Alternative Respiration Induced by Glucose Stimulation and Variation of Adenylate Energy Charge in Glucose-Starved Cells of Green Alga Chlorella Protothecoides

Effects of inhibitors and glucose on cytochrome and alternative respiration and on adenylate energy charge (AEC) in glucose starved Chlorella protothecoides were investigated. 1 mmol/L azide (NaN 3), which immediately caused an increase of O 2 uptake by inhibiting the cytochrome pathway and stimulating alternative respiration, resulted in a decrease of AEC value from 0.83 to 0.34 within 3 minutes. When 1 mmol/L salicylhydroxamic acid (SHAM) was added into the cell suspension, there was no apparent variation in AEC. Adding NaN 3 and SHAM together into cell suspension to inhibit both cytochrome and alternative pathways showed a same change of AEC as that of adding NaN 3 alone. When 2.0 mmol/L of glucose was added to a suspension of glucose starved cells, the O 2 uptake rate was immediately stimulated from 0.81 up to 1.34 [μmol/L O 2[DK]·min -1 ·(mL PCV) -1 ]. The respiration stimulated by glucose could be inhibited about 20% by adding 1 mmol/L SHAM. It was found by titration with SHAM in the absence and presence of NaN 3 that 53% of O 2 uptake went through the cytochrome pathway and 45% of the alternate pathway was operational in enhanced respiration. It implied that induced operation of the alternative respiratory pathway probably resulted from the burst of the electron flux into the electron transport chain by glucose stimulation. . The respiration stimulated by glucose could be inhibited about 20% by adding 1 mmol/L SHAM. It was found by titration with SHAM in the absence and presence of NaN 3 that 53% of O 2 uptake went through the cytochrome pathway and 45% of the alternate pathway was operational in enhanced respiration. It implied that induced operation of the alternative respiratory pathway probably resulted from the burst of the electron flux into the electron transport chain by glucose stimulation.

Effect of nitrogen and extraction method on algae lipid yield

Effects of nitrogen source and concentration as well as lipid extraction method on the lipid yield of autotrophic Scenedesmus dimorphus and heterotrophic Chlorella protothecoides were studied.Three concentration levels of nitrate,urea and glycine/yeast extract as the nitrogen source were investigated.The highest lipid yield of S.dimorphus in the 17-d autotrophic culture was 0.40 g/L from the 1.8 g/L urea medium,and the maximum lipid yield of C.protothecoides in the nine-day heterotrophic culture was 5.89 g/L from the 2.4 g/L nitrate medium.Four different cell disruption methods-bead-beater,French press,sonication and wet milling-were studied for their effectiveness in solvent extraction of algal lipids from S.dimorphus and C.protothecoides.Wet milling followed by hexane extraction was most effective for S.dimorphus lipid extraction,whereas bead-beater disruption followed by hexane extraction was best for C.protothecoides.