ß-Carotene production from sugarcane molasses by a newly isolated Rhodotorula toruloides L/24-26-1.

Production of carotenoids by yeast fermentation is an advantaged technology due to its easy scaling and safety. Nevertheless, carotenoid production needs an economic culture medium and other efficient yeast stains. The study aims to isolate and identify a yeast strain capable of producing carotenoids using a cost-effective substrate. A new strain was identified as Rhodotorula toruloides L/24-26-1, which can produce carotenoids at different pretreated and unpretreated sugarcane molasses concentrations (40 and 80 g/L). The highest biomass concentration (18.6 ± 0.6 g/L) was reached in the culture using 80 g/L of hydrolyzed molasses. On the other hand, the carotenoid accumulation reached the maximum value using pretreated molasses at 40 g/L (715.4 ± 15.1 µg/g d.w). In this case, the ß-carotene was 1.5 times higher than that on the control medium. The yeast growth in molasses was not correlated with carotenoid production. The most outstanding production of The DPPH, ABTS, and FRAP tests demonstrated the antioxidant activity of the obtained carotenogenic extracts. This research demonstrated the R. toruloides L/24-26-1 strain biotechnological potential for carotenoid compounds. The yeast produces carotenoids with antioxidant activity in an inexpensive medium, such as sulfuric acid pretreated and unpretreated molasses.

Rhodotorula mucilaginosa A8, a potential helper strain in a vitamin C microbial fermentation process.

In the vitamin C microbial fermentation system, oxidative stress limits the growth and 2-keto-l-gulonic acid (2-KLG, the precursor of vitamin C) production of Ketogulonicigenium vulgare. Most Bacillus strains, as helper strains, have been reported to release key biomolecules to reduce oxidative stress and promote the growth and 2-KLG production of K. vulgare. To understand the specific mechanism by which the helper strain and K. vulgare interact to reduce oxidative stress, a novel helper strain, Rhodotorula mucilaginosa A8, was used to construct a consortium in the co-culture fermentation system. Based on the activities of the antioxidant enzymes and quantitative polymerase chain reaction (qPCR) analysis, R. mucilaginosa A8 could reduce oxidative stress and increase 2-KLG production in K. vulgare by upregulating antioxidant enzyme activities and related gene-expression levels. In addition, the carotenoids of R. mucilaginosa promoted 2-KLG production in K. vulgare. Coculture of R. mucilaginosa with K. vulgare increased the yield of carotenoids. This study suggested that helper strains with the ability to reduce oxidative stress in K. vulgare would likely act as potential helper strains for facilitating 2-KLG biosynthesis. This work could provide a theoretical basis for the search for potential helper strains for vitamin C microbial fermentation and for the construction of synthetic microbial communities to produce valuable products.

Cultivation of yeasts on liquid digestate to remove organic pollutants and nutrients and for potential application as co-culture with microalgae.

In this study, the growth of yeast and yeast-like fungi in the liquid digestate from vegetable wastes was investigated in order to remove nutrients and organic pollutants, and for their application as co-culture members with green microalgae. The studied yeast strains were characterized for their assimilative and enzymatic profiles as well as temperature requirements. In the first experimental stage, the growth dynamics of each strain were determined, allowing to select the best yeasts for further studies. In the subsequent stage, the ability of selectants to remove organic pollutants was assessed. Different cultivation media containing respectively 1:3, 1:1, 3:1 vol ratio of liquid digestate and the basal minimal medium were used. Among all tested yeast strains, Rhodotorula mucilaginosa DSM 70825 showed the most promising results, demonstrating the highest potential for removing organic substrates and nutrients. Depending on the medium, this strain achieved 50-80% sCOD, 45-60% tVFAs, 21-45% TN, 33-52% PO43- reduction rates. Similar results were obtained for the strain Candida sp. OR687571. The high nutrient and organics removal efficiency by these yeasts could likely be linked to their ability to assimilate xylose (being the main source of carbon in the liquid digestate). In culture media containing liquid digestate, both yeast strains achieved good viability and proliferation potential. In the liquid digestate medium, R. mucilaginosa and Candida sp. showed vitality at the level of 51.5% and 45.0%, respectively. These strains seem to be a good starting material for developing effective digestate treatment strategies involving monocultures and/or consortia with other yeasts or green microalgae.

