Effects of yeast invertase on ethanol production in molasses

Ethanol fermentation by an alcohol yeast, YOY655, was slower in molasses than in a nutrition rich medium with the same sugar content. Osmolality was much higher in the molasses, and the slower fermentation in the molasses was ascribed to depressed fermentation under the high osmotic pressure. Yeast invertase was an important factor in regulation the osmolality and the fermentation rate in the molasses.     

Construction of a sucrose-fermenting bakers' yeast incapable of hydrolysing fructooligosaccharides.

Fructooligosaccharides stimulate the growth of intestinal bifidobacteria which are related to the favorable health and nutrition of humans and other animals. Since the efficient amount of fructooligosaccharide for an adult human is relatively large (about 5 g per day), its addition to daily foods like bakery goods might be beneficial. However, commercial Bakers' yeast hydrolyses fructooligosaccharides by the action of invertase encoded in SUC genes and ferments the resulting monosaccharides. According to the findings that strains carrying the MAL-constitutive gene and lacking the SUC gene fermented sucrose and not fructooligosaccharide, we constructed a sucrose-fermenting strain, YOY920, incapable of hydrolysing fructooligosaccharide, by cross-breeding a baking strain and a laboratory strain. In a molasses medium, the cell yield of YOY920 was comparable to that of a baking strain FSC6001, and much higher than that of the non-sucrose-fermenting strains. Although fructooligosaccharide inhibited the dough leavening ability of YOY920, white bread containing fructooligosaccharide could be produced in the defined dough formula using the new strain.     

Kinetics and thermodynamics of ethanol production by a thermotolerant mutant of Saccharomyces cerevisiae in a microprocessor-controlled bioreactor

AIMS: The present investigation deals with the development of thermotolerant mutant strain of yeast for studying enhanced productivity of ethanol from molasses in a fully controlled bioreactor. METHODS AND RESULTS: The parental culture of Saccharomyces cerevisiae ATCC 26602 was mutated using UV treatment. A single thermotolerant mutant was isolated after extensive screening and optimization, and grown on molasses medium in liquid cultures. The mutant was 1.45-fold improved than its wild parent with respect to ethanol productivity (7.2 g l-1 h-1), product yield (0.44 g ethanol g-1 substrate utilized) and specific ethanol yield (19.0 g ethanol g-1 cells). The improved ethanol productivity was directly correlated with titres of intracellular and extracellular invertase activities. The mutant supported higher volumetric and product yield of ethanol, significantly (P相似文献   

Ethanol fermentation of beet molasses by a yeast resistant to distillery waste water and 2-deoxyglucose

A flocculent killer yeast, Saccharomyces cerevisiae strain H-1, which was selected for ethanol fermentation of beet molasses, has a tendency to lose its viability in distillery waste water (DWW) of beet molasses mash after ethanol fermentation. Through acclimations of strain H-1 in DWW, strain W-9, resistant to DWW, was isolated. Strain M-9, resistant to 2-deoxyglucose was further isolated through acclimations of strain W-9 in medium containing 150 ppm 2-deoxyglucose. A fermentation test of beet molasses indicated that the ethanol productivity and sugar consumption were improved by strain M-9 compared to the parental strain H-1 and strain W-9. The concentration of ethanol produced by strain M-9 was 107.2 g/l, and the concentration of residual sugars, which were mainly composed of sucrose and fructose, were lower than those produced by the parental strain H-1 and strain W-9 at the end of fermentation of beet molasses.     

