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In this study, the digestion of yeast protein in the gastrointestinal tract of rats, and its effects on the blood biochemical parameters at different time points were investigated. Yeast protein was digested into peptides by pepsin in the stomach, broken down into dipeptides or amino acids by trypsin in the small intestine, and then absorbed by the rats or entered the colon. The peptide levels in gastric, small intestinal, and large intestinal digesta reached the highest level at 4 h, 2 h, and 8 h, respectively. Intact yeast protein in the gastric tract was found within 4 h, and no intact protein was present in intestinal digesta. Compared with gastric digesta, yeast protein intestinal digesta had much less distinguish and distinct stripes. Yeast protein ingestion increased the levels of immunoglobulin, high-density lipoprotein, and uric acid, and decreased the levels of total cholesterol, triglycerides, and low-density lipoprotein, while it did not significantly affect the levels of globulin, albumin, aspartate aminotransferase, and alanine aminotransferase in serum. This study demonstrated the digestion kinetics of yeast protein in the gastrointestinal tract of rats, and its beneficial effects on the blood biochemical parameters of rats and provided scientific evidence for yeast protein as an efficient and sustainable alternative protein source.

Arthrospiracell residue (ACR) is a byproduct of the spirulinaindustry that can be valorized into protein hydrolysates. In this study, we used alkaline protease to hydrolyze ACR and evaluated the effects of hydrolysis time on the properties and functionalities of the hydrolysates. We measured the degree of hydrolysis (DH), particle size, fluorescence, UV‒visible absorption, surface hydrophobicity, emulsification, solubility, and antioxidant activity of the hydrolysates. The DH reached a maximum of 10.2% ± 0.6% after 240 min. Hydrolysis also altered the structure and conformation of the ACR protein, as shown by changes in fluorescence, UV-visible absorption, and FTIR spectra. Hydrolysis enhanced the solubility, surface hydrophobicity, and emulsifying activity of the hydrolysates but not the emulsion stability. The hydrolysates also exhibited higher antioxidant activity than ACR. These results indicate that enzymatic hydrolysis can convert ACR into valuable protein hydrolysates.