Research On The Skin Care Effect Of Tilapia Skin Collagen And Polypeptides

In this paper, the extraction processing of acid-soluble collagen derived from tilapia skin was optimized, and the lipase was used to defat the fish skin in order to reduce the defatted time. The physical and chemical properties of collagen from tilapia skin were determined. The polypeptides with different molecular weight were prepared. The effects of collagen and polypeptides on skin were test using animal experiments in vivo.First, it was found that the most time-consuming step was organic solvent defatted step during collagen extraction experiment. The defatted processing of fish skin by organic solvent was replaced by lipase to shorten the defatted time. Based on single-factor experiments, it was found that enzyme dosage, defatted time and defatted temperature were the main factor in defatted process of tilapia skin. Box-Behnken central composite design combined with response surface methodology (RSM) was used to optimize the defatted conditions of tilapia skin. The optimal parameters of defatted processing of tilapia skin using the lipase were obtained. Under the optimum conditions of pH 9, enzyme dosage 0.5%, defatted temperature 39℃ and defatted time 56 min, the defatted rate of tilapia skin was 63.71%.Next, the physical and chemical properties of collagen extracted from above-mentioned treatment were tested. The results showed that collagen extracted from defatted tilapia skin with lactic acid had the maximum absorption peak at 280 nm and no strong absorption peak at 232 nm. It was similar to type I collagen UV absorption characteristics. SDS-PAGE electrophoresis pattern showed that the tilapia skin collagen consisted of three peptide chains α1, α2 and β, and the strip position indicated the complete triple helical structure of collagen. The thermal denaturation temperature of tilapia skin collagen obtained from thermal denaturation curvewas 32.7±0.25 ℃. As a result, the defatted processing by lipase did not affect the physical and chemical properties of tilapia skin collagen, and the time of defatted reduced greatly.Again, the polypeptides of collagen with different molecular weight (Mw) (Mw<3000 Da,3000 Da<Mw<5000 Da, Mw>5000 Da) were prepared using trypsin and alkaline protease at certain conditions. The averge purity of polypeptides was about 85%, which mixed with a small amount of water, salts and non-collagen protein. The averge molecular weight of polypeptides were determined by high performance liquid chromatography (HPLC). The results of purity and molecular weight of collagen polypeptides showed that they could be used as animal skin painting experiments.Finally, the collagen and polypeptides with different molecular weight were applied on rat skin for 45 day. The water content of stratum corneum, the whiteness and the microstructure of skin were tested, and the effects of collagen and polypeptides on rat skin were analysed.The results showed that the collagen and polypeptides could increase the water content of stratum corneum significantly. The effects of collagen and polypeptides on whiteness and microstructure of rat skin were different. Collagen, middle molecular weight (3000 Da<Mw<5000 Da) and high molecular weight (Mw>5000 Da) polypeptides acted well on the whiteness of skin, while low molecular weight (Mw<3000 Da) polypeptides had strong effects on the microstructure of skin.