A Tripartite Interaction among the Basidiomycete Rhodotorula mucilaginosa, N2-Fixing Endobacteria, and Rice Improves Plant Nitrogen Nutrition.

Nitrogen (N) limits crop yield, and improvement of N nutrition remains a key goal for crop research; one approach to improve N nutrition is identifying plant-interacting, N2-fixing microbes. Rhodotorula mucilaginosa JGTA-S1 is a basidiomycetous yeast endophyte of narrowleaf cattail (Typha angustifolia). JGTA-S1 could not convert nitrate or nitrite to ammonium but harbors diazotrophic (N2-fixing) endobacteria (Pseudomonas stutzeri) that allow JGTA-S1 to fix N2 and grow in a N-free environment; moreover, P. stutzeri dinitrogen reductase was transcribed in JGTA-S1 even under adequate N. Endobacteria-deficient JGTA-S1 had reduced fitness, which was restored by reintroducing P. stutzeri JGTA-S1 colonizes rice (Oryza sativa), significantly improving its growth, N content, and relative N-use efficiency. Endofungal P. stutzeri plays a significant role in increasing the biomass and ammonium content of rice treated with JGTA-S1; also, JGTA-S1 has better N2-fixing ability than free-living P. stutzeri and provides fixed N to the plant. Genes involved in N metabolism, N transporters, and NODULE INCEPTION-like transcription factors were upregulated in rice roots within 24 h of JGTA-S1 treatment. In association with rice, JGTA-S1 has a filamentous phase and P. stutzeri only penetrated filamentous JGTA-S1. Together, these results demonstrate an interkingdom interaction that improves rice N nutrition.

Overexpression and repression of key rate-limiting enzymes (acetyl CoA carboxylase and HMG reductase) to enhance fatty acid production from Rhodotorula mucilaginosa.

Implementing two-way strategies to enhance the lipid production in Rhodotorula mucilaginosa with the help of metabolic engineering was focused on the overexpression of acetyl coenzyme A carboxylase (ACC1 carboxylase) gene and repression of 3-hydroxy 3-methylglutaryl reductase (HMG-CoA reductase). Using an inducer (sodium citrate) and inhibitor (rosuvastatin), the amounts of biomass, lipid, and carotenoid were estimated. In the presence of inhibitor (200 mM), 62% higher lipid concentration was observed, while 44% enhancement was recorded when inducer (3 mM) was used. A combination of both inhibitor and inducer resulted in a 57% increase in lipid concentration by the oleaginous yeast. These results were again confirmed by real-time polymerase chain reaction by targeting the expression of the genes coding for ACC1 carboxylase and 13-fold increase was recorded in the presence of inducer as compared with control. This combined strategy (inducer and inhibitor use) has been reported for the first time as far as the best of our knowledge. The metabolic engineering strategies reported here will be a powerful approach for the enhanced commercial production of lipids.

Biosurfactant production from newly isolated Rhodotorula sp.YBR and its great potential in enhanced removal of hydrocarbons from contaminated soils.

