The effect of mixotrophy on microalgal growth, lipid content, and expression levels of three pathway genes in Chlorella sorokiniana

Nannochloropsis oculata CCMP 525, Dunaliella salina FACHB 435, and Chlorella sorokiniana CCTCC M209220 were compared in mixotrophic and photoautotrophic cultures in terms of growth rate, protein, and lipid content. Growth improved in glucose, and the biomass productivities of N. oculata, D. salina, and C. sorokiniana were found to be 1.4-, 2.2- and 4.2-fold that observed photoautotrophically. However, biomass and lipid production decreased at the highest glucose concentrations. Meanwhile, the content of protein and lipid were significantly augmented for mixotrophic conditions at least for some species. C. sorokiniana was found to be well suited for lipid production based on its high biomass production rate and lipid content reaching 51% during mixotrophy. Expression levels of accD (heteromeric acetyl-CoA carboxylase beta subunit), acc1 (homomeric acetyl-CoA carboxylase), rbcL (ribulose 1, 5-bisphosphate carboxylase/oxygenase large subunit) genes in C. sorokiniana were studied by real-time PCR. Increased expression levels of accD reflect the increased lipid content in stationary phase of mixotrophic growth, but expression of the acc1 gene remains low, suggesting that this gene may not be critical to lipid accumulation. Additionally, reduction of expression of the rbcL gene during mixotrophy indicated that utilization of glucose was found to reduce the role of this gene and photosynthesis.

[1]  N. Xu,et al.  Effects of organic carbon sources on growth, photosynthesis, and respiration of Phaeodactylum tricornutum , 2009, Journal of Applied Phycology.

[2]  Grover L Waldrop,et al.  Multi-subunit acetyl-CoA carboxylases. , 2002, Progress in lipid research.

[3]  M. Orús,et al.  Interactions between Glucose and Inorganic Carbon Metabolism in Chlorella vulgaris Strain UAM 101. , 1991, Plant physiology.

[4]  A. Dalai,et al.  Preparation and characterization of bio-diesels from various bio-oils. , 2001, Bioresource technology.

[5]  S. Jia,et al.  Growth characteristics of the cyanobacterium Nostoc flagelliforme in photoautotrophic, mixotrophic and heterotrophic cultivation , 2009, Journal of Applied Phycology.

[6]  W. Cong,et al.  Growth characteristics and eicosapentaenoic acid production by Nannochloropsis sp. in mixotrophic conditions , 2004, Biotechnology Letters.

[7]  Luísa Gouveia,et al.  Neochloris oleabundans UTEX #1185: a suitable renewable lipid source for biofuel production , 2009, Journal of Industrial Microbiology & Biotechnology.

[8]  A. Richmond,et al.  An industrial-size flat plate glass reactor for mass production of Nannochloropsis sp. (Eustigmatophyceae) , 2001 .

[9]  Feng Chen,et al.  High cell density culture of microalgae in heterotrophic growth , 1996 .

[10]  L. Barton,et al.  Microalgae as food and supplement. , 1991, Critical reviews in food science and nutrition.

[11]  Yanna Liang,et al.  Biomass and lipid productivities of Chlorella vulgaris under autotrophic, heterotrophic and mixotrophic growth conditions , 2009, Biotechnology Letters.

[12]  Feng Chen,et al.  Enhanced production of astaxanthin by the green microalga Chlorella zofingiensis in mixotrophic culture , 2004 .

[13]  Anna M. Lieb,et al.  The biological significance of substrate inhibition: A mechanism with diverse functions , 2010, BioEssays : news and reviews in molecular, cellular and developmental biology.

[14]  A. Phongdara,et al.  Cloning and expression of a plastid-encoded subunit, beta-carboxyltransferase gene (accD) and a nuclear-encoded subunit, biotin carboxylase of acetyl-CoA carboxylase from oil palm (Elaeis guineensis Jacq.) , 2008 .

[15]  Thomas D. Schmittgen,et al.  Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. , 2001, Methods.

[16]  M. M. Bradford.  A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. , 1976, Analytical biochemistry.

[17]  J. Sevilla,et al.  Mixotrophic growth of the microalga Phaeodactylum tricornutum: Influence of different nitrogen and organic carbon sources on productivity and biomass composition , 2005 .

[18]  Wen-Teng Wu,et al.  Cultivation of microalgae for oil production with a cultivation strategy of urea limitation. , 2009, Bioresource technology.

[19]  Xiao-Jun Ji,et al.  Enhanced docosahexaenoic acid production by reinforcing acetyl-CoA and NADPH supply in Schizochytrium sp. HX-308 , 2009, Bioprocess and biosystems engineering.

[20]  Yue Jiang,et al.  Differential lipid and fatty acid profiles of photoautotrophic and heterotrophic Chlorella zofingiensis: assessment of algal oils for biodiesel production. , 2011, Bioresource technology.

[21]  Martin A. J. Parry,et al.  Discoveries in Rubisco (Ribulose 1,5-bisphosphate carboxylase/oxygenase): a historical perspective , 2007, Photosynthesis Research.

[22]  Juan Yu,et al.  Changes in ultrastructure and responses of antioxidant systems of algae (Dunaliella salina) during acclimation to enhanced ultraviolet-B radiation. , 2009, Journal of photochemistry and photobiology. B, Biology.

[23]  Chiun-Hsun Chen,et al.  Lipid accumulation and CO2 utilization of Nannochloropsis oculata in response to CO2 aeration. , 2009, Bioresource technology.

[24]  Julian N. Rosenberg,et al.  A green light for engineered algae: redirecting metabolism to fuel a biotechnology revolution. , 2008, Current opinion in biotechnology.

[25]  Q. Hu,et al.  Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances. , 2008, The Plant journal : for cell and molecular biology.

[26]  Thomas G. Ludwig,et al.  The Anthrone Method for the Determination of Carbohydrates in Foods and in Oral Rinsing , 1956, Journal of dental research.

[27]  A. Otero,et al.  The cell composition of Nannochloropsis sp. changes under different irradiances in semicontinuous culture , 2004 .

[28]  Yasuro Kadono,et al.  Molecular Adaptation of rbcL in the Heterophyllous Aquatic Plant Potamogeton , 2009, PloS one.

[29]  P. Harrison,et al.  A BROAD SPECTRUM ARTIFICIAL SEA WATER MEDIUM FOR COASTAL AND OPEN OCEAN PHYTOPLANKTON 1 , 1980 .

[30]  Y. Sasaki,et al.  Plant Acetyl-CoA Carboxylase: Structure, Biosynthesis, Regulation, and Gene Manipulation for Plant Breeding , 2004, Bioscience, biotechnology, and biochemistry.

[31]  S. Harrison,et al.  Lipid productivity as a key characteristic for choosing algal species for biodiesel production , 2009, Journal of Applied Phycology.

[32]  R. Castenholz.  [3] Culturing methods for cyanobacteria , 1988 .

[33]  Ken Sasaki,et al.  Growth characteristics of Spirulina platensis in mixotrophic and heterotrophic conditions , 1993 .

[34]  M. Salvucci,et al.  Rubisco: structure, regulatory interactions, and possibilities for a better enzyme. , 2002, Annual review of plant biology.

[35]  W. J. Dyer,et al.  A rapid method of total lipid extraction and purification. , 1959, Canadian journal of biochemistry and physiology.