Reactive Species Responsible for Inactivating the Ice-nucleating Activity of Pseudomonas fluorescens KUIN-1 by an Ascorbic Acid–Cu(II) Ion System

Abstract

The reactive species for inactivating the ice-nucleating activity of Pseudomonas fluorescens KUIN-1 by copper salt in the presence of an ascorbic acid were investigated. Strain KUIN-1, ascorbic acid and copper salt were allowed to react for 3hr at 18°C, the ice-nucleating activity of this strain being markedly inactivated in the ascorbic acid–Cu(II) ion system. The scavengers for hydrogen peroxide prevented inactivation of the ice-nucleating activity of strain KUIN-1 by the ascorbic acid–Cu(II) ion system. The ice-nucleating activity of strain KUIN-1 was inactivated in a hydrogen peroxide-generating system, but not in a hydroxyl radical-generating system. The superoxide anion radical had a small effect on inactivating the ice-nucleating activity of strain KUIN-1. The degree of freezing injury to corn treated with the ascorbic acid–Cu(II) ion system and strain KUIN-1 was lower than that of corn treated with only strain KUIN-1.