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

doi:10.13560/j.cnki.biotech.bull.1985.2017-0519

Abstract

Abstract: Fast-growing Chlorella emersionii strain SXND-25 with great ability of purifying waste water was used as the target microalgae to investigate the effects of culture condition under varied nitrogen（N）concentration on microalgae biomass and oil yield,aiming at establishing an optimized culture system of such valued chlorella for commercial production of high quality biofuels. BG11 medium was used as the standard medium containing NaNO₃ as nitrogen（N）source（1 N）. This new strain of C. emersionii was continuously cultured in the medium 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 of optical 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 highest level 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 in the 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 on average. which was 1.4 folds of oil yield cultured in the standard medium（1 N）. Moreover,the fatty acid profile in the Chlorella cultured in 1/2 N-medium for 8 d was detected to be more suitable for production of high-quality biodiesel. In conclusion,comprehensive analysis of various indexes including biomass,oil content and oil yield per unit demonstrates that 0.75 g/L nitrogen concentration can be used as an optimized parameter for developing an effective cultivation system of this special Chlorella strain in producing high-quality biodiesel at large scale.

Key words: Chlorella emersionii, nitrogen-deficient cultivation, biomass, oil accumulation, fatty acid components

CHENG Wei-lan, SHAO Xue-mei, SONG Cheng-fei, SHI Fei-fei, JI Chun-li, LI Run-zhi. Effects of Nitrogen Stress on Growth and Oil Accumulation of Chlorella emersionii[J]. Biotechnology Bulletin, 2017, 33(11): 160-165.

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