One of the very promising methods in the field of bioremediation of hydrocarbons is the application of biosurfactant- producing microorganisms based on the use of wastewater as renewable substrates of culture media, contributing to the reduction of costs. With this aim, the production, characterization and properties of the yeast strain YBR producing a biosurfactant newly isolated from an oilfield in Algeria, using wastewater from olive oil mills (OOMW) as a substrate for a low-cost and effective production, have been investigated. Screening of biosurfactant production was carried out with different tests, including emulsification index test (E24), drop collapse test, oil spreading technique and measurement of surface tension (ST). The isolated yeast strain was found to be a potent biosurfactant producer with E24 = 69% and a significant reduction in ST from 72 to 35 mN m-1. The study of the cultural, biochemical, physiological and genetic characteristics of the isolate allowed us to identify it as Rhodotorula sp. strain YBR. Fermentation was carried out in a 2.5 L Minifors Bioreactor using crude OOMW as culture medium, the E24 value reached 90% and a reduction of 72 to 35 mN m-1 in ST. A biosurfactant yield = 10.08 ± 0.38 g L-1 was recorded. The characterization by semi-purification and thin layer chromatography (TLC) of the crude extract of biosurfactant showed the presence of peptides, carbohydrates and lipids in its structure. The crude biosurfactant exhibited interesting properties such as: low critical micellar concentration (CMC), significant reduction in ST and strong emulsifying activity. In addition, it has shown stability over a wide range of pH (2-12), temperature (4-100 °C) and salinity (1-10%). More interestingly, the produced biosurfactant has proven to be of great potential application in the remobilization of hydrocarbons from polluted soil with a removal rate of greater than 95%.

Fatty acids profiles and estimation of the biodiesel quality parameters from Rhodotorula spp. from Antarctica.

OBJECTIVE: Oleaginous yeasts are a renewable and alternative source of oil for third-generation biodiesel. This work aimed to evaluate the effects of glucose concentration (30-100 g L-1) on growth, lipid synthesis, and fatty acids (FA) profile of three Rhodotorula spp. (R. glacialis R15, R. glutinis R4, and R. glutinis R48) isolated from Antarctica, and estimate the key quality parameters of the biodiesel produced by yeasts to confirm their potential as feedstocks for third-generation biodiesel synthesis. RESULTS: Yeasts accumulated 50-69.5% of lipids (w/w) under nitrogen-limitation and glucose-excess (C/N = 40-133). Glucose concentration increase influenced positively lipid accumulation (69.5% w/w) and FA profile of R. glacialis R15. Lipid accumulation (53% on average) of R. glutinis strains was not significantly affected by glucose concentration; content of saturated (~ 30%) and polyunsaturated FA (~ 29-30%) was slightly influenced. FA profiles of lipids synthesized by R15, R4, and R48 are similar to vegetable oils used in biodiesel industry with C16 and C18 FA (95-99%) as the major components, and contain mainly oleic (C18:1), palmitic (C16:0), and linoleic (C18:2) acids, which are suitable for biodiesel synthesis. Estimated fuel properties for biodiesel produced by R15, R4, and R48 satisfied all the criteria established by ASTM D6751 and EN 14214 with good cetane number, iodine value, and oxidation stability. An improvement in biodiesel quality of R15 was observed with the glucose increase. The best global properties of biodiesel from R4 were obtained with 30 g L-1 of glucose. CONCLUSIONS: Rhodotorula spp. from Antarctica are promising candidates for third-generation biodiesel synthesis.

Reutilization of residual glycerin for the produce ß-carotene by Rhodotorula minuta.

This study aimed to evaluate the production of carotenoid pigments by Rhodotorula spp. in submerged fermentation, using residual glycerin from biodiesel production as a carbon source. Chromatographic analysis by HPLC showed that the residual glycerin used as substrate was 57.88% composed of glycerol. The best growth conditions were found in the fermentation medium composed of residual glycerin at a concentration of 30 g/L and pH 9. From all the Rhodotorula strains tested, R. minuta URM6693 was selected because of their performance and adaptation in all culture media assayed. The maximum volumetric production of carotenoids was found at 48 h (equivalent to 17.20 mg/L, for the R. minuta). The production of ß-carotene since the first 24 h of fermentation reach a final concentration of 1.021 mg/L. The yeast Rhodotorula minuta proved its capability to efficiently convert the substrate (mainly at the concentration of 50 g/L), obtaining products of biotechnological interest.

Microbial lipid production by oleaginous yeasts grown on Scenedesmus obtusiusculus microalgae biomass hydrolysate.

