Ferment Maltose Research Articles

Beer brewing using a fusant between a sake yeast and a brewer's yeast

Beer brewing using a fusant between a sake yeast (a lysine auxotrophic mutant of sake yeast K-14) and a brewer's yeast (a respiratory-deficient mutant of the top fermentation yeast NCYC1333) was performed to take advantage of the beneficial characteristics of sake yeasts, i.e., the high productivity of esters, high tolerance to ethanol, and high osmotolerance. The fusant (F-32) obtained was different from the parental yeasts regarding, for example, the assimilation of carbon sources and tolerance to ethanol. A brewing trial with the fusant was carried out using a 100- l pilot-scale plant. The fusant fermented wort more rapidly than the parental brewer's yeast. However, the sedimentation capacity of the fusant was relatively low. The beer brewed using the fusant contained more ethanol and esters compared to that brewed using the parental brewer's yeast. The fusant also obtained osmotolerance in the fermentation of maltose and fermented high-gravity wort well.

Beer Brewing Using a Fusant between a Sake Yeast and a Brewer's Yeast.

Beer brewing using a fusant between a sake yeast (a lysine auxotrophic mutant of sake yeast K-14) and a brewer's yeast (a respiratory-deficient mutant of the top fermentation yeast NCYC1333) was performed to take advantage of the beneficial characteristics of sake yeasts, i.e., the high productivity of esters, high tolerance to ethanol, and high osmotolerance. The fusant (F-32) obtained was different from the parental yeasts regarding, for example, the assimilation of carbon sources and tolerance to ethanol. A brewing trial with the fusant was carried out using a 100-l pilot-scale plant. The fusant fermented wort more rapidly than the parental brewer's yeast. However, the sedimentation capacity of the fusant was relatively low. The beer brewed using the fusant contained more ethanol and esters compared to that brewed using the parental brewer's yeast. The fusant also obtained osmotolerance in the fermentation of maltose and fermented high-gravity wort well.

Development of chromogenic agar medium for isolation of enterohaemorrhagic Escherichia coli O26

Agar media for isolation of enterohaemorrhagic Escherichia coli (EHEC) have been developed primarily for E. coli O157, because this bacterium has most frequently caused EHEC infection. However, there have been few studies for isolation of other serotypes of EHEC, and media appropriate for isolation of such organisms, especially from food samples, are not yet available. Among such serotypes, E. coli O26 has often been isolated from clinical specimens from patients and animals, but not from food samples in outbreaks, because of lack of an appropriate method for isolation. In this study, we tried to develop a new chromogenic agar medium for selective isolation of E. coli O26 using the characteristics of E. coli O26. Fifteen strains of E. coli O26, 11 strains of E. coli O157 and 36 strains of other sero-types E. coli were tested for fermentation of rhamnose, cellobiose, dulcitol, salicin, raffinose, sorbitol, sucrose, lactose, mannitol, arabinose, maltose, xylose and glucose. Rhamnose was fermented by all E. coli strains except for E. coli O26. The other substrates were not effective for differentiating E. coli O26 from the other strains of E. coli. Thus the medium containing rhamnose and 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside, which is a substrate of beta-galactosidase specific to coliforms, produced a color of E. coli O26 colonies different from colors of the other bacteria. Furthermore, cefixime and sodium tellulite were added to the composition of the medium for gaining higher selectivity.

Effects of the Escherichia coli sfsA gene on mal genes expression and a DNA binding activity of SfsA.

The sfsA gene was identified as one of the sfs genes the over-expression of which stimulates maltose fermentation of the Mal- Escherichia coli strain MK2001 (crp*1, cya:Km(r)). Expression from the malPQ promoter, which was measured using a chromosomally integrated malPp-lacZ fusion, was induced by over-expressing the sfsA gene in the crp*1, cya:Km(r) strain. The level of the MalE protein was increased in crp*1, cya:Km(r) cells over-producing SfsA. The SfsA protein was purified to homogeneity and tested for DNA binding activity. The purified SfsA protein binds to DNA non-specifically. All these results may suggest that SfsA functions as a DNA binding protein to induce the mal genes in coordination with CRP*1.

Protein phosphatase type-1 regulatory subunits Reg1p and Reg2p act as signal transducers in the glucose-induced inactivation of maltose permease in Saccharomyces cerevisiae.

