Isolation and identification of carotenoid producing yeast and evaluation of antimalarial activity of the extracted carotenoid(s) against P. falciparum

Background: Malaria is a big threat and one of the major diseases and important cause of human illness and death in developing countries, in which majority of deaths were found to be due to Plasmodium falciparum malaria. It is becoming a serious challenge to fight against malaria because of the emergence of Plasmodium falciparum strains resistant to all anti-malarial drugs. As microbial carotenoids are well-known anti-oxidants, performing critical functions in plants and animals, in this study, the extracted microbial carotenoids were tested for their anti-malarial activity. Methods: To determine the anti-malarial activity of microbial carotenoids, five isolated yeast strains were identified, and characterized for their carotenoid production. The evaluation of anti-malarial activity of extracted carotenoids was tested on Plasmodium falciparum strain 3D7 using in vitro growth inhibition assay. Data was analyzed by FACS (Fluorescence activated cell sorter) and counted via gold standard Geimsa-stained smears. Extracted yeast carotenoids showed a profound inhibitory effect at a certain concentration when compared to β- carotenoid as control. Results: Yeast carotenoids showed a profound inhibitory effect at a concentration of 10-3 µg/µl and 10-4µg/µl when compared to β- carotenoid as control. SYBR Green1 fluorescent dye was used to confirm the decrease in parasitemia at given range of concentration. Egress assay results suggested that treated parasite remained stalled at schizont stage with constricted morphology and were darkly stained. Non-toxicity of carotenoids on erythrocytes and on human liver hepatocellular carcinoma cells (HepG2 cells) was shown at a given concentration. Conclusions: Anti-oxidant and anti-carcinogenic activity of carotenoids is well established, so we embarked upon predicting anti-parasitic effects of yeast carotenoids to fight the dreaded disease, malaria. Results suggest that the extracted yeast carotenoids was able to kill the parasite by 98.3% and it was non-toxic to RBCs and HepG2 cells. This is the first report which provides strong evidence for anti-malarial effects of extracted yeast-carotenoids, which can be produced via a sustainable and cost-effective strategy and may be scaled up for industrial application. Keywords: Carotenoids, yeast, Rhodotorula, β carotene, Plasmodium falciparum, malaria

Evaluation of the process conditions for the production of microbial carotenoids by the recently isolated Rhodotorula mucilaginosa URM 7409

This study aimed to improve the physical and nutritional process conditions for the production of carotenoids by the newly isolated Rhodotorula mucilaginosa, a red basidiomycete yeast. The carotenoid bioproduction was improved using an experimental design technique, changing the process characteristics of agitation (130 rpm to 230 rpm) and temperature (25 °C to 35 °C) using seven experiments, followed by a 25-1 fractional design to determine the relevant factors that constitute the culture medium (glucose, malt extract, yeast extract, peptone and initial pH). A complete second order experimental design was then carried out to optimize the composition of the culture medium, the variables being yeast extract (0.5 to 3.5 g/L), peptone (1 to 5 g/L) and the initial pH (5.5 to 7.5), with 17 experiments. The maximum carotenoid production was 4164.45 μg/L (252.99 μg/g), obtained in 144 h in YM (yeast malt) medium with 30 g/L glucose, 10 g/L malt extract, 2 g/L yeast extract, 3 g/L peptone, an initial pH 6, 130 rpm and 25 °C, demonstrating the potential of this yeast as a source of bio-pigments. In this work, the nitrogen sources were the factors that most influenced the intracellular accumulation of carotenoids. The yeast R. mucilaginosa presented high production at a bench level and may be promising for commercial production.

Detection of pigments of halophilic endoliths from gypsum: Raman portable instrument and European Space Agency's prototype analysis

A prototype instrument, under development at the University of Leicester, for the future European Space Agency (ESA) ExoMars mission, was used for the analysis of microbial pigments within a stratified gypsum crust from a hypersaline saltern evaporation pond at Eilat (Israel). Additionally, the same samples were analysed using a miniaturized Raman spectrometer, featuring the same 532 nm excitation. The differences in the position of the specific bands, attributed to carotenoid pigments from different coloured layers, were minor when analysed by the ESA prototype instrument; therefore, making it difficult to distinguish among the different pigments. The portable Delta Nu Advantage instrument allowed for the discrimination of microbial carotenoids from the orange/green and purple layers. The purpose of this study was to complement previous laboratory results with new data and experience with portable or handheld Raman systems, even with a dedicated prototype Raman system for the exploration of Mars. The latter is equipped with an excitation wavelength falling within the carotenoid polyene resonance region. The ESA prototype Raman instrument detected the carotenoid pigments (biomarkers) with ease, although further detailed distinctions among them were not achieved.