No abstract

BackgroundThe ability of some microorganisms to accumulate lipids is well known; however, only recently the number of studies on microbial lipid biosynthesis for obtaining oleochemical products, namely biofuels and some building blocks for chemistry, is rapidly and spectacularly increased. Since 1990s, some oleaginous yeasts were studied for their ability to accumulate lipids up to 60–70% of their dry weight. Due to the vast array of engineering techniques currently available, the recombinant DNA technology was the main approach followed so far for obtaining lipid-overproducing yeasts, mainly belonging to the Yarrowia lipolytica. However, an alternative approach can be offered by worldwide diversity as source of novel oleaginous yeasts. Lipogenic aptitude of a number of yeast strains has been reviewed, but many of these studies utilized a limited number of species and/or different culture conditions that make impossible the comparison of different results. Accordingly, the lipogenic aptitude inside the yeast world is still far from being fully explored, and finding new oleaginous yeast species can acquire a strategic importance.Results Holtermanniella wattica, Leucosporidium creatinivorum, Naganishia adeliensis, Solicoccozyma aeria, and Solicoccozyma terricola strains were selected as a result of a large-scale screening on 706 yeasts (both Ascomycota and Basidiomycota). Lipid yields and fatty acid profiles of selected strains were evaluated at 20 and 25 °C on glucose, and on glycerol, xylose, galactose, sucrose, maltose, and cellobiose. A variable fatty acid profile was observed in dependence of both temperature and different carbon sources. On the whole, L. creatinivorum exhibited the highest performances: total lipid yield (YL) >7 g/l on glucose and glycerol, % of intracellular lipids on cell biomass (YL/DW) >70% at 20 °C on glucose, lipid coefficient (YL/Glu) around 20% on glucose, and daily productivity (YL/d) on glucose and sucrose >1.6 g/(l*d).ConclusionsThis study provides some meaningful information about the lipogenic ability of some yeast species. Variable lipid yields and fatty acid profiles were observed in dependence of both temperature and different carbon sources. L. creatinivorum exhibited the highest lipogenic performances.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0672-1) contains supplementary material, which is available to authorized users.

Abstract:The rising consumer requests for natural flavors and fragrances have generated great interest in the aroma industry to seek new methods to obtain fragrance and flavor compounds naturally. An alternative and attractive route for these compounds is based on bio-transformations. In this review, the application of biocatalysis by Non Conventional Yeasts (NCYs) whole cells for the production of flavor and fragrances is illustrated by a discussion of the production of different class of compounds,

Twenty yeast strains, representing a selection from a wider group of more than 60 isolates were isolated from cold environments worldwide (Antarctica, Iceland, Russia, USA, Italian and French Alps, Apennines). The strains were grouped based on their common morphological and physiological characteristics. A phylogeny based on D1/D2 ribosomal DNA sequences placed them in an intermediate position between Cryptococcus saitoi and Cryptococcus friedmannii; the ITS1 and ITS2 rDNA phylogeny demonstrated that these strains belong to two related but hitherto unknown species within the order Filobasidiales, albidus clade. These two novel species are described with the names Cryptococcus vaughanmartiniae (type strain DBVPG 4736(T)) and Cryptococcus onofrii (type strain DBVPG 5303(T)).

The objective of this study was to assess the in vitro effect of iodopropynyl butylcarbamate (IPBC) and amphotericin B (AMB) on Prototheca zopfii genotype 2 and Prototheca blaschkeae isolates recovered from dairy herds of Belgium, France, Italy, Germany, and Poland. The combination of IPBC with AMB on Prototheca isolates and toxicity of IPBC to the bovine mammary epithelial cells were also evaluated. The in vitro activity of IPBC and AMB against 96 isolates of P. zopfii genotype 2 and 42 isolates of P. blaschkeae was performed. Minimum inhibitory concentrations (MIC) and minimum algicidal concentrations (MAC) of IPBC and AMB were determined. To determine any synergistic, additive, or antagonistic effect of the combination of IPBC and AMB, 2-dimensional checkerboard combination tests were also performed to calculate fractional inhibitory concentrations. Cytotoxicity analysis of IPBC to the bovine mammary epithelial cell line was performed using a 3-(4,5-dimethyl-2-thiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The MIC for 50 and 90% of isolates (MIC and MIC, respectively) for IPBC were 4 and 8 mg/L versus 0.5 and 1 mg/L for AMB, respectively. The MIC profiles differed between P. zopfii genotype 2 and P. blaschkeae, with the latter species being more susceptible to both compounds. The MIC and MIC of IPBC were 4 and 8 mg/L for P. zopfii genotype 2 and 1 and 2 mg/L for P. blaschkeae, respectively. The MIC and MIC of AMB were both 1 mg/L for P. zopfii genotype 2 and 0.25 and 1 mg/L for P. blaschkeae, respectively. Both IPBC and AMB exhibited the ability to kill Prototheca spp. The MAC for 90% of isolates of IPBC was twice the MIC, whereas an 8-fold increase of the MIC was algicidal in the case of AMB. Overall, the combined use of IPBC and AMB exhibited an increased algicidal effect, albeit the fractional inhibitory concentration index showed synergistic activity only against 3 P. zopfii genotype 2 isolates. For all the remaining isolates (87.5%), this combination produced only an additive effect. The MTT assay results showed both IPBC and AMB, at the concentrations employed in the study, to be nontoxic to the epithelial mammary gland cells (cell viability >90%). Notably, only IPBC at the highest concentration (i.e., 8 mg/L) exerted a slight cytotoxic effect on the cell line tested (mean cell viability: 88.54 ± 3.88 and 90.66 ± 3.0, after 2 and 4 h of MTT treatment, respectively). The anti-Prototheca activity of IPBC was here demonstrated for the first time. In addition, the combined use of IPBC with AMB enhanced each other's effect, creating an additive rather than synergistic interaction. Both agents, used at concentrations corresponding to MIC values against Prototheca spp., showed no toxic effect for the mammary epithelial cells. In conclusion, IPBC, used either alone or in combination with AMB, can be considered a promising option in the treatment armamentarium for protothecal mastitis in dairy cows.