Malt Medium Research Articles

Evaluation of some selected antibiotics and dyes removal by fungi isolated from wastewater sludge

In developing countries, stabilization ponds are the most common facilities wastewater treatment, where microbial consortia are the workhorse for removing organic contaminants. Fungi play an important role in the removal of organic matter. However, their efficiency in removing recalcitrant pollutants such as antibiotics and dyes still needs to be determined. The present work evaluates four fungal strains isolated from wastewater treatment lagoon systems (aerobic-anaerobic-anoxic) to remove persistent organic pollutants: Tilmicosin, Enrofloxacin, and Methylthionine chloride in Malt medium rich in carbon and in Mineral medium with only mineral nutrients. Fungi were isolated from sludge obtained from lagoons and identified based on their morphology. Removal assays were conducted in synthetic wastewater, with variations in operating conditions such as fungus type, temperature, and residence time. The quantification of contaminants was performed using UV-V spectrometry, and data on pH, conductivity, and spore concentration were obtained. The results were analyzed using R software, version 4.0.2. The results indicate that adsorption is the primary pathway in all cases. It was found that the greater the amount of fungal biomass produced during the test, the greater the absorption of the mode; that was the case with the Malt medium and dyes tests compared to Mineral medium and antibiotics tests. The studied fungi poorly removed antibiotics, around 20% in Malta medium and less than 10% in mineral medium, but are more capable of adsorbing Methylene blue, around 70% in Malta medium and less than 20% in the mineral medium. These results indicate natural fungi role in removing persistent organic pollutants (POPs). This shows that this type of plant needs the support of ternary treatments to eliminate POPs such as antibiotics. Limiting the discharge of this type of POPs is recommended as they could risk the biological remediation system’s health. Nevertheless, Fungal species from these lagoon systems can be used in dye removal processes.

A closed-loop circularity in wood sugar as a renewable carbon source for fungal pigment production and application of pigments in wood colouration

The main objective is to demonstrate closed-loop circularity in the production of fungal pigment from renewable wood sugar hydrolysate (WSH) and impregnation of colour pigment into wood. Talaromyces sp 43 M, isolated from a New Zealand vineyard, was identified as Talaromyces ruber (TR) using multi-gene phylogenetic analysis. A mild pretreatment followed by ball milling was used to prepare Pinus radiata pulp which was enzymatically hydrolysed to generate WSH. Malt 30 g/L or WSH 40 g/L were optimum carbon sources when supplemented with peptone 10 g/L and meat extract 1 g/L as optimum nitrogen sources giving maximum production of extracellular pigment. TR completely metabolizes multiple carbon sources as well as fermentation inhibitors to elicit pigment production. The CIELAB colour characteristics of the pigment vary as a response to carbon sources (malt vs WSH) and fermentation time. The fluorescent pigment produced in malt and WSH medium were efficiently impregnated into wooden blocks.

The bio3 mutation in sake yeast leads to changes in organic acid profiles and ester levels but not ethanol production

Biotin is an essential coenzyme that is bound to carboxylases and participates in fatty acid synthesis. The fact that sake yeast exhibit biotin prototrophy while almost all other Saccharomyces cerevisiae strains exhibit biotin auxotrophy, implies that biotin prototrophy is an important factor in sake brewing. In this study, we inserted a stop codon into the biotin biosynthetic BIO3 gene (cording for 7,8-diamino-pelargonic acid aminotransferase) of a haploid sake yeast strain using the marker-removable plasmid pAUR135 and investigated the fermentation profile of the resulting bio3 mutant. Ethanol production was not altered when the bio3 mutant was cultured in Yeast Malt (YM) medium containing 10% glucose at 15°C and 30°C. Interestingly, ethanol production was also not changed during the sake brewing process. On the other hand, the levels of organic acids in the bio3 mutant were altered after culturing in YM medium and during sake brewing. In addition, ethyl hexanoate and isoamyl acetate levels decreased in the bio3 mutant during sake brewing. Metabolome analysis revealed that the decreased levels of fatty acids in the bio3 mutant were attributed to the decreased levels of ethyl hexanoate. Further, the transcription level of genes related to the synthesis of ethyl hexanoate and isoamyl acetate were significantly reduced. The findings indicated that although the decrease in biotin biosynthesis did not affect ethanol production, it did affect the synthesis of components such as organic acids and aromatic compounds. Biotin biosynthesis ability is thus a key factor in sake brewing.

