Effects of Fed-batch and Nitrogen-deficient Culture on Lipid Yield of Chlorella sp.

[Objective] This study was to realize high-density culture of Chlorella sp. as well as the culture with high lipid yield. [Method] Through analyzing the growth curve of Chlorella sp. cells, dextrose consumption curve, change curves of pH and dissolved oxygen, a fed-batch culture was conducted, followed by a nitrogen-deficient culture aiming at accumulating the lipids in Chlorella sp. cells when a high density of Chlorella sp. cells was obtained. [Result] After four batches of feeding were pro- vided, the biomass of Chlorella sp. reached up to 65.25 g/L, and the lipid content increased from 42.75% to 63.82% in Chlorella sp. cells, with the yield of 43.37 g/L in the following 12 hours of nitrogen-deficient culture. [Conclusion] Reasonable fed- batch can significantly improve the biomass of Chlorella sp., and the nitrogen-defi- cient culture further raises the lipid yield of Chlorella sp.

Biomass,nutrient uptake and fatty acid composition of Chlamydomonas sp.ICE-L in response to different nitrogen sources

Nitrogen removal from media by microalgae provides the potential benefit of producing lipids for biodiesel and biomass. However, research is limited on algal growth and biomass under different nitrogen sources and provides little insight in terms of biofuel production. We studied the influences of nitrogen sources on cell growth and lipid accumulation of Chlamydomonas sp. ICE-L, one of a promising oil rich micro algal species. Chlamydomonas sp.ICE-L grown in NH_4 Cl medium had maximum growth rate. While the highest dry biomass of 0.28 g/L was obtained in media containing NH_4NO_3, the highest lipid content of 0.21 g/g was achieved under nitrogendeficiency condition with a dry biomass of 0.24 g/L. In terms of total polyunsaturated fatty acids（PUFAs）production, NH_4NO_3 and NH_4 Cl media performed better than nitrogen-deficiency and KNO_3 media.Furthermore, NH_4NO_3 and NH_4 Cl media elucidated better results on C18：3 and C20：5 productions while KNO_3and-N conditions were better in C16：0, C18：1 and C18：2, comparatively.

Oxidative Stressand Antioxidant Responses in Young Leaves of Mulberry Plants Grown Under Nitrogen, Phosphorus or Potassium Deficiency

The aim of this study was to associate the generation of reactive oxygen species （ROS） with Induced antloxidant responses and disturbed cellular redox environment in the nitrogen-（N）, phosphorus-（P）, or potassium-（K） deftcient mulberry （Morus alba L. var. Kanva-2） plants. The indicators of oxidative stress and cellular redox environment and antioxldant defense-related parameters were analyzed. Oeficlency of N, P or K suppressed growth, accelerated senescence, and decreased concentrations of chloroplastic pigments and glutathione. Lipid peroxidation and activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase were also increased in these N, P, or K deprived plants. Concentration of hydrogen peroxide Increased in plants deficient in N or P. Oeficlency of N or P particularly altered the cellular redox environment as indicated by changes in the redox couples, namely ascorbic acid/total ascorbate decreased in P-, glutathione sulfydryl/total glutathione decreased in N-, and Increased in P-deficient plants. Activity staining of native gels for superoxide dismutase revealed Increased activity as Indicated by Increased intensity of bands, and induction of few new isoforms in P- and K-deficient plants. Oifferences in the patterns of superoxide dismutase isoforms and redox status （ascorbic acid/total ascorbate and glutathlone sulfydryl/total glutathione） Indicate that N-, P-, or K-deficiency altered antioxidant responses to varying extents in mulberry plants.