Use of the industrial yeastCandida utilis for cadmium sorption

The sorption ability of Candida utilis biomass for cadmium ions with accumulating competence of dried cells and cells in alginate was compared. After an optimization of process conditions (pH 5.5, biomass concentration 1 g/L and c0 50 mg/L), the cadmium sorption capacity of dried yeast biomass was perceptibly higher than that of the other tested adsorbents. Considering the sorption of the dried yeast biomass equal to 100 %, the cells in alginate reached 86 % while native cells showed only 42 %.     

Fermentation and microencapsulation of the nematophagous fungus <Emphasis Type="Italic">Hirsutella rhossiliensis</Emphasis> in a novel type of hollow beads

In this work, fermentation and formulation aspects of the nematophagous fungus Hirsutella rhossiliensis BBA were investigated. When incubated in 2% (w/w) glucose and 0.5% (w/w) yeast extract medium in a 1-L Erlenmeyer flask without baffles, heavy pellet formation was observed. Only 40% of the mycelium had a size less than 500 μm. When a flask with three baffles was used, the portion of mycelium <500 μm rose to 95%. In the next step, the influence of aeration rate and stirrer speed on production of finely dispersed mycelium in a stirred tank reactor was investigated. The best fermentation results were obtained at 0.4 vvm and 400 rpm stirrer speed with 90% mycelium <500 μm and 5 g/L biomass. Then, mycelium was microencapsulated in hollow beads based on sulfoethylcellulose (SEC). Experiments on the capsule nutrient reservoir showed that 15% (w/w) corn gluten and 0.5% (w/w) yeast extract could be replaced with 3% (w/w) autoclaved baker's yeast which was never used as capsule additive before. Radial growth of mycelium out of dried hollow beads containing 1% (w/w) biomass and 3% (w/w) baker's yeast was faster than for alginate beads containing equivalent amounts of biomass and yeast indicating a higher bio-control potential.     

Biosorption of Copper(II) by Live and Dried Biomass of the White Rot Fungi Phanerochaete chrysosporium and Funalia trogii

Biosorption is an innovative and alternative technology to remove heavy metal pollutants from aqueous solution using live, inactive and dead biomasses such as algae, bacteria and fungi. In this study, live and dried biomass of Phanerochaete chrysosporium and Funalia trogii was applied as heavy metal adsorbent material. Biosorption of copper(II) cations in aqueous solution by live and dried biomass of Phanerochaete chrysosporium and Funalia trogii was investigated to study the effects of initial heavy metal concentration, pH, temperature, contact time, agitation rate and amount of fungus. Copper(II) was taken up quickly by fungal biomass (live or dried) during the first 15 min and the most important factor which affected the copper adsorption by live and dried biomass was the pH value. An initial pH of around 5.0 allowed for an optimum adsorption performance. Live biomass of two white rot fungi showed a high copper adsorption capacity compared with dried biomass. Copper(II) uptake was found to be independent of temperature in the range of 20–45 °C. The initial metal ion concentration (10–300 mg/L) significantly influenced the biosorption capacity of these fungi. The results indicate that a biosorption as high as 40–60 % by live and dried biomass can be obtained under optimum conditions.     

Biosorption of copper by yeasts

Summary The ability to accumulate copper from aqueous solutions was determined with different yeast species. Yeast cells did not show any significant differences in process kinetics. The uptake was very fast and was influenced by environmental factors. The metal-accumulating capacity differed among the tested strains. The yeastsCandida tropicalis andPichia guilliermondii were chosen for extensive research. Cells of the stationary growth phase were able to adsorb a high amount of copper. The uptake capacity decreased with increasing biomass concentration. Copper adsorption obeyed the Freundlich isotherm. Optimal pH range was between 5 and 7. The biomass could be used repeatedly for biosorption after desorption by mineral acids.     

