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首页> 外文期刊>Biotechnology Progress >Effects of increasd impeller power in a production-scale aspergillus oryzae fermentation
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Effects of increasd impeller power in a production-scale aspergillus oryzae fermentation

机译：叶轮功率提高对米曲霉发酵生产规模的影响

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The goal in this study was to determine how increased impeller power affects enzyme expression in large-scale (80 m~3),fed-batch Aspergillus oryzae fermentations.An approximate 50% increase in average impeller power was achieved by increasing impleller diameter approximately 10%,while operatingat slightl reduced speed.Measured decreases in terminal(95%) mixing time show increased power improved bulk mixing.However,batches operated at increased power had lower recombinant enzyme productivity.Biiomass assays and image analysis tests showed no significant difference between"high power"and control batches,suggesting that slower growth,altered morphology,or increased hyphal fragmentation were not the cause of reduced porductivity.Off-linetests on the shear-thinning,highly viscous broth show oxygen limitation occurred after transport through the air-liquid interface andimply the limitation may involve bulk mixing.Specifically,oxygen transfer may be limited to a small zone surrounding each impeller.When this is the case,oxygen mass transfer will be determined by both impeller shear and fluid circulation,which have been characterized with the energy dissipation/circulation function (EDCF).EDCF values during control fermentations were approximately constant at 25kW m ~(-3) s~(-1),while EDCF values furing "high power"batches felllinearly form 40 to 15kW m~(-3) s~(-1).The point at which "high power"EDCF values drop below those in control fermentations corresponds almost exactly with the point at which product titer stops increasing.Thus,our findings duggest oxygen mass transfer was less efficient during the latter half of "high power"fermentations because of reductionsin impeller speed and subsequent decreases in EDCF values.This observation has clear implications during the scale-up of viscous fungal fermentations,implying that not only is the level of impeller power important,but also relevant is how this power is applied.
机译：本研究的目的是确定增加叶轮功率如何影响大规模（80 m〜3）喂食分批米曲霉发酵中的酶表达。通过将叶轮直径增加约10可将平均叶轮功率提高约50％ ％，同时以极低的速度运行。测得的末端混合时间减少（95％）显示功率提高了整体混合。但是，以更高的功率运行的批次降低了重组酶的生产率。生物量测定和图像分析测试表明，两者之间无显着差异。 “高功率”和控制批次，表明生长缓慢，形态改变或菌丝碎片增加并非降低产品性能的原因。对剪切稀化，高粘度肉汤的离线测试表明，氧气通过气液传输后出现了氧气限制界面可能暗示着可能涉及本体混合。具体而言，氧气转移可能会限制在每个离子周围的一个小区域在这种情况下，氧气的传质将取决于叶轮的剪切力和流体的循环，其特征在于具有能量耗散/循环功能（EDCF）。对照发酵过程中的EDCF值大约恒定在25kW m〜（ -3）s〜（-1），而“高功率”批次的EDCF值从40到15kW m〜（-3）s〜（-1）线性下降。“大功率” EDCF值降至低于这些值的点在对照发酵中，几乎完全与产物滴度停止增加的点相对应。因此，由于叶轮速度降低和随后的EDCF值降低，我们发现的结果表明，在“高功率”发酵的后半段，氧气质量转移效率较低。观察在粘性真菌发酵的规模扩大中具有明显的含义，这不仅意味着叶轮功率的水平很重要，而且这种功率的应用方式也很重要。

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