# Influence of process parameters on single-cell oil production by Cutaneotrichosporon oleaginosus using response surface methodology

## TL;DR

This study shows how adjusting temperature, pH, and oxygen levels can boost lipid production and tailor fatty acid profiles in a yeast, making it a better sustainable oil source for food, fuel, and materials.

## Contribution

The study introduces optimized cultivation conditions using response surface methodology to enhance lipid productivity and modulate fatty acid profiles in Cutaneotrichosporon oleaginosus.

## Key findings

- Lipid productivity increased by 46% under optimized oleate lipid titer conditions (27.6°C, pH 5.6, 10% DO).
- Temperature was the main factor influencing fatty acid saturation, while pH adjusted the C16/C18 ratio.
- The saturation degree of fatty acids could be modulated by more than 10% through process parameter adjustments.

## Abstract

The growing demand for sustainable lipid sources has fostered interest in single-cell oils from oleaginous yeasts as renewable alternatives to plant-derived and fossil-based oils, with applications in food, fuel, and material production. The oleaginous yeast Cutaneotrichosporon oleaginosus is of industrial relevance due to its ability to accumulate in excess of 60% (w/w) of its dry cell weight as lipids, while metabolizing a broad range of substrates. However, economic feasibility depends on improving productivity and adapting fatty acid profiles to application requirements.

This study investigated the influence of temperature, pH, and dissolved oxygen concentration (DO) on lipid production and fatty acid composition in C. oleaginosus ATCC 20509. A three-level, three-factor Box–Behnken design was applied to assess their effects on lipid titer, oleate lipid titer, and the proportions of saturated and unsaturated fatty acids. Response surface methodology was used to develop quadratic models, identify optimized conditions, and predict fatty acid compositions. Temperature and pH significantly affected both overall lipid titer and degree of saturation. In fed-batch cultivation with consumption-based acetic acid feeding and glucose as the initial carbon source, lipid productivity increased to 0.38 g/L/h under the optimized oleate lipid titer condition (27.6 °C, pH 5.6, 10% DO) and to 0.39 g/L/h under the optimized saturated fatty acid condition (30 °C, pH 7.0, 10% DO), corresponding to 46% and 50% increases compared to literature values (0.26 g/L/h; 28 °C, pH 6.5, 50% DO). The fatty acid profile could thus be precisely modulated by adjusting the process parameters, achieving a difference in the saturation degree of more than 10%. Temperature was identified as the main factor influencing saturation, while pH enabled adjustment of the C16/C18 ratio, resulting in a modulation of palmitic acid fraction within the total triglycerides of up to 13%.

These findings highlight the potential of optimizing cultivation parameters based on reaction surface methodology to simultaneously improve lipid productivity and functionality by tailoring the fatty acid profile to the desired application requirements, without resorting to genetic engineering. Moreover, these insights support a circular bio-based economy by enabling an efficient production of tailored microbial oils as renewable alternatives to plant-derived lipids.

The online version contains supplementary material available at 10.1186/s13068-025-02717-3.