| Summary: | Intestinal diseases are mainly caused by a decrease in the relative abundance of probiotics and an increase in the number of pathogenic bacteria due to dysbiosis of the intestinal flora. High degree polymerization isomaltooligosaccharide (IMO) can promote probiotic metabolism and proliferation. In this study, the dextranase (PsDex1711) gene of marine bacterial <i>Pseudarthrobacter</i> sp. RN22 was cloned and expressed in <i>Escherichia coli</i> BL21 (DE3). The optimal pH and temperature of the dextranase were 6.0 and 30 °C, respectively, showing the highest stability at 20 °C. The dextran T70 could be hydrolyzed to produce IMO3, IMO4, IMO5, and IMO6 with a high degree of polymerization. The hydrolysate of 1 mg/mL could significantly promote the growth of <i>Lactobacillus</i> and <i>Bifidobacterium</i> after 12 h culture and the formation of biofilms by 58.2%. The hydrolysates could promote the proliferation of probiotics. Furthermore, the IC<sub>50</sub> of scavenging rate of DPPH, hydroxyl radical, and superoxide anion was less than 20 mg/mL. This study provides a crucial theoretical basis for the application of dextranase such as pharmaceutical and food industries.
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