Autolysis in yeasts

The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear. Yeast cells ( Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30-60 degrees C (pH 7.0), and at pH 4.0-7.0 (40 degrees C) for 10-14 days. Up to 55% of total DNA was degraded, with consequent leakage into the extracellular environment of mainly 3'- and 5'-deoxyribonucleotides, and lesser amounts of polynucleotides. The rate and extent of DNA degradation, composition of the DNA degradation products and DNase activity were affected by temperature and pH. The highest amount of DNA degradation occurred at 40 degrees C and pH 7.0, where the highest DNase activity was recorded. DNase activity was lowest at 60 degrees C and pH 4.0, where the proportion of polynucleotides in the degradation products was higher.

Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 98%

Degradation of DNA during the autolysis of Saccharomyces cerevisiae

Zhao

Fleet

2003

“…Although a naturally occurring event, autolysis of yeasts can be induced by exposing the cells to elevated temperatures (40-60°C), salts, or organic solvents [2,3]. The basic biology and chemistry of yeast autolysis have been well-studied and reviewed [2][3][4][5][6][7][8]10], but much of the research has focussed on the autolytic breakdown of protein whereas the degradation of nucleic acids (DNA and RNA) has received much less attention.…”

Section: Introductionmentioning

confidence: 99%

Degradation of RNA during the autolysis of Saccharomyces cerevisiae produces predominantly ribonucleotides

Zhao

Fleet

2005

Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product, but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30-60 degrees C (pH 7.0), and at pH 4.0-7.0 (40 degrees C) for 10-14 days, and the RNA degradation products formed during the process were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular environment of mainly 3'-, 5'- and 2'-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases. The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation was fastest at 50 degrees C (pH 7.0). Autolysis at lower temperatures (30 degrees C and 40 degrees C) and at pH 5.0 and 6.0 favoured the formation of 3'-nucleotides, whereas autolysis at 40 degrees C and 50 degrees C (pH 7.0) favoured 5'- and 2'-nucleotides. The best conditions for the formation of the two flavour-enhancing nucleotides, 5'-AMP and 5'-GMP, were 50 degrees C (pH 7.0) and pH 4.0 (40 degrees C), respectively.

“…Autolysis of S. cerevisiae has been the subject of numerous articles, and its mechanism is well understood [5,6,19,27]. However, for the food grade lactoseutilizing yeast Kluyveromyces marxianus there is very little data available on yeast extract production [2,8,19].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Kluyveromyces marxianus as a source of yeast autolysates

Lukondeh

Ashbolt

Rogers

2003

Cells of Kluyveromyces marxianus FII 510700 and Saccharomyces cerevisiae CBS 1907 were autolysed in phosphate buffer, pH 4.5, for a maximum of 10 days to compare chemical changes that occur in the carbohydrate, protein, amino acid and nucleic acid content. Approximately 2.2-3% carbohydrate, 9.5-12% protein, 0.6-1.0% DNA and 6-7% RNA were recovered in the autolysates. The main amino acids were beta-alanine, phenylalanine, cysteine, methionine, glutamic acid and isoleucine. No significant differences in the yeast autolysates of K. marxianus and S. cerevisiae were observed. Consequently, K. marxianus produced from lactose-based media has potential as a source of yeast autolysates used in the food industry.