壳聚糖固定化木瓜蛋白酶的研究

以壳聚糖为载体,成二醛为交联剂将木瓜蛋白酶固定化。5％戊二醛在4-6℃下处理载体5h,加酶液(3.5mg/mL蛋白,pH7.2)固定12h,活力回收达32％,作用于酪蛋白的半衰期为36天,其表观K_m(酪蛋白)值为0.075％(W/V),溶液酶的K_m值为0.086％;最适pH7.0～7.5,溶液酶为7.0～8.5。固定化酶在pH8.5以下,溶液酶在9.0以下活力稳定。固定化酶在45℃以下,溶液酶在75℃以下稳定。用6mol/L脲洗脱固定化酶4次(5.5h)活力仍有54.5％。用固定化酶处理啤酒浊度比对照下降了1.5-3.7倍,蛋白质含量下降了44％,冷藏(4℃)120天无冷混浊现象发生并保持了啤酒原有风味和理化性状。

Immobilization of Papain on Deacetylated Chitin

Papain was immobilized on deacetylated chitin and crosslinked with glutaraldehyde. The optimum conditions for immobilization were as follows. Deacety- lated chitin was treated with 5% solution of gluaraldehyde at 4-6**********C for 5 hrs, then papain (2.5mg/mL, pH 7.2) was immobilized on the carrier (Tables 1-3, Fig.1).Enzyme activity recovery was 32%, the half-life of the immobilized papain (the time required for half of the original activity to be lost when hydrolyzing casein solution) was 36 days.The Km's (casein, in w/v percentage) of immobilized and soluble papain were 0.075% and 0.086% respectively (Fig.2).The optimum pH's for immobilized and soluble papain were 7.0-7.5 and 7.0-8.5 respectively (Fig.3) The immobilized papain was stable under 45*********C for 30 min, upon heat treatment, but the soluble papain was able to withstand higher temperatures upto 75********C, although the activity was slighter lower (Fig.4).The immobilized papain was relatively unsensitive to urea treatment and retained 54.5% of the original activity, even after bein eluted with urea solution (6mol/L) for four times within 5.5 hrs.Com-((6mol/ L) for four times within 5.5 hrs.Comparision of the turbidity of immobilized papain treated beer was decreased to about 1.5-3.7 times less than control while the protein content was decreased by 44%.Not much change in flavor and quality of the beer after immobilized papain treatment was found.