The REG1 gene encodes a regulatory subunit of the type-1 protein phosphatase (PP1) G1c7 in Saccharomyces cerevisiae, which directs the catalytic subunit to substrates involved in glucose repression. Loss of REG1 relieves glucose repression of many genes, including the MAL structural genes that encode the maltose fermentation enzymes. In this report, we explore the role of Reglp and its homolog Reg2p in glucose-induced inactivation of maltose permease. Glucose stimulates the proteolysis of maltose permease and very rapid loss of maltose transport activity - more rapid than can be explained by loss of the permease protein alone. In a reg1delta strain we observe a significantly reduced rate of glucose-induced proteolysis of maltose permease, and the rapid loss of maltose transport activity does not occur. Instead, surprisingly, the slow rate of proteolysis of maltose permease is accompanied by an increase in maltose transport activity. Loss of Reg2p modestly reduces the rates of both glucose-induced proteolysis of maltose permease and inactivation of maltose transport activity. Overexpression of Reg2p in a reg1delta strain suppresses the effect on maltose permease proteolysis and partially restores the inactivation of maltose transport activity, but does not affect the insensitivity of MAL gene expression to repression by glucose observed in this strain. Thus, protein phosphatase type-1 (Glc7p-Reglp and Glc7p-Reg2p) plays a role in transduction of the glucose signal during glucose-induced proteolysis of maltose permease, but only Glc7p-Reglp is involved in glucose-induced inactivation of maltose transport activity and glucose repression of MAL gene expression. Overexpression of REG1 partially restores proteolysis of maltose permease in a grr1delta strain, which lacks glucose signaling, but does not rescue rapid inactivation of maltose transport activity or sensitivity to glucose repression. A model for the role of Reglp and Reg2p in glucose signaling pathways is discussed. We also uncovered a previously unrecognized G2/M delay in the grr1delta but not the reg1delta strains, and this delay is suppressed by REG1 overexpression. The G1/S delay seen in grr1delta mutants is slightly suppressed as well, but REG1 overexpression does not suppress other grr1delta phenotypes such as insensitivity to glucose repression.

Analysis of the mechanism by which glucose inhibits maltose induction of MAL gene expression in Saccharomyces.

Expression of the MAL genes required for maltose fermentation in Saccharomyces cerevisiae is induced by maltose and repressed by glucose. Maltose-inducible regulation requires maltose permease and the MAL-activator protein, a DNA-binding transcription factor encoded by MAL63 and its homologues at the other MAL loci. Previously, we showed that the Mig1 repressor mediates glucose repression of MAL gene expression. Glucose also blocks MAL-activator-mediated maltose induction through a Mig1p-independent mechanism that we refer to as glucose inhibition. Here we report the characterization of this process. Our results indicate that glucose inhibition is also Mig2p independent. Moreover, we show that neither overexpression of the MAL-activator nor elimination of inducer exclusion is sufficient to relieve glucose inhibition, suggesting that glucose acts to inhibit induction by affecting maltose sensing and/or signaling. The glucose inhibition pathway requires HXK2, REG1, and GSF1 and appears to overlap upstream with the glucose repression pathway. The likely target of glucose inhibition is Snf1 protein kinase. Evidence is presented indicating that, in addition to its role in the inactivation of Mig1p, Snf1p is required post-transcriptionally for the synthesis of maltose permease whose function is essential for maltose induction.

Fermentation of starch by Klebsiella oxytoca p2, containing plasmids with alpha-amylase and pullulanase genes.

Klebsiella oxytoca P2(pC46), an ethanol-producing recombinant, has been evaluated in fermentation of maltose and starch. The maximum ethanol produced by P2(pC46) was 0.34 g ethanol/g maltose and 0.38, 0.40, or 0.36 g ethanol/g starch in fermentation of 1, 2, or 4% starch, representing 68, 71, and 64% the theoretical yield. The pC46 plasmid transformed to cells of K. oxytoca P2 reduced the ethanol production from maltose and starch. In fermentation of starch after its digestion at 60 degrees C for 24 h, in two-step fermentation, the time for maximum ethanol production was reduced to 12-24 h and the theoretical yield was around 90%. The increase in starch concentration resulted in lower alpha-amylase activity but in higher pullulanase activity. The high activity and thermostability of the amylolytic enzymes from this transformant suggest that it has a potential for amylolytic enzymes source.