Production ofBeauveria bassiana [Deuteromycotina: Hyphomycetes] in different liquid media and subsequent conidiation of dry mycelium

Mycelium ofBeauveria bassiana can be grown in liquid culture, filtered, and the mycelium dried. After rehydration the mycelium sporulates. Two carbohydrate sources (sucrose and maltose), and one nitrogen/vitamin source (yeast extract) were tested for mycelium growth and subsequent conidial production. Maximum mycelium growth (12.31 mg/ml), in liquid culture, was in the sucrose (3.5%)/yeast extract (3.5%) medium, but mycelium from a maltose (2%)/yeast extract (0.75%) medium produced the maximum of 4.62×10⁶ conidia/mg dry mycelium after incubation in moist Petri dishes. Using the data on mycelium yield (in liquid culture) and conidial production (by dry mycelium) it is calculated that the sucrose (3.5%)/yeast extract (3.5%) and the maltose (2%)/yeast extract (0.75%) media produce most conidia per media volume (an equivalent of 3.52–3.72×10⁷ conidia/ml).      

Removal of Heavy Metals by Waste Tea Leaves from Aqueous Solution

In this paper, tea leaves were shown to be an effective, low‐cost biosorbent. Removal of lead, iron, zinc and nickel from 20 mg/L metal solution by dried biomass of waste tea leaves amounted to 96, 91, 72 and 58 %, respectively, at equilibrium, which followed Langmuir and Freundlich adsorption isotherms. Adsorption of metal was in the order of Pb > Fe > Zn > Ni from 5–100 mg/L of metal solution. From a multi‐metallic mixture, 92.5, 84 and 73.2 % of lead, iron and zinc, respectively, were removed. Fourier transform infrared (FTIR) studies indicated that the carboxyl group was involved in the binding of lead and iron, whereas the amine group was involved in the binding of nickel and zinc. A flow through sorption column packed with dried biomass demonstrated a sorption capacity of 73 mg Pb/g of biomass, indicating its potential in cleaning metal containing wastewater. The metal laden biomass obtained could be disposed off by incineration.     

Copper removal by dry and re-hydrated biomass of Spirulina platensis

Dried and re-hydrated biomass of Spirulina platensis was employed as a sorbent in tests of copper removal from water. Biomass re-hydrated for 24 h before use exhibited a shorter adsorption time as well as an increased percentage removal when compared with simply dried biomass. The combined effects of the concentrations of re-hydrated biomass (from 1.0 to 4.0 g l-1) and copper (from 0.1 to 0.4 g l-1) were then investigated. Copper was almost entirely removed (91% removal) at relatively high biomass levels (X0>or=2.0 gDM l-1), while 1.0 gDM l-1 removed only 81% of copper present initially, suggesting a situation of excess metal with respect to the adsorption capacity of biomass. Additional tests performed with biomass re-hydrated for variable time demonstrated that no less than 48 h of this treatment are needed to ensure a satisfactory copper removal, while no significant improvement was detected using biomass re-hydrated for longer times.     

Biosorption of heavy metals by Saccharomyces cerevisiae

Abundant and common yeast biomass has been examined for its capacity to sequester heavy metals from dilute aqueous solutions. Live and non-living biomass of Saccharomyces cerevisiae differs in the uptake of uranium, zinc and copper at the optimum pH 4–5. Culture growth conditions can influence the biosorbent metal uptake capacity which normally was: living and non-living brewer's yeast: U > Zn > Cd > Cu; non-living baker's yeast: Zn > (Cd) > U > Cu; living baker's yeast: Zn > Cu (Cd) > U. Non-living brewer's yeast biomass accumulated 0.58 mmol U/g. The best biosorbent of zinc was non-living baker's yeast ( 0.56 mmol Zn/g). Dead cells of S. cerevisiae removed approximately 40% more uranium or zinc than the corresponding live cultures. Biosorption of uranium by S. cerevisiae was a rapid process reaching 60% of the final uptake value within the first 15 min of contact. Its deposition differing from that of other heavy metals more associated with the cell wall, uranium was deposited as fine-needle-like crystals both on the inside and outside of the S. cerevisiae cells.     

