Rouxii Strains Research Articles

Development of Internal Transcribed Spacer Regions Amplification Restriction Fragment Length Polymorphism Method and Its Application in Monitoring the Population of Zygosaccharomyces rouxii M2 in Miso Fermentation

Recently, the use of the dry yeast of Zygosaccharomyces rouxii M2 for miso (soybean paste) fermentation has been established. A molecular monitoring method was developed and validated in this study to analyze the population of Z. rouxii M2 during the fermentation. The method was based on the restriction patterns of internal transcribed spacer (ITS) regions of the rDNA using Hae III and Hha I. Among the homologous ITS regions of Z. rouxii strains, Z. rouxii M2 produced diagnostic bands by which it can be differentiated from the other strains used. The specific restriction bands were due to the difference in nucleotide sequence of two different copies of ITS of Z. rouxii M2. Both ITS copies showed 94% sequence similarity but a 13-bp nucleotide substitution and a 19-bp deletion were found in the ITS1 region. Phylogenetic trees were constructed based on ITS and 18S rDNA sequences and it was found that the ITS sequences provide better resolution for the classification of Z. rouxii M2. Since Z. rouxii M2 is a promising strain for use in miso fermentation as a dry starter, the method developed is significant in terms of industrial application in monitoring the growth of Z. rouxii M2 in miso fermentation.

The Zygosaccharomyces rouxii strain CBS732 contains only one copy of the HOG1 and the SOD2 genes

The osmotolerant yeast Zygosaccharomyces rouxii CBS732 contains only one copy of the ZrHOG1 and ZrSOD2-22 genes. Both genes were cloned and sequenced (Acc. Nos. AJ132606 and AJ252273, respectively) and their sequences were compared to homologous pairs of genes from Z. rouxii ATCC42981 (genes Z-HOG1, Z-HOG2, Z-SOD2, Z-SOD22). The CBS732 ZrHog1p is shorter than its ATCC42981 counterparts (380 aa residues vs. 407 and 420 aa, respectively) and is more similar to ATCC42981 Z-Hog2p than to Z-Hog1p. Also its promoter region corresponds to that one of Z-HOG2. The CBS732 ZrHOG1 promoter region is recognised by Saccharomyces cerevisiae, and the gene product (MAP kinase ZrHog1p) presence fully complements the osmosensitivity of a S. cerevisiae hog1 mutant strain. The CBS ZrSOD2-22 gene is highly similar to ATCC42981 Z-SOD2 but it contains also a segment of 15 aa residues specific for Z-SOD22. Z. rouxii ZrSod2-22 Na +/H + antiporter expressed in S. cerevisiae shows better activity toward toxic Na + and Li + cations than does S. cerevisiae's own Nha1 antiporter, and is efficient in improving the halotolerance of some S. cerevisiae wild types.

Commercial baker's yeast stability as affected by intracellular content of trehalose, dehydration procedure and the physical properties of external matrices.

The effects of vacuum-drying and freeze-drying on the cell viability of a commercial baker's yeast, Saccharomyces cerevisiae, strain with different endogenous contents of trehalose were analyzed. An osmotolerant Zygosaccharomyces rouxii strain was used for comparative purposes. Higher viability values were observed in cells after vacuum-drying than after freeze-drying. Internal concentrations of trehalose in the range 10-20% protected cells in both dehydration processes. Endogenous trehalose concentrations did not affect the water sorption isotherm nor the Tg values. The effect of external matrices of trehalose and maltodextrin was also studied. The addition of external trehalose improved the survival of S. cerevisiae cells containing 5% internal trehalose during dehydration. Maltodextrin (1.8 kDa) failed to protect vacuum-dried samples at 40 degrees C. The major reduction in the viability during the freeze-drying process of the sensitive yeast cells studied was attributed to the freezing step. The suggested protective mechanisms for each particular system are vitrification and the specific interactions of trehalose with membranes and/or proteins. The failure of maltodextrins to protect cells was attributed to the fact that none of the suggested mechanisms of protection could operate in these systems.

