利用Clostridium cellulolyticum與Clostridium xylanolyticum分解麻竹纖維

Abstract

梭狀芽孢桿菌屬之白蟻腸內共生菌Clostridium xylanolyticum與解纖維梭菌Clostridium cellulolyticum分別具有降解半纖維素與纖維素的能力，因此本研究希望藉由這兩株菌提升木質纖維的利用率以增加醱酵反應過程中酸醇產物的產量。 C. cellulolyticum雖為嚴格厭氧菌，但菌株接種時，可在非氮氣充填下之無菌操作台進行，因此僅有開管活化以及分裝開管所需之培養基時，必須在厭氧手套箱進行。此外經試驗發現C. cellulolyticum亦可培養於螺蓋試管，不須在培養嚴格厭氧菌之Hungate-type tube中，但培養條件仍與其他嚴格厭氧菌相同，需在培養基中添加還原劑。 藉由建立菌株的生長曲線得知C. cellulolyticum的遲滯期為0~9小時，對數期為9~20小時，幾乎沒有靜止期，世代時間為1.37小時，最佳接種時間為16~20小時。相較於之前的研究所建立之生長曲線，C. xylanolyticum的遲滯期為0~12小時，對數期為12~30小時，靜止期30~96小時，世代時間為2.4小時，最佳接種時間為24~30小時。 醱酵試驗依基質種類不同分為人工基質測試及天然基質醱酵兩種，在人工基質測試中，醱酵產物濃度在單一菌種與共培養醱酵三組試驗中沒有顯著差異；在天然基質醱酵試驗中，C. cellulolyticum能夠降解較多纖維素及半纖維素之含量，因此較C. xylanolyticum有利於麻竹纖維的分解，而共培養試驗之半纖維素含量減少最為顯著。

Clostridium xylanolyticum, a symbiotic bacterium in termite gut, and Clostridium cellulolyticum had been found could digest hemicellulose and cellulose, respectively. The objective of this study was to evaluate the possibility of improving the utilization rate of lignocellulose and hence to increase the production of acids and alcohol through fermentation by these two species of bacteria. Although C. cellulolyticum is an obligate anaerobe, it could be inoculated in the laminar flow hood without filling nitrogen. Only when opening the seeding bacterium ampoule and preparing the medium for activation, to maintain the anaerobic conditions by using the anaerobic glove box is necessary. It was also found that the conventional Hungate-type tube used in cultivation of C. cellulolyticum could be simply replaced by screw-cap test tubes, but similar to other obligate anaerobes, addition of reducing agent is still required. The growth curve of C. cellulolyticum showed 9 hrs of lag phase was existed and the following exponential phase was from 9 to 20 hrs, and no stationary phase was observed. The mean generation time was 1.37 hrs and the optimal inoculation period was between 16-20 hrs. According to the previous study, cell growth of C. xylanolyticum in modified PYG medium existed a 12 hrs lag phase, exponential phase was from 12 to 30 hrs, and stationary phase was from 30 to 96 hrs. The mean generation time was found to be 2.4 hrs, and the optimal inoculation period was between 24-30 hrs. Two fermentation tests using different substrates were conducted, artificial substrate fermentation and Ma Bamboo fermentation. In test of the artificial substrate fermentation, the products of co-culture and monoculture fermentation for both C. cellulolyticum and C. xylanolyticum had no significant difference. In monoculture of the Ma Bamboo fermentation, C. cellulolyticum presented better degradation ability about the cellulose and hemicellulose than that of C. xylanolyticum. Additionally, co-culture of the Ma Bamboo fermentation test showed better degradation ability in hemicelluloses than that of monoculture test.