Extraction of Natural Nanostructured Hydroxyapatite from Pacific Cod(Gadus macrocephalus)Bone with a Thermostable Collagenolytic Protease and Its ex vivo Intestinal Bioavailability

Natural nano-hydroxyapatite(HA)was extracted from Pacific cod(Gadus macrocephalus)bone with a thermostable col-lagenolytic protease in the present study.Conditions for the enzymatic reaction were optimized to be 60℃and pH 7.0,and a desir-able extraction efficiency was achieved by using the crude collagenolytic protease.Dynamic light scattering,transmission electron microscopy and energy-dispersive X-ray analysis revealed that nano-HA are anionic spherical(about 110nm)particles mainly com-prised of calcium and phosphorus at an approximate ratio of 5:3.As evaluated with the mouse ex vivo intestinal segments,the extracted nano-HA displayed comparable level of intestinal bioavailability to the positive control CaCl_(2).By treating with inhibitors(NaN3,ami-loride)and low temperature(4℃),clathrin-mediated endocytosis was assumed to involve the intestinal absorption of nano-HA.Over-all,the application of thermostable collagenolytic protease is proved to be a promising alternative method for nano-HA extraction from natural resource with improved ecological and biological value.

Application of acidic protease in the pickling to simplify the pelt bating process

Traditionally,universally used pelt bating technologies rely on the application of trypsin,neutral and alkaline microbial proteases but suffer from complicated operation,limited bating efficiency and unsatisfac-tory leather performance.Therefore,devising a new pelt bating approach to achieve high bating efficiency and excellent leather performance has always been wished for by the leather industry.To pursue this goal,years of persistent research work enabled us to develop a novel approach for pelt bating by means of acidic proteases in pickling process.Initially,basic enzymatic characteristics and bating effectiveness of several typical acidic pro-teases in pelt pickling medium were investigated;then,the bating effectiveness through the quantitative charac-terization of protease activity of the optimal acidic protease was compared with that of the conventional bating enzyme.The results indicated that all of the selected acidic proteases had good salt-tolerance and exhibited optimum activity at pH 3.0–4.0.The novel pickling-bating method based on microbial origin acidic protease L80A led to an outstanding performance on pelt bating at the dosage of 150 U/mL of collagenolytic activity.The bating effectiveness of acidic protease L80A was comparable to and even better than that of trypsin BEM due to its mod-erate proteolytic ability.Moreover,the deep and even penetration of acidic protease in the pelt permitted it to produce soft,organoleptically stable and overall better quality crust leather than that of the conventional trypsin bating method.Additionally,pelt bating was performed along with the pickling process without extra inactiva-tion and washing operation,making the bating operation more efficient,economical,and environment friendly.Results had made us to conclude that this cutting-edge acidic proteases based pickling-bating method could be the first step/way forward to replace the decades-old traditional pelt bating technology.