Optimization of culture conditions for the production of exopolysaccharides from marine isolate <i>Citrobacter</i> sp.

Exopolysaccharide (EPS) samples were collected from the Mandapam camp, India. Morphological, biochemical characterization and 16S rRNA gene sequencing were done and the candidate bacterium was confirmed as <i>Citrobacter</i> sp. EPS production was observed from bacteria in Malt medium broth (0.88 ± 0.04mg/ml). The optimal cultural conditions for EPS production were as follows: after 72 hours of incubation at pH 8.0 (0.75 ± 0.1 mg/ml), the temperature at 40⁰C (0.75 ± 0.1 mg/ml), 100 rpm (0.90 ± 0.1 mg/ml). In the experimentation, arabinose (carbon sources) (1. ± 0.120 mg/ml) and ammonium nitrate (nitrogen) (1.30 ± 0.1 mg/ml) showed better results for the yield of EPS. The highest production of EPS was recorded in Triton X-100 (surfactants) supplemented medium. The optimal production of EPS was obtained in 2.5% sodium chloride added medium. Then the 2.5% inoculum concentration better for maximizing the yield of EPS. The best yield of EPS was noticed in after 96 hours of incubation time.

Oxidative stress induced by plasma-activated water stimulates astaxanthin production in Phaffia rhodozyma

Astaxanthin is used extensively in the nutraceutical, aquaculture, and cosmetic industries. The current market necessitates higher astaxanthin production from Phaffia rhodozyma (P. rhodozyma) due to its higher cost compared to chemical synthesis. In this study, a bubble discharge reactor was developed to generate plasma-activated water (PAW) to produce PAW-made yeast malt (YM) medium. Due to oxidative stress induced by PAW, strains cultured in 15 and 30 min-treated PAW-made medium produced 7.9 ± 1.2 % and 12.6 ± 1.4 % more carotenoids with 15.5 ± 3.3 % and 22.1 ± 1.3 % more astaxanthin, respectively. Reactive oxygen species (ROS) assay results showed that ROS generated by plasma-water interactions elevated intracellular ROS levels. Proteomic analysis revealed increased expression of proteins involved in the cellular response to oxidative stress as well as carotenoid biosynthesis, both of which contribute to higher yields of astaxanthin. Overall, this study supports the potential of PAW to increase astaxanthin yields for industrial-scale production.

Absolute configuration of azaphilones from Monascus kaoliang KB9 and solvent effects on their keto and enol forms

Monascus fermented rice, also known as red yeast rice, exhibits a broad spectrum of biological activities due to its chemical constituents, such as monacolins and azaphilone pigments. Here, we cultured Monascus kaoliang KB9 in a liquid malt medium instead of on rice as a carbon source. Eleven known compounds (1–11) containing azaphilones and their early intermediate were isolated and identified. However, this was the first time that angular tricyclic azaphilones, monasfluols A (4) and B (7), acetyl-monasfluol A (5) and monasfluore A (6), were isolated from this species. Interestingly, all isolated tricyclic azaphilones existed exclusively in enol form in CD3OD, as evidenced by NMR spectroscopy. The absolute configuration of compounds 4–7 was also first experimentally identified based on ECD spectroscopy combined with conformational analyses using computational techniques. The assigned stereochemistry of Monascus azaphilones in this work provides essential structural information that will benefit future biological and pharmaceutical investigations.

