PLA降解菌論文：巨大芽孢桿菌(Bacillusmegaterium)的選育及其PLA降解酶的研究

1、PLA降解菌論文：巨大芽抱桿菌(Bacillus megaterium) 的選育及其PLA降解酶的研究【中文摘要】隨著對塑料制品需求的不斷增加，帶來了不可忽視 的能源危機和環(huán)境危機。普通塑料在自然環(huán)境下幾十年都不能被降解, 因此開發(fā)可降解塑料迫在眉睫。目前開發(fā)的可降解塑料主要是聚酯類 物質(zhì)，而其中 PLA 以其優(yōu)良的物理化學性能和潛在的成本優(yōu)勢尤受人 們的關(guān)注。 雖然PLA在生產(chǎn)和應用上有比較明顯的優(yōu)勢，但是它的生 物降解研究比較滯后。因此，本文從 PLA 降解菌株出發(fā)，從菌株的篩選 到鑒定,然后測定其最適產(chǎn)酶條件，并進行 PLA 降解酶的分離純化。本 文主要的工作內(nèi)容及結(jié)果如下:1.對遼寧省

2、撫順市撫順石油一廠污水 處理車間曝氣池中的活性污泥進行 PLA 降解菌株的篩選。獲得了一株 能夠降解 PLA 的菌株編號為 DS04-W 2.對篩選的 DS04-W 進行形態(tài) 學觀察，生理生化性質(zhì)測定，以及 16SrDNA 序列的測定，最后鑒定該菌 為 Bacillus megaterium( 巨大芽抱桿菌)。3.對 DS04W 菌降解 PLA 膜能力的測定，用掃描電鏡觀察 PLA 膜降解前后的形態(tài)變化。發(fā)現(xiàn)在 降解過程中透明度逐漸下降，表面變得粗糙，并且肉眼可見細微小泡 突起。該結(jié)果證明 DS04-W 菌株確實對 PLA 膜具有降解能力。4.最適 產(chǎn)酶條件的測定，首先從明膠、酪氨酸、酪蛋白、

3、酵母粉、蛋白胨中 選出最佳的誘導物，根據(jù)實驗結(jié)果選定為酵母粉；然后通過對溫度、pH 值、搖床轉(zhuǎn)數(shù)、接種量單因素水平進行測定，再進行四因素三水平的 正交實驗,確定最佳發(fā)酵條件為培養(yǎng)時間為 48h,培養(yǎng)基起始pH為8.5, 搖床轉(zhuǎn)速為 200r/min,種子培養(yǎng)基接種量為 6%(V/V)?！居⑽恼緼lo ng with the in creased to plastic products dema nd,it has brought the no ticeabl e en ergy crisis and the environment crisis.The ordinary plastic c

4、annot be degraded in the natural environment fordecades, therefore it is important to develop biodegradabl e plastic.Thedevelopme nt of biodegradable plastic mainly in clude polyesters, amongall polyesters, poly(L-Lactic acid) (PLA) is especially promising with itsexcelle nt physicochemical properti

5、es and the pote ntial price ben efit.Although PLA has dist inct adva ntagesin production and application over other polyesters, the study of itsbiodegradation is relatively lagging behind its syn thesis. In this thesis, wescree ning and appraisal from strains, determine the optimal conditions ofprod

6、ucting enzyme, isolate and purify of PLA degrading enzymes. Themajor results of the thesis are as follows:1. Poly (L-lactic acid)(PLA)-degrad ing stra in, was isolated by scree ning activated sludgeproduced from Fu shun petroleum factory. The PLA strain is numbered forDS04 - W.2. The DS04 W is obser

7、ved onmorphological, physiological and biochemical properties mensuration, anddetermine 16S rDNAsequenee. Finally the DS04Wis identified the bacterium Bacillus megaterium.3.The DS04WDacteria is determined the degradation ability of PLAfilm. The PLAfilm shape is observed with sca nning electro n micr

8、oscopy. Wefoundtransparency gradually declined, surface become coarse, and visible tosubtle vesicles swelled in degradation process. The result shows that theDS04- Wstrains of PLA has the degradation ability of PLA film.4. Theoptimal con diti ons of producti on PLA degrad ing en zyme is determ ined.

9、 First we should choose the best in ductor from gelat in, yeast powder,case in tyros ine, accord ing to the result of the experime nt selected foryeast powder for in ductor. Second we determ ine the temperature, pH ,wave bed RPM, ino culati on amount. Fin ally, through four factors of threelevels orthog onal experime nt, we determ ine the optimal ferme ntatio nconditions are 48h for training time, culture medium for 8.5, startingpHwave bed 200r/min, speed for seed mediuminoculatedqua ntity 6% (V/V).【關(guān)鍵詞】PLA 降解菌菌種鑒定最適產(chǎn)酶條