摘要微生物能在一定条件下将碳源高效转化成微生物油脂，对于破解自然资源日益匮乏与油脂需求却不断增长的难题具有重要的研究价值。本文对脱脂蚕蛹培养产油微生物裂殖壶菌的生物合成过程进行分析，通过调节温度、pH等环境因子和添加系列的前体以期获得高产的微生物油脂，并考察了前体对油脂代谢关键酶的相关影响。87116

首先，考察环境因子对裂殖壶菌合成油脂过程的影响。在温度18 ~28 ℃、盐浓度1。8~3。6 g/L和pH值4~7条件范围下，裂殖壶菌生长良好，油脂含量和DHA含量较高。当温度25 ℃、盐浓度1。8 g/L以及pH值为6时，生物量为25。68±0。88 g/L，油脂产量为19。80±1。26 g/L，DHA的产量为 4。21±0。37 g/L。因此，生物量提高了38。89%，油脂含量提高了12。31%，DHA含量提高了29。94%。

其次，考察添加前体对裂殖壶菌合成油脂过程中各指标的影响。添加柠檬酸为前体时，生物量随其添加量的变化不显著，而油脂和DHA含量变化显著。当其浓度为3 g/L时，油脂和DHA的含量分别为0。39±0。01 g/g和0。44±0。01 g/g，与对照组相比，提高了21。88%和25。71%。添加蚕蛹油为前体时，生物量有微量增加，油脂含量变化不显著，但DHA显著增加。当其浓度为0。08 g/L时，DHA含量为0。43±0。02 g/g，与对照相比，提高了21。88%。吐温-80对其生物量和油脂含量影响不显著，而对DHA影响显著。当添加0。06 g/L吐温-80，DHA含量为0。48±0。01 g/g，与对照组相比，提高了37。14%。

再次，对裂殖壶菌油脂代谢途径中的关键酶进行活性分析。添加柠檬酸后，苹果酸酶（Malic enzyme ME）、脂肪酸合成酶（Fatty acid synthetase FAS）和ATP-柠檬酸裂解酶（ATP-citrate lyase ACL）活性分别在72、56和46 h时达到最大值，为0。76±0。05、2。90±0。14和1。69±0。05 U/mg。添加蚕蛹油后，ME、FAS和ACL活性分别在64、56和56 h时达到最大值，为0。35±0。04、2。42±0。14和1。57±0。06 U/mg。添加吐温-80后，ME、FAS和ACL活性分别在32、40和48 h时达到最大值，为0。41±0。02、1。20±0。09和1。89±0。05U/mg。FAS和ACL的活性变化和油脂累积的变化趋势一致，但ME的活性变化与油脂累积的过程不同步。因此，FAS和ACL是油脂累积的限速酶。考虑到ME参与的三羧酸循环是NADPH的唯一来源，因此ME也是油脂累积的关键酶。

最后，探索裂殖壶菌利用产油酵母发酵液生产DHA的可行性。考虑到经济性和高效性，选取废水原液与蒸馏水的比例为2:1，初始培养基中甘油浓度为80 g/L，水解液添加量为10 g/L，DHA含量为0。37±0。01 g/g，与对照组相比，提高了18。75%。

毕业论文关键词：脱脂蚕蛹 ；产油微生物；前体物质；酶活；DHA

Abstract Microorganisms can efficiently convert carbon source into microbial oil under certain conditions, which is of great value to solve the problem of increasing scarcity of natural resources and the growing demand for oil。 The analysis of the whole process of defatted silkworm chrysalis cultivation oleaginous microorganisms, the increasing microbial oil production and key enzymes were conducted by regulating temperature, pH and other environmental factors and adding different precursors。 

First of all, the effect of environmental factors on the process of synthesis of oil from S。 limacinum SR21 was investigated。 When the temperature was in the range of 18 ~28 ℃, the salt concentration was in the range of 1。8~3。6 g/L and pH was in the 4~7, The biomass, oil content and DHA content of S。 limacinum SR21 were higher。 Suitable conditions were selected under the consideration of cell growth and oil production。 When the temperature was 25 ℃, the salt concentration was 1。8 g/L and pH was 6, the biomass of S。 limacinum SR21 was 25。68 ± 0。88 g/L, the oil content was 19。80 ±1。26 g/L and the DHA content was 4。21±0。37 g/L。 Therefore, the biomass was increased by 38。89 %, the oil content was increased by 12。31%, and the DHA content was increased by 29。94 %。