Increasing the Production of \u03b2-Glucan from Saccharomyces carlsbergensis RU01 by Using Tannic Acid

In this study, we increased β-glucan production from brewer’s yeast, Saccharomyces carlsbergensis RU01, by using tannic acid. High-pressure freezing and transmission electron microscopy (HPF-TEM) revealed that the yeast cell wall obtained from yeast malt (YM) medium supplemented with 0.1% w/v tannic acid was thicker than that of yeast cultured in YM medium alone. The production of β-glucan from S. carlsbergensis RU01 was optimized in 3% w/v molasses and 0.1% w/v diammonium sulfate (MDS) medium supplemented with 0.1% w/v tannic acid. The results showed that MDS medium supplemented with 0.1% w/v tannic acid significantly increased the dry cell weight (DCW), and the β-glucan production was 0.28±0.01% w/v and 11.99±0.04% w/w. Tannic acid enhanced the β-glucan content by up to 42.23%. β-Glucan production in the stirred tank reactor (STR) was 1.4-fold higher than that in the shake flask (SF) culture. Analysis of the β-glucan composition by Fourier transform infrared (FTIR) spectroscopy showed that the β-glucan of S. carlsbergensis RU01 cultured in MDS medium supplemented with 0.1% w/v tannic acid had a higher proportion of polysaccharide than that of the control. In addition, β-glucans from brewer’s yeast can be used as prebiotic and functional foods for human health and in animal feed.

COMPARATIVE EFFICACY OF FOUR ORGANIC SOLVENT FRACTIONS OF LEAF EXTRACT OF HEMP AGAINST Aspergillus versicolor

The fungus Aspergillus versicolor is generally found on food products and produces sterigmatocystin, a carcinogenic and hepatotoxic mycotoxin. This study reports the usefulness of polar and non-polar fractions of methanolic extract of hemp (Cannabis sativa L.) leaves against this fungus. Dried leaves of hemp were soaked in methanol for two weeks. After filtration and evaporation, water was added to the residual and partitioned with n-hexane, chloroform, ethyl acetate and n-butanol. Different concentrations of each fraction were prepared which ranged from 1.562 to 200 mg mL-1. Antifungal activity was carried out in malt extract broth medium. In general, all the concentrations of the four organic solvent fractions significantly controlled the growth of A. versicolor. There was 71–82%, 59–82%, 65–80% and 69–82% decline in biomass of A. versicolor due to n-hexane, chloroform, ethyl acetate and n-butanol fractions, respectively. It is concluded that different fractions of leaf extract of C. sativa has remarkable potential in controlling growth of A. versicolor.

Iron-enriched mycelia of edible and medicinal basidiomycetes

ABSTRACT Iron bioaccumulation in basidiomycetes is an alternative to recover ferrous sulphate from titanium dioxide pigment production and to produce an iron-enriched mycelial biomass. This study aimed to evaluate iron bioaccumulation capacity in vegetative mycelium of edible and medicinal fungi grown in malt extract liquid medium with different ferrous sulphate contents. Five basidiomycetes were grown in malt extract liquid medium with different iron contents from 0.116 to 100 mg L−1 iron. The iron content of dried mycelial biomass bioaccumulated with iron was determined by flame atomic absorption spectrophotometry. All fungi grew on the iron culture media and the mycelial biomass growth ranged from 3.24 ± 0.65a mg mL−1 to 12.46 ± 0.29 mg mL−1. Iron addition to culture media increased the iron content in the mycelial biomass from 4000–13,000-fold compared with control. Pleurotus ostreatus (2181 ± 218 mg kg−1) presented the greatest iron content in the mycelial biomass, followed by Schizophyllum commune (1769 ± 131 mg kg−1), Agaricus subrufescens (1272 ± 8.84 mg kg−1), and Ganoderma lucidum (840 ± 75 mg kg−1). P. ostreatus, followed by S. commune, and G. lucidum at 90 and 100 mg L−1 iron in the culture medium are the best choices to produce iron-enriched mycelial biomass. This extensive study of several edible and medicinal basidiomycetes grown in different iron contents was effective in recovering ferrous sulphate byproduct and transferring it to mycelium to produce a new nutraceutical food of iron-enriched mycelial biomass.

