• KSBB Journal
• /
• v.19 no.4
• /
• pp.245-249
• /
• 2004

A combined method of autolysis and enzymatic hydrolysis of baker's yeast was developed for the production of yeast extract, which is widely used as a natural food ingredient. From statistical analysis, NaCl and ethanol addition were found to be significantly effective factors in autolysis of yeast. The optimum dosages of salt and ethanol were 3% and 1%, respectively. Heat treatment and the use of cell lytic enzyme were not significantly effecting on the autolysis. Yeast hydrolysate was prepared by autolysis, followed by enzymatic hydrolysis using proteases, nuclease and deaminase. Additionally, the hydrolysate was processed by downstream process including Maillard reaction and debittering. The total dry matter yield and total nitrogen yield for the process were 76% and 59%, respectively. Compared to a process using brewer's yeast, when baker's yeast was used as a raw material, a higher recovery yield was obtained.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.13 no.3
• /
• pp.313-318
• /
• 1984

Some chemical, biochemical and physical treatments on the baker's yeasts (Saccharomyces cerevisiae) before 12-hour digestion at $50^{\circ}C$ were made to accelerate their autolysis. Dilute alkali treatment with 0.01N-NaOH solution showed a considerable increase in soluble nitrogen extraction only in the 6-hour initial autolysis. The addition of fresh yeast autolysate, 10% to the yeast slurry, could increase the autolysis rate from 65% to 83%. Microwave treatment of yeast slurry for 40 seconds also raised the autolysis rate by about 15%, while longer exposures to the microwave accompanying high temperatures repressed the autolysis process. Extrusion of the yeast cells with high pressures of 16,000 to 20,000 psi brought about significantly higher autolysis rate until the digestion time of 9 hours, but thereafter it showed a gradual drop in soluble nitrogen extraction.

• The Korean Journal of Food And Nutrition
• /
• v.8 no.4
• /
• pp.280-288
• /
• 1995

Because yeast is rich in vitamins, nucleotides and essential amino acids, it has been used as a nutrient and dietary supplements. Particularly yeast extract functions as a seasoning, flavor enhancer in meats. In this study, naturally occurring insoluble components during yeast extract process by autolysis were microanalyses by using SEM, XRD, HPLC, GC, FT-lR and DSC. On the basis of useful datas, authors have characterized the analytical points for the purpose of improving products in the preparation of yeast extract.

• Microbiology and Biotechnology Letters
• /
• v.43 no.3
• /
• pp.249-258
• /
• 2015

In this paper, the autolysis process of Saccharomyces cerevisiae FX-2 (S. cerevisiae FX-2) via, a variety of endogenous enzyme, was investigated systematically by analyzing changes in physicochemical parameters in autolysate, surface morphology and the internal structure of the yeast cells. As an explicit conclusion, the arisen autolysis depended on the pH and the optimal pH was found to be 5.5. Based on the experimental data and the characteristics of mycelia morphology, a hypothesis is put forward that simple proteins in yeast vacuolar are firstly degraded for utilization, and then more membrane-bound proteins are hydrolyzed to release hydrolytic enzymes, which arouse an enzymatic reaction to induce the collapse of the cell wall into the cytoplasm.

• Korean Journal of Food Science and Technology
• /
• v.27 no.1
• /
• pp.129-133
• /
• 1995

Continuous fermentations were performed in order to investigate the effect of culture condition on the yeast RNA accumulation and autolysis efficiency. The content of intracellular RNA increased with increasing dilution rate, showing its maximum value of 14.8% at D=0.35 $h^{-1}$. Also, both RNA productivity and specific RNA productivity tended to increase with the increase of dilution rate. The maximum biomass was obtained at $30^{\circ}C$ in the fixed dilution rate of 0.2 $h^{-1}$, whereas the maximum RNA content appeared at the lowest temperature experimented. Growth rate affected significantly on the yeast autolysis efficiency such that the extraction ratio(TN/TN) increased with increasing growth rate, whereas the hydrolysis ratio(AN/TN) was reversed. On the other hand, its efficiency was little affected by cultivation temperature.