Effects of culture conditions on ergosterol biosynthesis by Saccharomyces cerevisiae

Ergosterol is an essential component of yeast cells that maintains the integrity of the membrane. It was investigated as an important factor in the ethanol tolerance of yeast cells. We investigated the effects of brewing conditions on the ergosterol contents of S. cerevisiae K-9, sake yeast, several kinds of Saccharomyces cerevisiae that produce more than 20% ethanol, and X2180-1A, laboratory yeast. K-9 had a higher total ergosterol contents under all the conditions we examined than X2180-1A. Ethanol and hypoxia were found to have negative and synergistic effects on the total ergosterol contents of both strains, and significantly reduced the free ergosterol contents of X2180-1A but only slightly reduced those of K-9. The maintenance of free ergosterol contents under brewing conditions might be an important character of sake yeast strains. DNA microarray analysis also showed higher expression of ergosterol biosynthesis genes in K-9 than in X2180-1A.     

Production of ethanol by filamentous and yeast-like forms of <Emphasis Type="Italic">Mucor indicus</Emphasis> from fructose,glucose, sucrose,and molasses

The fungus Mucor indicus is found in this study able to consume glucose and fructose, but not sucrose in fermentation of sugarcane and sugar beet molasses. This might be an advantage in industries which want to selectively remove glucose and fructose for crystallisation of sucrose present in the molasses. On the other hand, the fungus assimilated sucrose after hydrolysis by the enzyme invertase. The fungus efficiently grew on glucose and fructose and produced ethanol in synthetic media or from molasses. The cultivations were carried out aerobically and anaerobically, and manipulated toward filamentous or yeast-like morphology. Ethanol was the major metabolite in all the experiments. The ethanol yield in anaerobic cultivations was between 0.35 and 0.48 g/g sugars consumed, depending on the carbon source and the growth morphology, while a yield of as low as 0.16 g/g was obtained during aerobic cultivation. The yeast-like form of the fungus showed faster ethanol production with an average productivity of 0.90 g/l h from glucose, fructose and inverted sucrose, than the filamentous form with an average productivity of 0.33 g/l h. The biomass of the fungus was also analyzed with respect to alkali-insoluble material (AIM), chitin, and chitosan. The biomass of the fungus contained per g maximum 0.217 g AIM and 0.042 g chitosan in yeast-like cultivation under aerobic conditions.     

Sedimentation characteristics and effect of molasses concentration and medium supplementation on the ethanol productivity of an ethanol tolerant palm wineSaccharomyces

Summary Sedimentation rates ranging from 58.82 to 93.10% were recorded for six palm wineSaccharomyces yeast isolates. Isolates S, J and A₃, gave values of 90.00, 91.95 and 93.10% respectively compared to 81.54% for a standard lager beer yeast. Fermentation of unclarified molasses medium 10–30° Brix with isolated J gave ethanol productivity of 74.35-67.07%. Soyabean, groundnut or castor oil seed meal supplements significantly enhanced ethanol productivity in all the molasses media.     

Genome-wide expression profile of sake brewing yeast under shaking and static conditions

To identify the genes responsible for characteristics, that are different as between sake brewing yeasts and laboratory yeast strains, we used a DNA microarray to compare the genome-wide gene expression profiles of a sake yeast, Saccharomyces cerevisiae K-9 (kyokai 9), and a laboratory yeast, S. cerevisiae X2180-1A, under shaking and static conditions.The genes overexpressed in K-9 more than in X2180-1A were related to C-metabolism, including the HXT, ATP, and COX genes, ergosterol biosynthesis, ERG genes, and thiamine metabolism, THI genes. These genes may contribute to higher growth rates and fermentation ability and the ethanol tolerance of sake yeast.The genes underexpressed in K-9 more than in X2180-1A were CUP1-1 and CUP1-2, PHO genes, which may explain the low copper tolerance and low acid phosphatase activity of sake yeast. These underexpressed genes agree with the features and the alteration of the genome structure of sake yeast.     

Fungal Invertase as an Aid for Fermentation of Cane Molasses into Ethanol

Comparative studies of the fermentation of cane molasses into ethanol by Saccharomyces cerevisiae in the presence or absence of fungal invertase were performed. When cane molasses was fermented by the yeast at 30°C and pH 5.0, the presence of the enzyme had no effect on ethanol production. At pH 3.5, ethanol production was increased by the addition of invertase. At 40°C, the addition of invertase increased ethanol production by 5.5% at pH 5.0 and by 20.9% at pH 3.5.     

