Rhodotorula mucilaginosa, a carotenoid producing yeast strain from a Patagonian high-altitude lake.

The red yeast Rhodotorula mucilaginosa strain CRUB 0138 (previously identified as R. lactosa) was isolated from a high-altitude Patagonian Lake Toncek (1700 m a.s.l.), and assigned with mucilaginosa species. Its biochemical, physiological and molecular features were assessed and compared to R. mucilaginosa PYCC 5166 type strain using a polyphasic approach; in addition, biomass and carotenoid pigment production at different C/N ratios were determined in an incubator shaker. Phenetic characterization by means of 70 current physiological tests including assimilation of aldaric acids and aromatic compounds, and also the ability to grow with amino acids as sole carbon sources, was carried out. According to numerical taxonomy calculations, similarity indexes between R. mucilaginosa CRUB 0138 and PYCC 5166 type strain were 0.86 and 0.77, corresponding to a complete set of physiological tests and MSP-PCR (Mini/Micro Satellite Primed PCR; (GTG)5, M13 and (GAC)5 primers were employed) fingerprinting. Killer activity against 2 native strains, Rhodosporidium kratochvilovae and R. mucilaginosa was detected. Maximum biomass-glucose conversion efficiency (87%) and maximum carotenoid yield (2.32 mg/L) were obtained at C/N = 5 in culture medium containing 10 and 40 g/L glucose, respectively. Different C/N ratios did not influence carotenoid pigment production but low C/N enhanced biomass yield.

Mycotoxin-producing potential of fungi isolated from amaranth seeds in Argentina.

To evaluate the potential for mycotoxin production by molds in amaranth grains, the mycoflora was determined both before and after surface disinfection on dichloran-chloramphenicol-peptone agar (DCPA) and dichloran-18% glycerol agar (DG18). On both media Aspergillus, Penicillium, Fusarium and Alternaria were the predominant genera. A flaus and A. parasiticus were the Aspergillus species most frequently isolated. P. chrysogenum was the species most common among the penicillia. F. equiseti was the predominant Fusarium species. Isolates of Aspergillus, Penicillium and Fusarium were screened for mycotoxin production on sterile rice substrate and also using a simple screening method. Toxinogenic strains of A. flavus and A. parasiticus (aflatoxins), A. versicolor (sterigmatocystin), P. citrinum (citrinin), P. viridicatum (penicillic acid), F. moniliforme, F. equiseti and F. semitectum (zearalenone), were encountered. The simple screening method for toxinogenic molds showed good performance for the detection of molds producing aflatoxins and zearalenone compared with mycotoxins production on the natural substrate.

Natural occurrence of zearalenone and toxicogenic fungi in amaranth grain.

Zearalenone was detected as the natural contaminant in two samples of Amaranthus cruentus grains (1980 micrograms/kg and 420 micrograms/kg, respectively). Fungi isolated from these samples were screened for mycotoxin production. Two of eight isolates of Fusarium (F. equiseti and F. moniliforme) produced zearalenone. One of four isolates of Aspergillus flavus and all four isolates of A. parasiticus produced aflatoxins. Other species potentially toxicogenic such as Aspergillus versicolor, Penicillium viridicatum, P. puberulum, P. crustosum, P. citrinum, P. expansum and Fusarium solani were also found.