Immobilized and Free Cells of Geotrichum candidum for Asymmetric Reduction of Ketones: Stability and Recyclability.
Immobilized and Free Cells of Geotrichum candidum for Asymmetric Reduction of Ketones: Stability and Recyclability.
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用于酮不对称还原的白地霉固定化和游离细胞：稳定性和可回收性
DOI：
10.3390/molecules23092144
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发表时间：
2018-08-27
期刊：
影响因子：
--
通讯作者：
Chen BS
中科院分区：
文献类型：
--
作者：
Liu H;de Souza FZR;Liu L;Chen BS
海洋真菌白地霉（Geotrichum candidum AS 2.361）是本课题组先前报道的一株对映选择性还原酮的活性菌株。虽然一些其他的地霉菌株也被发现从陆地来源，其稳定性和可重复使用的信息是稀缺的。本文从pH耐受性、热稳定性、贮存稳定性和重复使用性等方面对G. candidum AS 2.361用于一系列芳香酮的不对称还原反应。制备了两种不同的固定化细胞（琼脂固定化和海藻酸钙固定化）以及游离细胞。对于三种底物（1-（3-溴苯基）乙-1-酮（1b）、1-（2-氯苯基）乙-1-酮（1d）和苯乙酮（1g）），琼脂上的固定化细胞的生物还原活性比游离细胞有很大提高，产率提高到97%，ee值为99%。固定化细胞在pH 3.5-11范围内保持90%以上的活性，而游离细胞对碱性和酸性条件高度敏感。在热稳定性方面，琼脂固定化细胞在60 °C孵育1h后，其活性保持在99%以上，而游离细胞在相同条件下几乎没有活性。固定化细胞在4 °C下稳定80天而没有任何活性损失，而游离细胞在4 °C下储存6天后活性开始降低。固定化细胞在4次重复使用后仍保持近99%的活性，而游离细胞在第3次重复使用时几乎失去了所有的活性。
Marine-derived fungus Geotrichum candidum AS 2.361 was previously reported by our group as an active strain for the enantioselective reduction of ketones. Although some other Geotrichum strains were also found from the terrestrial sources, information on their stability and reusability is scarce. Herein, the stabilities—in terms of pH tolerance, thermostability, and storage stability, and reusability—of G. candidum AS 2.361 were described for the asymmetric reduction of a series of aromatic ketones. Two differently immobilized cells (agar immobilization and calcium alginate immobilization) as well as free cells were prepared. For three substrates (1-(3-bromophenyl) ethan-1-one (1b), 1-(2-chlorophenyl) ethan-1-one (1d), and acetophenone (1g)) immobilized cells on agar showed a great improvement in the bioreduction activities compared to the free cells, increasing yields up to 97% with ee values of 99%. Cells immobilized on agar/calcium alginate could maintain more than 90% of the original activities within the assayed pH ranges of 3.5–11, while free cells were highly sensitive to alkaline and acidic conditions. Concerning thermostability, immobilized cells on agar kept 99% of their original activities after incubation at 60 °C for 1 h, while almost no activity was detected for the free cells under the same condition. Immobilized cells were stable at 4 °C for 80 days without any activity loss, while free cells started to decrease the activity after storage at 4 °C for six days. The immobilized cells retained almost 99% activity after four reuse cycles, while free cells lost almost all the activities at on the third cycle.
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作者：
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