A novel source of the cardiac glycoside digoxin from the endophytic fungus Epicoccum nigrum: isolation, characterization, production enhancement by gamma irradiation mutagenesis and anticancer activity evaluation.

Different endophytic fungi were isolated and screened for their digoxin-producing ability. Strain improvement and different culture conditions were studied for more effective production of digoxin. Among the isolated fungi, an isolate produced digoxin in a concentration of 2·07mgl-1 . The digoxin-producing fungal isolate was identified as Epicoccum nigrum Link according to the morphological features and phylogenetic analyses. The potentiality of the fungal strain for production enhancement of digoxin was performed by gamma radiation mutagenesis. Gamma irradiation dose of 1000Gy intensified the digoxin yield by five-fold. Using this dose, a stable mutant strain with improved digoxin productivity was isolated and the stability for digoxin production was followed up across four successive generations. In the effort to increase digoxin magnitude, selection of the proper cultivation medium, addition of some elicitors to the most proper medium and several physical fermentation conditions were tested. Fermentation process carried out in malt extract autolysate medium (pH 6·5) supplemented by methyl jasmonate and inoculated with 2ml of 6-day-old culture and incubated at 25°C for 10days stimulated the highest production of digoxin to attain 50·14mgl-1 . Moreover, cytotoxicity of digoxin separated from the fungal culture was tested against five different cancer cell lines. Based on the MTT assay, digoxin inhibited the proliferation of the five different cancer cell lines and the recorded 50% inhibitory concentration ranged from 10·76 to 35·14μgml-1 . This is the first report on the production and enhancement of digoxin using fungal fermentation as a new and alternate source with high productivity. These findings offer new and alternate sources with excellent biotechnological potential for digoxin production by fungal fermentation. Moreover, digoxin proved to be a promising anticancer agent whose anticancer potential should be assessed in prospective cancer therapy.

CAROTENOID-PRODUCING YEASTS IN THE BRAZILIAN BIODIVERSITY: ISOLATION, IDENTIFICATION AND CULTIVATION IN AGROINDUSTRIAL WASTE

ABSTRACT Different yeast strains from forests located in southern Brazil, with potential to produce carotenoids, were isolated. Three microorganisms were selected as potential carotenoid producers. Sporiodiobolus pararoseus, Rhodotorula mucilaginosa and Pichia fermentans were grown in Yeast Malt (YM) medium and the carotenoids produced identified as cryptoxanthin and β-carotene. In order to reduce production costs, agroindustrial residues were used in the formulation of medium A (parboiled rice water and crude glycerol) and medium B (parboiled rice water and sugar cane molasses). The highest carotenoid production was obtained with S. pararoseus. It reached 905.30 μ gL-1 (122.82 μg g-1) in YM medium, 820 μg L-1 (68.04 μg g-1) in medium B and 710 μg L-1 (86.46 μg g-1) in medium A. R. mucilaginosa exhibited the best performance in medium B (360 μg L-1 and 30.16 μg g-1) and a new microorganism - P. fermentans - reached 48% (medium A) and 78% (medium B) of the value found in YM medium. Therefore, the agroindustrial residues under evaluation, which replaced the commonly used nitrogen and carbon sources in culture media, enabled the isolated yeasts to yield carotenoids.

Carotenoid Production by Rhodotorula mucilaginosa in Batch and Fed-Batch Fermentation Using Agroindustrial Byproducts.

