The purpose of this study is to improve the enzymatic properties of the endo 1 ,4β glucanase using Pichia yeast cell‐surface‐display technique .The results were as follows :SDS‐PAGE result showed that the molecular weight of the displayed endo 1 ,4 β glu‐canase (Displayed endo 1 ,4 β glucanase ,DEG ) was 34 .1 kDa .Compared with the free endo 1 ,4 β glucanase (Free endoglucanas ,FEG) ,DEG had the same substrate specificity for CMC‐Na .The optimum temperature and pH value of DEG were still 70 ℃ and 4 .0 ,re‐spectively ,but the affinity of DEG for substrate was reduced .The activities of DEG were maintained 60% between pH 2 .5 and pH 8 .5 ,which were 0 .5 times higher than that of FEG . No loss of activity was found at 70 ℃ .Moreover ,the activity was 1 .5 times higher than FEG under the same conditions . DEG activity was still retained 65% activity after reusing 10 rounds .The tolerance of DEG for Co2+ ,Mn2+ ,Hg2+ and other heavy metal ions were greatly increased .These data showed that the enzymatic properties of DEG were definitely improved including its acid‐thermal stability ,resistance to heavy metal ions and operational stability . T hereby ,DEG ,as a yeast w hole cell biocatalyst ,has a broad application prospects in various fields of cellulose degradation .%本研究目的是利用毕赤酵母细胞表面展示技术来改善内切1，4β葡聚糖酶的酶学性质。结果显示， SDS PAGE显示展示酶（DEG）的分子量为34．1 kDa ，对CMC‐Na有底物专一性。与游离酶（FEG）相比，DEG的最适作用温度和最适作用pH值未发生变化，分别为70℃和4．0；对底物的亲和力降低；pH2．5～8．5时酶活残留率为60％，比游离酶高0．5倍；温度70℃时酶活无损失，残留率为102％，同等条件下比游离酶高1．5倍；DEG重复使用10次以后保留活性仍为65％；而且展示酶对Co2＋、Mn2＋、Hg2＋等重金属离子的耐受力也大大增强。本研究结果表明，展示内切1，4β葡聚糖酶的酶学性质得到大幅度改善，其酸热稳定性、重金属离子耐受性和操作稳定性均有所提高，DEG作为一种酵母全细胞生物催化剂在各种纤维素降解领域具有很广阔的应用前景。
展开▼
