Fractional factorial design-based evaluation of physicochemical parameters affecting biodiesel properties from Chlorella sp. PG96
Journal
Aquacultural Engineering
ISSN
0144-8609
Date Issued
2026-01
Author(s)
Abstract
Biodiesel, as a renewable energy source synthesized through the transesterification of algal lipids, has received increasing attention in recent years. The quality of biodiesel derived from microalgal lipids depends largely on the composition of fatty acid methyl ester in the fuel.
This research employed a fractional factorial design (2 ¹¹⁻⁷) to statistically screen eleven independent factors, including NaHCO3, CO2, MgSO4.7H2O, K2HPO4, NaNO3, NH4Cl, salinity, light spectrum, aeration rate, light intensity, and temperature, for achieving a rich fatty acid profile by Chlorella sp. PG96 (a strain isolated from municipal wastewater), as well as the synthesis of superior-quality biodiesel. The effects of all eleven physicochemical factors and their interactions on the growth characteristics (biomass and lipid production) of Chlorella sp. PG96 were thoroughly investigated in our previous study.
According to the experimental results of the present study, the maximum concentrations of palmitic acid (32.23 ± 2.87 %), oleic acid (31.53 ± 3.31 %), saturated fatty acids (38.07 ± 4.03 %), and monounsaturated fatty acids (33.63 ± 3.36 %) in microalgal lipids were obtained when Chlorella sp. PG96 was grown at a low NaHCO3 concentration (0 mg L⁻¹) and white light irradiation. The estimated values of biodiesel properties such as iodine value, unsaturation degree, oxidation stability, cetane number, higher heating value, density, and kinematic viscosity were all in accordance with the quality benchmarks established by ASTM and EN 14214.
The findings further demonstrated that temperature and light intensity represented the key determinants influencing fatty acid composition. Aeration rate and salinity had the most significant effects on the cetane number index, whereas the oxidation stability of algal oil was markedly affected by the concentrations of NaNO₃ and NaHCO₃. Moreover, ammonium as a nitrogen source and bicarbonate as a carbon source exhibited greater significance in fatty acid biosynthesis compared with nitrate and CO₂, respectively.
The interactions between NaHCO₃ and the light spectrum, as well as between NaHCO₃ and NH₄Cl, were found to be the most significant for all measured responses. It is suggested that Chlorella sp. PG96, when cultivated with elevated NH₄Cl concentration and light intensity but under reduced temperature (320 mg L⁻¹, 22,500 Lux, and 20 °C, respectively), may act as a promising feedstock for biodiesel production.
This research employed a fractional factorial design (2 ¹¹⁻⁷) to statistically screen eleven independent factors, including NaHCO3, CO2, MgSO4.7H2O, K2HPO4, NaNO3, NH4Cl, salinity, light spectrum, aeration rate, light intensity, and temperature, for achieving a rich fatty acid profile by Chlorella sp. PG96 (a strain isolated from municipal wastewater), as well as the synthesis of superior-quality biodiesel. The effects of all eleven physicochemical factors and their interactions on the growth characteristics (biomass and lipid production) of Chlorella sp. PG96 were thoroughly investigated in our previous study.
According to the experimental results of the present study, the maximum concentrations of palmitic acid (32.23 ± 2.87 %), oleic acid (31.53 ± 3.31 %), saturated fatty acids (38.07 ± 4.03 %), and monounsaturated fatty acids (33.63 ± 3.36 %) in microalgal lipids were obtained when Chlorella sp. PG96 was grown at a low NaHCO3 concentration (0 mg L⁻¹) and white light irradiation. The estimated values of biodiesel properties such as iodine value, unsaturation degree, oxidation stability, cetane number, higher heating value, density, and kinematic viscosity were all in accordance with the quality benchmarks established by ASTM and EN 14214.
The findings further demonstrated that temperature and light intensity represented the key determinants influencing fatty acid composition. Aeration rate and salinity had the most significant effects on the cetane number index, whereas the oxidation stability of algal oil was markedly affected by the concentrations of NaNO₃ and NaHCO₃. Moreover, ammonium as a nitrogen source and bicarbonate as a carbon source exhibited greater significance in fatty acid biosynthesis compared with nitrate and CO₂, respectively.
The interactions between NaHCO₃ and the light spectrum, as well as between NaHCO₃ and NH₄Cl, were found to be the most significant for all measured responses. It is suggested that Chlorella sp. PG96, when cultivated with elevated NH₄Cl concentration and light intensity but under reduced temperature (320 mg L⁻¹, 22,500 Lux, and 20 °C, respectively), may act as a promising feedstock for biodiesel production.