A technology for obtaining a protein concentrate from yeast biomass of Kluyveromyces marxianus van der Walt (1965)

Lack of protein in the diet leads to a violation of nitrogen metabolism. Experts estimate that the feed protein market will exceed US $ 200 billion by 2024. In Russia, the deficit of fodder proteins is more than 1 million tons. Traditional protein sources cannot meet the daily need for food and feed proteins because of economic and social reasons, so there is a growing interest in alternative protein sources. This communication presents the results of obtaining a protein concentrate based on the biomass of thermotolerant yeast K. marxianus grown on a waste of oilseed production that is little used in bioconversion - sunflower husk. Yeast of this type increases the digestibility of feed, is used in the food industry for the fermentation of soy milk, soft cheese and as a flavor enhancer. The aim of the study was to develop a technology for obtaining a protein concentrate from the yeast biomass of K. marxianus and to substantiate the feasibility of its use as a feed and food additive. The K. marxianus Y-4570 strain was selected as a result of screening on sunflower husk fermentolysate as the most productive in terms of biomass accumulation (up to 30 g/l) and crude protein (59.29±2.96 %). Using a multicyclic semi-continuous method, yeast was cultured in a laboratory fermenter on a saline medium with sunflower husk fermentolysate to obtain protein biomass. Technological parameters were determined to obtain the protein concentrate containing at least 60 % of the true protein, no more than 2 % of lipids and no more than 2 % of nucleic acids. The biomass was defatted with 60 % ethyl alcohol with a hydromodule of 1:2.5 at 60 °С for 1 hour. The residual lipid content was 1.94±0.09 %. Denucleinization was performed by activating the cell’s own endonucleases at 40-60 °С. Nucleic acids were removed at a 50 °С for 1 hour with a hydromodule 1:7. The residual content of nucleic acids was 1.97±0.10 %. The final product contains 65.94±3.14 % of true protein, which meets the requirements for protein concentrates. Analysis of the amino acid profile of the protein concentrate showed that the content of almost all essential amino acids exceeds that in the original yeast biomass, with the exception of glycine, leucine and histidine. A relative increase in the content of amino acids occurs due to the removed lipids, nucleic acids, the loss of moisture and the concentration of substances of the original biomass with drying. Protein concentrate based on the biomass of the yeast K. marxianus Y-4570 is intended for use as a feed and food additive in order to enrich products with essential amino acids.