Ergothioneine (ERG) is an unusual thio-histidine betaine amino acid that has potent antioxidant activities. It is synthesised by a variety of microbes, especially fungi (including in mushroom fruiting bodies) and actinobacteria, but is not synthesised by plants and animals who acquire it via the soil and their diet, respectively. Animals have evolved a highly selective transporter for it, known as solute carrier family 22, member 4 (SLC22A4) in humans, signifying its importance, and ERG may even have the status of a vitamin. ERG accumulates differentially in various tissues, according to their expression of SLC22A4, favouring those such as erythrocytes that may be subject to oxidative stress. Mushroom or ERG consumption seems to provide significant prevention against oxidative stress in a large variety of systems. ERG seems to have strong cytoprotective status, and its concentration is lowered in a number of chronic inflammatory diseases. It has been passed as safe by regulatory agencies, and may have value as a nutraceutical and antioxidant more generally.

Biobased C4-dicarboxylic acids are attractive sustainable precursors for polymers and other materials. Commercial scale production of these acids at high titers requires efficient secretion by cell factories. In this study, we characterized 7 dicarboxylic acid transporters in Xenopus oocytes and in Saccharomyces cerevisiae engineered for dicarboxylic acid production. Among the tested transporters, the Mae1(p) from Schizosaccharomyces pombe had the highest activity toward succinic, malic, and fumaric acids and resulted in 3-, 8-, and 5-fold titer increases, respectively, in S. cerevisiae, while not affecting growth, which was in contrast to the tested transporters from the tellurite-resistance/dicarboxylate transporter (TDT) family or the Na+ coupled divalent anion–sodium symporter family. Similar to SpMae1(p), its homolog in Aspergillus carbonarius, AcDct(p), increased the malate titer 12-fold without affecting the growth. Phylogenetic and protein motif analyses mapped SpMae1(p) and AcDct(p) into the voltage-dependent slow-anion channel transporter (SLAC1) clade of transporters, which also include plant Slac1(p) transporters involved in stomata closure. The conserved phenylalanine residue F329 closing the transport pore of SpMae1(p) is essential for the transporter activity. The voltage-dependent SLAC1 transporters do not use proton or Na+ motive force and are, thus, less energetically expensive than the majority of other dicarboxylic acid transporters. Such transporters present a tremendous advantage for organic acid production via fermentation allowing a higher overall product yield.

L-(+)-Ergothioneine (ERG) is an unusual, naturally occurring antioxidant nutraceutical that has been shown to help reduce cellular oxidative damage. Humans do not biosynthesise ERG, but acquire it from their diet; it exploits a specific transporter (SLC22A4) for its uptake. ERG is considered to be a nutraceutical and possible vitamin that is involved in the maintenance of health, and seems to be at too low a concentration in several diseases in vivo. Ergothioneine is thus a potentially useful dietary supplement. Present methods of commercial production rely on extraction from natural sources or on chemical synthesis. Here we describe the engineering of the baker's yeast Saccharomyces cerevisiae to produce ergothioneine by fermentation in defined media. After integrating combinations of ERG biosynthetic pathways from different organisms, we screened yeast strains for their production of ERG. The highest-producing strain was also engineered with known ergothioneine transporters. The effect of amino acid supplementation of the medium was investigated and the nitrogen metabolism of S. cerevisiae was altered by knock-out of TOR1 or YIH1. We also optimized the media composition using fractional factorial methods. Our optimal strategy led to a titer of 598 ± 18 mg/L ergothioneine in fed-batch culture in 1 L bioreactors. Because S. cerevisiae is a GRAS (“generally recognized as safe”) organism that is widely used for nutraceutical production, this work provides a promising process for the biosynthetic production of ERG.

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Ergothioneine is a naturally occurring antioxidant that has shown potential in ameliorating neurodegenerative and cardiovascular diseases. In this study, we investigated the potential of the Crabtree‐negative, oleaginous yeast Yarrowia lipolytica as an alternative host for ergothioneine production. We expressed the biosynthetic enzymes EGT1 from Neurospora crassa and EGT2 from Claviceps purpurea to obtain 158 mg·L−1 of ergothioneine in small‐scale cultivation, with an additional copy of each gene improving the titer to 205 mg·L−1. The effect of phosphate limitation on ergothioneine production was studied, and finally, a phosphate‐limited fed‐batch fermentation in 1 L bioreactors yielded 1.63 ± 0.04 g·L−1 ergothioneine in 220 h, corresponding to an overall volumetric productivity of 7.41 mg·L−1·h−1, showing that Y. lipolytica is a promising host for ergothioneine production.

20 cerevisiae, yeast, nutraceutical 21 22 Abbreviations: ERG L-(+)-ergothioneine, HCO S-(hercyn-2-yl)-L-cysteine S-oxide, PBS 23 phosphate-buffered saline, PI propidium iodide, PLP pyridoxal 5'-phosphate, SAM S-adenosyl-24 L-methionine 25 26Abstract 27 L-(+)-Ergothioneine is an unusual, naturally occurring antioxidant nutraceutical that has been 28 shown to help reduce cellular oxidative damage. Humans do not biosynthesise it, so can acquire 29 it only from their diet; it exploits a specific transporter (SLC22A4) for its uptake. ERG is 30 considered to be a nutraceutical and possible vitamin that is involved in the maintenance of 31 health, and seems to be at too low a concentration in several diseases in vivo. Ergothioneine is 32 thus a potentially useful dietary supplement. Present methods of commercial production rely on 33 extraction from natural sources or on chemical synthesis. Here we describe the engineering of 34 the baker's yeast Saccharomyces cerevisiae to produce ergothioneine by fermentation in defined 35 media. After integrating combinations of ERG biosynthetic pathways from different organisms, 36 we screened yeast strains for their production of ERG. The highest-producing strain was also 37 engineered with known ergothioneine transporters. The effect of amino acid supplementation of 38 the medium was investigated and the nitrogen metabolism of S. cerevisiae was altered by knock-39 out of TOR1 or YIH1. We also optimized the media composition using fractional factorial 40 methods. Our optimal strategy led to a titer of 598 ± 18 mg/L ergothioneine in fed-batch culture 41 in bioreactors. Because S. cerevisiae is a GRAS ('generally recognised as safe') organism that is 42 2 widely used for nutraceutical production, this work provides a promising process for the 43 biosynthetic production of ERG. 44 45