Physiological Characteristics of a Film-forming Strain ofZygosaccharomyces rouxii, and Its Cellular Fatty Acid Synthesis

Some physiological characteristics of Zygosaccharomyces rouxii strain No. F51, forming a film only on saline media, were investigated. When the strain was statically cultivated in a NaCl-hypertonic medium, it produced ethanol accompanied with the consumption of glucose in the early stage of the cultivation. Subsequently, the strain assimilated the resulting ethanol to form a film on the surface of the medium after the consumption of glucose. Isobutyl and isoamyl alcohols were transiently accumulated in the medium at an unusually high concentration during the film-forming growth of the strain. The total amount of lipids readily extracted from the film-forming cells (F-cells) grown in a hypertonic medium was about 4-fold as much as that extracted from the sedimentary cells (S-cells) grown in a salt-free hypotonic medium. The total amount of higher fatty acids (C14-Cl8) from F-cells was over twice as much as that from S-cells. Oleic and linoleic acids were the major fatty acid in F-cells. The quantity ratio ...

Production of single cell protein from olive mill waste water by yeasts

Abstract Studies have been made of the growth of three yeasts Candida krusei, Saccharomyces chevalierie and Saccharomyces rouxii on olive mill wastewater (OMW). The cultures were made in a shaker flask culture and in a fermentor in order to select organisms which can produce large quantities of biomass. Three yeasts have been selected that will tolerate the polyphenols. They can be used to reduce Biological Oxygen Demand (BOD) (40–50%), and perhaps become a source of Single Cell Protein (SCP) for supplementation of animal feeds. Concentration of protein of 3.35 g 1‐1 and yield of 0.45g of biomass per g of glucose based on glucose consumption were obtained using Saccharomyces rouxii strain.

Activity of different 'killer' yeasts on strains of yeast species undesirable in the food industry

Killer strains of the genera Saccharomyces, Hansenula and Kluyveromyces were tested for killing activity against yeasts that cause trouble in the food industry (in the genera Zygosaccharomyces, Kloeckera, Saccharomycodes and Schizosaccharomyces). Saccharomyces strains killed only Zygosaccharomyces rouxii strains, while non-Saccharomyces strains showed a wider anti-yeast spectrum. The Kluyveromyces phaffii killer strain was of particular interest because of its killer action against Kloeckera apiculata, Saccharomycodes ludwigii and Zygosaccharomyces rouxii.

Activity of different ‘killer’ yeasts on strains of yeast species undesirable in the food industry

Killer strains of the genera Saccharomyces, Hansenula and Kluyveromyces were tested for killing activity against yeasts that cause trouble in the food industry (in the genera Zygosaccharomyces, Kloeckera, Saccharomycodes and Schizosaccharomyces). Saccharomyces strains killed only Zygosaccharomyces rouxii strains, while non-Saccharomyces strains showed a wider anti-yeast spectrum. The Kluyveromyces phaffii killer strain was of particular interest because of its killer action against Kloeckera apiculata, Saccharomycodes ludwigii and Zygosaccharomyces rouxii.

A serological typing method for salt-tolerant yeasts in soy sauce mashes.

The serological grouping of yeasts in soy sauce mashes was attempted. Twenty-one representative strains of salt-tolerant yeasts isolated from soy sauce mashes were divided into 5 groups as to the differences in the agglutination patterns with 4 factor sera, 4, 10, 20 and 35. Furthermore, 2 other groups of yeasts were detected in soy sauce mashes. Some yeasts responsible for the characteristic flavor were included in the individual groups. Changes in the yeast-flora during the fermentation of soy sauce mashes could be monitored easily by means of the serological grouping system. Among Zygosaccharomyces rouxii strains isolated from soy sauce mashes, no differences in thermostable antigens or PMR spectra of cell wall polysaccharides were found. Over 95% of the moromi-mash yeasts that showed a positive reaction with factor serum 35 exhibited 4-ethyl-2-methoxyphenol (4EG) productivity.

Miso. III. Pure culture fermentation with Saccharomyces rouxii.

Excellent miso has been prepared with soybean grits inoculated with a pure culture of Saccharomyces rouxii strain NRRL Y-2547. Pure culture inoculum of this osmophilic yeast was prepared by growing the culture in aerated flasks on a yeast extract medium with a salt concentration equal to that used in the manufacture of miso. It has also been found possible to make miso from whole beans with the above culture. The advantages of pure culture fermentation in producing miso are discussed.