摘要
本文就近年來本研究室在脂肪酶與澱粉酶在生物技術上應用之研究成果簡要介紹。(一)脂肪酶固定化：固定化脂肪酶之優點包括：可重覆使用酵素、產物易於分離、可連續操作和增加酵素穩定性。我們已發展數種有效的方法將脂肪酶固定在六種不同的擔體上，其中以Chitosan-carbodiimide-glutaraldehytde多點結合的固定化方法最能增加酵素的穩定性。(二)脂肪酶新功能和在有機劑中之催化反應：脂肪酶不僅可以水解三甘油脂（為脂肪酶之天然基質）生產脂肪酸，還可以催化一些非天然基質用來生產有用的物質，例如，Aspergillus niger來源的脂肪酶以glucose pentaacetate為受質時能進行位置特異性(regiospecific)的水解或醇解(alcoholysis)，可以生產1-hydroxy glucose tetraacetate。一種Pseudomonas來源的脂肪酶在乙醇和異丙醇中，能將三甘油脂轉換成特定的脂肪酸酯(fatty acid esters)、單甘油脂和雙甘油脂，Cadida rugosa來源的脂肪酶在有機溶劑環境中可用來區別D-、L-型薄荷醇。脂肪酶在有機溶劑中的催化反應會受到反應前的pH值，亦即pH值記憶(pH memory)和最適水分含量(optimal water content)的影響。而有機溶劑的極性也會影響脂肪酶催化活性。(三)脂肪酶之穩定性及特異性：固定化、化學修飾、基質工程(medium engineering)和基因工程等方法均可被用來增加酵素的穩定性和改變特異性，例如Aspedrgillus niger來源的脂肪酶經過acetamination或加入carbohydrates可增加質熱穩定性。又如培養Cadida rugosa時改變培養條件或在培養基中添加不同碳源時，不僅增加脂肪酶的生產，同時也會影響脂肪酶產生型式。最近一種新型脂肪酶基因已從Vibrio minicus被選殖出來，並在E. coli中表現，如此脂肪酶的穩定性及特異性亦可利用定位基因突變法(site-specific mutations)加以改進。(四)利用澱粉酶生產高麥芽糖漿和高蛋白質食品：具熱安定性質的α-澱粉酶在殺菌條件下能被用來液化澱粉，同時蛋白質會凝集而沉澱，經過遠心分離，上澄液可被β-澱粉酶和澱粉去分枝酵素作用，產生高麥芽糖漿，而沉澱部分則可製成高蛋白質食品，這種理想製程可應用於工業上，加工含高量澱粉的農作物，例如稻米、甘藷等。
關鍵字
無資料並列摘要
Lipases and amylases are widely used in biotechnological applications. This paper describes some recent discoveries in our laboratory that relate to the biochemistry and biotechnology of lipases and amylases. 1. Lipase immobilization: Immobilized lipase has advantages including repeated usage of the enzyme, ease of product separation, continuous operation, and improved enzyme stability. We have developed several efficient methods to couple lipases to six different types of material: PVC, chitosan, chitin, agarose, Sepharose, and Trisacryl. A multiple point attachment method using a chitosan-carbodiimide-glutaraldehyde system with greatly enhances lipase stability is especially useful. 2. New functions of lipase, and catalysis in organic mediua: Lipases can not only be used for the hydrolysis of natural substrates (triglycerides) to produce fatty acids but can also be used for the bioconversion of many synthetic substrates to produce useful compounds. A. niger lipase can catalyze the regiospecific hydrolysis or alcoholysis of glucose pentaacetate to produce 1-hydroxy glucose tetraacetate. A Pseudomonas lipase in ethanol and isopropanol can efficiently convert triglycerides to their respective fatty acid esters, at room temperature. C. rugosa lipase is an excellent catalyst for the optical resolution of dl-menthol in organic solvent. Lipase catalysis in organic solvent has pH memory and optimal water content. The polarity of the organic solvent can change the lipase specificity. 3. Engineering lipase stability and specificity: Immobilization, chemical modification, medium engineering, and genetic engineering can be used for improving enzyme stability and specificity. The thermostability of A. niger lipase can be greatly enhanced by acetamidniation or by the addition of carbohydrates. Changes in culture conditions such as the surfactant and the carbon source can not only significantly increase the C. rugosa lipase production but can also change the patterns of lipase multiple forms. Therefore, the specificity and stability of the crude lipase can be controlled by medium engineering. A gene coding for a novel lipase of Vibrio mimicus has been recently cloned, sequenced, and expressed in E. coli. The lipase stability and specificity would be engineered by site specific mutations. 4. Production of high-maltose syrup and high-protein food by amylases: Thermostable α-amylase can be used to liquefy the starch of rice flour in an autoclave and coagulate the protein. After centrifugation, the supernatant can be converted into high- maltose Syrup by β-amylase and debranching enzymes. This novel enzymatic process is natural and efficient, and which can greatly increase the commercial value of starch-containing agricultural products such as rice.