title: Carbon-to-nitrogen ratio affects the biomass composition and the fatty acid profile of heterotrophically grown Chlorella sp. TISTR 8990 for biodiesel production.
abstract: Chlorella sp. TISTR 8990 was cultivated heterotrophically in media with various initial carbon-to-nitrogen ratios (C/N ratio) and at different agitation speeds. The production of the biomass, its total fatty acid content and the composition of the fatty acids were affected by the C/N ratio, but not by agitation speed in the range examined. The biomass production was maximized at a C/N mass ratio of 29:1. At this C/N ratio, the biomass productivity was 0.68gL(-1)d(-1), or nearly 1.6-fold the best attainable productivity in photoautotrophic growth. The biomass yield coefficient on glucose was 0.62gg(-1) during exponential growth. The total fatty acids (TFAs) in the freeze-dried biomass were maximum (459mgg(-1)) at a C/N ratio of 95:1. Lower values of the C/N ratio reduced the fatty acid content of the biomass. The maximum productivity of TFAs (186mgL(-1)d(-1)) occurred at C/N ratios of 63:1 and higher. At these conditions, the fatty acids were mostly of the polyunsaturated type. Allowing the alga to remain in the stationary phase for a prolonged period after N-depletion, reduced the level of monounsaturated fatty acids and the level of polyunsaturated fatty acids increased. Biotin supplementation of the culture medium reduced the biomass productivity relative to biotin-free control, but had no effect on the total fatty acid content of the biomass.
authors.affiliation: Biotechnology Program, School of Agricultural Technology, Walailak University, Nakhon Si Thammarat 80161, Thailand.
authors.forename: Somruethai
authors.initials: S
authors.lastname: Singhasuwan
authors.affiliation: Biotechnology Program, School of Agricultural Technology, Walailak University, Nakhon Si Thammarat 80161, Thailand. Electronic address: cwanna35@gmail.com.
authors.forename: Wanna
authors.initials: W
authors.lastname: Choorit
authors.affiliation: Department of Biotechnology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand.
authors.forename: Sarote
authors.initials: S
authors.lastname: Sirisansaneeyakul
authors.affiliation: Department of Civil Engineering, Walailak University, Nakhon Si Thammarat 80161, Thailand.
authors.forename: Nakhon
authors.initials: N
authors.lastname: Kokkaew
authors.affiliation: School of Engineering, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Chisti
mesh_terms: D056804:Biofuels; D018533:Biomass; D001710:Biotin / Q000494:pharmacology; D002244:Carbon / Q000378:metabolism*; D002708:Chlorella / Q000187:drug effects / Q000254:growth & development*; D004952:Esters / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D052836:Heterotrophic Processes / Q000187:drug effects; D009584:Nitrogen / Q000378:metabolism*
chemical_list: D056804:Biofuels; D004952:Esters; D005227:Fatty Acids; D001710:Biotin; D002244:Carbon; D009584:Nitrogen
keywords: Biodiesel; C/N ratio; Chlorella; Fatty acid composition; Heterotrophic growth; Microalgae