Characterization of pigment produced by high carotenoid yielding bacteria Paracoccus marcusii RSPO1 and evaluation of its anti-diabetic, anti-microbial and antioxidant properties

High pigment producing bacteria was isolated and identified as Paracoccus marcusii RSPO1 using biochemical and 16s rRNA identification. Bacterial pigment production was optimised using parameters like inoculum size, nitrogen source, pH, temperature, and agitation speed. Carotenoids production was 7,240 ± 41 µg L−1 after optimization. The silica column purified pigment was characterized using UV-visible spectroscopy, TLC, FTIR, LC-ESI-MS and NMR, which revealed its composition as astaxanthin, zeaxanthin, ζ-carotene and β-zeacarotene. The inhibition assays against α-amylase and α-glucosidase showed IC50 values as 226 µg ml−1 and 0.7548 µg ml−1 respectively. The MIC of 1000 µg ml−1 of carotenoid was found to be effective against Escherichia coli and Enterobacter aerogenes when tested for antibacterial activity. Moreover, antioxidant activity of carotenoid sample was also determined where antioxidant potential of extracted carotenoid for DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) inhibition were 65 ± 0.06% and 42 ± 07% respectively at 20 µg ml−1 concentration.