# Salinity-driven canthaxanthin enhancement in Chlorosarcinopsis PY02: a practical spot test for microalgal bioprocess optimization

## TL;DR

This study shows that salt stress increases canthaxanthin production in the microalga Chlorosarcinopsis PY02, offering a practical method for sustainable antioxidant production.

## Contribution

A simple spot-test method is introduced to optimize microalgal bioprocesses for enhanced ketocarotenoid production under salt stress.

## Key findings

- Peak canthaxanthin content of 294.55 µg/g dry weight was achieved at 10 g/l NaCl.
- Salt-only treatment produced the highest canthaxanthin yield of 0.80 mg/l.
- The spot-test method proved effective for strain and condition optimization in microalgal bioprocesses.

## Abstract

As society rapidly ages, the escalating global demand for natural, high-value antioxidants – particularly ketocarotenoids such as canthaxanthin – is driving intensive research into their sustainable bioproduction. This study investigates the potential of the green microalga Chlorosarcinopsis PY02 as a novel microbial cell factory for enhanced ketocarotenoid production under abiotic stress conditions.

We optimized bioprocess parameters using a simple, spot-test-based high-throughput screening technique, evaluating algal growth and pigment accumulation on tris acetate phosphate agar supplemented with various sodium chloride concentrations (0–15 g/l).

Peak canthaxanthin content (294.55 µg/g dry weight) was observed at 10 g/l NaCl, while biomass yield was highest at 12 g/l. Combining salt stress with a 50% nitrogen reduction increased total carotenoid productivity (highest with 10 g/l NaCl: 3.10 mg/l) but did not enhance canthaxanthin levels; the salt-only treatment produced the highest canthaxanthin yield (0.80 mg/l). Pigment identification and quantitative profiling were performed using thin-layer chromatography and spectrophotometry, confirming the efficiency of the production process.

These findings highlight Chlorosarcinopsis PY02 as a promising candidate for sustainable, large-scale production of ketocarotenoids. The study also demonstrates a cost-effective and scalable approach for inducing carotenoid biosynthesis in Chlorosarcinopsis PY02, with strong relevance for sustainable pigment production. The simple visual screening method provides a practical tool for preliminary strain and condition optimization in microalgal bioprocess development.