Advances in biosorption of metals: Selection of biomass types

Abstract: Within the past decade, the potential of metal biosorption has been well established. For economic reasons, of particular interest are abundant biomass types either generated as a waste by-product of large-scale industrial fermentations or certain metal-binding algae found in large quantities in the sea. Some of these high metal-sorbing biomass types serve as a basis for newly developed metal biosorption processes foreseen particularly as a very competitive means for detoxification of metal-bearing industrial effluents. Ions of lead and cadmium, for instance, have been found to be bound very efficiently from very dilute solutions by the dried biomass of some ubiquitous brown marine algae such as Ascophyllum and Sargassum which accumulate more than 30% of biomass dry weight in the metal. Mycelia of industrially steroid-transforming fungi Rhizopus and Absidia are excellent biosorbents lbr lead, cadmium, copper, zinc, and uranium, binding also other heavy metals up to 25% of the biomass dry weight. The common yeast Saccharomyces cerevisiae is a 'mediocre' metal biosorbent. Construction of biosorption isotherm curves serves as a basic technique assisting in evaluation of the metal uptake by different biosorbents. The methodology is based on batch equilibrium sorption experiments extensively used for screening and quantitative comparison of new biosorbent materials. Experimental methodologies used in the study of biosorption and selected recent research results demonstrate the route to novel biosorbent materials some of which can even be repeatedly regenerated for re-use.     

Higher fatty acids of Candida lipolytica grown in n-alkanes by the industrial method ("Toprina")]

The present study deals with the composition of superior fatty acids of total lipids, polar lipids, and neutral lipids from dried biomass of Candida lipolytica grown by industrial process ("Toprina") on n-alkanes (C10-C20) extracted from petroleum. The data related to our knowledge about yeast and Candida lipolytica, lead to the conclusion that fatty acids feature of "Toprina" are similar to the Candida lipolytica ones grown in batch culture at the same conditions. In addition, a possible physiologic role of 17:1 and 17:2 is considered, in the perspective of the utilization of "Toprina" in animal food.     

ATP levels in phosphate-deregulated and arsenate-resistant mutants of Streptomyces noursei

Mycelial levels of ATP and glucose-6-phosphate were investigated in mutants of streptothricin-producing S. noursei JA 3880b differing from the wild-type strain in antibiotic formation, in the control by inorganic phosphate of the secondary metabolism, and in the resistance to growth inhibition by toxic arsenate ions. As compared with the ancestral strain, mutants exhibited a lower content of ATP in the mycelium while addition of 0.1 M arsenate to growing cultures provoked only moderate changes in the level of this high-energy metabolite. The results suggest that there exists a correlation between growth resistance to arsenate and insensitivity to phosphate inhibition of the secondary metabolism, on the one hand, and the capacity to produce streptothricin-type antibiotics, on the other.     

Heavy metals biosorption from aqueous solution by simple eucaryotic organisms

Biosorption of cadmium and chromium (III) ions by means of selected yeast species has been estimated. Kinetics and equilibrium measurements have shown the reliable efficiency of both metals removal for Candida tropicalis. The influence of pH and ionic strength on biosorption process has been examined as well. For both metals the adsorption isotherms have been presented. The equilibrium of chromium (III) sorption has appeared compatible to Langmiur model and the maximum sorption capacity has been determined.     

Characterization of Pb<Superscript>2+</Superscript> biosorption from aqueous solution by<Emphasis Type="Italic"> Rhodotorula glutinis</Emphasis>

The yeast Rhodotorula glutinis was examined for its ability to remove Pb(2+) from aqueous solution. Within 10 min of contact, Pb(2+) sorption reached nearly 80% of the total Pb(2+) sorption. The optimum initial pH value for removal of Pb(2+ )was 4.5-5.0. The percentage sorption increased steeply with the biomass concentration up to 2 g/l and thereafter remained more or less constant. Temperature in the range 15-45 degrees C did not show any significant difference in Pb(2+ )sorption by R. glutinis. The light metal ions such as Na(+), K(+), Ca(2+), and Mg(2+) did not significantly interfere with the binding. The Langmuir sorption model provided a good fit throughout the concentration range. The maximum Pb(2+ )sorption capacity q(max) and Langmuir constant b were 73.5 mg/g of biomass and 0.02 l/mg, respectively. The mechanism of Pb(2+) removal by R. glutinis involved biosorption by direct biosorptive interaction with the biomass through ion exchange and precipitation by phosphate released from the biomass.     

