| 1. | The a - aldc can decarboxylate a - acetolactate directly to form acetoin without the formation of diacetyl
15ppm就会产生类似馊饭的味道。 |
| 2. | Aldc information technology - data compression algorithm - adaptive lossless data compression algorithm for information interchange
信息技术.数据压缩算法.信息交换自适应无损数据压缩 |
| 3. | The primary structure is unchanged in the evolved a - aldc , which implies that the catalytic mechanism of the evolved enzyme remained the same
但该酶的基本结构没有改变，暗示该突变酶的催化机理与天然酶相同。 |
| 4. | Therefore , we selected the method of directed evolution to modify the a - aldc gene in order to obtain the mutants with high enzyme activity in low temperature
为此，我们采用定向进化的方法对酶基因进行改造，以期获得更适合于啤酒发酵的表达- aldc的工程菌株。 |
| 5. | By adding a - aldc to the fermenting wort , a - acetolactate will be removed as soon as it is formed , thereby which can avoid the formation of diacetyl and reduce or even skip the period for maturation
如在啤酒主发酵阶段或熟化阶段加入- aldc酶制剂，则可大大缩短啤酒熟化期，从而提高设备利用率和节省能源。 |
| 6. | Because the catalytic site of a - aldc has not been certified and the catalytic mechanism has to be also further proved , it is difficult to enhance the enzyme activity in low temperature by the rational design
由于- aldc的活性部位尚未完全确定，催化机理也需进一步证实，在这种条件下通过酶的合理化设计来提高酶在低温下的活力有一定困难。 |
| 7. | Both the ph stability and thermostabilization of evolved a - aldc were higher than those of wild - type enzyme . this mutant is more suitable for the industrial production of beer . the replacement of arg results in partial disruption of the a - helix
并对天然酶和突变酶的酶学性质进行了分析，结果表明突变酶的ph稳定性和热稳定性均优于天然酶，更适合啤酒发酵。 |
| 8. | Approximately 7000 colonies were screened . one mutant was obtained , and its enzyme activity is 2 . 09 - fold higher than that of wild - type a - aldc in low temperature . the two nucleotide substitutions were occurred in the evolved a - aldc gene
根据定向进化的基本思想，我们利用易错pcr的方法，筛选了近7000个菌落，最终得到了一株在低温下也有较高酶活力的突变体。 |
| 9. | However , the normal temperature of fermentation is 10 c and the optimum temperature of a - aldc is 30 - 40 c , which indicted that the activity of a - aldc in the normal temperature of fermentation is 15 - 20 % of that in the optimum temperature
但是在啤酒生产中，正常的发酵温度约为10 ，而该酶的最适温度为30 40 ，在正常发酵温度下，酶活力只能达到最高活力的15 20 。 |
| 10. | It clearly allows us to engineer enzymes with novel functions and features by strategies , such as error - prone pcr , dna shuffling and stagger extension process ( step ) , when very little is known about spatial configuration of proteins . therefore millions of years in nature can in principle be accomplished in the test within several years . according to the basic idea of directed evolution , we modified the a - aldc gene by error - prone pcr
它不需要事先了解酶的空间结构和催化机制，而通过在体外模拟自然进化机制(随机突变，重组和自然选择) ，利用易错pcr ， dna改组，交错延伸等方法，改造酶基因，定向选择(或筛选)有价值的非天然酶，短期内在试管中完成在自然界需要几百万年的进化过程。 |