Due to increasing oil prices and climate change concerns, biofuels have become increasingly important as potential alternative energy sources. However, the use of arable lands and valuable resources for the production of biofuel feedstock compromises food security and negatively affect the environment. Single cell oils (SCOs), accumulated by oleaginous yeasts, show great promise for efficient production of biofuels. However, the high production costs attributed to feedstocks or raw materials present a major limiting factor. The fermentative conversion of abundant, low-value biomass into microbial oil would alleviate this limitation. Here, we explore the feasibility of utilizing microalgae-based cell residues as feedstock for yeast oil production. We developed an efficient, single-step enzymatic hydrolysis to generate Scenedesmus obtusiusculus hydrolysate (SH) without thermo-chemical pretreatment. With this eco-friendly process, glucose conversion efficiencies reached 90-100%. Cutaneotrichosporon oleaginosus, Cryptococcus curvatus and Rhodosporidium toruloides were cultivated on SH as sole nutrients source. Only C. oleaginosus was able to accumulate intracellular lipids, with a 35% (g lipid/g DCW) content and a yield of 3.6 g/L. Our results demonstrate the potential valorization of algal biomass into desired end-products such as biofuels.

Multi-omics metabolism analysis on irradiation-induced oxidative stress to Rhodotorula glutinis.

Oxidative stress is induced in many organisms by various natural abiotic factors including irradiation. It has been demonstrated that it significantly improves growth rate and lipid production of Rhodotorula glutinis. However, the specific mechanism of how irradiation influences the metabolism of R. glutinis remains still unavailable. To investigate and better understand the mechanisms involved in irradiation-induced stress resistance in R. glutinis, a multi-omics metabolism analysis was implemented. The results confirmed that irradiation indeed not only improved cell biomass but also accelerated the production of carotenoids and lipids, especially neutral lipid. Compared with the control, metabolome profiling in the group exposed to irradiation exhibited an obvious difference in the activation of the tricarboxylic acid cycle and triglyceride (TAG) production. The results of proteome analysis (data are available via ProteomeXchange with identifier PXD009678) showed that 423 proteins were changed significantly, and proteins associated with protein folding and transport, the Hsp40 and Sec12, were obviously upregulated, indicating that cells responded to irradiation by accelerating the protein folding and transport of correctly folded proteins as well as enhanced the degradation of misfolded proteins. A significant upregulation of the carotenoid biosynthetic pathway was observed which revealed that increased carotenoid content is a cellular defense mechanism against oxidative stress generated by irradiation. Therefore, the results of comprehensive omics analysis provide intensive insights on the response mechanism of R. glutinis to irradiation-induced oxidative stress which could be helpful for using irradiation as an effective strategy to enhance the joint production of the neutral lipid and carotene.

Simultaneous mitigation of aluminum, salinity and drought stress in Lactuca sativa growth via formulated plant growth promoting Rhodotorula mucilaginosa CAM4.

In the present study, a potent Aluminum (Al) resistant yeast strain CAM4 was isolated from rhizosphere soil of Rubus geoides, grown in acidic Andisols and identified as Rhodotorula mucilaginosa by 18S rRNA gene sequence analysis. The strain CAM4 was selected in terms of abiotic stress tolerance to Al, salinity and drought with multiple plant growth promoting (PGP) traits. Besides, strain CAM4 also exhibited Al removal efficiency (80-88%) from the culture medium even under combined stresses of salinity and drought. The sawdust-based formulation of strain CAM4 (sawdust-molasses 5%-PEG 1%-strain CAM4) showed higher cell viability of up to 24 weeks (8.54 log CFU g-1). Inoculation of formulated strain CAM4 significantly enhanced the various morphological and biochemical characters of Lactuca sativa grown under abiotic stress conditions. The formulated strain CAM4 also reduced the accumulation of Al in L. sativa as well that conferring Al tolerance to the plants. The study concludes that strain CAM4 could be used as a biofertilizer for healthy and safe crop production in soils, with Al toxicity as well as combined salt and drought stresses.

Biochemical changes of polysaccharides and proteins within EPS under Pb(II) stress in Rhodotorula mucilaginosa.

