碳源对粉核油球藻生长和脂肪酸组成特性的影响

研究了不同碳源类型（CO2、NaHCO3和葡萄糖）及其浓度对粉核油球藻（Pinguiococcus pyrenoidosus CCMP 2078）生长及脂肪酸组成的影响。结果表明：（1）培养液中适量添加碳源促进了粉核油球藻的生长，三种碳源的适宜添加浓度分别是0.5% CO2，5mmol/L NaHCO3和20g/L葡萄糖，对数生长末期的细胞密度分别是对照的3.10倍、1.47倍和2.78倍；（2）除了低浓度葡萄糖外，其他碳源类型和浓度均降低了TPUFA和EPA占总脂肪酸的比例，提高了TSFA的比例，胞内EPA和TSFA含量均下降；（3）低浓度碳源提高了TSFA和EPA产量。通入0.5% CO2培养的EPA和TSFA产量分别是对照的2.30倍和2.69倍，5mmol/L NaHCO3培养的TSFA产量是对照的1.85倍，5g/L和10g/L葡萄糖培养的EPA和TSFA产量最高分别可达对照的2.11倍和1.58倍。因此，通入低浓度CO2最有利于粉核油球藻的生长以及EPA和饱和脂肪酸的生产，EPA和饱和脂肪酸含量的提高主要是通过生物量的增大来实现的。

Effects of carbon sources on growth and fatty acid composition of Pinguiococcus pyrenoidosus CCMP 2078

Microalgae are potential sources of polyunsaturated fatty acids (PUFAs), mainly EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid). However, the EPA productivity of microalgae is lower compared with bacteria and fun-gi, and the reason is mainly the low growth rate and biomass under photoautotrophic conditions. To promote the EPA pro-ductivity, culture conditions such as culture temperature, irradiance, pH, nutrition sources and concentrations have been investigated. Nevertheless, some microalgae grow rapidly and have a higher biomass under mixotrophic conditions than which under photoautotrophic conditions. Pinguiococcus pyrenoidosus belongs to Pinguiophyceae, Pinguiococcus genara. The percentage of rude lipid content of the microalgae is 27.45% , among which EPA and saturated fatty acids (14:0, 16:0 ) are high, but the contents of other kinds of fatty acids are very low. So Pinguiococcus pyrenoidosus is a good materi-al for producing PUFAs and saturated fatty acids. So far, there is little information about the mixotrophic growth on the growth rate and fatty acid composition of the microalgae. In order to determine the optimal culture conditions, EPA pro-ductivity and saturated fatty acids productivity, effects of different carbon resources ( inorganic carbon compounds and or-ganic carbon compounds) on the growth and fatty acid composition in P. pyrenoidosus CCMP 2078 were investigated. The experimental method included the following three parts: First, three different concentration levels of CO2 were set, namely 0.5% , 1.0% and 1.5% ; Second, four different concentration levels of NaHCO3 were set, namely 5, 10, 20 and 25retool/L; Third, four different concentration levels of glucose were set, namely 5, 10, 20 and 40g/L, respectively. Pa-rameters of cell density and fatty acid composition were measured. The results showed that (1) Growth of P. pyrenoidosus CCMP 2078 was promoted by adding proper concentrations of carbon sources. The optimal concentrations of carbon sources for growth were 0.5% CO2, 5mmol/L NaHCO3 and 20g/L glucose, and the cell density of late logarithmic phage were 3.10-fold, 1.47-fold and 2.78-fold of that obtained under control; (2) When added the carbon sources except the low concentration of glucose, the percentages of TPUFA (Total polyunsaturated fatty acids)and EPA, and cell EPA and TSFA (Total saturated fatty acids) content were all lowered, but the percentage of TSFA was increased ; (3) The yield of SFAs (Saturated fatty acids)and EPA were enhanced when added low concentrations of carbon sources. The yield of EPA and TSFA were 2.30-fold and 2.69-fold when added 0.5% CO2 of those obtained under control, respectively. The yield of TSFA was 1.85-fold when added 5mmol/L NaHCO3 of that obtained under control. The maximum yield of EPA and TSFA were 2.11-fold and 1.58-fold when added 5g/L and 10g/L glucose of those obtained under control, respectively. Therefore, low concentration of CO2 was the optimal culture condition for the growth of P. pyrenoidosus CCMP 2078, and also for the yield of EPA and SFAs. The increases of EPA and TSFA were resulted by the enhancement of the biomass concentration.