Effect of Arginine on Growth of Probiotic Lactobacillus Rhamnosus GG

Objectives: The objectives of the study were to examine the effect of (1) arginine on growth of probiotic Lactobacillus rhamnosus GG (LR) and (2) the combination of arginine with LR on growth of cariogenic Streptococcus mutans (SM).
Methods: Lactobacillus rhamnosus GG was cultured using Culturelle® probiotics in BHI broth. 0.5% (Group 1), 1% (Group 2), and 2% (Group 3) L-arginine in 0.9% sodium chloride (NaCl) were delivered (twice/24h) to LR (10⁷ CFU/ml) in a 96-well microplate; while only 0.9% NaCl (Group 4) was added to LR in the control group. The growth of LR was assessed using XTT assay, MTT assay and confocal laser scanning microscopy (CLSM). The effect of different concentrations of L-arginine (0.5%/1%/2%) in 0.9% NaCl treatment (twice/24h) with LR (10⁷ CFU/ml) on growth of SM (10⁷ CFU/ml) was evaluated by determining CFUs of SM on agar media. Data were analyzed with one-way ANOVA/Kruskal-Wallis test, followed by SNK/Dunn’s post-hoc test with significance set at 0.05.
Results: From XTT and MTT assays, growth of LR with 2% L-arginine was significantly higher than the other groups (p<0.001). No significant difference in growth of LR was observed among 0.5% L-arginine, 1% L-arginine and 0.9% NaCl groups (p>0.05). CLSM showed that 2% L-arginine increased biofilm thickness of LR when compared to the other groups. The combination of 2% L-arginine with LR significantly inhibited growth of SM (p=0.002) and reduced biofilm biomass (p<0.001) when compared to the other groups. No significant difference in growth and biofilm biomass of SM was found among 0.5% L-arginine/LR, 1% L-arginine/LR and the control groups (p>0.05).
Conclusions: Arginine enhances growth of Lactobacillus rhamnosus GG. The combination of 2% L-arginine with Lactobacillus rhamnosus GG synergistically inhibits growth of Streptococcus mutans and can possibly form a potent anti-caries synbiotics for daily use in caries prevention for high-risk patients.