Lysis of viable yeast cells by enzymes of Arthrobacter luteus

Abstract

Some organisms capable of lysing viable yeast cells were isolated from brewery sewage by the enrichment culture method by intermittent feeding with brewer's yeast. The strain (B 111-1) showing the highest lytic activity was identified as Arthrobacter luteus.The activity of Arthrobacter luteus, B 111-1, to lyse viable yeast cells appeared in the culture medium in the early stationary phase of the bacterial growth. The pattern of change in lytic activity during cultivation was different from those of β-1, 3-glucanase and protease activities suggesting that some additional factors are essential for the lysis of viable yeast cells.The pH value of culture medium during cultivation influenced the development of the activity considerably. The pH value first decreased and then increased with the appearance of lytic activity.The activity to lyse viable yeast cells developed adaptively when the organism was cultivated in a medium containing yeast cells or β-1, 3-glucan, suggesting that the latter causes induction.Cell-free culture fluid of the organism showed a lytic activity- on cells of brewer's yeast at all stages of growth and on viable cells of yeast strains belonging to a wide range of genera. However, it did not lyse viable cells of the yeasts Rhodoturula, Pichia, and Hansenula, or viable and heat-treated cells of bacteria and molds.The lytic activity of the cell-free culture fluid was not lost by dialysis. It was salted out at 0.395 saturation of ammonium sulfate and was lost on incubation at 60° for 5min. It was also inactivated by such protein denaturing agents as mercuric chloride, sodium laurylbenzene sulfonate, and silver nitrate, indicating that the lytic activity was due to enzymes. The optimum pH for lysis of viable yeast cells was 7.0-8.0. The lytic activity was relatively stable between pH 5 and 10.