A Two-Stage Adaptive Laboratory Evolution Strategy to Enhance Docosahexaenoic Acid Synthesis in Oleaginous Thraustochytrid

Abstract

Thraustochytrid is a promising algal oil resource with the potential to meet the demand for docosahexaenoic acid (DHA). However, oils with high DHA content produced by genetic modified thraustochytrids are not accepted by the food and pharmaceutical industries in many countries. Therefore, in order to obtain non-transgenic strains with high DHA content, a two-stage adaptive laboratory evolution (ALE) strategy was applied to the thraustochytrid Aurantiochytrium sp. Heavy-ion irradiation technique was first used before the ALE to increase the genetic diversity of strains, and then two-step ALE: low temperature based ALE and ACCase inhibitor quizalofop-p-ethyl based ALE were employed in enhancing the DHA production. Using this strategy, the end-point strain E-81 with a DHA content 51% higher than that of the parental strain was obtained. The performance of E-81 strain was further analyzed by component analysis and quantitative real-time PCR. The results showed that the enhanced in lipid content was due to the up-regulated expression of key enzymes in lipid accumulation, while the increase in DHA content was due to the increased transcriptional levels of polyunsaturated fatty acid synthase. This study demonstrated a non-genetic approach to enhance lipid and DHA content in non-model industrial oleaginous strains.

Marine thraustochytrid: exploration from taxonomic challenges to biotechnological applications

“…They found that stress conditions such as low temperature (Ma et al, 2017), low or high dissolved oxygen (Sun et al, 2016;Heggeset et al, 2019) and nitrogen starvation (Chen et al, 2022) could stimulate the accumulation of intracellular lipids. Laboratory domestication and phased cultivation strategies (Wang et al, 2021a;Chen et al, 2022) have been developed. Additionally, the inclusion of lipase inhibitors (Orlistat) (Ma et al, 2021), antioxidants (Zhang et al, 2020) and plant hormones (Yu et al, 2016) in the culture medium can influence PUFAs metabolism and promote lipid accumulation.…”

“…are permitted for use as nutritional additives, but not whole cells. Moreover, oils with high DHA content produced from genetically modified thraustochytrids are not accepted by the food and pharmaceutical industries in many countries (Wang et al, 2021a). Upon the European Commission's request, the European Food Safety Authority (EFSA) Panel on Nutrition, Novel Foods and Food Allergens (NDA) evaluated the safety of S. sp.…”

Integration of the Exogenous Tuning of Thraustochytrid Fermentation and Sulfur Polymerization of Single-Cell Oil for Developing Plant-like Oils

“…Recently, the role of adaptative lab evolution as a non-genetic approach to improve lipid (especially DHA) accumulation [ 11 ] and introduction of chemical modulators in the fermentation medium have been proposed to improve lipid yields [ 7 , 12 ]. Low-molecular-weight compounds such as propyl gallate [ 7 ], butanol [ 13 ], ascorbic acid [ 14 ], naphthoxyacetic acid (BNOA) [ 12 ] and phytohormones, such as kinetin (KIN), jasmonic acid (JA) and gibberellic acid (GA) [ 15 ], and sesamol [ 16 ], when added to the fermentation medium, could enhance lipid production with reference to polyunsaturated fatty acids (DHA, etc.).…”