Flower Yeasts From Northern Thailand Emerge as Potent Natural Ergothioneine Producers

Flowers in northern Thailand harbor yeasts that quietly manufacture one of the food industry’s most sought-after antioxidants. Screening 305 yeast strains isolated from 61 flower samples, researchers found that 205 basidiomycetous strains could produce ergothioneine (EGT), a sulfur-containing amino acid derivative prized for its antioxidant and free radical-scavenging properties. The survey, published in the Journal of Agriculture and Food Research, also reports the first evidence of EGT production in 18 yeast genera and 60 species, substantially widening the known taxonomic breadth of natural EGT producers.

The standout performer was Pseudozyma chiangmaiensis strain SDBR-CMU980, which yielded 13.72 mg/L of EGT under initial screening conditions, ahead of Moesziomyces antarcticus SDBR-CMU634 at 12.73 mg/L and Papiliotrema tectonae SDBR-CMU632 at 12.00 mg/L. Overall yields among producing strains ranged from 0.02 to 13.72 mg/L. Notably, all 63 ascomycetous yeasts in the collection, all belonging to the subphylum Saccharomycotina, failed to produce any detectable EGT, a pattern consistent with comparative genomic findings that the fungal egt1 biosynthetic gene is absent from Saccharomycotina members.

The research team, led by Pratthana Kodchasee and Nakarin Suwannarach of Chiang Mai University, identified the strains using morphology plus sequencing of the D1/D2 domain of the large subunit rRNA gene and the internal transcribed spacer region. EGT was extracted from dried cells by heating in water at 90 °C, then quantified by high-performance liquid chromatography with UV detection at 254 nm, using a calibration curve spanning 62.5 to 500 μg/mL with a strong linear fit. Each strain was analyzed in triplicate.

To push yields higher, the team tested the three amino acids that feed the fungal EGT pathway: histidine, which supplies the imidazole backbone; methionine, a precursor for S-adenosylmethionine, the methyl donor that converts histidine into hercynine; and cysteine, which contributes sulfur in later steps. Across 17 representative high-producing strains plus one non-producing control, histidine and methionine supplementation generally boosted EGT, while cysteine alone often helped little or even reduced accumulation, possibly because excess cysteine is toxic to yeast or diverts sulfur flux toward glutathione.

Under precursor supplementation, P. chiangmaiensis SDBR-CMU980 reached 29.19 ± 0.53 mg/L, statistically tied with P. pollinicola SDBR-CMU619 at 28.31 ± 0.14 mg/L. Principal component analysis with K-means clustering cleanly separated the strains into high, moderate, low, and non-producing groups, with histidine plus methionine, methionine alone, and the three-amino-acid combination contributing most to the variation along the first principal component.

A stepwise optimization of culture conditions for SDBR-CMU980 then delivered the study’s headline number. The best initial medium pH was 4.0, a 5% inoculum ratio proved sufficient, a histidine-to-methionine ratio of 0.75:0.25 was optimal, and a total precursor concentration of 2 g/L maximized production at 41.17 ± 1.62 mg/L. Extending cultivation to seven days raised intracellular EGT to 42.16 ± 2.32 mg/L, a 2.37-fold improvement over the 17.76 mg/L baseline in unsupplemented yeast malt extract broth. Extracellular EGT appeared after day seven, coinciding with declining intracellular levels and rising culture pH, suggesting the compound leaks out as cells lyse.

The researchers partially purified the yeast-derived EGT by preparative flash chromatography, enriching it from 425 mg/g of dry extract to 650 mg/g with a recovery of roughly 91.8%. In DPPH, ABTS, and FRAP antioxidant assays, the partially purified EGT performed statistically identically to a commercial EGT standard, with IC50 values of 20.15, 122.42, and 30.08 μg/mL respectively, versus 19.07, 120.01, and 29.80 μg/mL for the standard.

Stability testing boded well for food applications. The purified EGT retained more than 90% of its content across pH 5 to 8, survived two to three autoclave cycles at 121 °C with about 95% retention, stayed above 98% after up to 10 minutes of microwave irradiation, and kept more than 90% through five days at 100 °C. The main vulnerability was redox-active metals: copper ions cut retention to 58.54% at 1,000 μM CuCl2, and ferric iron reduced it to roughly 42.89% at 1,000 μM FeCl3, whereas calcium chloride left more than 95% intact at every concentration tested.

In a final functional test, supplementing cultures of the probiotic bacteria Heyndrickxia coagulans and Lacticaseibacillus rhamnosus with the partially purified EGT increased viable cell counts during the active growth phase, with H. coagulans responding best at 250 mg/L and L. rhamnosus at 100 mg/L. The authors caution that these controlled-cultivation results do not prove EGT enhances probiotic viability in real foods, and that simulated gastrointestinal studies are needed. Even so, the combination of a naturally derived, thermally robust antioxidant and a scalable yeast fermentation platform positions this Thai flower yeast as a credible candidate for future functional food and nutraceutical development.

Subject of Research: Screening and fermentation optimization of flower-associated yeasts from northern Thailand for natural ergothioneine production.

Article Title: Anthophilous yeasts from northern Thailand as natural sources of ergothioneine with optimized production for food and nutraceutical applications

Article References: Kodchasee, P., Kumla, J., Kathongthung, C., Senwanna, C., Singsalood, S., Duangkon, N., & Suwannarach, N. (2026). Anthophilous yeasts from northern Thailand as natural sources of ergothioneine with optimized production for food and nutraceutical applications. Journal of Agriculture and Food Research, 32, Article 103406. https://doi.org/10.1016/j.jafr.2026.103406

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103406

Keywords: ergothioneine, anthophilous yeasts, Pseudozyma chiangmaiensis, northern Thailand, fermentation optimization, antioxidant, probiotics, functional foods, basidiomycetous yeasts, HPLC, nutraceuticals, Anthophilous