Effects of temperature shifts on growth rate and lipid characteristics of Synechocystis sp. PCC6803 in a bench-top photobioreactor

Synechocystis sp. PCC6803 exhibited a high degree of variation in biomass and lipid production rates in response to temperature changes in a photobioreactor. Compared with an optimal temperature of 30–33 °C, a higher temperature of 44 °C and lower temperatures of 22 °C and 18 °C severely inhibited the specific growth rate (up to a 66% decrease), biomass production rate (up to a 71% decrease), nutrient utilization rates (up to a 77% decrease), and lipid production rate (up to a 80% decrease). Temperature stress triggered changes in the relative percentage of individual fatty acids (mainly for C16:0 and C18:3), and degree of unsaturation significantly changed: 0.87 at 30 °C, 0.62 at 44 °C, and 1.29 at 18 °C. Although PCC6803 survived temperature stress and maintained its predominate position in the culture, it could not fully recover from long-term temperature stress. Thus, avoiding prolonged exposure to extreme temperature is crucial for using PCC6803 as feedstock for biofuel production.

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► Temperature shifts significantly affected the lipid production rate of Synechocystis.
► Exposure to 44 °C, 22 °C, and 18 °C severely inhibited lipid production.
► Temperature shifts also triggered major variations in individual fatty acids in the lipids.
► The degree of unsaturation changed from 0.87 at 30 °C, to 0.62 at 44 °C, and to 1.29 at 18 °C.
► Prolonged exposure of Synechocystis to extreme temperatures must be avoided if biofuel production is the goal.