New separation methodologies for the distinction of the growth phases of Saccharomyces cerevisiae cell cycle

In the present work two separation techniques, namely the gravitational field-flow fractionation (GrFFF) and the reversed-flow gas chromatography (RFGC), are proposed for the distinction of the growth phases of Saccharomyces cerevisiae (AXAZ-1) yeast cycle at different temperatures (30 °C, 25 °C, 20 °C, and 15 °C) and pH (2.0, 3.0, 4.0 and 5.0) values. During the fermentation processes, differences observed in the peak profiles, obtained by GrFFF, can be related with the unlike cell growth. The distinction of the phases of AXAZ-1 cell cycle with the GrFFF, was also confirmed with the RFGC technique, which presented similar fermentation time periods for the alcoholic fermentation phases. Simultaneously, the reaction rate constant for each phase of the fermentation process and the activation energies were determined with the aid of the RFGC technique. Finally, the application of both the GrFFF and the RFGC techniques, in combination with high-performance liquid chromatography, allowed us to find the ideal experimental conditions (temperature and pH) for the alcoholic fermentation by AXAZ-1. The results indicate that S. cerevisiae cells performed better at 30 °C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. Moreover, the pH of the medium (pH 5.0) resulted in higher fermentation rates and ethanol productivities.     

Freeze-Dried Saccharomyces cerevisiae Cells Immobilized on Potato Pieces for Low-Temperature Winemaking

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae AXAZ-1 yeast cells on potato pieces. This biocatalyst was subjected to freeze-drying, and the effect of several protective agents and storage at 5 °C, up to 9 months, on viability and fermentative activity of yeasts cells were studied. From several protective agents tested, sodium glutamate preserved the viability of immobilized yeast cells at high levels even after 9-month storage. The freeze-drying biocatalyst was used for repeated batch fermentations of grape must at low temperatures until 5 °C. The produced wines analyzed for volatile byproducts by GC and GC/MS and the results showed that the freeze-dried biocatalysts, with sodium glutamate as protectant, produced wines with higher formation of esters than free cells and having at least similar aromatic profile to those produced by wet biocatalysts.     

Volatiles Formation from Grape Must Fermentation Using a Cryophilic and Thermotolerant Yeast

Grape must fermentation performance and volatiles formation by simultaneously cryophilic and thermotolerant yeast (strain AXAZ-1), isolated from grapes in Greece, was evaluated in a wide temperature range (5?C40°C). Yeast strain was immobilized on brewer??s spent grains (BSG) and the formed biocatalyst was introduced into a Multi-Stage Fixed Bed Tower (MFBT) bioreactor. Almost complete sugar utilization from the aforementioned biocatalyst was observed in a wide temperature spectrum, ranging from 5?°C to 37?°C, while at 40?°C residual sugar was up to 29?g/l. Time to complete fermentation with the immobilized yeast ranged from 290?h at 5?°C and 120?h at 40?°C to 25?h at 33?°C. The daily ethanol productivity reached maximum (88.6?g/l) and minimum (5.6?g/l) levels at 33?°C and 5?°C, respectively. The aroma-related compounds?? profiles of immobilized cells at different fermentation temperatures were evaluated by using solid phase microextraction (SPME) gas chromatography/mass spectrometry (GC/MS). Must fermentation resulted in a high-quality fermentation product due to the low concentrations of higher and amyl alcohols at all temperatures tested. AXAZ-1 is a very promising strain for quality wine production, as it is capable of performing fermentations of high ethanol concentration and productivities in both low and high temperatures.     

New alcohol resistant strains ofSaccharomyces cerevisiae species for potable alcohol production using molasse

Two alcohol resistant strains of Saccharomyces cerevisiae species were isolated from a Greek vineyard plantation. The strain AXAZ-1 gave a concentration of 17.6% v/v alcohol and AXAZ-2 16.5%, when musts from raisin and sultana grapes, respectively, were employed in alcoholic fermentations. They were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker's yeast. Specifically, using an initial [symbol: see text] Be density of 16 [symbol: see text] Be at the repeated batch fermentation process, in the first as well as fourth batch, the better AXAZ-1 gave final [symbol: see text] Be densities of 6.0 and 10.5 respectively, and the baker's yeast 11.6 and 14.5.     

