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

Abstract

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.

Effect of nitrogen limitation on cell growth, lipid accumulation and gene expression in Chlorella sorokiniana

“…However, the alga culturing in strict heterotrophy is more expensive than in photoautotrophy. Mixotrophic cultivation is not only complement photoautotrophy with organ carbon, but also can reduce the cost of heterotrophic microalgal culture and improve the lipid content (Wan et al 2011). Hence, the microalga cultured under mixotrophic condition can exhibit higher biomass and lipid content.…”

“…The genus Chlorella is the oldest commercial application of microalgae and can be grown in photo/mixo/heterotrophic mode of culture. C. sorokiniana is a promising freshwater non-motile unicellular alga, accumulating high amounts of lipids and proteins (Wan et al 2011). C. sorokiniana is one of potential microalgal species used for the lipid production.…”

Cloning and expression analysis of accD gene in Chlorella protothecoides FACHB-2

“…The transcription of the four genes appears to be coordinated, and maybe the level of accD subunit is a determinant of ACCase level (Madoka et al, 2002;Ke et al, 2000), so the transcription abundance of accD gene can reflect the response of ACCase to changing culture conditions. Since it is considered to be very important in regulating fatty acid and thus oil biosynthesis, the genetics of ACCase has been well studied in many plants; as for oleaginous microalgae, only Wan et al (2011) reported recently in C. sorokiniana that increased lipid contents in stationary phases of mixotrophic growth were related to increased expression levels of accD gene. Our results showed that the expression levels of accD gene began to increase during the exponential phases under heterotrophic cultivations, but elevated expression of this gene did not lead to elevation of lipid contents in the same degree as in the stationary phases.…”

“…It was reported in another algal species Chlorella sorokiniana that increased expression levels of accD (heteromeric acetylCoA carboxylase beta subunit) might account for the increased lipid content in stationary phase of mixotrophic growth (Wan et al, 2011). The species in the genus Chlorella are usually from different circumstances, and the same metabolic pathways in two species often response differently to the same environmental condition (Cha et al, 2011).…”

Features of cell metabolism of Chlamydomonas reinhardtii CC-124 wild strain [137c] under mixotrophic and phototrophic cultivation

“…В силу различных свойств белковых соединений именно они обусловливают многообразие ответных реакций водорослей на различные воздействия. Известно, что в условиях выращивания водорослей в миксотрофной и автотрофной культурах можно получить биомассу с совершенно разным выходом белка, аминокислот, каротиноидов, липидов и других важных соединений (Wan et al, 2011).…”