Effect of glycosylation on yeast invertase oligomer stability

Yeast external invertase is a glycoprotein that exists as a dimer that can associate to form tetramers, hexamers, and octamers (Chu, F., Watorek, W., and Maley, F. (1983) Arch. Biochem. Biophys. 223, 543-555; Esmon, P. C., Esmon, B. E., Schauer, I. E., Taylor, A., and Schekman, R. (1987) J. Biol. Chem., 262, 4395-4401), a process that is facilitated by the attached oligosaccharide chains. We have studied this association by high performance liquid chromatography on a gel filtration matrix, by which procedure wild-type bakers' yeast invertase gives two peaks, and invertase from a core mutant (mnn1 mnn9) of Saccharomyces cerevisiae X2180 gives three peaks. Concentration of an invertase solution by freezing drives the dimers into higher aggregates that, at 30 degrees C, re-equilibrate to a mixture of smaller forms, the composition of which depends on pH, concentration, and time. The invertase from a mutant, mnn1 mnn9 dpg1, which underglycosylates its glycoproteins and produces invertase with 4-7 oligosaccharide chains, forms oligomers of much lower stability than the mnn1 mnn9 invertase, which has 8-11 carbohydrate chains. Both of these mutants release external invertase from the periplasm into the medium during growth, but we conclude that defects in the cell wall structure may be more important in this release than an altered tendency of the invertases to aggregate. Investigation of aggregate formation by electron microscopy revealed that all invertases, including the internal nonglycosylated enzyme, form octamers under appropriate conditions.     

Batch fermentation kinetics of sugar beet molasses by Zymomonas mobilis

A new osmotolerant mutant strain of Zymomonas mobilis was successfully used for ethanol production from beet molasses. Addition of magnesium sulfate to hydrolyzed molasses allowed repeated growth without the need of yeast extract addition. The kinetics and yields parameters of fermentation on media with different molasses concentrations were calculated. The anabolic parameters (specific growth rate, mu, and biomass yield, Y(X/S)) were inhibited at elevated molasses concentrations while the catabolic parameters (specific ethanol productivity, q(p), and ethanol yield, Y(p/s)) were not significantly affected. In addition to ethanol and substrate inhibition, osmotic pressure effects can explain the observed results.     

Effect of carbon and nitrogen sources on growth and biological efficacy of Pseudomonas fluorescens and Bacillus subtilis against Rhizoctonia solani, the causal agent of bean damping-off

One of the most important environmental factors that regulate the growth and antagonistic efficacy of biocontrol agents is the medium. The aim of this paper was to find the nitrogen and carbon sources that provide maximum biomass production of strains P-5 and P-6 (Pseudomonas fluorescens), B-3 and B-16 (Bacillus subtilis) and minimum cost of media, whilst maintaining biocontrol efficacy. All of the strains were grown in seven liquid media (pH=6.9) including: sucrose + yeast extract, molasses of sugar beet + yeast extract in 2:1 and 1:1 w/w ratios, molasses of sugar beet + urea, nutrient broth, molasses and malt extract, at an initial inoculation of 1 x 10(5) CFU ml(-1). Cells from over night cultures used to inoculate soil at 1 x 10(9) CFU cm(-3) soil. At the same time, fungal inoculum (infected millet seed with Rhizoctonia solani) was added to soil at the rate of 2 g kg(-1) soil. Results indicated that growth of P-6, B-3 and B-16 in molasses + yeast extract (1:1 w/w) medium was significantly higher than in the other media. Molasses + yeast extract (1:1 and 2:1 w/w) media supported rapid growth and high cell yields in P-5. In greenhouse condition, results indicated that the influence of the media on the biocontrol efficacy of P-5, P-6, B-3 and B-16 was the same and Pseudomonas fluorescens P-5 in molasses and malt extract media reduced the severity of disease up to 72.8 percent. On the other hand, there were observed significant differences on bean growth after one month in greenhouse. P-5 in molasses + yeast extract (1:1 w/w) medium had the most effects on bean growth promotion. In this study molasses media showed good yield efficacy in all of the strains. The high sucrose concentration in molasses justifies the high biomass in all of the strains. Also, the low cost of molasses allows its concentration to be increased in media. On the other hand, yeast extract was the best organic nitrogen source for antagonist bacteria but it is expensive for an industrial process. So it should be replaced by another industrial product instead of yeast extract, which confirm by an economic and technological study. The results obtained in this study could be used to provide a reliable basis to increase the population of biocontrol agents in fermentation process.     