SUMMARYCarotenoids are natural pigments that can be produced through biotechnological processes. However, the costs are relatively high and can be minimized by using lower-cost substrates as alternative nutrient sources. The fed-batch fermentation is one of the techniques used to obtain a high biomass concentration and/or maximum production. Thus, the aim of this work is to produce carotenoids in batch and fed-batch fermentation with the yeast Rhodotorula mucilaginosa CCT 7688 using agroindustrial byproducts in the culture medium. Carotenoid production was increased using experimental designs, which modified the concentration of the agroindustrial medium. In batch production the highest concentrations of total carotenoids (1248.5 μg/L) and biomass (7.9 g/L) were obtained in the medium containing 70 g/L sugar cane molasses and 3.4 g/L corn steep liquor at 25 °C and 180 rpm in 168 h, demonstrating an increase of 17% when compared to the standard yeast malt medium (1200 μg/L). In the fed-batch production, different feeding strategies were tested with 30 g/L sugar cane molasses and 6.5 g/L corn steep liquor, reaching a total carotenoid production of 3726 μg/L and biomass concentration of 16 g/L. Therefore, the strategy of the fed-batch process resulted in an increase in the carotenoid production of approx. 400% compared to that in the batch process (740.3 μg/L). Thus, the R. mucilaginosa strain has the potential to produce carotenoids in agroindustrial medium.

Growth and carotenogenesis in Rhodosporidium diobovatum IMB Y-5023: effects of culture medium and illumination intensity.

The oleaginous yeast Rhodosporidium diobovatum is a poorly described producer of carotenoids and may be of interest in biotechnology. This study investigated the effects of culture medium and illumination on effective carotenoid production by R. diobovatum IMB Y-5023. Yeast was cultured on carrot, bran extract, and modified yeast malt (YM) medium at illuminations in the 0-5000 lx range. Biomass, total carotenoids and their profile were assessed after cultivation. In order to compare samples, cluster analysis and principal component analysis were used to visualize the relationships between the variables and samples. Results show that it is not illumination but culture medium that is the main factor determining the quantity and proportions of carotenoids produced by R. diobovatum IMB Y-5023. The yeast grew and produced pigments throughout the tested range of illumination intensity. The modified YM medium was optimal for carotenogenesis. In cultures on that medium, the highest carotenoid yields of 24.98 mg g-1 dry cell weight and 77 mg L-1 were recorded. It was found that this yeast is capable of assimilating oligosaccharides and can grow and produce carotenoids in low-glucose media containing DP3 and DP4. Moreover R. diobovatum IMB Y-5023 produced lycopene as the main pigment independently of the culture conditions.

Chromium tolerance, oxidative stress response, morphological characteristics, and FTIR studies of phytopathogenic fungus Sclerotium rolfsii.

Sclerotium rolfsii is one of the most destructive fungal plant pathogens that can infect over 500 plants and can adapt to diverse environmental conditions. The present research work was carried out to evaluate the impact of both hexa- and trivalent chromium (Cr) on growth, morphology, enzymatic characteristics, and metal accumulation in S. rolfsii under laboratory conditions. Experiments were performed in both malt extract broth and agar growth medium amended with six different concentrations (10, 20, 40, 60, 80, and 100ppm) of each Cr(III) and Cr(VI) ions inoculated with fungus and incubated for 6-7days at 25±3°C. In broth medium, the total protein content was declined and activities of antioxidant enzymes were increased with an increase in metal concentrations. Lower concentrations (10ppm) of the metal ions stimulated the growth of fungus and higher concentrations (60-100) inhibited it. The Fourier transform infrared spectroscopy (FTIR) assessment showed hydroxyl, carboxyl, and amine groups as major metal binding sites. In agar medium, tolerance index was decreased up to 0.56 at 10-80ppm of Cr(III) and up to 0.62 at 10-60ppm of Cr(VI). Considerable modifications were observed in hyphal and sclerotial morphology with an increase in concentration of metal ions. The current study concluded that interference of Cr with growth and physiological process of S. rolfsii could affect its infection level on its host plant. This study provides important information regarding cultivation of susceptible plant varieties in Cr-polluted soil as evidenced by pathogen growth up to 50ppm of Cr(III) and Cr(VI) ions.

