Polyphasic in Vitro Characterization of the Pigment-Producing Microfungus Rhodotorula Sp. For Potential Application as a Probiotic in Mariculture

Why It Matters

The findings offer a viable, non‑antibiotic probiotic alternative that can enhance disease resistance, oxidative stability, and nutritional value in farmed fish, addressing sustainability challenges in the fast‑growing aquaculture sector.

Key Takeaways

• Isolate produces 0.73 g L⁻¹ biomass and 398 µg g⁻¹ carotenoids.
• Pigment shows λmax 458 nm, peak accumulation on day 5.
• PUFA content 28% of lipids; lysine 61.9 g kg⁻¹.
• Strong DPPH (60%) and ABTS (96%) radical scavenging.
• Inhibits Vibrio pathogens; zones up to 25 mm.

Pulse Analysis

Aquaculture now accounts for over half of global aquatic animal production, yet reliance on antibiotics has sparked resistance concerns and regulatory pressure. Researchers are turning to probiotics as a sustainable alternative, traditionally focusing on bacterial strains. Recent interest in microfungi, especially carotenoid‑producing yeasts, stems from their dual role as bioactive compound factories and gut‑friendly microbes, offering antioxidant, immunomodulatory, and nutritional benefits that align with the industry's push for cleaner, healthier feeds.

In a 2026 Frontiers in Nutrition study, a novel Rhodotorula paludigena isolate from Indian mangrove leaves underwent a comprehensive polyphasic evaluation. The fungus grew robustly in YEPD medium, reaching 0.73 g L⁻¹ dry weight and synthesizing 398 µg g⁻¹ of carotenoids with a λmax of 458 nm, peaking on day five. Antioxidant assays showed impressive radical‑scavenging capacities—60% DPPH and 96% ABTS at 300 mg mL⁻¹. The crude extract inhibited major fish pathogens, including Vibrio harveyi, with inhibition zones up to 25 mm, and biofilm formation was markedly reduced. While simulated gastric fluid lowered viability, the strain survived intestinal conditions, and its nutritional profile featured 40% protein, 28% polyunsaturated fatty acids and a lysine concentration of 61.9 g kg⁻¹, surpassing conventional fish‑meal sources.

These attributes position Rhodotorula sp. as a next‑generation probiotic candidate capable of delivering functional pigments, health‑boosting antioxidants, and essential nutrients in a single organism. For feed manufacturers, integrating such a microfungus could reduce reliance on synthetic additives and antibiotics, improve fish growth performance, and meet consumer demand for sustainable aquaculture products. Future work should scale fermentation, refine pigment extraction, and validate efficacy through in‑vivo trials, paving the way for commercial adoption in the multi‑billion‑dollar aquafeed market.