Strain variation in microalgal lipid production during mixotrophic growth with glycerol

• The maximum growth rate under mixotrophic conditions varied greatly with strain.
• Glycerol increased the growth rate 2.4-fold.
• Glycerol increased biomass 1.9-fold.
• Glycerol increased total lipid production 40–60% in some strains.
• Strain PCH02 showed a large increase in lipid with glycerol addition.

Algal cultivation at high latitudes is challenged by the relatively low annual solar flux. One possible scenario to overcome this limitation is the use of mixotrophic growth to potentially boost biomass and lipid production. Here the effect of glycerol addition on the growth and lipid production by twelve indigenous microalgae was examined. The results show that there is considerable strain dependent variation in the maximum growth rate under mixotrophic conditions with the addition of glycerol causing in some cases up to a 2.4-fold increase in growth rate and a up to a 1.9-fold increase in biomass. In addition, glycerol increased total lipid production 40–60% in some strains. These results also show the value in screening culture collections for desired traits independent of strain identification since here one (PCH02) of the five Chlorella strains showed a large increase in lipid with glycerol.