氮胁迫对埃氏小球藻生长及油脂积累的影响

Effects of Nitrogen Stress on Growth and Oil Accumulation of Chlorella emersionii

以生长快、可除污的埃氏小球藻株系SXND-25为试材,研究不同氮浓度培养条件对其生物量和油脂产量的影响,以期建立优化培养体系利用该株小球藻生产优质生物燃油。以硝酸钠为氮源、BG11培养基中的氮浓度为基准(1.5 g/L),设置氮浓度梯度对小球藻进行培养。通过光密度测定、尼罗红染色、转酯化法抽提油脂和GC分析,对小球藻生物量、油脂含量及脂肪酸组分进行分析。结果显示,培养8 d时,在氮浓度为1.5 g/L时,生物量达到最大,干重为3.4 g/L,而油脂含量仅为28.24%,油脂产量为0.96 g/L;在氮浓度为0 g/L时生物量最小,干重为0.49 g/L,而油脂含量最高,为44.57%,油脂产量为0.22 g/L;在氮浓度为0.75 g/L时,干重为3.2 g/L,油脂含量为40.36%,油脂产量最高为1.3 g/L,是标准氮浓度下油脂产量的1.4倍。0.75 g/L氮浓度下连续培养8 d,藻油脂肪酸组成更适于制取优质生物柴油。综合生物量、油脂含量及脂肪酸组成等指标,确定0.75 g/L氮浓度为该埃氏小球藻株系规模化培养以生产优质生物燃油的优化参数。

Fast-growing Chlorella emersionii strain SXND-25 with great ability of purifying waste water was used as the target microalgaeto investigate the effects of culture condition under varied nitrogen（N）concentration on microalgae biomass and oil yield,aiming atestablishing an optimized culture system of such valued chlorella for commercial production of high quality biofuels. BG11 medium was usedas the standard medium containing NaNO_3 as nitrogen（N）source（1 N）. This new strain of C. emersionii was continuously cultured in themedium containing different nitrogen concentrations in the medium set as 0 g/L（0 N）,0.375 g/L（1/4 N）,0.75 g/L（1/2 N）,1.125 g/L（3/4 N）,and 1.5 g/L（1 N）,respectively. The biomass,oil content and fatty acid composition of the microalgae were analyzed by means ofoptical density measurement,Nile red staining,direct ester extraction of oil and GC analysis. When cultured in 1 N-medium for 8 d,the C.emersionii increased its biomass up to the maximum level with 3.4 g/L dry weight（DW）,whereas oil content was only 28.24% of DW,with 0.96 g/L oil yield on average. Culture of 8 days at 0 N-medium led to the minimum biomass of the C. emersionii with 0.49 g/L DW,but the highestlevel of oil accumulation（44.57% of DW）and small average oil yield（0.22 g/L）. Notably,cultivation of 8 d in 1/2 N-medium resulted inthe C. emersionii to achieve high biomass（3.2 g/L DW）and moderate oil contents（40.36% of DW）,but the highest oil yield of 1.3 mg/L onaverage. which was 1.4 folds of oil yield cultured in the standard medium（1 N）. Moreover,the fatty acid profile in the Chlorella cultured in1/2 N-medium for 8 d was detected to be more suitable for production of high-quality biodiesel. In conclusion,comprehensive analysis of variousindexes including biomass,oil content and oil yield per unit demonstrates that 0.75 g/L nitrogen concentration can be used as an optimizedparameter for developing an effective cultivation system of this special Chlorella strain in producing high-quality biodiesel at large scale.