The Thermal Properties and Nutritional Value of Biomass of Oleaginous Yeast Rhodotorula sp. during Glucose Fed-Batch Cultivation in Medium with Waste Nitrogen

Abstract

The biotechnological processing of oleaginous yeast biomass should be comprehensively managed using the zero-waste policy. This study focused on the biomass of the red yeast Rhodotorula obtained from a medium containing waste nitrogen. The cells accumulate lipids in intracellular lipid droplets; however, they are also rich in protein. Therefore, the nutritional value of lipid and protein, according to their fatty acid and amino acid composition, is a necessary step for practical application. For the very first time, this study focused on understanding the influence of temperature on powdered red yeast biomass to study components phase transition or chemical reactions by using DSC. Rhodotorula glutinis var. rubescens was cultivated in a glucose fed-batch in a potato wastewater medium, where the biomass yield was powdered, and lipid and fatty acid, protein, and amino acid compositions were determined. The DSC diagrams of red yeast biomass were characterized by two small and mild endothermic peaks, indicating the presence of fat and the presence of low molecular weight carbohydrates and a distinct peak associated with the presence of crystalline sugars. The nutritional quality of the lipid fraction as atherogenicity (0.223), thrombogenicity index (0.438), PUFA/SFA (0.24), and the n-6/n-3 ratio (3.275) was adequate for the recommendation and resulted from the fatty acid composition. The yeast protein was characterized by a high content of glutamic acid (99 mg/1 g of protein), and a value of essential amino acid index of protein suggested a superior amino acid composition compared to the FAO/WHO standard. Despite a high essential amino acid index (>120), yeast protein was characterized by a low content of Lys or Met.