Engineering strategies for enhanced heterologous protein production by Saccharomyces cerevisiae.

Microbial proteins are promising substitutes for animal- and plant-based proteins. S. cerevisiae, a generally recognized as safe (GRAS) microorganism, has been frequently employed to generate heterologous proteins. However, constructing a universal yeast chassis for efficient protein production is still a challenge due to the varying properties of different proteins. With progress in synthetic biology, a multitude of molecular biology tools and metabolic engineering strategies have been employed to alleviate these issues. This review first analyses the advantages of protein production by S. cerevisiae. The most recent advances in improving heterologous protein yield are summarized and discussed in terms of protein hyperexpression systems, protein secretion engineering, glycosylation pathway engineering and systems metabolic engineering. Furthermore, the prospects for efficient and sustainable heterologous protein production by S. cerevisiae are also provided.

Investigation into antifreeze performances of natural amino acids for novel CPA development.

Cryopreservation can prolong the viability of cells and help meet the demand for biosamples of high medical value. Cryoprotectants (CPAs) can mitigate unavoidable cell cryoinjury caused by the formation and growth of ice crystals during freeze-thaw cycles. Therefore, the development of efficient and biocompatible CPAs has attracted extensive attention. In this work, the antifreeze performances of 18 water-soluble natural amino acids were systematically investigated by wet experiments and molecular dynamics simulations to explore their potentials as CPAs. Phenylalanine has an amphipathic structure with excellent ice recrystallization inhibition (IRI) activity, and methionine exhibits optimal depressing freezing point ability. Combining phenylalanine or methionine with osmolyte (proline) as CPAs can maintain normal morphology of sheep red blood cells (RBCs), and the recovery of sheep RBCs reaching 85 and 71%, respectively, while only 32% in the 20% (w/v) glycerol solution. This study demonstrates the potential of amino acid-based CPAs and reveals the synergistic effect of IRI activity and osmotic pressure regulation in cryopreservation.