box so that the membranes just produced can be washed immediately. The continuous operation used BSH medium and repeated every 4 days as a cycle. It was found that adding 50ml fresh medium in each cycle gave the best yield. Also, controlling the residual medium at 20ml remaining after each cycle as the bacteria source of next cycle gave highest production. Good BC production was obtained when BSH medium with glucose concentration 80g/L was used during the 28days cultivation, but the yield decreased with increasing glucose concentration. The continuous operation’s results showed that the first two cycles had different behaviors from other cycles. So it was difficult to predict the results of continuous cultivation based on results of batch cultivation. It was because of the difference of initial cell concentration and medium composition between the first two cycles and the others. It was found that adding certain concentration of gluconic acid during batch cultivation could result in similar results as continuous cultivation. The average amounts of BC produced per day by continuous mothod was 2 to 7 times higher than tradition batch cultivation. Contiunous cultivation also reduced the operating cost due to avoiding repeated preculture and cleaning steps.