Environmental control of lipid and biomass production in two diatom species

Biomass and neutral lipid accumulation were examined in Chaetoceros muelleri var. subsalsum and Navicula saprophila using a multivariate, fractional factorial design. Variables included were conductivity, temperature, nitrogen concentration, silicon concentration, time (culture age), and alkalinity. Measured characteristics included nile red fluorescence (as a measure of neutral lipid content) and ash-free dry weight (AFDW). Nitrogen concentration was the variable with the greatest effect on neutral lipid and ash-free dry weight accumulation over the ranges tested. Increasing conductivity in the range examined had a significant, negative impact on neutral lipid accumulation in both of these strains, while increasing alkalinity had a positive effect on lipid and ash-free dry weight in both strains. Experimental designs such as those described here have great potential utility in biological systems with complex interactions.