Increasing the Triacylglycerol Content in Dunaliella tertiolecta through Isolation of Starch-Deficient Mutants

Abstract

The production cost of biodiesel from microalgae is still not competitive, compared with that of petroleum fuels. The genetic improvement of microalgal strains to increase triacylglycerol (TAG) accumulation is one way to reduce production costs. One of the most promising approaches is the isolation of starch-deficient mutants, which have been reported to successfully increase TAG yields. To date, such a stable mutant is not available in an oleaginous marine microalga, despite several advantages of using marine species for biodiesel production. Algae in the genus Dunaliella are known to tolerate high salt concentration and other environmental stresses. In addition, the cultivation processes for large-scale outdoor commercialization have been well established for this genus. In this study, Dunaliella tertiolecta was used to screen for starch-deficient mutants, using an iodine vapor-staining method. Four out of 20,016 UV-mutagenized strains showed a substantial reduction of starch content. A significantly higher TAG content, up to 3-fold of the wild-type level, was observed in three of the mutants upon induction by nitrogen depletion. The carotenoid production and growth characteristics of these mutants, under both normal and oxidative stress conditions, were not compromised, suggesting that these processes are not necessarily affected by starch deficiency. The results from this work open up new possibilities for exploring Dunaliella for biodiesel production.

β-carotene Production of UV-C Induced Dunaliella salina Under Salt Stress

“…Similar result was reported by Sharma et al 6 , who reported that continuous UV-C radiation for 24 h rapidly induced carotenoid biosynthesis in D. salina and the total carotenoids and β-carotenoid were doubled in 24 h. UV-C has been successfully used to generate microalgae mutants 14 . Sirikhachornkit et al 8 , found that the UV-C induced total carotenoid content of D. tertiolecta. UV-C played an important role on the induction of expression of genes that are encoding the antioxidant.…”

“…UV-C radiation induced mutation of several genera of green algae especially in Chlamydomonadales including Chlamydomonas and Dunaliella. UV-C radiation affected on growth and photosynthesis which resulted in accu-mulation of starch and pigment 5,6,7,8 . Sirikhachornkit et al 8 , studied utilize of UV-C to isolate Dunaliella mutant.…”

“…UV-C radiation affected on growth and photosynthesis which resulted in accu-mulation of starch and pigment 5,6,7,8 . Sirikhachornkit et al 8 , studied utilize of UV-C to isolate Dunaliella mutant. These mutants produced total carotenoid higher than the original wild type did.…”

Enhanced Production of Fatty Acids via Redirection of Carbon Flux in Marine Microalga Tetraselmis sp.

“…In recent years, numerous studies have been reported for enhancing lipid content or productivity via the regulation of algal metabolic pathways [10][11][12]. Lipids and carbohydrates are important energy storage molecules in microalgae.…”

Photosynthetic efficiency in microalgal lipid production

“…This starchless mutant shows potential for large scale food and biofuel production. Similar mutations have been generated in other microalgal strains and have been studied intensively for biomass productivity, lipid content, carbon partitioning and photosynthetic efficiency (Li et al, 2010a;Ramazanov and Ramazanov, 2006;Siaut et al, 2007;Sirikhachornkit et al, 2016;Vonlanthen et al, 2015;Wang et al, 2009;Work et al, 2010 (Krienitz and Bock, 2012). The starchless mutant of A. obliquus (slm1) was generated as described by de Jaeger et al (2014).…”