Effect of direct arginine supplementation on growth of Lacticaseibacillus rhamnosus GG

The study aimed to examine the effect of direct arginine (Arg) supplementation on Lacticaseibacillus rhamnosus GG (LRG) growth.

The probiotic LRG ATCC 53103 was routinely cultured in MRS broth and adjusted to 10⁷ CFU/ml. l-Arg at 0.25 % and 0.5 % w/v. was directly supplemented to MRS broth containing LRG. Then, LRG with/without supplemented Arg was characterised to determine growth curves for 72 h under a CO₂-driven, environment-controlled spectrophotometer. Whereas, end-point McFarland spectrophotometric, metabolic assays (XTT and WST-8), colony forming units (CFU) assessment, live/dead bacterial confocal imaging, and viable DNA quantification were undertaken after 24 h CO₂ incubation to determine LRG growth with/without supplemented Arg.

Growth curve analysis revealed similar absorbance profiles with LRG and LRG+0.25 % Arg with no overlaps to LRG+0.5 % Arg; with a similar trend observed as per end-point McFarland spectrophotometric assessment. The % viability estimated by metabolic assays with LRG and LRG+0.25 % Arg was significantly lower than LRG+0.5 % Arg (p < 0.05). As per CFU assessment, CFU/ml for LRG+0.25 % Arg and LRG+0.5 % Arg was significantly higher than LRG control (p < 0.05). LRG live-dead proportions determined using confocal imaging denote no differences between the groups (p > 0.05), with live cell proportions significantly higher than the dead cells (p < 0.05). However, LRG cellular density appeared to increase with increasing concentrations of Arg. Additionally, the viable cells quantified with PMA-qPCR significantly increased with increasing concentrations of Arg (p < 0.05).

Direct supplementation of 0.5 % Arg to LRG enhances LRG growth, demonstrating a promising synbiotic potential. CLINICAL SIGNIFICANCE (48 WORDS): Primary caries prevention is initiated at biofilms using biotic strategies that modulate the microbiome matrix to maintain ecological homeostasis. The results of the present study establish a deliverable synbiotic of Arg and probiotic Lacticaseibacillus rhamnosus GG, demonstrating a promising synergism between interventions in the milieu targeted for high caries-risk individuals.