Isolation and Identification of Lactobacillus reuteri of Duck Origin and Optimization of Growth Conditions

This study aimed to screen Lactobacillus reuteri strains with potential probiotic properties from duck sources and optimize their primary growth conditions using response surface methodology (RSM). The findings provide a theoretical foundation for the practical application of L. reuteri and lay the groundwork for the development of high-value-added probiotic products. Fresh duck intestinal contents were used as the enrichment source, and L. reuteri isolation medium (LRIM) was employed to selectively isolate and purify strains. The isolated strains were identified through 16S rDNA sequencing, confirming one strain as L. reuteri, designated LS-15. Subsequent experiments optimized the growth conditions and medium composition of L. reuteri LS-15 using the single-factor method, based on De Man, Rogosa, and Sharpe (MRS) medium. The results revealed that carbon source, nitrogen source, and pH significantly influenced the growth of LS-15. Using response surface methodology, the optimal growth conditions for L. reuteri LS-15 were determined to be: 35g/L sucrose, 51g/L tryptone, and initial pH value of 6.5, an incubation temperature of 35℃, and a cultivation time of 12 h. Under these optimized anaerobic conditions, the viable cell count of L. reuteri LS-15 reached 6.7 × 10⁹ CFU/mL, representing a 22.3-fold increase compared to the pre-optimization cell count of 3.0 × 10⁸ CFU/mL. These findings offer valuable insights into the growth optimization of L. reuteri LS-15 and its potential for probiotic applications.