Effects of a Saccharomyces cerevisiae culture on in vitro mixed ruminal microorganism fermentation.

Previous research has shown that Saccharomyces cerevisiae culture increases lactate utilization and cellulose digestion by pure cultures of ruminal bacteria. Based on these pure culture results, in vitro mixed ruminal microorganism fermentations were conducted to determine the effects of 0.35 and 0.73 g/L of Sacc. cerevisiae culture on the fermentation of ground corn, maltose, alfalfa hay, bermudagrass hay, and lactate. In addition, experiments were performed to evaluate the effects of Sacc. cerevisiae culture and monensin on the mixed ruminal microorganism fermentation. In the presence of ground corn, both concentrations of Sacc. cerevisiae culture had little effect on final pH or fermentation products, except the 0.35 g/L treatment increased valerate concentration. Saccharomyces cerevisiae culture had little effect on final pH or fermentation products in maltose or lactate fermentations. When alfalfa hay was the substrate, 0.73 g/L of Sacc. cerevisiae culture increased propionate concentration and both treatments decreased the acetate to propionate ratio. In the case of Coastal bermudagrass hay, 0.73 g/L Sacc. cerevisiae culture increased concentrations of acetate, propionate, CH4, butyrate, isovalerate, valerate, and decreased the acetate to propionate ratio, whereas both treatments increased total volatile fatty acid concentrations. Similar to alfalfa hay, in vitro dry matter disappearance of Coastal bermudagrass hay was numerically increased in the presence of Sacc. cerevisiae culture. Monensin altered the fermentation by decreasing concentrations of CH4 and lactate and increasing concentrations of propionate. There was no interaction between Sacc. cerevisiae culture and monensin. In conclusion, the incorporation of Sacc. cerevisiae culture into mixed ruminal microorganism fermentations of ground corn, maltose, or lactate had little effect on final pH and fermentation products. However, in the presence of alfalfa hay or Coastal bermudagrass hay Sacc. cerevisiae culture increased concentrations of several fermentation products and numerically increased in vitro dry matter disappearance of forage fiber.

Identification of Bacillus anthracis strains in China.

As part of a project to establish a reference strain collection, phenotypic, biochemical and genetic analyses were carried out on 84 strains of Bacillus anthracis, 81 of them of Chinese origin from various sources. Particular differences from reports on isolates of other origins were the possession of fimbriae and single polar flagella with consequent motility in 77, self-agglutination by 64 and failure to ferment maltose in 60 of the Chinese strains. The findings were considered to be of significance to identification, classification and evolution of B. anthracis.

Genetic evidence that high noninduced maltase and maltose permease activities, governed by MALx3-encoded transcriptional regulators, determine efficiency of gas production by baker's yeast in unsugared dough.

Strain selection and improvement in the baker's yeast industry have aimed to increase the speed of maltose fermentation in order to increase the leavening activity of industrial baking yeast. We identified two groups of baker's strains of Saccharomyces cerevisiae that can be distinguished by the mode of regulation of maltose utilization. One group (nonlagging strains), characterized by rapid maltose fermentation, had at least 12-fold more maltase and 130-fold-higher maltose permease activities than maltose-lagging strains in the absence of inducing sugar (maltose) and repressing sugar (glucose). Increasing the noninduced maltase activity of a lagging strain 13-fold led to an increase in CO2 production in unsugared dough. This increase in CO2 production also was seen when the maltose permease activity was increased 55-fold. Only when maltase and maltose permease activities were increased in concert was CO2 production by a lagging strain similar to that of a nonlagging strain. The noninduced activities of maltase and maltose permease constitute the largest determinant of whether a strain displays a nonlagging or a lagging phenotype and are dependent upon the MALx3 allele. Previous strategies for strain improvement have targeted glucose derepression of maltase and maltose permease expression. Our results suggest that increasing noninduced maltase and maltose permease levels is an important target for improved maltose metabolism in unsugared dough.

