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Inducing expression and the reaction characteristic of nitrile hydratase (NHase) from Rhodococcus sp.SHZ-1 were investigated. The results showed that the expression of NHase was greatly enhanced with the cooperation of acrylonitrile and ammonium chloride as inducer in the medium and the specific activity of NHase was increased of 44%. Then the temperature, pH, concentration of acrylonitrile and acrylamide were evaluated, which affected the activity and reaction characteristic of NHase. It was found that the temperature and concentration of acrylamide were the most important factors for the catalyzation of NHase. The optimal catalysis temperature of NHase from Rhodococcus sp. SHZ-1 was 30℃, and the activation energy of the hydration of NHase was 90.2kJ·mol-1 in the temperature range from 5℃ to 30℃. Km of NHase was 0.095mol.L-1 using acrylonitrile(AN)as substrate, and NHase activity was inhibited seriously when acrylonitrile concentration was up to 40g·L-1, the substrate inhibition constant Ki is 0.283mol·L-1. Moreover, the NHase from Rhodococcus sp. SHZ-1 had very strong tolerance to acrylamide, in which the final concentration of acrylamide reached to 642g·L-1 and the residual activity of NHase still maintained 8.6% of the initial enzyme activity. 相似文献
22.
通过研究发酵过程中溶氧、生物量、腈水合酶活力以及残糖的变化规律和搅拌速度、通气量、接种量及诱导剂对产腈水合酶的影响,确立了5L发酵罐中Rhodococcus sp.SHZ-1腈水合酶的高酶活发酵工艺参数。结果表明,发酵过程中溶氧控制在30%以上有利于菌体快速生长和腈水合酶的合成。在pH7.2,温度30℃的发酵条件下,适宜的腈水合酶合成工艺条件为:接种量10%,通气量1.0vvm,搅拌速度采用由初始的200r/min调至500r/min的变速调控方式,同时于48h补加产酶诱导剂,发酵液腈水合酶的最高酶活力达到了9500U/mL,是摇瓶培养时最高酶活力8208U/mL的1.2倍,且比未进行工艺优化时最大产酶期缩短了20～24h,其最佳产酶期为52～60h。 相似文献
23.
以胡萝卜及甘薯的原浆、牛乳为乳酸菌的发酵基质，经加工处理、调配后进行乳酸发酵，通过正交试验确定其最适的工艺条件。结果表明：牛乳用量为75％，甘薯浆与胡萝卜汁的体积比为2：1，糖用量5％，前发酵温度为40．5℃，前发酵时间为7．5h，接种量为5％时，制得的胡萝卜、甘薯发酵酸奶的凝乳状态、口感、色泽、风味最好。 相似文献
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