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首页> 外文期刊>Journal of Agricultural and Food Chemistry >Water activity effects on geranyl acetate synthesis catalyzed by novozym in supercritical ethane and in supercritical carbon dioxide.
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Water activity effects on geranyl acetate synthesis catalyzed by novozym in supercritical ethane and in supercritical carbon dioxide.

机译：在超临界乙烷和超临界二氧化碳中，水活性对酚醛清漆酶催化乙酸香叶酯合成的影响。

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摘要

The esterification reaction of geraniol with acetic acid catalyzed by Novozym was studied in supercritical ethane (sc-ethane) and in supercritical carbon dioxide (sc-CO(2)). Water activity (a(W)) had a very strong effect on enzyme activity, with reaction rates increasing up to a(W) = 0.25 and then decreasing for higher a(W). Salt hydrate pairs could not prevent changes in a(W) during the course of reaction but were able to control a(W) to some extent and had a beneficial effect on both initial rates of esterification and conversion in sc-ethane. The enzyme was more active in sc-ethane than in sc-CO(2), confirming the deleterious effect of the latter already observed with some enzymes. Temperatures between 40 and 60 degrees C did not have a strong effect on initial rates of esterification, although reaction progress declined considerably in that temperature range. For the mixture of 50 mM acetic acid plus 200 mM geraniol, 100% conversion was achieved at a reaction time of 10 h at 40 degrees C, 100 bar, an a(W) of incubation of 0.25, and a Novozym concentration of 0.55 mg cm(-)(3) in sc-ethane. Conversion was below 50% in sc-CO(2) at otherwise identical conditions. With an equimolar mixture of the two substrates (100 mM), 98% conversion was reached at 10 h of reaction in sc-ethane (73% conversion in sc-CO(2)).
机译：在超临界乙烷（sc-乙烷）和超临界二氧化碳（sc-CO（2））中，研究了香叶醇与Novozym催化的乙酸酯化反应。水分活度（a（W））对酶活性有很强的影响，反应速率增加到a（W）= 0.25，然后随着较高的a（W）而降低。盐水合物对不能阻止反应过程中a（W）的变化，但能够在一定程度上控制a（W），并且对酯化反应的初始速率和在sc-乙烷中的转化率都有有益的影响。该酶在sc-乙烷中比在sc-CO（2）中更具活性，这证实了已经用某些酶观察到的后者的有害作用。尽管在该温度范围内反应进度大大降低，但40至60摄氏度之间的温度对初始酯化速率没有强烈影响。对于50 mM乙酸和200 mM香叶醇的混合物，在40℃，100 bar，孵育的a（W）为0.25和诺维辛浓度为0.55 mg的条件下，于10小时的反应时间达到100％的转化率于sc-乙烷中的cm（-）（3）。在其他条件相同的条件下，sc-CO（2）中的转化率低于50％。使用两种底物的等摩尔混合物（100 mM），在sc-乙烷中反应10小时可达到98％的转化率（在sc-CO（2）中为73％的转化率）。

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