利用 Bacillus sp. 相關菌株生產聚羥基丁酸(PHB)與聚羥基戊酸（PHV）共聚物及其性質探討

Abstract

Polyhydroxylalkanoates (PHA) are biodegradable polyesters that are accumulated in various microorganisms as intracellular carbon and energy storage material under nutrient-limited conditions. This study aimed to screen better production strains in order to obtain more efficient production of Polyhydroxylalkanoates from Bacillus sp. YW1, Bacillus sp. YW2 and Bacillus sp. YW3. This studies shown that these strains could be improved to grow and further synthesize PHB using various carbon sources. This work also suggests that the bacterial growth could be improved which the medium contain various organic acids. On the other hand, these strains could accumulate PHA when adding tryptone in media. A semi-synthesized medium (LBS medium) was developed for this study which could be able to support the growth of this Bacillus sp. YW1 and Bacillus sp.YW2 with 10 g/L PHB production and PHB content over 30%, respectively. Temperature, pH and agitation rate are common environmental factors that play a crucial role in cell growth and PHB production. The optimal culture condition 30℃, pH 7, 200 rpm was used as the standard experimental condition. From this work, we found that the strains Bacillus sp. YW1 and YW2 could be induced to accumulate PHV over 12 %. PHA in the cell were purified primarily via different methods. The chemical structure and molecular masses of the purified PHA product were confirmed by nuclear magnetic resonance (1H-NMR & 13C-NMR) spectrometer and Gas Chromatography-Mass spectrometry (GC-MS), respectively. The property of the PHAs produced by Bacillus sp. strains isolated in this study was in consistent with the standard purchased from Sigma Co., indicating that Bacillus sp. strains are PHBV-synthesizing strain. Further analysis indicated that the PHV mole% of YW1 and YW2 strains were around 30%. According to analysis of GPC, the average Molecule weight was Mw=300,000 to 400,000; the strains YW1’s PDI was 4.71 and YW2’s PDI was 2.62. Besides, the data of TGA illustrated that PHBV has stable heat property. Moreover, the PHBV may be half-crystal polymer using DSC.