1. 毕业设计（论文）的内容和要求

生物表面活性剂（surfactin）是由一条β-羟基脂肪酸和具有不同手性的七氨基酸缩肽通过内酯键连接而成；它是芽孢杆菌产生的一种次级代谢产物，具有可降解，低毒的特点，在医药、食品、生物修复、生物防治等方面具有很大的潜在应用价值。

相比于已经深入研究的nrps催化surfactin肽环结构的合成，surfactin分子中脂酰基结构的合成途径研究则显得很单薄。

surfactin中脂肪链的长度一般为c12-c16，通常以c14和c15组分为主（~60-80%），脂肪酸组分的结构差异也会对物理化学性质和生物活性产生显著的影响。

2. 参考文献

[1] Zhu L, Xu Q, Jiang L, Huang H, Li S. Polydiacetylene-based high-throughput screen for surfactin producing strains of Bacillus subtilis [J]. Plos One, 2014, 9(2): e88207. [2] Yi G, Liu Q, Lin J, Wang W, Huang H, Li S. Repeated batch fermentation for surfactin production with immobilized Bacillus subtilis BS‐37: two‐stage pH control and foam fractionation [J]. Journal of Chemical Technology and Biotechnology, 2017, 92(3): 530-535. [3] Coutte F, Lecl#232;re V, B#233;chet M, Guez JS, Lecouturier D, Chollet-Imbert M, Dhulster P. Effect of pps disruption and constitutive expression of srfA on surfactin productivity, spreading and antagonistic properties of Bacillus subtilis 168 derivatives [J]. Journal of Applied Microbiology, 2010, 109(2): 480-491. [4] Dhali D, Coutte F, Arias AA, Auger S, Bidnenko V, Chataign#233; G, Lalk M, Niehren J, Sousa JD, Versari C, Jacques P. Genetic engineering of the branched fatty acid metabolic pathway of Bacillus subtilis for the overproduction of surfactin C14 isoform [J]. Biotechnology Journal, 2017. [5] Youssef NH, Duncan KE, McInerney MJ. Importance of 3-hydroxyfatty acid composition of lipopeptides for biosurfactant activity [J]. Applied and Environmental Microbiology, 2005, 71(12): 7690#8211;7695. [6] Liu Q, Lin J, Wang W, Huan H, Li S. Production of surfactin isoforms by Bacillus subtilis BS-37 and its applicability to enhanced oil recovery under laboratory conditions [J]. Biochemical Engineering Journal, 2015, 93: 31-37. [7] Yao S, Lu Z, Hao T, LV F, Bie X. Effect of amino acids and carbon backbone precursors on surfactin biosynthesis [J]. Journal of Nanjing Agricultural University, 2014, 37(2): 139-145. 姚树林, 陆兆新, 郝天怡, 吕凤霞, 别小妹. 氨基酸和碳架物质前体对 surfactin 生物合成的影响 [J]. 南京农业大学学报, 2014, 37(2)：139-145. [8] Liu J, Yang J, Yang S, Ye R, Mu B. Effects of different amino acids in culture media on surfactin variants produced by Bacillus subtilis TD7 [J]. Applied Biochemistry and Biotechnology, 2012, 166(8): 2091-2100. [9] Coutte F, Niehren J, Dhali D, John M, Versari C, Jacques P. Modeling leucine's metabolic pathway and knockout prediction improving the production of surfactin, a biosurfactant from Bacillus subtilis [J]. Biotechnology Journal, 2015, 10(8): 1216-1234. [10] Kraas FI, Helmetag V, Wittmann M, Strieker M, Marahie MA. Functional dissection of surfactin synthetase initiation module reveals insights into the mechanism of lipoinitiation [J]. Chemistry Biology, 2010, 17(8): 872-880. [11] Singh A K，Zhang Y, Zhu K，et al. FabH selectivity for anteiso branched-chain fatty acid precursors in low-temperature adaptation in Listeria monocytogenes[J]. FEMS microbiology letters, 2009, 301(2): 188-192. [12] Park J H Lee S Y. Metabolic pathways and fermentative production of L -aspartate family amino acids [J]. Biotechnology Journal, 2010, 5(6): 560-577.

3. 毕业设计（论文）进程安排

12.1~12.31 文献查阅及资料研读 1.1~1.17 确定实验方案及开题报告写作 1.18~3.28 基因的敲除 4.1~4.30 分析方法与发酵工艺建立 5.1~5.31 实验结果分析