Wort sugars uptake rate and cell cycle of brewing yeast. II. Cell cycle of three brewing yeast strains during pilot plant fermentation.

Abstract

The objective of this work was to study the cell cycle of three strains of lager yeast in relation to the number of elevated cells in wort and utilization of main wort sugars.Yeast strains No. 2, 7 and 95 (marked in accordance with RIBM 655 - Culture Collection of Brewing Yeasts) were used in the study. The experiments were carried out in pilot plant scale fermenter at the temperature of 13 °C. The original gravity of wort was 12 % and the malt in grist was partly substituted by unmalted barley. During pilot plant fermentation were observed differences between the studied strains in rise number of elevated cells in wort. The strain No. 7 showed the shortest and fastest phase rise number of elevated cells in wort, next was strain No. 2. The strain No. 95 showed the slowest and longest phase rise number of elevated cells in wort. These results were in correlation with wort sugar uptake rate observed for tested strains. Cell cycle was monitored by propidium iodide staining with evaluation by flow cytometry. During pilot plant fermentations were determinate maxim percentage substitution in population G2/M phase of cell cycle. Expressive growth of percentage substitution G2/M cells was observed during first tens hours of fermentation for all tested strains. The fastest maximum G2/M cells in population was observed for strain No. 7, next were strains No. 2 and 95, this was in relation to process number of elevated cells in wort. Decrease of G2/M phase cells in population was in accordance with maximum extract uptake rate (utilisation of maltose). The slowest decrease of G2/M phase cells in population of strain No. 95 was in relation to its slowest maltose utilisation.The objective of this work was to study the cell cycle of three strains of lager yeast in relation to the number of elevated cells in wort and utilization of main wort sugars.Yeast strains No. 2, 7 and 95 (marked in accordance with RIBM 655 - Culture Collection of Brewing Yeasts) were used in the study. The experiments were carried out in pilot plant scale fermenter at the temperature of 13 °C. The original gravity of wort was 12 % and the malt in grist was partly substituted by unmalted barley. During pilot plant fermentation were observed differences between the studied strains in rise number of elevated cells in wort. The strain No. 7 showed the shortest and fastest phase rise number of elevated cells in wort, next was strain No. 2. The strain No. 95 showed the slowest and longest phase rise number of elevated cells in wort. These results were in correlation with wort sugar uptake rate observed for tested strains. Cell cycle was monitored by propidium iodide staining with evaluation by flow cytometry. During pilot plant fermentations were determinate maxim percentage substitution in population G2/M phase of cell cycle. Expressive growth of percentage substitution G2/M cells was observed during first tens hours of fermentation for all tested strains. The fastest maximum G2/M cells in population was observed for strain No. 7, next were strains No. 2 and 95, this was in relation to process number of elevated cells in wort. Decrease of G2/M phase cells in population was in accordance with maximum extract uptake rate (utilisation of maltose). The slowest decrease of G2/M phase cells in population of strain No. 95 was

Keywords

• brewing yeast
• yeast strains
• cell cycle