Background:
As society rapidly ages, the escalating global demand for natural, high-value antioxidants, particularly ketocarotenoids like 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.

Material and methods:
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).

Results:
Peak canthaxanthin content (294.55 µg/g DW) was observed at 10 g/L NaCl, while biomass yield was highest at 12 g/L. Combining salt stress with 50% nitrogen reduction increased total carotenoid productivity (3.10 mg/L total carotenoids) but did not improve canthaxanthin; the salt-only treatment yielded the highest canthaxanthin production (0.80 mg/L). Pigment identification and quantitative profiling were conducted using TLC and spectrophotometry, confirming the efficiency of the production process.

Conclusions:
These findings strongly position Chlorosarcinopsis PY02 as a promising candidate for sustainable, large-scale ketocarotenoid bioproduction. The study also demonstrates a cost-effective and scalable approach to induce carotenoid biosynthesis in Chlorosarcinopsis PY02, with relevance to sustainable pigment production processes. The simple visual screening method offers a useful practical tool for preliminary strain and condition optimization in microalgal bioprocess development.