• KSBB Journal
• /
• v.13 no.3
• /
• pp.308-311
• /
• 1998

A novel process was developed to simultaneously produce invertase and yeast extract from baker's yeast using ultrafiltration (UF) and microfiltration (MF) membrane processing. After the extraction of invertase under the optimal condition obtained in this study, invertase was separated from yeast cells using a hollow fiber membrane with a pore size of 0.1 $\mu\textrm{m}$. The resulting permeate containing invertase was concentrated using a hollow fiber membrane with a nominal molecular weight cut-off of 30 kDa. The yeast cell and permeate solutions, which were obtained after MF and UF membrane processing, respectively, were mixed together, and the autolysis was performed at 50$^{\circ}C$ in the presence of 5% (w/v) ethanol and 1% (w/v) NaCl. As a result, the yeast extract and invertase could be simultaneously produced from baker's yeast by this novel process.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.7
• /
• pp.1041-1046
• /
• 2006

Selenium-containing peptide (selenium peptide) was produced by autolysis of total proteins of Saccharomyces cerevisiae grown with inorganic selenium. Selenium peptide exhibited antioxidant activity as a glutathione peroxidase (GPx) mimic, and its activity was dependent on the hydrolysis methods. The GPx-like activity of the hydrolyzed selenium peptide increased 2.7-folds when digested by protease, but decreased by acid hydrolysis. During the autolysis of the yeast cell, the GPx-like activity and selenium content increased 4.3- and 2.3-folds, respectively, whereas the average molecular weight (MW) of selenium peptide decreased 70%. The GPx-like activity was dependent on the MW of selenium peptide and was the highest (220 U/mg protein) at 9,500 dalton. The maximum GPx-like activity (28,600 U/g cell) was obtained by 48 h of autolysis of the cells, which were precultured with 20 ppm of selenate. Selenium peptide showed little toxicity, compared with highly toxic inorganic selenium. These results show the potential of selenium peptide as a nontoxic antioxidant that can be produced by simple autolysis of yeast cells.

• Korean Journal of Food Science and Technology
• /
• v.35 no.2
• /
• pp.201-205
• /
• 2003

The optimum autolysis conditions were investigated to prepare yeast autolyzate (extract) using yeast slurry collected from brewery plants. Brewers yeast slurry was washed with caustic soda to eliminate bitter hof substances attached to yeast cell walks. The pH of brewers yeast slurry was adjusted to 9.8 with caustic soda, and centrifuged at 3,000 rpm for 5 min. The supernatant was discarded, and the bottom cake was rehydrated and collected. Bitterness unit (BU) of washed yeast slurry was 24.1 BU, below the threshold value of 25.0. Yeast extract could be obtained from washed brewers yeast slurry at maximum yield up to 38% by autolyzing at pH 6.8 and $53^{\circ}C$ for 20 h.

• Microbiology and Biotechnology Letters
• /
• v.25 no.5
• /
• pp.512-519
• /
• 1997

RNA accumulating strain of Torulopsis versatilis MT-1 was cultured in molasses medium for higher contents of RNA in cell. Yeast cells were harvested at logarithmic phase on synchronous culture. Yield of cells on dry base to input sugar was 59.5%. Crude protein content was 55.1% in cell. RNA content was 13.9%. Some problems found in the process for the preparation of yeast extracts were improved by the addition of culture broth of Streptomyces faecalis MSF which secrete RNase (5' nuclease and 5' adenylic acid deaminase). When the culture broth of S. faecalis MSF was added in autolysis process 46% of RNA in cell was converted to I and G(5' inosinic acid and 5' guanylic acid) in extract. By addition of 3-7% culture broth of S.faecalis MSF in autolysis or enzymolysis process at the start or early stage, RNA in extract was converted easily to I and G and protein in cells was easily extracted and hydrolyzed to amino acid. Taste of those yeast extracts was delicious. The yeasty smell in yeast extracts was removed. And cell debris was easily removed from extract.

• Korean Journal of Food Science and Technology
• /
• v.13 no.3
• /
• pp.181-187
• /
• 1981

The changes in the chemical composition of yeast extracts during autolysis and their effect to the sensory quality were studied with baker's yeast, Saccharomyces cerevisiae. The amounts of extracted solids, proteins, amio-N. amino acids, especially glutamic acid, alanine and lysine, increased by the autolysis time up to 48 hrs. The results of sensory evaluation made by the multiple paired comparision test and Duncan's test indicated a significant difference is taste by the time of autolysis. In the profile test, the flavor character notes expressed by the panel were 17 different characters, 11 in aroma and 6 in taste. The character notes and the intensity of flavor changed with the time of autolysis. The sharp and beany flavor of the extracts which was autolyzed for 4 hours turned into meaty and worty flavor by 48 hours of autolysis. A proper arrangement of the flavor characters in the quantitative descriptive chart could provide a weighted value of the flavor grade. The aroma grade index and the taste grade index correlated to the amplitudes of the profile test.