issatchenkia orientalis
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The trend to search novel natural antifungal compounds has recently been increasing. Interspecific interactions between 30 Macromycetes species and fungal pathogens (Issatchenkia orientalis, Candida albicans strains) have been evaluated using dual culture plate assay. Interaction reactions between studied fungi were different: deadlock after mycelia contact or at a distance, overgrowth without initial deadlock, partial or complete replacement after initial deadlock with contact. Domination of replacement (78.7 %) of pathogenic fungi by Macromycetes was established. Complete replacement was almost twice more frequent (30.7 %) than partial replacement (19.3 %). These results clearly indicate effectiveness of Macromycetes against pathogenic fungi via contact antagonism. Strong antagonistic activity with high antagonistic index (AI) was established by xylotrophic species Ganoderma applanatum (AI = 22.5), Lentinula edodes (AI = 21.0), Flammulina velutipes, Irpiciporus litschaueri and Pleurotus ostreatus (AI = 20.5), leaf litter decay fungus Crinipellis schevczenkoi (AI = 21), and soil saprotroph   Lyophyllum shimeji (AI = 21).

The interest in using non-conventional yeasts to produce value-added compounds from low cost substrates, such as lignocellulosic materials, has increased in recent years. Setting out to discover novel microbial strains that can be used in biorefineries, an Issatchenkia orientalis strain was isolated from waste cooking oil (WCO) and its capability to produce ethanol from wheat straw hydrolysate (WSHL) was analyzed. As with previously isolated I. orientalis strains, WCO-isolated I. orientalis KJ27-7 is thermotolerant. It grows well at elevated temperatures up to 42 °C. Furthermore, spot drop tests showed that it is tolerant to various chemical fermentation inhibitors that are derived from the pre-treatment of lignocellulosic materials. I. orientalis KJ27-7 is particularly tolerant to acetic acid (up to 75 mM) and tolerates 10 mM formic acid, 5 mM furfural and 10 mM hydroxymethylfurfural. Important for biotechnological cellulosic ethanol production, I. orientalis KJ27-7 grows well on plates containing up to 10% ethanol and media containing up to 90% WSHL. As observed in shake flask fermentations, the specific ethanol productivity correlates with WSHL concentrations. In 90% WSHL media, I. orientalis KJ27-7 produced 10.3 g L−1 ethanol within 24 h. This corresponds to a product yield of 0.50 g g−1 glucose (97% of the theoretical maximum) and a volumetric productivity of 0.43 g L−1 h−1. Therefore, I. orientalis KJ27-7 is an efficient producer of lignocellulosic ethanol from WSHL.

PurposeMixed fermentation with Saccharomyces cerevisiae and non-Saccharomyces yeasts has become an oenlogical tool to improve wines’ organoleptic properties. However, the maximum utilization of this method is dependent upon understanding the influence of mixed cultures on the physiology of S.cerevisiae and non-Saccharomyces yeasts.Design/methodology/approachIn this study, the supernatants from 48 h mixed-culture fermentation were added to the pure cultures of Issatchenkia orientalis and Saccharomyces, respectively. And the authors used RNA sequencing to determine the transcriptome change of I.orientalis and S.cerevisiae in a mixed culture.FindingsThe results showed that multiple genes associated with cell growth and death were differentially expressed. Genes related to biosynthesis of amino acids were enriched among those upregulated in the mixed-fermentation supernatant. Meanwhile, the differential expression level of genes encoding enzymes essential for formation of aroma compounds was found in the single and in the mixed fermentation. The high expression level of molecular chaperones Hsp70, Hsp90 and Hsp110 suggests that metabolites of mixed-culture fermentation may lead to aggregation of misfolded proteins. Moreover, upregulation of ethanol dehydrogenase I ADH1 in the mixed-culture fermentations was highlighted.Originality/valueThis is the first time that RNA-seq was used to analyze changes in the transcriptome of mixed cultures. According to the results the authors’ manuscript provided, an integrated view into the adaptive responses of S.cerevisiae and non-Saccharomyces yeasts to the mixed-culture fermentation is benefit for the potential application of S.cerevisiae and non-Saccharomyces yeasts in fruit wine brewing.

Kvasci su česti zagađivači mliječnih proizvoda, međutim, koriste se i kao starter kulture za poboljšavanje svojstava finalnog proizvoda. Njihova prisutnost u povećanom broju može prouzročiti nepoželjne promjene mliječnih proizvoda, kao što su neugodan miris, okus i izgled. Klasična identifikacija kvasaca na temelju morfoloških i biokemijskih svojstava spora je i nepouzdana. Cilj rada bio je identificirati kvasce iz 30 uzoraka mlijeka i svježeg sira te ustvrditi pripadaju li izolirani kvasci u poželjne ili nepoželjne vrste, odnosno predstavljaju li potencijalni rizik po zdravlje ljudi. Izolirani kvasci identificirani su sekvenciranjem D1/D2 regije gena 28 S rRNK. Dobivenim sekvencama ustvrđeno je da izolirani kvasci pripadaju vrstama: Kluyveromyces marxianus, Candida tropicalis, Trichosporon coremiiforme, Rhodotorula mucilaginosa, Trichosporon ovoides, Pichia kudriavzevii, Issatchenkia orientalis, koje se smatraju kvascima zagađenja te Debaryomyces hansenii vrsti koja se može koristiti i kao starter kultura. S obzirom da kvasci nisu termorezistentni mikroorganizmi, trebali bi biti uklonjeni tijekom pasterizacije, no u tradicionalnom načinu proizvodnje sira mlijeko se termički ne obrađuje, stoga je povećan rizik od pojavnosti kvasaca u finalnom proizvodu. Izolirane se vrste vrlo često nalaze i u okolišu i/ili na ljudima, odnosno životinjama. Stoga se nameće zaključak kako se glavnina kontaminacije kvascima događa kao posljedica neadekvatne higijenske prakse.

Heparin-based silver nanoparticles (AgHep-NPs) and gold nanoparticles (AuHep-NPs) were produced by a photochemical method using silver nitrate and chloroauric acid as metal precursors and UV light at 254 nm. UV–Vis spectroscopy graphs showed absorption for AgHep-NPs and AuHep-NPs at 420 nm and 530 nm, respectively. TEM revealed a pseudospherical morphology and a small size, corresponding to 10–25 nm for AgHep-NPs and 1.5–7.5 nm for AuHep-NPs. Their antifungal activity against Candida albicans, Issatchenkia orientalis (Candida krusei), and Candida parapsilosis was assessed by the microdilution method. We show that AgHep-NPs were effective in decreasing fungus density, whereas AuHep-NPs were not. Additionally, the viability of human gingival fibroblasts was preserved by both nanoparticle types at a level above 80%, indicating a slight cytotoxicity. These results are potentially useful for applications of the described NPs mainly in dentistry and, to a lesser extent, in other biomedical areas.