L-tyrosine

The cultivation of Paenibacillus larvae, the etiological agent of American foulbrood, traditionally relies on media containing animal-derived nutrients. In response to ethical and practical concerns associated with such components, we developed and validated a new culture medium based on an algae extract. The formulation includes Chlorella as the principal nutrient source and is supplemented with uric acid and L-tyrosine to support spore germination under conditions resembling the honeybee larval gut. The method includes optimized procedures for dissolving sparingly soluble components and minimizing nutrient degradation. Performance of the new medium was comparable to that of MYPGP and other conventional media in supporting spore germination and vegetative growth of P. larvae. • Eliminates the need for animal-derived components through the use of microalgal nutrients • Supports robust germination and colony development of P. Larvae • Provides an ethical and cost-efficient medium suitable for diagnostic and research applications.

The increasing threat of antibiotic-resistant bacteria has prompted the search for alternatives to antibiotic growth promoters (AGPs). Phenyl lactate (PLA) was recently reported to exert an effect on broiler growth promoters in high doses; however, it is not registered as a feed additive. L-tyrosine (L-Tyr), a metabolite of PLA, is often used in the livestock industry. In this study, we evaluated the effects of L-Tyr on gut microbiota, tight junction integrity, and immune response using epithelial cells (Caco-2) as well as various immune cells, including natural killer cells, macrophages, and dendritic cells. We found that L-Tyr improved tight junction integrity at low concentrations, similar to AGPs. In addition, L-Tyr reduced several pro-inflammatory cytokines (TNF-α, IL-6, and IL-12p70) from macrophages and dendritic cells, as well as IFN-γ from natural killer cells, at lower concentrations than AGPs. L-Tyr was metabolized by various microbial species; however, the dissolution tests indicated that enteric-coated L-Tyr was more effective than non-coated L-Tyr at low doses. These findings indicate that coated L-Tyr may serve as an alternative to AGPs, mitigating the risk of antimicrobial resistance.