Byproducts from the winery industry contain many bioactive compounds that are considered high-value-added compounds. White grape pomace (GP) is rich in carbohydrates; consequently, it can be used as a raw material for subsequent bioprocesses. In the present study, low-temperature hydrothermal treatments were carried out using different operational conditions regarding temperature (65–95 °C), time (120–240 min), and sulfuric acid addition at various concentrations (5–15% v/v). The results showed that by using a temperature of 65 °C, a period of 120 min, and 15% (v/v) of H₂SO₄, it was possible to obtain a liquid phase rich in phenols and carbohydrates, with total phenol compounds corresponding to 2113 ± 140 mg of gallic acid/kg GP and composed mainly of 3-hydroxytyrosol (1330 ± 22 mg/kg GP). In parallel, carbohydrate solubilization reached 245 g glucose/kg GP. These results demonstrate the promising potential of hydrothermally treated grape pomace as raw material for biorefinery processes.

In this research, six strains of oleaginous yeasts native to southern Chile were analyzed for their biotechnological potential in lipid accumulation. For this purpose, the six strains, named PP1, PP4, PR4, PR10, PR27 and PR29, were cultivated in a nitrogen-deficient synthetic mineral medium (SMM). Then, two strains were selected and cultivated in an industrial residual “vinasse”, under different conditions of temperature (°C), pH and carbon/nitrogen (C/N) ratio. Finally, under optimized conditions, the growth kinetics and determination of the lipid profile were evaluated. The results of growth in the SMM indicate that yeasts PP1 and PR27 presented biomass concentrations and lipid accumulation percentages of 2.73 and 4.3 g/L of biomass and 36.6% and 45.3% lipids, respectively. Subsequently, for both strains, when cultured in the residual vinasse under optimized environmental conditions, biomass concentrations of 14.8 ± 1.51 g/L (C/N 80) and 15.83 ± 0.57 g/L (C/N 50) and lipid accumulations of 28% and 30% were obtained for PP1 and PR27, respectively. The composition of the triglycerides (TGs), obtained in the culture of the yeasts in a 2 L reactor, presented 64.25% of saturated fatty acids for strain PR27 and 47.18% for strain PP1. The saturated fatty acid compositions in both strains are mainly constituted of fatty acids, myristic C 14:0, heptadecanoic C 17:0, palmitic C 16:0 and stearic C 18:0, and the monounsaturated fatty acids constituted of oleic acid C 18:1 (cis 9) (28–46%), and in smaller amounts, palmitoleic acid and heptadecenoic acid. This work demonstrates that the native yeast strains PP1 and PR27 are promising strains for the production of microbial oils similar to conventional vegetable oils. The potential applications in the energy or food industries, such as aquaculture, are conceivable.

It is known that selenium (Se) is an essential trace element, important for the growth and other biological functions of fish. One of its most important functions is to contribute to the preservation of certain biological components, such as DNA, proteins, and lipids, providing protection against free radicals resulting from normal metabolism. The objective of this study was to evaluate and optimize selenium accumulation in the native yeast Rhodotorula mucilaginosa 6S. Sodium selenite was evaluated at different concentrations (5–10–15–20–30–40 mg/L). Similarly, the effects of different concentrations of nitrogen sources and pH on cell growth and selenium accumulation in the yeast were analyzed. Subsequently, the best cultivation conditions were scaled up to a 2 L reactor with constant aeration, and the proteome of the yeast cultured with and without sodium selenite was evaluated. The optimal conditions for biomass generation and selenium accumulation were found with ammonium chloride and pH 5.5. Incorporating sodium selenite (30 mg/L) during the exponential phase in the bioreactor after 72 h of cultivation resulted in 10 g/L of biomass, with 0.25 mg total Se/g biomass, composed of 25% proteins, 15% lipids, and 0.850 mg total carotenoids/g biomass. The analysis of the proteomes associated with yeast cultivation with and without selenium revealed a total of 1871 proteins. The results obtained showed that the dynamic changes in the proteome, in response to selenium in the experimental medium, are directly related to catalytic activity and oxidoreductase activity in the yeast. R. mucilaginosa 6S could be an alternative for the generation of selenium-rich biomass with a composition of other nutritional compounds also of interest in aquaculture, such as proteins, lipids, and pigments.

