Mycocinogenic yeasts isolated from Amazon soils of the Maracá Ecological Station, Roraima-Brazil

Abstract

The 240 yeasts isolated from soils of the Maracá Ecological Station in the Brazilian Amazon were identified and screened for mycocin production. These strains included 82% of ascomycetous and 18% basidiomicetous affinities and the prevalent species were Candida etchellsii, Candida famata, Candida robusta, Candida rugosa, Candida valida, Debaryomyces hansenii, Cryptococcus albidus, Cryptococcus laurentii, Rhodotorula glutinis, Rhodotorula minuta and Rhodotorula mucilaginosa. Mycocins able to kill some yeasts were produced by 6 strains identified as Issatchenkia sp., Saccharomyces exiguus?, Williopsis saturnus, var. subsufficiens, and 3 W. saturnus according to 26S rDNA D1/D2 region sequence and phenotypic data.

Candida krusei and Kloeckera apis inhibit the causal agent of pineapple fusariosis, Fusarium guttiforme

“…Mycocinogenic activity was evaluated in triplicate by cultivating the isolates in Yeast Malt (YM) media (0.3 % yeast extract; 0.3 % malt extract; 0.5 % peptone; 1 % glucose; 2 % agar) with 0.003 % methylene blue, pH 4.2 with 0.01 M citrate buffer an indicator of the presence of killer toxins (Somers & Bevan 1969;Vital et al 2002). Killer toxin activity was defined as a region of blue coloured cells, or by a clear zone of inhibition bounded by blue coloured cells, surrounding the wells.…”

“…Killer toxin activity was defined as a region of blue coloured cells, or by a clear zone of inhibition bounded by blue coloured cells, surrounding the wells. A solid medium was used as the medium state is very important, since mycocins are more stable in solid than in liquid media, because agitation can cause their inactivation (Vital et al 2002).…”

“…A suspension of 1 ml of 10 5 conidia ml À1 was spread on the surface of the assay medium and the potential killer toxin producing yeasts (grown on agar slants for 48 h/28 C) were inoculated in the centre of the plates. Plates were incubated for 5 d at 28 C and observed daily (Vital et al 2002;Vadkertiov a & Sl avikov a 2007). Candida albicans (12A) was used as sensitive control (Carreiro et al 2002).…”

“…Candida albicans (12A) was used as sensitive control (Carreiro et al 2002). Yeasts were considered as mycocinogenic when a clear zone with no growth, or an adjacent blue zone indicating cellular death of the sensitive isolate was produced (Vital et al 2002).…”

Enhancing the Microbiological Stability of Malt and Beer - A Review

“…Some yeast strains produce and excrete extracellular toxins, zymocins, which are lethal to sensitive yeast strains 210 . It has been possible to engineer resistant yeast strains by transferring genes coding for resistance into sensitive strains.…”