High Produciton and Application of a Novel Ice-nucleating Matter from Microorganisms

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Xanthomonas campestric pv. translucens IF013599 could produce xanthan gum (18.5 mg/100 mg, lactose) with lactose as the growth substrate in spite of a low level of beta-galactosidsse. This productivity contspondsd to one-fifth of that with glucose. This strain could also produce ice-nucleating matter having an ice-nucleating temperature, T50, of -2.8* with xanthan gum in the culture broth. We found that this strain produced both matenals in the whey medium from which the insoluble components had been removed The production of xanthan with ice-nucleating material reached a maximum after cultivation for 168 h uuder optimum conditions. Furthennore, the xanthan obtained had a low viscosity because of its variant structure revealed, by the TLC and HPLC analyses, to be lacking pyruvic acid.Also, the extracellular ice-nucleating matter produced by the ice-nucleating bacterium, Pseudomonos fluorescens KUIN-1, was punfiedto an apparent homogeneity. The shape of this EIM was spherical with the d … More iameter of 10-100 nm without a vesicle. The ice-nucleating activity and the stability of this EIM were similar to that of cell in this strain. It had become apparent that this ElM had class A (wanner at -5.0ﾟC), B(-6--7ﾟC) and C(coldur at -7.5ﾟC) stnictures constituting different components like that of the ElM from Erwinia uredovora KUIN-3. The components of the ElM were protein (56%), lipid (15%), saccharide (10%) and polyamine (19%). Based on the SDS-PAGE analysis with Western-blotting, the main band, that is, for ice-nucleating protein (INP), was 110,000 Da, and minor bands were also attributed to the possible INP-degrading proteins. The fatty acid components of the lipids were the same as those of the inner and outer membranes. The saccharied was composed of glucose, galactosamine, rhamnose, etc. Cachverine, spermidine and putrescine were present as the components of the EIM.This EIM had the distinct ability of freeze-concentrating wine and vinegar. This is the first report for the purification of the EIM that is produced by an ice-nucleating bacterium belonging to the genus Pseudomonas and for the application of the ElM in freeze-concentration of foods. Less