Comparison of Alcoholic Fermentation Performance of the Free and Immobilized Yeast on Water Hyacinth Stem Pieces in Medium with Different Glucose Contents

Ethanol fermentation with Saccharomyces cerevisiae cells was performed in medium with different glucose concentrations. As the glucose content augmented from 200 to 250 g/L, the growth of the immobilized cells did not change while that of the free cells was reduced. At higher glucose concentration (300, 350, and 400 g/L), the cell proliferation significantly decreased and the residual sugar level sharply augmented for both the immobilized and free yeast. The specific growth rate of the immobilized cells was 27–65 % higher than that of the free cells, and the final ethanol concentration in the immobilized yeast cultures was 9.7–18.5 % higher than that in the free yeast cultures. However, the immobilized yeast demonstrated similar or slightly lower ethanol yield in comparison with the free yeast. High fermentation rate of the immobilized yeast was associated with low unsaturation degree of fatty acids in cellular membrane. Adsorption of S. cerevisiae cells on water hyacinth stem pieces in the nutritional medium decreased the unsaturation degree of membrane lipid and the immobilized yeast always exhibited lower unsaturation degree of membrane lipid than the free yeast in ethanol fermentation.     

Preprocessed barley,rye, and triticale as a feedstock for an integrated fuel ethanol-feedlot plant

Rye, triticale, and barley were evaluated as starch feedstock to replace wheat for ethanol production. Preprocessing of grain by abrasion on a Satake mill reduced fiber and increased starch concentrations in feedstock for fermentations. Higher concentrations of starch in flours from preprocessed cereal grains would increase plant throughput by 8–23% since more starch is processed in the same weight of feedstock. Increased concentrations of starch for fermentation resulted in higher concentrations of ethanol in beer. Energy requirements to produce one L of ethanol from preprocessed grains were reduced, the natural gas by 3.5–11.4%, whereas power consumption was reduced by 5.2–15.6%.     

Impact of High Temperature on Ethanol Fermentation by Kluyveromyces marxianus Immobilized on Banana Leaf Sheath Pieces

Ethanol fermentation was carried out with Kluyveromyces marxianus cells at various temperatures (30, 35, 40, and 45 °C). Fermentation performance of the immobilized yeast on banana leaf sheath pieces and the free yeast were evaluated and compared. Generally, ethanol production of the immobilized and free yeast was stable in a temperature range of 30–40 °C. Temperature of 45 °C restricted yeast growth and lengthened the fermentation. The immobilized yeast demonstrated faster sugar assimilation and higher ethanol level in the fermentation broth in comparison with the free yeast at all fermentation temperatures. Change in fatty acid level in cellular membrane was determined to clarify the response of the free and immobilized yeast to thermal stress. The free cells of K. marxianus responded to temperature increase by increasing saturated fatty acid (C16:0 and C18:0) level and by decreasing unsaturated fatty acid (C18:1 and C18:2) level in cellular membrane. For fermentation at 40 °C with immobilized cells of K. marxianus, however, the changes were not observed in both saturated fatty acid (C16:0) and unsaturated fatty acid (C18:1 and C18:2) level.     

Effect of germ and fiber removal on production of ethanol from corn

Ethanol fermentations were conducted using both whole corn, and corn with 100% of the germ, and a portion (∼74%) of the fiber removed. Ethanol production increased 11% in the germ and fiber-removed corn vs the whole corn. The protein content of distiller's dried grains and solubles increased from 30 to 36%, and phosphate levels were 60% lower in corn with germ and fiber removed vs whole corn. Removal of germ and fiber prior to fermentation allows higher starch loading and results in increased ethanol production. The integration of germ and fiber removal in the dry-grind ethanol industry could increase capacity and add valuable coproducts, resulting in increased productivity and profits.     

