| This experiment is to probe the factors, such as the effect of the kid's suckling, the butchering age and the ay of the abomasums treatment on the chymosin activity;the activation of the prochymosin; the purification and separation of chymosin and the characterization of chymosin and pepsin, using Cuan Zhong dairy kid's abomasums as material, which would provide the theoretic base for the exploitation of the kid chymosin and its application to the cheese production.The research on the condition of kid's suckling indicates that the highest milk-dotting activity(26108su/g)was obtained for the whole suckling section, whereas proteolytic activity were no significant different between the whole suckling and random section(p>0.05),but proteolytic activity(1925u/g) was highest for the complete grass-feeding, which demonstrated suckling could stimulate the continuous secretion of chymosin in the abomasum. The experiment on butchering age showed that it was 5d after the kid birth that the ratio of clotting activity and proteolytic activity(C/P)was the highest, which was a best age for extracting kid chymosin.The methods of the abomasums treatment suggested that the freezing method had least influence on milk-clotting activity, while the salting air-drying and natural air-drying went to another extreme. Meanwhile, the partial proenzyme from the abomasums would be activated automatically by the latter two methods.As the kid chymosin was extracted by the traditional way and the buffering way at different pH values, its activity mainly depended on the salt concentration, extraction time and temperature, the ratio of buffer and abomasums and extraction times. With the increasing salt concentration, milk-clotting activity became higher and higher, then reached its peak, and then decreased gradually; In the early extraction, the speed was quick, the milk-clotting activity was increased obviously. After it amounted to the maximum, the activity became steadily lower steadily; the increasing temperature in extracting could improve the extraction activity, but too high temperature could result in the denaturation and inactivation; The greater the ratio of abomasums and butter and was, the quicker speed was when the enzymes was drawn out, and after extracting for twice, most of the enzymes in the abomasums could be drawn out. The result oforthogonal experiment were as follows:1.by the traditional method, using 8% salt concentration, 1:20 ratio of abomasums and butter, 30℃extraction temperature and 48h extraction time, the highest activity could be obtained; 2.In buttering way at pH4.5, pH5.4and pH6.0 respectively, using 6%,8%and8% salt concentration,1: 15,1:20and 1:15 ratio of abomasums and butter,30℃ ,3 0℃ and25℃ extracting temperature,60h,60h and 48h extraction time, the highest activity could be obtained. From above it could be see that it was the buffering way at pH5.4 that the largest enzyme yield could be obtained.In addition, the application of the supersonic wave to the extraction of kid's chymosin was studied in the experiment. And the results showed that the supersonic extraction could shorten the extraction time greatly, which could have the same effect for 40min as the traditional way of 48h. The greatest activity could be obtained on the condition of 8% salt concentration, 1:20 ratio of abomasums and butter, 30W/cm2 supersonic strength and 40min extraction time.The kid chymosin was secreted as being the form of non-activated prochymosin, and its activation depended on pH value, salt concentration and temperature. The lower the pH value was, the higher activated speed become. It needed only 5-10min to activate at pH2.0, 30min at pH3.0. But the activated chymosin wasn't somewhat stable enough at the lower pH value. The activated speed was improved by the increasing salt concentration. It was very slow at 5℃ but become higher above 25℃.The enzyme from abomasums used in cheese production was rough extracts containing chymosin and pepsin. Through the gel filtration chromatography and ion exchange c...
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