口かみ 「もろみ」 の発酵と微生物

Each Subject (male and female) made Kuchikami rice moromi (mash) by chewing 200 g or 300 g of steamed rice. After 2 days, the chewed moromi contained 11.2-14.9% of direct reducing sugar, 23.5-33.8% of total sugar and an acidity of 1.2-1.7 ml, respectively. The presence of maltose, maltotriose and glucose were confirmed by qualitative thin laver chromatorapic analysis. The concentration of these saccharides showed a slight difference depending on the person chewing the moromi and the period (days) after chewing. The moromi produced 0.2-5.8% of alcohol after 15-36 days of fermentation. It also contained 2.5-11.7% of direct reducing sugar, 13.0-17.0% of total sugar, an acidity of 10.5-32.5 ml and an amino acidity of 0.6-3.0 ml, respectively. Saccharomyces sp. with glucose and maltose fermentation ability, and Lactic acid bacteria were universally isolated from moromi. However, the isolation of film forming yeasts (Pichia sp. and Hansenula sp.) differed between each moromi.

Extrapelvic manifestations of gonorrhea

Gonococci are small, aerobic, nonmotile, gram-negative diplococci that belong to the genus Neisseria. Gonococci attach to mucosal epithelium and within 24–48 hours they penetrate into the cells where they multiply and then pass through the epithelial cells into the submucosal tissues. Here the organisms either cause local inflammation or enter the blood vessels to cause disseminated disease. Disseminated gonococcal infection occurs in 0.5–3 percent of patients with mucosal infection. Early extrapelvic clinical manifestations include arthritis, tenosynovitis, and dermatitis. Later clinical manifestations of extrapelvic gonorrhea include endocarditis, perihepatitis, osteomyelitis, permanent joint damage, or even rarer complications such as pericarditis or meningitis. Disseminated gonococcal infection results from bacteremic dissemination of N gonorrhoeae. When disseminated gonococcal infection is suspected, a minimum of three blood cultures should be obtained. In addition, N gonorrhoeae can be recovered from a mucosal site in at least 80% of affected patients. Thus, mucosal culture should also be obtained. A positive laboratory diagnosis of N gonorrhoeae requires that the organism be grown and identified as an oxidase-positive, gram-negative diplococcus that ferments glucose but fails to ferment maltose or sucrose. Isolation by culture remains the standard test for diagnosis of N gonorrhoeae, although a DNA probe is commercially available. Hospitalization is recommended for initial therapy. The antibiotic of choice for disseminated gonococcal infection is ceftriaxone.

Fermentation of maltose and starch by Klebsiella oxytoca P2

Klebsiella oxytoca P2, which has genes from Zymomonas mobilis encoding the alcohol dehydrogenase and pyruvate decarboxylase integrated in its chromosome, fermented 50 g maltose/l to 25.4 g of ethanol/l. It also fermented 10, 20 and 40 g starch/l yielding 4, 8.4, and 17.7 g ethanol/l, respectively, representing 72, 75 and 78% of the theoretical yield. © Rapid Science Ltd. 1998

Lactobacillus helveticus heterogeneity in natural cheese starters: the diversity in phenotypic characteristics.

The study of wild strains from natural habitats is a useful means of understanding better the heterogeneity within a species of biotechnological importance, and of obtaining atypical isolates with unknown capabilities. In the present research carried out on different Lactobacillus helveticus strains isolated from natural cheese starters, it was observed that several biotechnologically important characteristics can differ greatly between strains. Biotypes were found which differ in terms of fructose, maltose and trehalose fermentation, acidifying activity, proteolytic and peptidase activity, and antibiotic and lysozyme resistance. The possibility of choosing Lact. heleveticus strains with specific biotechnological profiles will influence the quality and the variety of dairy products.

Identificación y caracterización de bacterias acidolácticas aisladas de chorizos tradicionales elaborados en Castilla y León / Identification and characterization of lactic acid bacteria isolated from traditional chorizo made in Castilla-León

A total of 516 strains of lactic acid bacteria isolated from chorizo made in Castilla-León (Spain) were characterized. Strains were isolated at three different stages: minced meat, half ripened chorizo and ripened chorizo. According to the Schillinger and Lücke classification, 355 strains (68.8%) were Lactobacillus sake, 85 strains (16.5%) were Lactobacillus curvatus, 32 strains (6.2%) belonged to the genus Pediococcus, and 44 strains which were not included in the previous species were grouped as Lactobacillus sp. Strains of L. sake and L. curvatus could be separated into four groups each, on the basis of fermentation of maltose and lactose. Group S1 (maltose-, lactose-négative L. sake) predominated (39.5%). Many strains of this group fermented the following carbohydrates: glucose, ribose, galactose, sucrose, melibiose and trehalose.