Production of fuel ethanol from rye and triticale by very-high-gravity (VHG) fermentation

Very-high-gravity (VHG) rye and triticale mashes, containing about 28.5 g dissolved solids/100 mL of mash supernatant, were prepared by adjusting water:grain ratios to 2:1. Because of high viscosity, which develops during mashing, it was necessary to pretreat ground rye-water slurries with viscosity-reducing enzymes. There were no viscosity problems during the preparation of triticale mashes. Fermentations were conducted at 20°C, with and without 16 mM urea as a nitrogenous supplement. All fermentations were completed within 120–144 h. Supplementation with urea shortened the times required for completion of fermentation by 33% for triticale and by 40% for rye. The fermentation efficiencies for both grains ranged between 90 and 93%. These values are comparable to those reported for wheat, implying competitiveness of rye and triticale as fermentation feedstocks to replace wheat. The final ethanol yields were 409 L for rye and 417–435 L for triticale/t (dry basis). For a given size of fermentation vessel, 33% more grain was used in the VHG fermentation process than in normal gravity fermentation. This resulted in a 35–56% increase in ethanol concentration in the beer, when fermentors were filled to a constant volume. The corresponding reduction in water use by about one-third would result in savings in energy consumption in mash heating, mash cooling, and ethanol distillation. Fermentation efficiencies and final ethanol yields obtained per unit weight of grain fermented were not significantly different from the normal gravity fermentations.     

Ethanol Production by Fermentation Using Immobilized Cells of Saccharomyces cerevisiae in Cashew Apple Bagasse

In this work, cashew apple bagasse (CAB) was used for Saccharomyces cerevisiae immobilization. The support was prepared through a treatment with a solution of 3% HCl, and delignification with 2% NaOH was also conducted. Optical micrographs showed that high populations of yeast cells adhered to pre-treated CAB surface. Ten consecutive fermentations of cashew apple juice for ethanol production were carried out using immobilized yeasts. High ethanol productivity was observed from the third fermentation assay until the tenth fermentation. Ethanol concentrations (about 19.82–37.83 g L^?1 in average value) and ethanol productivities (about 3.30–6.31 g L^?1 h^?1) were high and stable, and residual sugar concentrations were low in almost all fermentations (around 3.00 g L^?1) with conversions ranging from 44.80% to 96.50%, showing efficiency (85.30–98.52%) and operational stability of the biocatalyst for ethanol fermentation. Results showed that cashew apple bagasse is an efficient support for cell immobilization aiming at ethanol production.     

Low-temperature brewing by freeze-dried immobilized cells

We propose a novel biocatalyst in brewing. A cryotolerant strain of Saccharomyces cerevisiae was immobilized on delignified cellulosic material followed by freeze-drying of the immobilized cells without the use of any cryoprotectant. The freeze-dried immobilized biocatalyst was used in repeatedbatch fermentation of wort and showed reduced fermentation time and increased productivities as compared with free freeze-dried cells (FFDCs). It also demonstrated suitability for low-temperature brewing (5 and 0°C). The fermentation time in repeated-batch fermentations at 15°C was 1.5–2 d for a period of 13 mo, showing a high operational stability of the system. At 0°C the freeze-dried immobilized biocatalyst showed a 2- to 3.5-fold decrease in fermentation time in comparison with FFDCs. Polyphenol contents, bitterness, and diacetyl concentration were lower in beers produced by freezedried immobilized cells as compared with FFDCs. At 0°C polyphenols were 40% lower than at 15°C. Higher alcohols were reduced and ethyl acetate increased in comparison with FFDCs. Amyl alcohols at 0°C were lower than half of their content at 15°C, while ethyl acetate was 31 mg/L at 0°C and 18 mg/L at 15°C. These data justify the improved aroma and taste of beers produced by freeze-dried immobilized biocatalyst mainly at low temperatures.     

Effect of freeze-dried immobilized cells on delignified cellulosic material in low-temperature and ambient-temperature wine making

In this article, were port on wine making by freeze-dried immobilized cells on delignified cellulosic material for ambient and low temperatures. Biocatalyst supported by freeze-dried delignified cellulosic (FDC) material recovered after the first repeated-batch fermentations the fermentation efficiency and startup, which become about equal to those of biocatalyst supported by wet delignified cellulosic material. The FDC biocatalyst was suitable for wine making at low temperatures (5–15°C), and produced wine of 12% alcoholic degree, with the main volatiles contained in the wine and reduced by a decrease in temperature. The fermentation efficiency was not affected by total acidity of must, while an increase in initial Be density improved percentages of higher alcohols and ethylacetate. The quality of the wine was validated by a preliminary taste test to be in the range of acceptable to excellent.     

