Peptide synthesis routes For more than a century, peptide synthesis has had a significant impact in several fields including pure organic synthesis and protein chemistry. The formation of pep- tides usually occurs via repetitive amidation reactions. The N-terminal amino group and the carboxylic group of an incoming amino acid are coupled to produce the peptide bond. Bruce Merrifield was one of the pioneers of utilizing insoluble resins as support during the synthesis of pep- tides that could then be cleaved off at the end of the process to isolate the final peptide in solution [42,43]. Quickly these strategies were adopted in solid-phase peptide synthesis. However, remaining challenges include matrix swelling, limited selection of linker groups, and the neces- sity of using protecting groups for some amino acids. Over the last 15 years, advances in the peptide industry have lowered the cost of raw materials and improved the chromatographic methods used for peptide purification. It should be mentioned that the number of animal-derived peptides on the market is decreasing implying that the solid phase methods are becoming more economics. In addition, the use of enzymatic procedures (reversed pro- teolysis) to synthesize specific sequences is gaining renewed interest