CELL CULTLURE ENGINEERING AND OPTIMAL CONDITIONS OF GREEN AND BROWN MICROALGAE FOR LIPID PRODUCTION

Algal engineering is gaining increasing attention due to the demand for economical
bioenergy production, environmental remediation and high value biochemicals. Lipids
and fatty acids are the target compounds for bioenergy. Optimum pH_ salinity,
photoperiod, light intensity and macronutrients can enhance algal biomass and lipid
productivity. Our study described the growth parameters that could affect locally-isolated
green Nannochloropsis oculata and Tetraselmis suecica and brown Isochrysis galbana and Pavlova lutheri microalgae. Optimization was carried out using
Response Surface Methodology (RSM) to elucidate interaction between factors and to
predict optimum levels for further validation. The cell densities, dry weight and lipid
content increased with the increase of pH_ salinity, photoperiod and light intensity for
all the four tested species. The optimum pH and salinity were pH 8-9 and salinity of
35-40 ppt to achieve cell dry weight of 0.58-0.82 g L' 1
: and lipid content of 27.4-
37.3%. The maximum cell dry weight of 0.66-0.84 g L' 1
: and lipid content of 23.9-
36.6% were achieved at optimal 19.3-24 h illumination and light intensity of 162-198
μmol photons m· 2s 1
. The highest lipid accumulation of 37.3, 23.6, 28.3 and 37.2%
with slightly reduced cell growth of 0.64, 0.49, 0.54 and 0.38 g L- 1 were achieved for
,V oculala, T suecica, I galbana and P. lulheri respectively, when cultures were
grown under deficiency conditions of 10-65 g L- 1 KN03, 3-7.5 g L- 1 Na2HP04 and 2.5
g L'1 FeCI;. The interactions of pH, salinity, photoperiod and light intensity and
macronutrients significantly influenced the biomass and lipid content positively. The
interaction of phosphate-phospate for N oculata and nitrate-nitrate for I galbana may
affect cell growth negatively. The interaction of nitrate, phosphate, phosphatephosphate
and ferum-ferum interactions may all affect lipid content negatively. The
r2of 78.7-95.1% for biomass and 80.1-97.5% for lipid and mean absolute error
percentage between experimental and predicted values of 0.02-0.042% and 0.6 I-
1.66% t(Jr biomass and lipid content suggest good agreements between experimental
and predicted values.