Banana as Adjunct in Beer Production: Applicability and Performance of Fermentative Parameters

Traditionally, the raw materials for beer production are barley, hops, water, and yeast, but most brewers use also different adjuncts. During the alcoholic fermentation, the contribution of aroma compounds from other ingredients to the final beer flavor depends on the wort composition, on the yeast strain, and mainly on the process conditions. In this context, banana can also be a raw material favorable to alcoholic fermentation being rich in carbohydrates and minerals and providing low acidity. In this work, the objective was to evaluate the performance of wort adjusted with banana juice in different concentrations. For this, static fermentations were conducted at 15 °C at pilot scale (140 L of medium). The addition of banana that changed the concentration of all-malt wort from 10 °P to 12 and 15 °P were evaluated (°P is the weight of the extract or the sugar equivalent in 100 g solution, at 20 °C). The results showed an increase in ethanol production, with approximately 0.4 g/g ethanol yield and 0.6 g/L h volumetric productivity after 84 h of processing when concentrated wort was used. Thus, it was concluded that banana can be used as an adjunct in brewing methods, helping in the development of new products as well as in obtaining concentrated worts.     

Effects of Poly(Ethylene Glycol) on the Physical Properties of Blended Molecules of Starch and Poly(Ethylene-co-Acrylate,Ammonium Salt)

Abstract

A mixture of starch (36%) poly(ethylene-co-acrylate, ammonium salt) (41%), water (12.5%), urea (8.4%), and poly(ethylene glycol) (M _n 4600) (2.1%) were converted to plastic test pieces by extruding (130°C), drying and grinding (25°C), and hot pressing (175°C). After equilibration at ?50% relative humidity and 25°C, the test pieces contained 3.5–4.6% moisture and 2.3% poly(ethylene glycol) (PEG). Among wheat, corn, potato, and rice starches, the wheat starch (WS) blend showed the highest Young's modulus (181.3 MPa), whereas the corn starch (CS) blend had a modulus and elongation that almost matched those of lowdensity polyethylene. When PEG was eliminated from the WS formulation, tensile strength remained constant, but Young's modulus doubled. The modulus decreased continually as test pieces absorbed water up to 27% moisture, but elongation and argon laser light transmittance were optimum at ?12% moisture. Differential scanning calorimetry indicated that PEG formed a solid inclusion complex with amylose upon drying at 60°C, but no complex was detected in dilute alkali by optical rotation.     

Fluorescence monitoring of immobilzed microorganisms in cultures

An experimental reactor system for monitoring the fluorescence of suspended and immobilized cells is described. The growth of S. cerevisiae was monitored during batch fermentations by fluorescence of the culture. Thus, it was possible to use this intracellular parameter to study the influence of immobilization on cells. The fermentations were done under aerobic conditions with suspended and immobilized cells. A comparison of these two systems showed that the rate of ethanol consumption was significantly slower for the cells immobilized in calcium alginate. This reduced rate of oxidative decomposition may be due to mass-transfer limitations of oxygen. Pulse experiments with different substrates (glucose and ethanol) were made to monitor the changes in cell metabolism. The reactor system presented is also suitable as a “toxin guard system”, because substances toxic to cells, such as 2,4-dinitrophenol, cause clearly visible changes in the fluorescence of the immobilized cells.     

Production of Lactic Acid from Raw Sweet Potato Powders by Rhizopus Oryzae Immobilized in Sodium Alginate Capsules

Rhizopus oryzae immobilized in calcium alginate was applied in lactic acid fermentation with unhydrolyzed raw sweet potato powders as the sole carbon source. The effects of sodium alginate concentration, calcium chloride concentration, and the immobilized bead diameter on lactic acid production were investigated. Increase in sodium alginate concentration during the gelation process would harden the immobilized capsule, which led to a decrease in lactic acid production. The increase in calcium chloride would increase the thickness of the immobilized capsule, which would increase the mass transfer resistance. Nevertheless, while the calcium chloride was lower than 15%, it would not have obvious effects on lactic acid production. A larger bead could have more space for cell growth, which led to the maximum lactic acid production observed at the 5-mm bead diameter. Moreover, results of repeated-batch operation suggested that immobilized cells could have higher stability in lactic acid production than free cells. The total cumulative lactic acid in immobilized-cell operation could increase by 55% as compared with free-cell operation after 216 h (seven repeated-batches), and no loss of amylolytic activity was observed. The results indicated that immobilized R. oryzae by Ca-alginate could be suitable for lactic acid production from unhydrolyzed raw potato powders.     