Metal-binding capacity of arbuscular mycorrhizal mycelium

Experiments with excised mycelium of several Glomus spp. with different histories of exposure to heavy metals were carried out to measure their capacities to bind Cd and Zn. Cd sorption was followed for up to 6 h of incubation to determine its time course relationships. Controls treated with a metabolic inhibitor were included to evaluate whether sorption was due to active uptake or passive adsorption. The effect of ion competition (effects of Ca or Zn on Cd sorption) and general measurements of cation exchange capacity (CEC) of roots and hyphae were also performed. The results showed that AM mycelium has a high metal sorption capacity relative to other microorganisms, and a CEC comparable to other fungi. Metal sorption was rapid (<30 min) and appeared mainly to be due to passive adsorption. Adsorption was highest in a metal-tolerant G. mosseae isolate and intermediate for a fungus isolated from a soil treated with metal-contaminated sludge. The former adsorbed up to 0.5 mg Cd per mg dry biomass, which was three times the binding capacity of non-tolerant fungi, and more than 10 times higher than reported values for, e.g., the commonly used biosorption organism Rhizopus arrhizus. The implications of these results for AM involvement in plant protection against excess heavy metal uptake are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ion exchange during heavy metal bio-sorption from aqueous solution by dried biomass of macrophytes

In this study, potentials of oven dried biomass of Eichhornia crassipes, Valisneria spiralis and Pistia stratiotes, were examined in terms of their heavy metal (Cd, Ni, Zn, Cu, Cr and Pb) sorption capacity, from individual-metal and multi-metal aqueous solutions at pH 6.0+/-0.1 (a popular pH of industrial effluent). V. spiralis was the most and E. crassipes was the least efficient for removal of all the metals. Cd, Pb and Zn were efficiently removed by all the three biomass. Cd was removed up to 98% by V. spiralis. Sorption data for Cr, Ni and Cd fitted better to Langmuir isotherm equation, while, the sorption data for Pb, Zn and Cu fitted better to Freundlich isotherm equation. In general, the presence of other metal ions did not influence significantly the targeted metal sorption capacity of the test plant biomasses. Ion exchange was proven the main mechanism involved in bio-sorption and there was a strong ionic balance between adsorbed (H(+) and M(2+)) to the released ions (Na(+) and K(+)) to and from the biomass. No significant difference was observed in the metal exchanged amount, by doubling of metal concentration (15-30 mg/l) in the solution and employing individual-metal and multi-metal solutions.     

Studies on chromium(VI) adsorption-desorption using immobilized fungal biomass

The aim of this study was to investigate the Cr(VI) biosorption potential of immobilized Rhizopus nigricans and to screen a variety of non-toxic desorbing agents, in order to find out possible application in multiple sorption-desorption cycles. The biomass was immobilized by various mechanisms and evaluated for removal of Cr(VI) from aqueous solution, mechanical stability to desorbents, and reuse in successive cycles. The finely powdered biomass, entrapped in five different polymeric matrices viz. calcium alginate, polyvinyl alcohol (PVA), polyacrylamide, polyisoprene, and polysulfone was compared for biosorption efficiency and stability to desorbents. Physical immobilization to polyurethane foam and coir fiber was less efficient than polymer entrapment methods. Of the different combinations (%, w/v) of biomass dose compared for each matrix, 8% (calcium alginate), 6% (polyacrylamide and PVA), 12% (polyisoprene), and 10% (polysulfone) were found to be the optimum. The Cr sorption capacity (mg Cr/g sorbent) of all immobilized biomass was lesser than the native, powdered biomass. The Cr sorption capacity decreased in the order of free biomass (119.2) > polysulfone entrapped (101.5) > polyisoprene immobilized (98.76) > PVA immobilized (96.69) > calcium alginate entrapped (84.29) > polyacrylamide (45.56), at 500 mg/l concentration of Cr(VI). The degree of mechanical stability and chemical resistance of the immobilized systems were in the order of polysulfone > polyisoprene > PVA > polyacrylamide > calcium alginate. The bound Cr(VI) could be eluted successfully using 0.01 N NaOH, NaHCO3, and Na2CO3. The adsorption data for the native and the immobilized biomass was evaluated by the Freundlich isotherm model. The successive sorption-desorption studies employing polysulfone entrapped biomass indicated that the biomass beads could be regenerated and reused in more than 25 cycles and the regeneration efficiency was 75-78%.     

