# Upregulation of Canthaxanthin Biosynthesis by Paracoccus bogoriensis PH1 from Hot-Spring Origin via Sustainable Fermentation Strategy in Laboratory-Scale Bioreactor

## TL;DR

This study improves canthaxanthin production by a hot-spring bacterium using optimized fermentation conditions in a bioreactor.

## Contribution

A pH-shift strategy and optimized bioreactor conditions significantly enhance canthaxanthin yield from Paracoccus bogoriensis PH1.

## Key findings

- A two-stage pH control technique increased canthaxanthin production by 1.61-fold in bioreactor conditions.
- Optimized conditions using PPSYE medium achieved 0.84 mg/L of canthaxanthin with high antioxidant activity.
- The process reduces contamination risks and energy demands for sustainable industrial production.

## Abstract

This study presents a systematic approach to optimize growth and enhance canthaxanthin pigment production by a hot spring dweller, Paracoccus bogoriensis PH1. Various parameters affecting pigment production by this bacterial strain were first optimized at the flask scale and subsequently at the 1 L bioreactor scale. A novel culture medium was developed, and an optimized process was designed using a pH-shift strategy with appropriate temperature and aeration rate. Purified canthaxanthin exhibited antioxidant activity, as determined using the ABTS assay. The optimized conditions identified in this study can potentially reduce the risk of contamination and energy demands for cooling, thereby offering an advantage for the sustainable industrial production of canthaxanthin from natural sources.

Canthaxanthin is a significant carotenoid that is synthesized by specific microorganisms. It has multiple functions and has been utilized in food and feed supply chains. This research focused on improving canthaxanthin production by Paracoccus bogoriensis PH1, an orange-pigmented bacterium isolated from hot springs. Canthaxanthin production was optimized in flask-scale cultures by varying the pH, temperature, nutritional sources, aeration rates, and agitation techniques. Flask culture cultivation indicated that canthaxanthin production by this strain was influenced by pH stress mechanisms, resulting in the establishment of a two-stage pH control (pH-shift) technique to enhance cell mass and pigment production. The optimum flask conditions were refined for application in a 1 L bioreactor. An optimized cultivation procedure was established utilizing a Polypeptone Sucrose Yeast Extract (PPSYE) medium, with a pH transition from 7 to 11, incubation at 40 °C, agitation at 250 rpm, and aeration at 2 vvm for 48 h. This process resulted in a 3.12-fold increase in total carotenoid content and a 1.61-fold increase in canthaxanthin production, achieving 0.84 ± 0.06 mg/L compared to pre-optimized flask cultures in TSYEB medium (pH 7 at 37 °C, 72 h). Purified canthaxanthin from P. bogoriensis PH1 exhibited antioxidant activity in the ABTS assay.