Abstract
The oleaginous yeast Schwanniomyces occidentalis was previously isolated because of its excellent suitability to convert lignocellulosic hydrolysates into triacyl glycerides: it is able to use a broad range of sugars and is able to tolerate high concentrations of lignocellulosic hydrolysate inhibitors. Compared to other oleaginous yeasts S. occidentalis however produces a low content of unsaturated fatty acids. We show here that the linoleic acid content can be significantly improved by (over)expression Δ12-desaturases derived from S. occidentalis and Fusarium moniliforme. Expression was stable for the homologous expression but decreased during heterologous expression. Both homologous and heterologous expression of mCherry-Δ12-desaturase led to a 4-fold increase in linoleic acid from 0.02 g/g biomass to 0.08 g/g biomass resulting in the production of 2.23 g/L and 2.05 g/L of linoleic acid.
Highlights
Polyunsaturated fatty acids, such as linoleic acid and linolenic acid, are widely used for the production of lubricants, resins, plastics and alkyd paints (Joseph et al, 2004; Köckritz and Martin, 2008; Nasrollahi et al, 2018; Orellana-Coca et al, 2005; van Gorkum and Bouwman, 2005)
We identified a putative Δ12-desaturase sequence in the genome of S. occidentalis based on homology with the functionally annotated Δ12desaturases of Kluyveromyces lactis and Lachancea kluyveri (De Angelis et al, 2016; Watanabe et al, 2004)
The F. moniliforme FAD2, which was previously expressed in Rhodosporidium toruloides to increase linoleic acid content, shared an identity of 49.4% with our putative sequence
Summary
Polyunsaturated fatty acids, such as linoleic acid and linolenic acid, are widely used for the production of lubricants, resins, plastics and alkyd paints (Joseph et al, 2004; Köckritz and Martin, 2008; Nasrollahi et al, 2018; Orellana-Coca et al, 2005; van Gorkum and Bouwman, 2005). Polyunsaturated fatty acids containing lipids have a good nutritional value, are utilized for health applications and have been associated with reduced atherosclerosis, inflammation and carcinogenesis (Bellou et al, 2016a; Calder, 2010; Saini and Keum, 2018). Due to the inability of humans and other higher animals to synthesize certain polyunsaturated fatty acids, such as linoleic acid, they depend on acquiring them via dietary uptake from common sources, such as soy oil and flaxseed oil (Saini and Keum, 2018). Polyunsaturated fatty acids (PUFAs) are formed from stearic acid, which is converted by a Δ9-desaturase (Ole1) to oleic acid. Oleic acid can subsequently be converted to linoleic acid by a Δ12-desaturase (FAD2) and to α-linolenic acid by a Δ15-desaturase (FAD3), or to γlinoleic acid by a Δ6-desaturase. Subsequent elongation and desaturation lead to the formation of longer chain PUFAs such as arachidonic acid and eicosapentaenoic acid (Hao et al, 2016; Leonard et al, 2004)
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