Abstract Sophorolipids (SLs) are promising biosurfactants with diverse industrial and biomedical applications; however, optimising their production efficiency remains a challenge. This study investigates the effect of carbon-to-nitrogen (C/N) ratios on SL production by Starmerella riodocensis GT-SL1R and evaluates the antimicrobial and anti-inflammatory properties of partial purified SLs. Among the tested C/N ratios (25–200), the highest SL production (26.71 ± 2.01 g·L⁻¹) was achieved at a C/N of 100, with a yield of 0.27 ± 0.0 g·g⁻¹ after 7 days. High C/N conditions (≥ 100) upregulated key SL biosynthesis genes (CYP52M1, UgtA1, UgtB1, At, and Sble), supporting enhanced SL production. Scale-up fermentation in a 5 L bioreactor further improved SL production to (55.94 ± 1.17 g·L⁻¹), outperforming S. bombicola BCC5426 (50.49 ± 1.97 g·L⁻¹). Structural characterisation revealed a predominance of lactonic SLs. SLs exhibited strong antimicrobial activity against Cutibacterium acnes, Staphylococcus epidermidis and Staphylococcus aureus and demonstrated potent anti-inflammatory effects by inhibiting nitric oxide production (IC50 = 21.93 ± 5.95 µg mL⁻¹), with lower cytotoxicity than indomethacin. These findings highlight S. riodocensis GT-SL1R as a promising candidate for industrial SL production and biomedical applications.
Sapsirisuk et al. (Wed,) studied this question.