Abstract
Biodiesel and natural products derived from microalgae require a smaller land area and have higher production rates compared to plants and animals and has recently attracted considerable interest. However, biodiesel production from microalgal triacylglycerol is still far from commercial realization due to its high production cost. One way to overcome this obstacle is to improve the triacylglycerol accumulation and couple its production with other high-value compounds. Of particular interest is the sterol biosynthetic pathway with squalene as an intermediate due to its close relationship with triacylglycerol and carotenoid biosynthetic pathways. Besides, both squalene and carotenoids are isoprenoid lipids that have health benefits. Perturbation of one pathway has been suggested to affect other pathways. Three terbinafine-sensitive mutants of the green microalga Chlamydomonas reinhardtii were isolated using terbinafine, a drug that inhibits squalene epoxidase, leading to squalene accumulation. One of the mutants, tfs2, accumulated twice the amount of wild-type triacylglycerol. As well as squalene accumulation, the presence of terbinafine further increased the triacylglycerol content. The level of prenyl lipid carotenoid and chlorophyll was also more significant than that of the wild type. Growth and photosynthesis were not compromised in this mutant. This is the first study that has demonstrated a mutant screening method to improve the co-production of TAG and isoprenoid lipids in a green microalgae.
Highlights
The chlorophyll content in tfs[2] was the least affected by this condition, and this mutant was able to maintain the highest level of chlorophyll compared to the other strains
In Chlamydomonas, treatment with the sterol production inhibitor, fenpropimorph, resulted in the conversion of polar lipid of chloroplast membrane to TAG (Kim et al, 2015). These results demonstrate a close relationship between membrane lipids and storage lipids, which could be used to develop strategies to produce certain types of lipid
A mutant screening to improve the co-production of TAG and isoprenoids was performed using the green microalga Chlamydomonas reinhardtii, based on a close regulatory relationship between the fatty acid biosynthesis pathway and the isoprenoid synthesis pathway
Summary
To quantify the squalene level using high-performance liquid chromatography (HPLC), the total lipid sample was dissolved in 250 L of acetonitrile and filtered through a 0.2 m PTFE filter. Squalene was detected at 195 nm, and was quantified using a previously generated standard curve of peak area vs known squalene amount (Lu et al, 2004). The sample was analyzed using a gas chromatography-mass spectrometry (GCMS-QP2020; Shimadzu, Kyoto, Japan) equipped with an DB-5MS capillary column (30 m × 0.25 mm, film thickness 0.25 mm, Agilent Technologies, Santa Clara, CA), carrier gas: He (1 mL min–1), oven temperature: 150–300°C (increase rate 20°C min–1). The ionization voltage was 70 eV, and the scan range was 40–500 Da. The ergosterol and 7dehydroporiferasterol peaks were identified by their respective standards (Sigma-Aldrich), and the contents were compared by peak areas
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
