|Abstract: ||聚羥基丁酯(PHB)具有良好的生物降解性、生物相容性及熱塑性等特質，可用來取代傳統高分子材料，避免造成環境的負擔。本研究主要探討放線菌Streptomyces sp. 77T-4對PHB薄膜的分解行為和機制；另外，藉由製備PHB/PVAc和PHB/Biomax摻合薄膜，比較其放線菌Streptomyces sp. 77T-4分解行為的差異。利用溶劑揮發法和融熔熱壓法分別製備表面多孔性和緻密性的PHB薄膜，將所製備的薄膜，經由菌體分解後，由SEM、DSC、GPC、重量損失分析及表面接觸角等測量分解過程中的變化。經由SEM觀察結果，放線菌Streptomyces sp. 77T-4會分泌PHB分解酵素來侵蝕材料的表面，雖然PHB/PVAc和PHB/Biomax摻合薄膜表面皆有分解的現象，但依然可分辨各自為完全相容的摻合系統和不相容的摻合系統。而且發現PHB材料的表面積越大，菌體接觸到高分子的機率越多，而分泌PHB分解酵素的時間會提早，材料的分解程度也會增加；若再利用PHB懸浮液誘導放線菌Streptomyces sp. 77T-4後，可提升材料分解的效率。並且依據DSC和GPC的測試結果，不同分解時間下PHB薄膜的結晶度和分子量，不會隨著分解時間的改變而變化，這是由於PHB分解酵素分解PHB高分子鏈的速度比酵素擴散進入材料的速度還要快速的原因。依據上述結果，本實驗推擬出放線菌Streptomyces sp. 77T-4分解PHB薄膜之機制為 – 初期，菌體會逐漸適應PHB高分子，而活化PHB分解酵素合成機制。之後，則會開始大量的的生產PHB分解酵素，使酵素經擴散作用進入PHB薄膜，造成薄膜表面產生均勻的孔洞，而釋放寡聚物(oliomer)或是羥基丁酸單體，則可作為 Streptomyces sp. 77T-4之營養源而被吸收。|
Poly(3-hydroxybutyrate)(PHB) has many good characteristics, like biodegradable, biocompatiblity and plasticity, etc, it’s could be use to substitute for the traditional polymeric materials and avoid to be a environmental burden. This research mainly discusses the degradation behavior and mechanism of Streptomyces sp. 77T-4 on PHB film. Moreover, respectively make the PHB/PVAc and PHB/Biomax blend films, compared with the difference of their degradation behaviors with Streptomyces sp. 77T-4. Using the solution-evaporation and thermal pressurization to make the films with respectively the surface of porous and dense, and after the degradation by bacteria, exact the change between original and final one by SEM, DSC, GPC, thickness-loss analysis and weight-loss analysis.
As the result of the SEM, we found that the PHB degradation enzyme Streptomyces sp. 77T-4 secreted can erosion the material surface. Although the surface of PHB/PVAc and PHB/Biomax blend films both have the phenomenon of erosion, but it still could be differentiate to the two different system of miscible system and immiscible system.
And as the results of the degradation analyses by Streptomyces sp. 77T-4, the bigger of the surface area of PHB material, the more probability of the bacterium touch polymers, and the faster the PHB degradation enzyme secreted, and then the extent of material degradation would be increased. If using PHB suspension to induces Streptomyces sp. 77T-4 to secrete the degradation enzyme, may promote the efficiency of the degradation of PHB film. And by the tests of the DSC and GPC, we found that under the different degradation time, the crystallinity and the molecular weight of the PHB film will not change, because of the speed of the PHB degradation enzyme degraded the PHB polymer chain is faster than the speed of the enzyme diffused into the material.
Based on the above results, the progress had extrapolated the degradation mechanism of PHB film by Streptomyces sp. 77T-4 to be – the initial period, 77T-4 would adapt the PHB high polymer gradually, and activate the synthesis mechanism of the PHB degradation enzyme. Afterward, 77T-4 would massively product PHB decomposition enzyme, and the enzyme entered into the PHB film through diffusion to make the even pores on the film surface, and released oligomers or the hydroxy-butyric acid monomer which may be nutrition of source and absorb by the 77T-4.