Microorganisms have been widely applied to heavy metal adsorption due to their strong secretion of extracellular polymeric substances (EPS). This study explored the responses of Rhodotorula mucilaginosa (R1, a red yeast with substantial EPS supply) under Pb stress. The maximum sorption of Pb cations by R1 was ~650 mg/L. In particular, despite the declined microbial biomass, the total Pb sorption after incubation was actually elevated in the solution with high Pb concentration. At 0-1000 mg/L Pb(NO3)2 level, the longitudinal sizes of the yeast capsules increased from 2.04 to 2.90 µm. At 1500 mg/L, however, the survived yeast started to lose the membrane integrity of the cells. Meanwhile, the percentages of organic carbon contents of EPS decreased from 40% to 33% when the Pb(NO3)2 concentration raised to 2500 mg/L, confirming the incorporation of Pb2+ cations into the fungal EPS during the sorption. For the survived R1 cells, function of polysaccharides to resist Pb toxicity only worked at extremely high Pb(NO3)2 levels (>= 1500 mg/L). In contrast, proteins showed continuously enhanced ability to resist Pb toxicity, consistent with their increasing content (per cell) in the EPS. Moreover, ATR-IR spectra showed that the intensity of amide II peak at 1540 cm-1 was significantly increased, indicating elevated glutathione (GSH) in EPS. This suggested that GSH could be the critical Pb-binding component in EPS proteins. This study hence elucidated roles of polysaccharides and proteins in EPS under the toxicity caused by heavy metals.

Allium sativum Extract Chemical Composition, Antioxidant Activity and Antifungal Effect against Meyerozyma guilliermondii and Rhodotorula mucilaginosa Causing Onychomycosis.

Onychomycosis is a major health problem due to its chronicity and resistance to therapy. Because some cases associate paronychia, any therapy must target the fungus and the inflammation. Medicinal plants represent an alternative for onychomycosis control. In the present work the antifungal and antioxidant activities of Alium sativum extract against Meyerozyma guilliermondii (Wick.) Kurtzman & M. Suzuki and Rhodotorula mucilaginosa (A. Jörg.) F.C. Harrison, isolated for the first time from a toenail onychomycosis case, were investigated. The fungal species were confirmed by DNA molecular analysis. A. sativum minimum inhibitory concentration (MIC) and ultrastructural effects were examined. At the MIC concentration (120 mg/mL) the micrographs indicated severe structural alterations with cell death. The antioxidant properties of the A. sativum extract were evaluated is a rat turpentine oil induced inflammation, and compared to an anti-inflammatory drug, diclofenac, and the main compound from the extract, allicin. A. sativum reduced serum total oxidative status, malondialdehyde and nitric oxide production, and increased total thiols. The effects were comparable to those of allicin and diclofenac. In conclusion, the garlic extract had antifungal effects against M. guilliermondii and R. mucilaginosa, and antioxidant effect in turpentine-induced inflammation. Together, the antifungal and antioxidant activities support that A. sativum is a potential alternative treatment in onychomycosis.

Effect of exogenous stress factors on the biosynthesis of carotenoids and lipids by Rhodotorula yeast strains in media containing agro-industrial waste.

In this study, we aimed to determine the effect of exogenous stress factors (sodium chloride as osmotic stressor, hydrogen peroxide as an inducer of oxidative stress, white light irradiation, and low temperature) on the biosynthesis of carotenoids and lipids by red yeast (Rhodotorula glutinis, R. mucilaginosa, and R. gracilis) during cultivation in media containing potato wastewater and glycerol. According to our results, the yeast were able to grow and biosynthesize lipids and carotenoids in the presence of the applied stress factors. Low temperature caused an increase in the biosynthesis of intracellular lipids and carotenoids. R. gracilis synthesized lipids (21.1 g/100 gd.w.) and carotenoids (360.4 µg/gd.w.) in greater quantities than that of other strains. Under these conditions, there was also an increase in the content of unsaturated fatty acids, especially linoleic and linolenic acids. The highest percentage of polyunsaturated fatty acid (PUFA) (30.4%) was synthesized by the R. gracilis yeast after cultivation at 20°C. Their quantity was 2.5-fold greater than that of the biomass grown in control conditions. The contribution of individual carotenoid fractions depended both on the yeast strain and the culture conditions. Induction of osmotic stress and low temperature intensified the biosynthesis of ß-carotene (up to 73.9% of the total carotenoid content). In oxidative stress conditions, yeast synthesized torulene (up to 82.2%) more efficiently than under other conditions, whereas white light irradiation increased the production of torularhodin (up to 20.0%).