Headspace gas chromatography (HS-GC) analysis of imperative flavor compounds in Lactobacilli-fermented barley and malt substrates

The kinetics of volatile flavor compounds produced during the fermentation of cereal substrates inoculated with potentially probiotic lactobacilli were determined by HSGC. Barley and malt substrates were single cultured with Lactobacillus acidophilus, Lactobacillus reuteri, and Lactobacillus plantarum. The volatile flavor profiles were unique for each of the formulations. Acetaldehyde, acetone and ethyl acetate concentrations (2.86, 1.82, and 0.39 mg/ L, respectively) were significantly higher in L. plantarum fermented malt substrates. L. reuteri produced greater values of ethanol in the malt medium (2,300 mg/L) and the three lactobacilli strains produced diacetyl only in the malt substrate. These results suggest that the cereal substrate plays a meaningful role for the production of imperative flavor compounds in Lactobacillus-fermentations. Furthermore, the enzymatic systems of particular lactobacilli strains have the ability to produce flavor compounds at concentrations that can significantly influence the organoleptic quality of non-dairy fermented products for potential development.

Characterising the synbiotic beverages based on barley and malt flours fermented by Lactobacillusdelbrueckiiandparacaseistrains

This research was conducted to study physicochemical characteristics of fermented cereal-based beverages. The changes in levels of microbial population, pH, total titrable acidity (TTA), sugars (fructose, maltose and glucose), and organic acids (lactic and citric acids) of these beverages were determined during 48 h fermentation of malt, barley and barley-malt media by two potentially probiotic strains of Lactobacillus paracasei and Lactobacillus delbrueckii. Results showed that the selected probiotics well grew on single and mixed substrates without any supplementation. The highest microbial growth (9.7 log cfu/ml) was found in malt medium after 15 h fermentation. A significant decrease in pH value to 4.25 and a considerable increase in TTA level to 2.96 g/100 g lactic acid were obtained by initial 6-h fermentation of L. paracasei on malt medium. High-performance liquid chromatography analysis showed that lactic acid and glucose, respectively, were the major produced acid and metabolised sugar in the developed beverages. Higher sugar consumption by L. paracasei in comparison to L. delbrueckii was also observed. L. paracasei synthesised 5.12, 11.22 and 7.64 g lactic acid/l in the media containing barley, malt and barley-malt, respectively. Moreover, malt-based beverages fermented with L. delbrueckii were the best sample due to the highest cell viability (1.2×106 cfu/ml) after 4 weeks under cold-storage.

Biodegradation of Chlorpyrifos by Whole Cells of Marine-Derived Fungi Aspergillus sydowii and Trichoderma sp

This paper describes the screening of the growth of seven marine-derived fungi strains in the presence of chlorpyrifos in solid medium. The strains that showed best growth were A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932. Biodegradation reactions were performed in 10, 20 and 30 d in liquid medium containing commercial chlorpyrifos and mycelia from the selected strains. In 30 d, A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932 were able to degrade on average 63% and 72% of chlorpyrifos, respectively, and reduce the concentration of 3,5,6-trichloro-2-pyridinol, the metabolite formed by the enzymatic hydrolysis of chlorpyrifos. In 30 d, A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932 could use chlorpyrifos as sole source of carbon with low biodegradation percentages, 24% and 5%, respectively. Spontaneous hydrolysis was evaluated in malt medium, with the complete disappearance of chlorpyrifos. In distilled water, 61% of chlorpyrifos was hydrolyzed in 30 d.

Screening of basidiomycetes in submerged cultivation based on antioxidant activity.

