固定化脂肪酶合成二元酸酯

The syntheses of dicarboxylic esters by immobilized lipase from Candida sp. -1619 were investigated. The reaction system was composed of 1 mmol dicarboxylic acid, 2 mmol alcohol, 3 mL hexane and 15 mg celite-adsorbed im mobilized lipase(300 u), in a closed 100 mL Erlenmeyer flask, shaken at 40°C for 5h. Sebacic acid was the best substrate among nine dicarboxylic acids selected. Among the 18 saturated fatty n-alcohols, the alcohols with carbon chain length rangin from C4～C18 had good reactivity. The primary alcohols had much better reactivities than corresponding secondary alcohols and multihydroxy-alcohols. Tertiary alcohols showed no reactivity. Hydrocarbons, benzene, toluene, xylene and te trachloride were favorite reactants among 15 organic solvents selected, in none-solvent stationary system, (5 mmol sebacic acid, 10 mmol dndecanol, 150 mg immobilized lipase(3000 u))reacted without plug for 3.5h, the optimum temperature was 60°C. The conversion degree was over 92% when reaction carried out at 50～90°C for 17h. The suitable reaction pH ranged from 6～8. The reactant was developed on GF254 plate(hexane ethyl ether acetic acid = 30201 ( V V V).There were three spots with different Rf value at 0.96, 0.55 and 0 corresponding to product, oleyl alcohol and sebacic acids, respectively.     

三醋酸纤维素包埋产青霉素酰化酶的大肠杆菌细胞

三醋酸纤维素包埋细胞较其他固定化方法有较多的优点,制备过程既不用加热也无需冷冻;有较好的机械强度,为使用、保存、运输均带来了方便,本文报道这一研究结果。     

具有高活力天门冬氨酸酶的大肠杆菌AS1．881固定化细胞

1．大肠杆菌Asl．881是一株天门冬氨酸酶的高产菌株,每毫升培养物为2000单位左右,约相当于每克湿细胞10万单位。 2．比较了琼脂凝腔包埋法和聚丙烯酰胺凝肢包埋法两种制备固定化细胞的方法,前者较后者有较大的优越性：收率高,无毒,成本低,方法简便. 3．比较了固定化细胞和自然细胞天门冬氨酸酶的一些生物化学性质：pH、温度和二价金属离子对两者酶促反应速度的影响相似;固定化细胞热稳定性较差,但Mn2+,Mg2+,Ca2+,Fc2+等二价金属离子对热钝化有保护作用;在底物和pH6.5柠檬酸缓冲液中于37℃保温,两种细胞的酶活力均有显著提高。 4．固定化细胞柱可被用于连续生产L一天门冬氨酸,包埋80克湿细胞的固定化细胞柱在37℃连续工作20天,可催化约1000升1M反丁烯二酸铵完全转化为L-天门冬氨酸,并保存其大部分酶活力。     

酶法合成糖及糖醇酯

以脂肪酸为酰基供体,糖和糖醇为酰基受体,利用吸附到涤棉布上的假丝酵母脂肪酶作催化剂,在含叔丁醇的系统中,研究了酯化反应条件。酯化最适温度和pH值分别为40℃～45℃和50～75。在酰基供体中,以亚油酸和油酸最好,C8到C22的饱和脂肪酸的酯化程度相仿。在23种糖和糖醇中,果糖、木糖、海藻糖、山梨糖、木糖醇、甘露醇以及异丙基葡萄糖和甲基葡萄糖比其它酰基受体的酯化率高。糖醇的酯化程度明显高于相应的糖。此外,酰基供体与受体的摩尔比大于2∶1时,有利于酯化。在由30mmol(085g)油酸,02mmol山梨醇(0036g),3mL叔丁醇和30mg固定化酯肪酶(600u)组成的反应系统中,40℃震荡反应48h,以等摩尔的底物计算,酯化程度达到90%以上。反应产物经薄层色谱鉴定为单酯和双酯。