CAR gene cluster and transcript levels of carotenogenic genes in Rhodotorula mucilaginosa.

A molecular approach was applied to the study of the carotenoid biosynthetic pathway of Rhodotorula mucilaginosa. At first, functional annotation of the genome of R. mucilaginosa C2.5t1 was carried out and gene ontology categories were assigned to 4033 predicted proteins. Then, a set of genes involved in different steps of carotenogenesis was identified and those coding for phytoene desaturase, phytoene synthase/lycopene cyclase and carotenoid dioxygenase (CAR genes) proved to be clustered within a region of ~10 kb. Quantitative PCR of the genes involved in carotenoid biosynthesis showed that genes coding for 3-hydroxy-3-methylglutharyl-CoA reductase and mevalonate kinase are induced during exponential phase while no clear trend of induction was observed for phytoene synthase/lycopene cyclase and phytoene dehydrogenase encoding genes. Thus, in R. mucilaginosa the induction of genes involved in the early steps of carotenoid biosynthesis is transient and accompanies the onset of carotenoid production, while that of CAR genes does not correlate with the amount of carotenoids produced. The transcript levels of genes coding for carotenoid dioxygenase, superoxide dismutase and catalase A increased during the accumulation of carotenoids, thus suggesting the activation of a mechanism aimed at the protection of cell structures from oxidative stress during carotenoid biosynthesis. The data presented herein, besides being suitable for the elucidation of the mechanisms that underlie carotenoid biosynthesis, will contribute to boosting the biotechnological potential of this yeast by improving the outcome of further research efforts aimed at also exploring other features of interest.

Yeasts from skin colonization are able to cross the acellular dermal matrix.

In recent decades, the prognosis for burn patients has improved considerably with the development of specialized care. The acellular dermal matrix (ADM) is a totally artificial acellular device that functions to control water loss, prevent penetration by bacteria and allow migration of endothelial cells and fibroblasts from patient tissues. However, little is known about its effectiveness against yeasts. The present study evaluated the capacity of colonization and migration of some human commensal yeasts. Three clinical isolates from skin scales, identified as Candida parapsilosis, Candida glabrata and Rhodotorula mucilaginosa, were used. Their ability to cross the ADM was evaluated. After three days, all isolates had crossed the ADM. C. parapsilosis showed the lowest growth, while R. mucilaginosa showed intermediate and C. glabrata the highest growth. In the plates incubated for seven days, the growth of C. parapsilosis and C. glabrata increased by 1 log over the third day. All isolates have the capacity to colonize and migrate through the matrix, increasing the potential risk to burn patients, who can develop severe and even fatal infections by invasive fungi.

In situ microstructure and rheological behavior of yeast biofilms from the juice processing industries.

The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula mucilaginosa, Candida krusei, C. kefyr and C. tropicalis) isolated from the juice processing industries have been investigated. Variables studied were: the food matrix (apple/pear juice), the sugar concentration (6/12 °Bx) and the hydrodynamic conditions (static/turbulent flow). A range of environmental cues were included as the mechanical properties of biofilms are complex. Yeast counts were significantly higher in turbulent flow compared with under static conditions. The thickness of the biofilm ranged from 38 to 148 µm, from static to turbulent flow. Yeast biofilms grown under turbulent flow conditions were viscoelastic with a predominant solid-like behavior and were structurally stronger than those grown under static conditions, indicating gel-type structures. Only the type of flow had a significant effect on [Formula: see text] and G*. Flow velocity and nutrient status modulated the biofilm thickness, the biomass and the mechanical properties. A better knowledge of the factors controlling biofilm formation will help in the development of control strategies.

