Valorization of Cyprinus Carpio skin for biocompatible collagen hydrolysates with potential application in foods, cosmetics and pharmaceuticals

Fish collagen is reported with an increased bioavailability as compared to other sources, the extraction being performed on secondary sources as skin, bones, scales, or fins resulted after fish processing. The aim of the present study was to obtain biocompatible collagen hydrolysates from waste Cyprinus carpio skin, the main aquaculture species in Romania using an inexpensive and “green” neutral hydrolysis process. Neutral hydrolysis of pretreated fish skins performed for 6 h at a temperature of 135 °C and a pressure of 315 kPa produced collagen hydrolysates in 24.6–35.5% yields depending on the adopted pretreatment procedure. The extensive characterization of hydrolysate samples revealed a high purity degree (98% protein content, undetected ash content, pH value in the range 6–7), also confirmed by the absence of undesired aggregates in the characteristic fibril structure as determined by electronic microscopy. A specific collagen hydrolysate random coil structure and the absence of triple helix was determined by FTIR analysis and sustained by CD spectroscopy and X-Ray diffraction. The biocompatibility assessment for the obtained fish collagen hydrolysates revealed no cytotoxic effect on Human keratinocytes, with an 80% cell viability, superior as compared to conventional bovine collagen hydrolysate. Neutral hydrolysis of waste Cyprinus carpio skin yielded collagen hydrolysates with determined characteristics and biocompatibility superior to bovine collagen, suitable for application in foods, cosmetics and pharmaceutical industry.