Enhancement of the expression of icenucleation activity of Pseudomonas fluorescens MACK-4 isolated from mackerel

Abstract

The growth of Pseudomonas fluorescens MACK-4 isolated from mackerel in dextrin and starch broths was faster than that grown in other broths. The highest ice-nucleating activity (INA) was observed on those grown in media with sorbitol, mannose or starch using peptone as a nitrogen source. According to OD₆₀₀, the cells seemed to be difficult to grow in media with inorganic substances, malt extract or gelatine nitrogen sources. However, rapid growth was observed on the media with peptone, yeast extract, tryptone or skim milk. The concentrations of carbon or nitrogen sources did not significantly affect the INA. The INA was greatly induced when the growth temperature was shifted from 30 to 5°C. However, it was not affected by transferring the cells into media with a deficiency of nutrients. According to the chemical agents and metal effects on INA, the active site on the proteins of INA components might contain an SH group.