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求翻译 英译中,两段话,翻译好的加分~~~
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4. Other antifoam effects — fermentation In continuously agitated fermentation reactors the objective is rapid mass transfer of oxygen from entrained air bubbles to the fermentation broth without buildup of excess foam. In the absence of additives the air bubbles are frequently stabilized by proteins, some produced during the process, which adsorb at the bubble surfaces and form rather rigid films (see a recent review in this journal on stabilization of foams by proteins [13]). Such rigid films are undesirable both because they inhibit convection near the air–water surfaces, thereby reducing mass transfer rates, and because they stabilize foam. In one systeminvestigated by Calik et al. [26], silicone oils with hydrophobic particles did destabilize the foam but did not improve mass transfer because proteins were still able to occupy the air–water surfaces being generated continuously. They found that a particular surfactant with two polar groups to assure a bolaform configuration and loose packing at the interface andwith a short fluorocarbon chain (in addition to the hydrocarbon chain) to assure adequate surface activity was able to occupy the bubble surfaces and prevent formation of a rigid protein film. As a result, the surfaces remained mobile with good mass transfer rates. The loose packing also favored bubble coalescence, thereby preventing foam buildup. The literature of the past few years suggests that preventing foam buildup during fermentation is a widespread problem and that different antifoam methods may be required in different systems. A typical fermentation reactor consists of a lower agitated portion with individual dispersed bubbles and an upper foam layer of high gas content. Agitation continuously generates new bubbles, which rise to the foam layer and coalesce.Modeling this behavior in the presence of antifoam drops or particles is a challenge although initial efforts have been made [27]. [ Last edited by lsyfdcg on 2012-3-8 at 17:17 ] |
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money4u
至尊木虫 (著名写手)
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Mally89: 金币+1 2012-03-17 08:58:03
Mally89: 金币+30, 翻译EPI+1, 代lz发放BB,欢迎常来!~ 2012-03-20 12:24:40
Mally89: 金币+1 2012-03-17 08:58:03
Mally89: 金币+30, 翻译EPI+1, 代lz发放BB,欢迎常来!~ 2012-03-20 12:24:40
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你的金币还真是不多!虽专业不同,还是支持一下吧,专业方面就别有太高的要求了。 --------- 4. 其他消泡-发酵 连续搅拌发酵釜的目标是将夹带的气泡中的氧气快速大量的传入到发酵液中而不产生多余的泡沫。在没有添加剂的情况下,气泡很快就被蛋白质所稳定,工艺过程中产生的一些蛋白质吸附在气泡表面并形成一层相当硬的膜(参见本期刊最近关于蛋白质稳定泡沫作用的评述文章 [13])。因为它既抑制了气-液面的流动而降低物质传输率,同时也使泡沫更稳定,所以这层硬膜并非工艺所需要的。在Calik等所研究的一个系统中,含有厌水粒子的硅油确实使泡沫去稳定化,但却并未改善物质传输率,因为蛋白质仍能占据源源不断所产生的气泡表面。他们发现,既带可确保波拉型亲水结构及在界面处的疏松填充的两个极性团,又带可保证足够表面活性的短氟碳化合物链(除碳氢化合物链)的特定的表面活性剂,能够占据泡沫表面并防止硬蛋白质膜的形成,其结果是表面既保持很好的物质传输率, 疏松填充也使气泡易于破灭,从而防止泡沫的形成。最近几年的文献认为,防止发酵过程中泡沫的形成是广泛存在的问题,并且系统不同所要求的消泡方法也不同。典型的发酵釜由单独散泡的底部搅拌器,和高气体含量的泡沫层组成。连续搅拌新产生的气泡,上升到泡沫层后破灭。尽管已经做出了很多努力,但建立起目前消泡液或消泡粒子的作用模型,仍是一项挑战[27]。 |

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