Submerged cultivation of medicinal basidiomycetes is a reproducible and efficient method of producing mycelia and metabolites. The antioxidant activity indicates its medicinal properties and is an important tool for basidiomycete screening. In this study, we analyzed the production of mycelial biomass and exopolysaccharides and the antioxidant activity of basidiomycete strains in submerged cultivation. Twenty-five strains were used for submerged cultivation in extract malt medium, and the production of mycelial biomass and exopolysaccharides was evaluated. Antioxidant activity was determined using the 1,1-diphenyl-2-picrylhydrazyl method. Among the 25 evaluated strains, Lentinus crinitus produced the highest biomass, reaching 1190 ± 52 mg·L(-1)day(-1); Agaricus subrufescens strains had the highest exopolysaccharide production from 18.96 ± 0.15 to 20.97 ± 2.10 mg L(-1)·day(-1). Additionally, A. subrufescens showed the highest total antioxidant activity, reinforcing the therapeutic potential of this basidiomycete. No significant correlation was found between mycelial biomass or exopolysaccharide production and antioxidant activity; however, the results depended on each species and the strains of the same species. We found large variations in the production of mycelial biomass and exopolysaccharides and in antioxidant activity among different species and among strains of the same species. Thus, evaluating the total antioxidant activity is an important tool for identifying strains with biotechnological potential.

One strain-many compounds (OSMAC) method for production of polyketides, azaphilones, and an isochromanone using the endophytic fungus Dothideomycete sp.

Polyketides 1–6 were produced by a one strain-many compounds (OSMAC) approach using the endophytic fungus Dothideomycete sp. CRI7 as a producer. Metabolite production of the fungus Dothideomycete sp. CRI7 was sensitive to sources of potato and malt extract used for the preparation of PDB and Czapek malt media, respectively. Three hitherto unknown metabolites were obtained from the fungus CRI7 grown in PDB medium prepared from a commercial potato powder instead of fresh tubers of potato, while three others were obtained from the fungus cultivated in Czapek malt medium. Moreover, a source of malt extract used in the Czapek malt medium was found to influence metabolite production by the fungus CRI7. Structure elucidation of these compounds was achieved by analysis of spectroscopic data, as well as by single crystal X-ray analysis. Two of the compounds showed weak cytotoxic activity, while the remainders were inactive toward the cell lines tested. One compound exhibited radical scavenging activity with an IC50 value of 21.7μM, and inhibited aromatase with an IC50 value of 12.3μM.

Fermentation profile of Saccharomyces cerevisiae and Candida tropicalis as starter cultures on barley malt medium.

Saccharomyces cerevisiae C8-5 and Candida tropicalis F0-5 isolated from traditional sorghum beer were tested for kinetic parameters on barley malt extract, YPD (863 medium) and for alcohol production. The results showed that C. tropicalis has the highest maximum growth rate and the lowest doubling time. Values were 0.22 and 0.32h(-1) for maximum growth rate, 3h 09min and 2h 09min for doubling time respectively on barley malt extract and YPD. On contrary, glucose consumption was the fastest with S. cerevisiae (-0.36 and -0.722g/l/h respectively on barley malt extract and YPD). When these two yeasts were used as starters in pure culture and co-culture at proportion of 1:1 and 2:1 (cell/cell) for barley malt extract fermentation, we noticed that maltose content increased first from 12.12g/l to 13.62-16.46g/l and then decreased. The highest increase was obtained with starter C. tropicalis + S. cerevisiae 2:1. On contrary, glucose content decreased throughout all the fermentation process. For all the starters used, the major part of the ethanol was produced at 16h of fermentation. Values obtained in the final beers were 11.4, 11.6, 10.4 and 10.9g/l for fermentation conducted with S. cerevisiae, C. tropicalis, C. tropicalis + S. cerevisiae 1:1 and C. tropicalis + S. cerevisiae 2:1. Cell viability measurement during the fermentation by using flow cytometry revealed that the lowest mean channel fluorescence for FL3 (yeast rate of death) was obtained with C. tropicalis + S. cerevisiae 2:1 after 48h of fermentation.