Extraction of mannoprotein from Saccharomyces cerevisiae and analysis of its chemical composition and molecular structure

The purpose of this study was to screen the method with the highest yield of mannoprotein (MP) without damaging their functional structure. The recovery rates of the extracts, protein, and mannose were determined along with the mannose/protein ratio, molecular weight and distribution, monosaccharide and amino acid compositions, and secondary structures of the three MP extracts to compare the extraction methods. The MP extracts recovery rate prepared by the thermal method was significantly higher (35.89%) than those obtained using fermentation (31.66%) and SDS treatment (19.77%). Three protein bands with similar molecular weights of 59, 47, and 34 kDa were detected in the MPs obtained via the different extraction methods. The thermally extracted MP has a broader molecular weight distribution. After purification, the proportion of mannose in the polysaccharide parts of the MPs increased from 6-7 to 90.4-91.3%. The essential amino acid content of the hot-extracted MP (170.07 mg/g) was the highest. The thermally extracted MP had similar secondary structural characteristics to that isolated at room temperature, and had a higher protein characteristic peak intensity. In general, the heating method to extract yeast mannoprotein is time-saving and efficient.