Isolation of Rhodotorula mucilaginosa from blood cultures in a tertiary care hospital.

Rhodotorula species have traditionally been considered as one of common non-virulent environmental inhabitant. They have emerged as an opportunistic pathogen, particularly in immunocompromised hosts and most infections have been associated with intravenous catheters in these patients. We review the isolates in blood cultures of Rhodotorula mucilaginosa in our Hospital. We describe the demographic and clinical features of the cases and the antifungal susceptibility profiles of the isolates. Selected patients had an isolation of R. mucilaginosa in blood cultures in our tertiary care Hospital. All data were collected retrospectively from clinical records during 5 years. We report 8 isolates in blood, two of them were considered contaminants. Immunosuppression, surgery, previous antibiotic therapy were common clinical features. For all the isolates, minimum inhibitory concentration (MIC) values were high for echinocandins and azoles and low for amphotericin B and 5-flucytosine. One strain showed atypical susceptibility profile. Rhodotorula mucilaginosa may be present on the skin and blood cultures can be contaminated. Fungaemia due to R. mucilaginosa is a rare clinical entity which requires risk factors but clinically relevant because of the multiresistant profile. Rhodotorula mucilaginosa shows high MIC values for azoles and echinocandins, therefore amphotericin B and flucytosine must be administered as antifungal therapy.

Biodegradation and detoxification of aliphatic and aromatic hydrocarbons by new yeast strains.

Seeking new efficient hydrocarbon-degrading yeast stains was the main goal of this study. Because microorganisms are greatly affected by the environmental factors, the biodegradation potentiality of the microorganisms varies from climatic area to another. This induces research to develop and optimize the endemic organisms in bioremediation technology. In this study, 67 yeast strains were tested for their growth potentiality on both aliphatic and aromatic hydrocarbons. The most efficient six strains were identified using sequence analysis of the variable D1/D2 domain of the large subunit 26S ribosomal DNA. The identity of these strains was confirmed as Yamadazyma mexicana KKUY-0160, Rhodotorula taiwanensis KKUY-0162, Pichia kluyveri KKUY-0163, Rhodotorula ingeniosa KKUY-0170, Candida pseudointermedia KKUY-0192 and Meyerozyma guilliermondii KKUY-0214. These species are approved for their ability to degrade both aliphatic and aromatic hydrocarbons for the first time in this study. Although, all of them were able to utilize and grow on both hydrocarbons, Rhodotorula taiwanensis KKUY-0162 emerged as the best degrader of octane, and Rhodotorula ingeniosa KKUY-170 was the best degrader of pyrene. GC-MS analysis approved the presence of many chemical compounds that could be transitional or secondary metabolites during the utilization of the hydrocarbons. Our results recommend the application of these yeast species on large scale to approve their efficiency in bioremediation of oil-contamination of the environment. Using these yeasts, either individually or in consortia, could offer a practical solution for aquatic or soil contamination with the crude oil and its derivatives in situ.

Production and partial characterization of ß-1,3-glucanase obtained from Rhodotorula oryzicola.

The current study aims to assess the kinetics of population growth of Rhodotorula oryzicola and the production of ß-1,3-glucanase (EC 3.2.1.39) enzyme by this yeast. It also aims to obtain the optimum conditions of ß-1,3-glucanase enzymatic activity by varying the pH as well as to study the enzyme thermostability. R. oryzicola population doubled within 12 hr. During this period, 9.26 generations were obtained, with 1 hr and 29 min of interval from one generation to the other, with specific growth rate (µ) of 0.15 (hr-1). The entire microorganism growth process was monitored during ß-1,3-glucanases production, and the maximum value was obtained in the stationary phase in the 48-hr fermentation period. pH and temperature optimum values were 4.7 and 96°C, respectively. The enzyme maintained 88% of its activity when submitted to the temperature of 90°C for an incubation period of 1 hr. The results show that the enzyme can be used in industrial processes that require high temperatures and acidic pH.