Fermentation of “Quick Fiber” produced from a modified corn-milling process into ethanol and recovery of corn fiber oil

Approximately 9% of the 9.7 billion bushels of corn harvested in the United States was used for fuel ethanol production in 2002, half of which was prepared for fermentation by dry grinding. The University of Illinois has developed a modified dry grind process that allows recovery of the fiber fractions prior to fermentation. We report here on conversion of this fiber (Quick Fiber [QF]) to ethanol. QF was analyzed and found to contain 32%wt glucans and 65%wt total carbohydrates. QF was pretreated with dilute acid and converted into ethanol using either ethanologenic Escherichia coli strain FBR5 or Saccharomyces cerevisiae. For the bacterial fermentation the liquid fraction was fermented, and for the yeast fermentation both liquid and solids were fermented. For the bacterial fermentation, the final ethanol concentration was 30 g/L, a yield of 0.44 g ethanol/g of sugar(s) initially present in the hydrolysate, which is 85% of the theoretical yield. The ethanol yield with yeast was 0.096 gal/bu of processed corn assuming a QF yield of 3.04 lb/bu. The residuals from the fermentations were also evaluated as a source of corn fiber oil, which has value as a nutraceutical. Corn fiber oil yields were 8.28%wt for solids recovered following prtetreatment.     

Sorption and desorption of water vapor by grains of native starch of some crops

The sorption-desorption of water vapor by grains of potato, corn, and wheat native starch is studied. It is shown that water vapor is mainly sorbed inside starch grains. A model is proposed for water vapor sorption by starch grains. Constructed sorption isotherm is shown to adequately describe the process in a wide humidity range. The kinetics of the sorption and desorption of water vapor by starch grains is shown to have an abnormal character.     

Fermentation Efficiency of Cells Immobilized on Delignified Brewers' Spent Grains after Low- and High-Temperature Thin Layer Thermal Drying

Low-cost dried yeasts immobilized on delignified brewers' spent grains for use in wine making and brewing were produced by simple thermal drying techniques. To optimize the thermal drying process, vacuum and air stream conditions were examined. Drying of thin layers of the biocatalysts was performed at low (30–38 °C) and high temperatures (40–70 °C). The fermentation efficiency of the thermally dried biocatalysts was acceptable, with immobilized cells showing a significantly higher thermotolerance compared with free cells. Immobilized cells dried at high temperatures presented slightly improved glucose fermentation efficiency compared with the low-temperature dried biocatalysts. Gas chromatography–mass spectrometry analysis of aroma volatiles of the fermented products revealed an increase of esters, lower higher alcohol formation, and significantly lower concentration of carbonylic compounds.     

Dry Red Wine Making Using Yeast Immobilized on Cork Pieces

The commercial Saccharomyces cerevisiae Uvaferme 299 wine yeast was immobilized on cork pieces to produce a biocatalyst for use in dry red wine making. The immobilized biocatalyst was suitable for clarified and non-clarified grape must fermentation at ambient and low temperatures (0–25 °C). Fermentation times were low and very low amounts of residual sugar were detected, showing suitability for dry wine production. The presence of suspended solids in the non-clarified must did not affect the activity of the immobilized cells. Complete fermentation of sugars at 0 °C was possible with immobilized Uvaferme 299, although not a cryotolerant strain, indicating a cryoprotective effect of cork. The presence of cork did not affect the composition of major volatiles with methanol and acetaldehyde kept at low levels. Reduction of amyl alcohols on total volatiles was also observed in wines fermented at low temperatures. Differences in the headspace aroma profile in wines produced by immobilized and free cells were found by GC–MS analysis, but no cork taint compounds were detected.