| In this paper, the formation of trehalose from maltose by trehalose synthase was studied. The research contains four parts: screening trehalose synthase producing strain from those collected in Polar Regions, strain identification, determination of the factors influencing the crude enzyme reaction, and the preliminary optimization of fermentation medium.Among 83 and 20 strain samples from polar soils and oceans, strain S1 was obtained for the highest trehalose conversion rate from maltose e of about 75.2%. The enzymatic reaction product was identified to be trehalose by the methods of thinner layer chromatography (TLC), DNS, and high performance liquid chromatography (HPLC). The trehalose synthase of S1 was detected to be an intracellular enzyme with the activity of 7.30 u/g wet cells.S1 was identified for further research. The bacterium belongs to Pseudomonas according to "Bergey's Manual of Systematic Bacteriology"(1984, 8th edition) by various experiments on strain morphology, culture, physiology and biochemistry. It was further classified as Pseudomonas putida S1 by 16S rDNA alignment. S1 showed the highest trehalose synthase activity compared with other strains in the genus.Factors influencing enzymatic reaction were analysed for enzyme assay and industrial application in the future. The standard enzyme assay was performed at 20℃ in constant water bath for 20 minutes after mixing with 25mM phosphate buffers (pH 8.1), 0.5mL 4% maltose and 0.5 mL crude enzyme. 1 unit of trehalose synthase was identified as the formation of 1μmol trehalose per minute.The fermentation medium was optimized. The optimal medium components for the highest biomass and enzyme activity were: glucose 28.9 g/L, maltose 12.4 g/L, peptone 5.0 g/L, yeast extract 1.86 g/L, Na2HPO4·12 H2O 0.5g/L, and Na3C6H5O7·2 H2O 0.5 g/L, and pH was 7.5.The optimized biomass and enzyme activity rose up to 29.8 g/L and 8.42 u/g wet cells from the original 15.1 g/L and 7.3 u/g wet cells levels.
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