Introduction: The rapid global expansion of aquaculture has intensified the demand for sustainable and alternative lipid sources for fish feed formulations, driving interest in microbial platforms with specialized metabolic capabilities. Among these, oleaginous yeasts have emerged as promising candidates due to their ability to accumulate substantial intracellular lipid reserves and to modulate fatty acid composition in response to environmental and nutritional cues. Methods: In this study, the lipid production potential and physiological responses of two native yeast strains isolated from volcanic soils of southern Chile were investigated. The strains were identified by ITS sequencing as Solicoccozyma gelidoterrea (7C) and Rhodotorula mucilaginosa (Rho 6S). Growth kinetics, substrate utilization, and lipid accumulation were systematically evaluated under different carbon sources, carbon-to-nitrogen (C/N) ratios, and temperature regimes (7–25 °C). Response surface methodology was applied to determine the combined effects of nutritional and thermal factors on biomass production and lipid yield, while fatty acid composition was analyzed to elucidate lipid remodeling strategies. Results and Discussion: R. mucilaginosa exhibited pronounced metabolic versatility, characterized by higher maximum specific growth rates on alternative carbon sources such as xylose, sucrose, and raffinose. Under optimal conditions (25 °C and C/N 20), this strain achieved a lipid content of 30% and a biomass concentration of 2.54 g/L. In contrast, S. gelidoterrea displayed a distinct physiological profile associated with cold adaptation, reaching optimal lipid accumulation at 7 °C and C/N 20, with 26.6% lipid content and 2.11 g/L biomass. Increasing the C/N ratio to 90 significantly constrained lipid accumulation in both strains, highlighting the central role of nitrogen availability in regulating yeast lipid metabolism. Fatty acid profiling revealed clear species-specific lipid remodeling patterns: R. mucilaginosa produced a nutritionally favorable lipid profile enriched in mono and polyunsaturated fatty acids, reflected by high MUFA/SAFA and PUFA/SAFA ratios. In contrast, S. gelidoterrea exhibited a distinctive lipid profile dominated by monounsaturated fatty acids, particularly oleic acid, under nitrogen limited and low temperature conditions, and demonstrated the capacity to synthesize long chain polyunsaturated fatty acids under stress conditions, suggesting the activation of adaptive and stress responsive lipid metabolic pathways. Conclusion: This study provides the first evidence of lipid accumulation and fatty acid composition in S. gelidoterrea and puts into evidence contrasting lipid metabolic strategies among native oleaginous yeasts. Collectively, these findings contribute to a deeper understanding of fungal lipid physiology and environmental adaptation and support the potential of native yeast strains as sustainable lipid sources for functional foods and aquaculture nutrition.

Thraustochytrids are aquatic unicellular protists organisms that represent an important reservoir of a wide range of bioactive compounds, such as essential polyunsaturated fatty acids (PUFAs) such as arachidonic acid (ARA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), which are involved in the regulation of the immune system. In this study, we explore the use of co-cultures of Aurantiochytrium sp. and bacteria as a biotechnological tool capable of stimulating PUFA bioaccumulation. In particular, the co-culture of lactic acid bacteria and the protist Aurantiochytrium sp. T66 induce PUFA bioaccumulation, and the lipid profile was evaluated in cultures at different inoculation times, with two different strains of lactic acid bacteria capable of producing the tryptophan dependent auxins, and one strain of Azospirillum sp., as a reference for auxin production. Our results showed that the Lentilactobacillus kefiri K6.10 strain inoculated at 72 h gives the best PUFA content (30.89 mg g⁻¹ biomass) measured at 144 h of culture, three times higher than the control (8.87 mg g⁻¹ biomass). Co-culture can lead to the generation of complex biomasses with higher added value for developing aquafeed supplements.