First Report on Biosynthesis of Riboflavin by Microbacterium proteolyticum BWBTDIPO1 - Extraction, Characterization...

The sustainable and cost-effective biosynthesis of valuable nutraceuticals like Riboflavin from natural sources is a major challenge for researchers. Bacterial strains having the potential for Riboflavin overproduction without manipulation in genetic makeup are a rare phenomenon. The present investigation reports for the first time a newly isolated gram-positive, rod-shaped, indigenous bacterial monoculture, identified as Microbacterium proteolyticum (GenBank Acc. No.: PQ517523), to be a promising Riboflavin producer. Growth kinetics recorded the optimum growth in Luria Bertini broth media, where a maximum specific growth rate of 0.887 h^- 1 was achieved at 6-8 h of growth. Riboflavin yield was evaluated to be 459.31 ± 22.79 mg/L, approximating 49.79 ± 1.29 mg per gram of bacterial biomass. Production kinetic analysis performed using the Luedeking-Piret model revealed mixed production by the strain with both growth-associated (α = 0.244) and non-growth-associated (β = 0.16) characteristics, and a high yield coefficient of 0.304. In-silico validation for Riboflavin production in 45 species under the Microbacterium genus revealed the metabolic production pathway using the KEGG and MetaCyc databases, which showed the involvement of the rib operon. Studies with the BioCyc collection predicted the worldwide abundance of reports on the Microbacterium sp. to date, as per its region and environmental niche. Extraction and characterisation of crude Riboflavin via UV-Vis spectroscopy, Fourier Transform Infrared spectroscopy, and Proton Nuclear Magnetic Resonance further confirmed the chemical nature of the coloured component to be Riboflavin. This study brings to light a new bacterial strain, which is a potential Riboflavin producer with promising future implications in the pharmaceutical, food, and cosmetic industries.