Amanullah A, Blair R, Nienow AW, Thomas CR
Centre for Bioprocess Engineering, School of Chemical Engineering, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Biotechnol Bioeng. 1999 Feb;62(4):434-446. doi: 10.1002/(sici)1097-0290(19990220)62:4<434::aid-bit6>3.0.co;2-d.
The effects of agitation on fragmentation of a recombinant strain of Aspergillus oryzae and its consequential effects on protein production have been investigated. Constant mass, 5.3-L chemostat cultures at a dilution rate of 0.05 h-1 and a dissolved oxygen level of 75% air saturation, have been conducted at 550, 700, and 1000 rpm. These agitation speeds were chosen to cover a range of specific power inputs (2.2 to 12 kW m-3) from realistic industrial levels to much higher values. The use of a constant mass chemostat linked to a gas blender allowed variation of agitation speed and hence gas hold-up without affecting the dilution rate or the concentration of dissolved oxygen. The morphology of both the freely dispersed mycelia and clumps was characterized using image analysis. Statistical analysis showed that it was possible to obtain steady states with respect to morphology. The mean projected area at each steady state under growing conditions correlated well with the 'energy dissipation/circulation" function, [P/(kD3tc)], where P is the power input, D the impeller diameter, tc the mean circulation time, and k is a geometric constant for a given impeller. Rapid transients of morphological parameters in response to a speed change from 1000 to 550 rpm probably resulted from aggregation. Protein production (alpha-amylase and amyloglucosidase) was found to be independent of agitation speed in the range 550 to 1000 rpm (P/V = 2.2 and 12.6 kW m-3, respectively), although significant changes in mycelial morphology could be measured for similar changes in agitation conditions. This suggests that mycelial morphology does not directly affect protein production (at a constant dilution rate and, therefore, specific growth rate). An understanding of how agitation affects mycelial morphology and productivity would be valuable in optimizing the design and operation of large-scale fungal fermentations for the production of recombinant proteins. Copyright 1999 John Wiley & Sons, Inc.
研究了搅拌对米曲霉重组菌株破碎的影响及其对蛋白质生产的后续影响。在550、700和1000 rpm的转速下，以0.05 h-1的稀释率和75%空气饱和度的溶解氧水平，在5.3-L恒化器中进行了恒定质量培养。选择这些搅拌速度是为了涵盖从实际工业水平到更高值的一系列特定功率输入（2.2至12 kW m-3）。使用与气体混合器相连的恒定质量恒化器可以改变搅拌速度，从而改变气体滞留率，而不会影响稀释率或溶解氧浓度。使用图像分析对自由分散的菌丝体和菌团的形态进行了表征。统计分析表明，在形态方面有可能获得稳态。生长条件下每个稳态的平均投影面积与“能量耗散/循环”函数[P/(kD3tc)]密切相关，其中P是功率输入，D是叶轮直径，tc是平均循环时间，k是给定叶轮的几何常数。从1000 rpm到550 rpm的速度变化导致形态参数的快速瞬变可能是由聚集引起的。发现在550至1000 rpm范围内（P/V分别为2.2和12.6 kW m-3）蛋白质产量（α-淀粉酶和淀粉葡糖苷酶）与搅拌速度无关，尽管在搅拌条件有类似变化时可以测量到菌丝体形态的显著变化。这表明菌丝体形态不会直接影响蛋白质产量（在恒定稀释率以及因此恒定的比生长速率下）。了解搅拌如何影响菌丝体形态和生产力对于优化用于生产重组蛋白的大规模真菌发酵的设计和操作将是有价值的。版权所有1999约翰威立父子公司。
