Effect of pH and starvation shocks on omega3 fatty acids level in Chlorella sp.

Effect of pH and starvation shocks on omega3 fatty acids level in Chlorella sp.

Chlorella sp. has been widely used as animal feed additives because of its high content of proteins, fatty acids, dietary fibers, carotenoids, vitamins, minerals, and other bioactive compounds. The biochemical compositions of microalgae is altered with the change in pH, temperature, photoperiod, salinity and metal content in the culture media. Moreover the studies demonstrated that N and/or P limitation in growth media causes metabolism alterations that induce lipid accumulation. The aim of this study was to evaluate the effect of pH and starvation shocks individually and in combinations on docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA), linoleic acid and linolenic acid in Chlorella sp. The algae were cultivated in ten-liter conical flasks for biomass production for 12 days using Guillard medium (f/2). The cells were reared at 0.5 molar salinity (29 ppt), under 3500 lux light intensity with a 12L:12D photoperiod and 21ºC temperature. After 12 days when the cell reached to its optimum density they were centrifuged. The pellet were then resuspended in fresh sea water thoroughly and transferred into 16 containers with 10 liter volume including 3 treatments and a control group in four replicates. The algae in treatments 2 to 4 were subjected to starvation, pH + starvation and pH respectively. The pH shock used in this research was pH=11. The results revealed that the docosahexaenoic acid (0.74±0.05) and linolenic acid (12.01±0.80) under pH + starvation shock on day 18 and at the end of light period exhibited significantly higher value in compare to control group (p 0.05). Furthermore At the end of day 18, Linoleic acid under pH shock and at the end of dark period showed significantly higher value compare to control. While the arachidonic acid level exhibited significantly higher level in chlorella under pH+ starvation shock (2.03±0.13) and at the end of light period (p 0.05).Based on this study, the best result obtained for induction of omega3 fatty acids production in chlorella sp. was using the combination of nutrients starvation and high basic pH (pH=11) at the end of light photoperiod.

Chlorella sp. has been widely used as animal feed additives because of its high content of proteins, fatty acids, dietary fibers, carotenoids, vitamins, minerals, and other bioactive compounds. The biochemical compositions of microalgae is altered with the change in pH, temperature, photoperiod, salinity and metal content in the culture media. Moreover the studies demonstrated that N and/or P limitation in growth media causes metabolism alterations that induce lipid accumulation. The aim of this study was to evaluate the effect of pH and starvation shocks individually and in combinations on docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA), linoleic acid and linolenic acid in Chlorella sp. The algae were cultivated in ten-liter conical flasks for biomass production for 12 days using Guillard medium (f/2). The cells were reared at 0.5 molar salinity (29 ppt), under 3500 lux light intensity with a 12L:12D photoperiod and 21ºC temperature. After 12 days when the cell reached to its optimum density they were centrifuged. The pellet were then resuspended in fresh sea water thoroughly and transferred into 16 containers with 10 liter volume including 3 treatments and a control group in four replicates. The algae in treatments 2 to 4 were subjected to starvation, pH + starvation and pH respectively. The pH shock used in this research was pH=11. The results revealed that the docosahexaenoic acid (0.74±0.05) and linolenic acid (12.01±0.80) under pH + starvation shock on day 18 and at the end of light period exhibited significantly higher value in compare to control group (p 0.05). Furthermore At the end of day 18, Linoleic acid under pH shock and at the end of dark period showed significantly higher value compare to control. While the arachidonic acid level exhibited significantly higher level in chlorella under pH+ starvation shock (2.03±0.13) and at the end of light period (p 0.05).Based on this study, the best result obtained for induction of omega3 fatty acids production in chlorella sp. was using the combination of nutrients starvation and high basic pH (pH=11) at the end of light photoperiod.