Strain variation and morphogenesis of yeast- and mycelial-phase Candida albicans in low-sulfate, synthetic medium.

A low-sulfate synthetic medium was developed in which pure cultures of yeast- and mycelial-phase Candida albicans could be cultivated for investigations of the molecular biology of dimorphism. The medium contained ammonium ions, phosphate buffer, salts, glucose, and biotin. Morphogenesis was found to be dependent upon the strain of C. albicans. Of six strains tested in the low-sulfate medium at 37 degrees C, three formed mixed cultures of yeasts, true mycelium and pseudomycelium, two formed pure cultures of true mycelium, and one maintained yeast growth. All six strains produced pure cultures of yeasts at 24 degrees C. The buffering capacity of the medium maintained the pH at 6.9 even at high-density cell growth. The low concentration of sulfate and the absence of amino acids in the medium provided conditions in which to radiolabel cellular constituents with [35S]sulfate. For molecular investigations, the use of two strains is suggested, one forming yeasts and one forming true mycelium in low-sulfate medium at 37 degrees C, thus providing controls for both strain variation and for molecular changes induced by environmental change but unrelated to morphogenesis.     

Removal of cadmium by Pleurotus sajor-caju basidiomycetes

The bioaccumulation of cadmium by the white rot fungus Pleurotus sajor-caju onto dry biomass was investigated using aqueous media with concentrations in the range of 0.125 mM–1.0 mM The highest cadmium uptake (between 88.9 and 91.8%) was observed with aerobic fungal biomass from the exponential growth phase. Up to 1.0 mM cadmium gradually inhibited mycelium development, but never blocked it completely. Freeze-dried, oven-dried and non-metabolizing live Pleurotus sajor-caju biomass types were tested for their capacity to adsorb the test ion Cd²⁺ within the pH range of 4.5 to 6.0. Freeze–dried biomass proved to be the most efficient biomass type for Cd²⁺ metal adsorption. Therefore, Pleurotus sajor-caju may be used for heavy metal removal and bioremediation.     

Effect of excess ethanol on the growth of yeasts of the genus Candida during continuous cultivation

The effect of flow rates and a specific ethanol load on the growth of Candida utilis and Candida krusei was studied in the process of one-step and three-step cultivation. The productive capacity of fermenters and the economic coefficient of yeast biomass production were shown to depend on the ability of microbial populations to assimilate a certain quantity of a carbon substrate per unit time. When a specific ethanol load exceeds the optimal one, the respiratory activity of a population and the economic coefficient of growth fall down whereas the accumulation of metabolites in the cultural broth increases. The steady state of biomass can be maintained in the process of continuous cultivation by inhibiting the yeast growth with an excess of ethanol.     

Inhibition of Candida valida growth by copper ions]

The high toxicity of copper ions for Candida valida growth was established at pH-auxostat regime. The value of mu max decreased even at the residual Cu2+ concentration 1.0 mg/l. The inhibition constant (Ki) that characterized a copper ion concentration at which yeast specific growth rate was halved was equal to 7.7 mg/l. A linear dependence of 1/mu max on a residual concentration of copper ions indicates that yeast growth inhibition is due to inhibition of one enzymic reaction which is the most sensitive to copper. Yeast growth inhibition by copper was accompanied by accumulation of Cu2+ ions in biomass, a decrease in nucleic acid and true protein contents, and changes in amino acid composition of protein. The amounts of cystine and cysteine in protein increased and tryptophane content decreased with inhibition of yeast growth. Yeast growth inhibition by copper did not affect the lipid content but significantly reduced the degree of unsaturation due to a decrease in the amounts of polyunsaturated linoleic and alpha-linolenic acids.