Abstract:Lactobacillus paracasei were isolated from soy sauce residue by traditional microbial culture method, and identified by morphological observation, physiological and biochemical characteristics test, and 16S rRNA gene sequence analysis. Their tolerance to artificial gastrointestinal juice, hydrophobic capacity, and antioxidant capacity were also studied. Ten strains of Lactobacillus paracasei were isolated from soy sauce residue, of which eight were L. paracasei subsp. paracasei, named HT31, HT51, HT90, HT111, HT125, HT159, HT253, and HT256; two of them were L. paracasei subsp. tolerans, named HT155 and HT158. The results of simulated gastrointestinal fluid tolerance test showed that the viability of strains HT31, HT111 and HT155 reached (86.33 ±1.24)%, (31.37±0.50)%, (57.43±1.56)%. After 8 hours of culture in simulated gastrointestinal fluid, the viability of strains HT31, HT111 and HT155 reached (60.22±0.16)%, (62.18±0.70)%, and (52.84±0.56)%, respectively. The results of hydrophobicity test showed that the hydrophobicity of strains HT31, HT111 and HT155 reached (18.52±0.76)%, (26.51±0.66)%, and (25.41±0.58)%. The results of antioxidant test showed that the DPPH scavenging rate of cell suspension of strain HT31 was (26.25±0.01)%, and its DPPH scavenging rate of cell-free extract was (16.03±0.03)%. The hydroxyl radical scavenging rate of cell-free extract of strain HT31 was (42.88±0.21)%, and its hydroxyl radical scavenging rate of cell-free extract was (27.74±0.01)%. The result showed that strain HT31 had good capacity of tolerance to simulated gastrointestinal juice, hydrophobic and antioxidant.