Production of bio-ethanol from soybean molasses by Saccharomyces cerevisiae at laboratory, pilot and industrial scales

The aim of this work was to develop an economical bioprocess to produce the bio-ethanol from soybean molasses at laboratory, pilot and industrial scales. A strain of Saccharomyces cerevisiae (LPB-SC) was selected and fermentation conditions were defined at the laboratory scale, which included the medium with soluble solids concentration of 30% (w/v), without pH adjustment or supplementation with the mineral sources. The kinetic parameters - ethanol productivity of 8.08g/Lh, Y(P/S) 45.4%, Y(X/S) 0.815%, m 0.27h(-1) and mu(X) 0.0189h(-1) - were determined in a bench scale bioreactor. Ethanol production yields after the scale-up were satisfactory, with small decreases from 169.8L at the laboratory scale to 163.6 and 162.7L of absolute ethanol per ton of dry molasses, obtained at pilot and industrial scales, respectively.     

Rtm1: A Member of a New Family of Telomeric Repeated Genes in Yeast

We have isolated a new yeast gene called RTM1 whose overexpression confers resistance to the toxicity of molasses. The RTM1 gene encodes a hydrophobic 34-kD protein that contains seven potential transmembrane-spanning segments. Analysis of a series of industrial strains shows that the sequence is present in multiple copies and in variable locations in the genome. RTM loci are always physically associated with SUC telomeric loci. The SUC-RTM sequences are located between X and Y' subtelomeric sequences at chromosome ends. Surprisingly RTM sequences are not detected in the laboratory strain X2180. The lack of this sequence is associated with the absence of any SUC telomeric gene previously described. This observation raises the question of the origin of this nonessential gene. The particular subtelomeric position might explain the SUC-RTM sequence amplification observed in the genome of yeasts used in industrial biomass or ethanol production with molasses as substrate. This SUC-RTM sequence dispersion seems to be a good example of genomic rearrangement playing a role in evolution and environmental adaptation in these industrial yeasts.     

Ethanol tolerance, sugar tolerance and invertase activities of some yeast strains isolated from steep water of fermenting cassava tubers

E kunsanmi , T.J. & O dunfa , S.A. 1990. Ethanol tolerance, sugar tolerance and invertase activities of some yeast strains isolated from steep water of fermenting cassava tubers. Journal of Applied Bacteriology 69 , 672–675.
Thirteen yeasts isolated from the steep water of fermenting cassava tubers were screened for ethanol tolerance. Three strains which showed measurable growth in medium containing 10% (v/v) ethanol were also sugar-tolerant and grew well in medium containing 25% (w/v) glucose. One of the strains, YC3, was found to possess much higher invertase activity than the other two and could be of value in ethanol production from molasses. Further search for industrially useful yeasts in African fermented foods is suggested.     

Ethanol production by thermotolerant yeast and its UV resistant mutants.

