Hydroxynitrile lyase (HNL) catalyzed enantioselective CC bond formation is an efficient approach to synthesize chiral cyanohydrins which are important building blocks in the synthesis of a number of fine chemicals, agrochemicals and pharmaceuticals. Immobilization of HNL is known to provide robustness, reusability and in some cases also enhances activity and selectivity. We optimized the preparation of immobilization of Baliospermium montanum HNL (BmHNL) by cross linking enzyme aggregate (CLEA) method and characterized it by SEM. Optimization of biocatalytic parameters was performed to obtain highest % conversion and ee of (S)-mandelonitrile from benzaldehyde using CLEA-BmHNL. The optimized reaction parameters were: 20 min of reaction time, 7 U of CLEA-BmHNL, 1.2 mM substrate, and 300 mM citrate buffer pH 4.2, that synthesized (S)-mandelonitrile in ∼99% ee and ∼60% conversion. Addition of organic solvent in CLEA-BmHNL biocatalysis did not improve in % ee or conversion of product unlike other CLEA-HNLs. CLEA-BmHNL could be successfully reused for eight consecutive cycles without loss of conversion or product formation and five cycles with a little loss in enantioselectivity. Eleven different chiral cyanohydrins were synthesized under optimal biocatalytic conditions in up to 99% ee and 59% conversion, however the % conversion and ee varied for different products. CLEA-BmHNL has improved the enantioselectivity of (S)-mandelonitrile synthesis compared to the use of purified BmHNL. Nine aldehydes not tested earlier with BmHNL were converted into their corresponding (S)-cyanohydrins for the first time using CLEA-BmHNL. Among the eleven (S)-cyanohydrins syntheses reported here, eight of them have not been synthesized by any CLEA-HNL. Overall, this study showed preparation, characterization of a stable, robust and recyclable biocatalyst i.e. CLEA-BmHNL and its biocatalytic application in the synthesis of different (S)-aromatic cyanohydrins.

中文翻译：

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固定的Balosospermum montanum羟腈裂解酶催化合成手性氰醇。

羟基腈裂解酶（HNL）催化的对映选择性CC键形成是合成手性氰醇的有效方法，手性氰醇是许多精细化学品，农用化学品和药物合成中的重要组成部分。已知HNL的固定可提供鲁棒性，可重复使用性，并且在某些情况下还可以增强活性和选择性。我们通过交联酶聚集体（CLEA）法优化了褐藻（Balospermium montanum HNL）固定化的制备（BmHNL），并通过SEM对其进行了表征。使用CLEA-BmHNL进行了生物催化参数的优化，以从苯甲醛获得最高的％转化率和ee（S）-扁桃腈的ee。优化的反应参数为：反应时间20分钟，7 U CLEA-BmHNL，1.2 mM底物和300 mM柠檬酸盐缓冲液pH 4.2，合成了约99％ee和约60％转化率的（S）-扁桃腈。与其他CLEA-HNL不同，在CLEA-BmHNL生物催化中添加有机溶剂的ee％或产物转化率没有提高。CLEA-BmHNL可以成功地连续使用八个循环，而不会损失转化率或产物形成，并且可以进行五个循环，对映选择性几乎没有损失。在最佳的生物催化条件下，合成了11种不同的手性氰醇，其ee高达99％，转化率高达59％，但是不同产品的转化率和ee有所不同。与使用纯化的BmHNL相比，CLEA-BmHNL提高了（S）-扁桃腈合成的对映选择性。首次未使用BmHNL测试的九种醛首次使用CLEA-BmHNL转化为其相应的（S）-氰醇。在本文报道的十一种（S）-氰醇合成中，其中的八种尚未由任何CLEA-HNL合成。总的来说，这项研究显示了稳定，健壮和可回收的生物催化剂CLEA-BmHNL的制备，表征以及其在不同（S）-芳族氰醇合成中的生物催化应用。