Improved total carotenoid content from Planococcus plakortidis NIOT3 through microwave assisted extraction and genome-guided pathway annotation

Abstract

With an increasing demand for natural colorants, marine microbes have become attractive targets for novel natural colorants like carotenoids. Microbial carotenoid extraction by green approach is advantageous over traditional methods which minimize energy usage and reduce extraction time. In the current study, an orange pigmented marine bacterium Planococcus plakortidis NIOT3 was isolated from the Sesostris bank of Arabian Sea and found to produce desirable level of total carotenoids (320 ± 24 µg/g DW) when grown in rich medium. An energy efficient green approach using Microwave Assisted Extraction was evaluated for carotenoid yield by one factor and statistical optimization of the MAE process conditions including exposure time, alkali concentration and Solid:Liquid ratio which resulted in a 3.26 fold increase in total carotenoid content of 2835 ± 152 µg/g DW. Genome sequencing and annotation revealed genes that are involved in C30 carotenoid biosynthesis. C30 carotenoids like glycosylated diapolycopene and methyl-5-glucosyl-5,6-dihydro-apo-4,4’-lycopenoate produced by NIOT3 were identified by LC-MS analyses as major products. Additionally, LC-MS analysis revealed a minor product with a molecular weight of m/z of 568.84 which corresponds to zeaxanthin, a C40 carotenoid. The study highlights the biotechnological potential of P. plakortidis in carotenoid production.