Comparative evaluation of glucose and glycerol as carbon sources for violacein synthesis in Janthinobacterium lividum

Background: Violacein is a purple pigment synthesized by select Gram-negative bacteria, including Janthinobacterium lividum, with potential antimicrobial and competitive advantages in environmental niches. Despite extensive research, the optimal conditions for violacein production remain incompletely understood. Objective: This study investigates the influence of different carbon sources (glucose and glycerol) on violacein production by J. lividum over time and examines the relationship between bacterial viability and pigment synthesis. Materials and Methods: J. lividum was cultured in LB medium supplemented with either 1% glucose (LB-U) or 1% glycerol (LB-Y). Violacein production was monitored using optical density measurements at 585 nm (OD585) and confirmed by high-performance liquid chromatography (HPLC). Colony-forming unit (CFU) counts were determined at multiple time points over 120 hours. Results: Glycerol-supplemented media demonstrated superior violacein production compared to glucose-supplemented media. In LB-Y conditions, violacein production reached 1.0 OD585 by 120 hours, while LB-U conditions achieved only 0.1 OD585. HPLC analysis confirmed violacein identity with a characteristic peak at 16.40 minutes retention time. Bacterial viability remained higher in violacein-positive cultures during the death phase. Conclusion: These findings demonstrate that carbon source selection critically influences violacein biosynthesis in J. lividum, with glycerol promoting enhanced production while glucose suppresses pigment synthesis. The results suggest violacein may contribute to bacterial survival under stress conditions.