Detection of maltose fermentation genes in the baking yeast strains of Saccharomyces cerevisiae.

The presence of any one of the five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 and MAL6) confers the ability to ferment maltose on the yeast Saccharomyces cerevisiae. Each locus is composed of three genes encoding maltose permease, alpha-glucosidase and MAL activator. Chromosomal DNA of seven representative baking strains has been separated by pulse-field gel electrophoresis and probed with three genes in MAL6 locus. The DNA bands to which all of the three MAL-derived probes simultaneously hybridized were chromosome VII carrying MAL1 in all of the strains tested, chromosome XI carrying MAL4 in six strains, chromosome III carrying MAL2 in three strains and chromosomes II and VIII carrying MAL3 and MAL6, respectively, in the one strain. The number of MAL loci in baking strains was comparable to those of brewing strains.

Protoplast fusion between Lactobacillus casei and Lactobacillus acidophilus

From the fusion between Lactobacillus casei and Lactobacillus acidophilus, 8 fusants were selected: Four were able to ferment maltose, lactose, galactose and mannose, but two had greater abilities of acid production than parents. Increased values of up to 7.6–8 % in β -galactosidase activity were obtained from two when compared to that of L. acidophilus, whereas another 2 had activities of 800 and 548 nmol/mg protein/min comparable to that of L casei giving a value of 400 nmol/mg protein/min in phospho-β-galactosidase activity.

Genetic differences between nitrate-negative and nitrate-positive C. pseudotuberculosis strains using restriction fragment length polymorphisms

Corynebacterium pseudotuberculosis has been classified into two biotypes according to ability to breakdown nitrate (Biberstein et al., 1971). Restriction enzyme analysis (REA) has shown to reflect this differentiation, but numerous bands generated by this technique make interpretation difficult (Songer et al., 1988). Restriction fragment length polymorphism's (RFLP's) has become an accepted genetic tool and was used in this study to determine if differences in nitrate reduction and other phenotypic characteristics could be identified genetically. Thirteen C. pseudotuberculosis isolates from four species of domestic animals from different parts of the world were investigated for phenotypic and genetic differences. Three closely related bacteria, Corynebacterium ulcerans, Actinomyces pyogenes (previously C. pyogenes), and Rhodococcus equi (previously C. equi) were included in the study to determine if the RFLP bands were unique to C. pseudotuberculosis. All C. pseudotuberculosis isolates were positive for urease production. Some differences in maltose and sucrose fermentation ability and nitrate reduction were recorded. Genetic differences were identified between the nitrate-positive group and the nitrate-negative group using non-radioactive ribosomal RNA (rRNA) probes Southern blotted to restriction digests of ApaI, PstI, and Sst I. A small number of bands were seen, with distinct differences between the nitrate-positive and the nitrate-negative strains. No genetic variations were seen between strains which reflected differences in carbohydrate fermentation. Strains isolated from different animal species and from different parts of the world could not be differentiated genetically using these three restriction enzymes.

Co-metabolism of citrate and maltose byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain: effect on growth, end-products and sourdough fermentation

Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism.

Development of New Strains for the Food Industry

AbstractThis review examines the desired characteristics and possibilities of genetic manipulation of industrial yeasts. Brewing, wine, and distillers' yeasts are characterized by good utilization of sugar, alcohol tolerance and production, flavor and aroma, flocculation, fermentation rate, cropping ratio, ability to utilize trisaccharides, dextrines and starch, rapid onset of fermentation, nonfoaming fermentation, and low H2S production. The characteristics required for a good bakers' yeast include high potential glycolytic activity, ability to adapt rapidly to changing substrates, high invertase activity, high potential maltose fermentation rate and quality in terms of dough fermentation, storage ability, and osmotic resistance to salts and sugars. In all of these cases, the major desirable factors are under genetic control and hence are potentially subject to improvement by genetic manipulation. However, this control is thought to be governed by several, in most cases, unidentified genes. So, although most genetic techniques developed for laboratory yeasts are potentially applicable to the study and improvement of the properties of industrial yeast strains, traits such as homothallism, aberration in mating behavior, polyploidy, aneuploidy, poor sporulation and poor spore viability, etc., make conventional hybridization and isolation of single spore clones more difficult.