Six thermotolerant yeasts were isolated at 37 degrees C from over-ripe grapes by serial dilution technique using glucose yeast extract medium. Purified yeast cultures were screened for ethanol production at 37 degrees C by batch fermentation, using cane molasses containing 20% sugars. Sugar conversion efficiency of these isolates varied from 66.0 to 88.5% and ethanol productivity from 1.11 to 1.73 ml/l/h. The highest ethanol producing isolate was exposed to UV radiations and 13 mutants were picked up from the UV treatment exhibiting 0.1 to 1.0%, survival. The UV mutants varied in cell size from parent as well as among themselves. Determination of ethanol produced by all the mutants revealed that only five mutants resulted in 4.5 to 6.2% increase in sugar conversion and 8.25 to 18.56% increase in ethanol concentration coupled with maximum ethanol productivity of 2.4 ml/l/h in 48 h of batch fermentation of cane molasses (20% sugars) at 37 degrees C temperature.     

SIMILARITY OF THE KINETICS OF INVERTASE ACTION IN VIVO AND IN VITRO. III

1. The relationship of sucrose and water concentration to invertase activity in vivo and in vitro has been studied under the same environmental conditions. 2. The sucroclastic activity of S. cerevisiae cells and of invertase solutions prepared from them reacts to changes in sucrose and water concentration in an identical manner. 3. The invertase contained in living yeast cells is just as freely exposed to the conditions of sucrose and water concentrations of the suspending medium as it would be if it were contained in a cell-free solution. Weight is added to the previous suggestion (2) that yeast invertase exerts its physiological activity in a region quite close to the surface of the cell.     

Influence of growth factor supplements on butyric acid production from sucrose byClostridium butyricum

During batch fermentation of sucrose to butyric acid byClostridium butyricum the effect of growth factor supplementation was determined: addition of yeast extract (5 g/L) stimulated most. Using biotin as the sole growth factor, average productivity was definitely lower. Beet molasses as a combined source of carbon and growth factor were effective only at a high concentration (150 g/L). The optimal butyric acid production (45 g/L, yield 45%) was achieved with sucrose concentration of 100 g/L in a medium supplemented with yeast extract (5 g/L). It represents an average productivity of 0.90 gL⁻¹ h⁻¹ and relative butyric acid concentration of 91%.     

Immobilized Sclerotinia sclerotiorum invertase to produce invert sugar syrup from industrial beet molasses by product

The fungus Sclerotinia sclerotiorum produces invertase activity during cultivation on many agroindustrial residues. The molasses induced invertase was purified by DEAE-cellulose chromatography. The molecular mass of the purified enzyme was estimated at 48 kDa. Optimal temperature was determined at 60 °C and thermal stability up to 65 °C. The enzyme was stable between pH 2.0 and 8.0; optimum pH was about 5.5. Apparent K_m and V_max for sucrose were estimated to be respectively 5.8 mM and 0.11 μmol/min. The invertase was activated by β-mercaptoethanol. Free enzyme exhibited 80 % of its original activity after two month’s storage at 4 °C and 50 % after 1 week at 25 °C. In order to investigate an industrial application, the enzyme was immobilized on alginate and examined for invert sugar production by molasses hydrolysis in a continuous bioreactor. The yield of immobilized invertase was about 78 % and the activity yield was 59 %. Interestingly the immobilized enzyme hydrolyzed beet molasses consuming nearly all sucrose. It retained all of its initial activity after being used for 4 cycles and about 65 % at the sixth cycle. Regarding productivity; 20 g/l of molasses by-product gave the best invert sugar production 46.21 g/day/100 g substrate related to optimal sucrose conversion of 41.6 %.     

Acceleration of ethanolic fermentation by zeolites

Summary Ethanolic fermentation of glucose by Saccharomyces cerevisiae was accelerated in presence of Silicalite only when the yeast was highly flocculent, the zeolite lowering floc size. With the sucrose and molasses, however, fermentation was accelerated even when the yeasts have low flocculence, the zeolite enhancing invertase activity of the yeast cells.