Production of prodigiosin by a drug-resistant Serratia rubidaea HB01 isolated from sewage

Abstract

Production of green pigments has drawn great attention recently in various applications like foods, cosmetics, nutraceuticals, and pharmaceuticals as it counters the harmful effects of synthetic dyes. Use of green natural products, especially microbe-derived colours in food and cosmetics is rapidly developing for its eco-friendly nature and cost effectiveness. In this study, a red pigment producing rod-shaped, Gram-negative bacterium Serratia rubidaea HB01 was isolated from domestic sewage. The isolate exhibited wide resistance to various groups of antibiotics, including Aminoglycosides, Lincosamides, Macrolides, Nitroimidazoles, Penicillins, Quinolones, and Tetracyclines. The isolate S. rubidaea HB01 significantly produced red prodigiosin pigment (17.9 mg ml−1). The production of prodigiosin was highly pH sensitive and growth media specific. The UV–Vis spectrum of the red pigment dissolved in methanol showed a maximum absorption at 536 nm in neutral pH. Red fraction with Rf value 0.38 purified by thin layer chromatography (TLC) was further subjected to liquid chromatography and mass spectrometric (LC–MS) analysis. Moreover, a strong band of pyrrolenine (C = N) at vmax 1639 was found comparable to prodigiosin as observed from Fourier-transform infrared (FTIR) spectra. Alongside, the presence of a typical methoxy group with chemical shifts at δ 4.0 ppm and δ 58.5 ppm was revealed by 1H and 13C nuclear magnetic resonance (NMR) spectra respectively, confirming the red pigment produced to be prodigiosin. The molecular weight of the prodigiosin was identified as 323 (m/z 324, [M + H]+). Serratia species that typically develop antibiotic resistance mechanisms are already known to produce antibiotics (carbapenem and bacteriocins) and prodigiosin pigment by integrating Quorum Sensing (QS) with overlapping pigment production regulatory systems (pigP). Consequently, mutations in this regulatory region may influence the production of prodigiosin and antibiotic resistance mechanisms.