Versatile modeling and optimization of fed batch processes for the production of secreted heterologous proteins with Pichia pastoris
Versatile modeling and optimization of fed batch processes for the production of secreted heterologous proteins with Pichia pastoris
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DOI：
10.1186/1475-2859-5-37
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发表时间：
2006-12-11
影响因子：
6.4
通讯作者：
Mattanovich, Diethard
中科院分区：
文献类型：
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作者：
Maurer, Michael;Kuehleitner, Manfred;Mattanovich, Diethard
背景：异源蛋白质的分泌既取决于生物量浓度，也取决于特定产物的分泌速率，而这又不是在不同的特定生长速率下是恒定的。由于加料分批过程通常不会在整个加料阶段保持一个稳定状态，因此用数学方法对其进行建模和优化并不是一件容易的事。结果：在Microsoft Excel电子表格中基于迭代计算建立了加料分批过程中的产品积累模型，并利用Solver软件对介质加料的时间进程进行了优化，以最大化体积生产率。最佳进料阶段为最大比生长速率下的指数进料阶段，然后是进料速率线性增加并逐渐降低比生长速率的阶段。后一阶段也可以通过变分的精确数学处理来建模，然而，在某些不确定的参数下，得到生长函数的显式形状。为了评价后者，需要一个数值最优搜索算法。增长函数的显式形状提供了其他证据，证明Excel模型产生的数据是正确的。在两个独立的补料分批培养中进行的实验评估结果表明，与优化的模型数据具有良好的相关性，体积生产率提高了2.2倍。结论：该方法的优点是易于使用和灵活，使用每个科学家和工程师都熟悉的软件，计算快速，使预测变得非常容易，使许多选择可以在计算机上快速测试。其他选择，如进一步的生物和技术限制，或针对特定生产力和生物质产量的不同功能，可以很容易地整合在一起。
Background: Secretion of heterologous proteins depends both on biomass concentration and on the specific product secretion rate, which in turn is not constant at varying specific growth rates. As fed batch processes usually do not maintain a steady state throughout the feed phase, it is not trivial to model and optimize such a process by mathematical means.Results: We have developed a model for product accumulation in fed batch based on iterative calculation in Microsoft Excel spreadsheets, and used the Solver software to optimize the time course of the media feed in order to maximize the volumetric productivity. The optimum feed phase consisted of an exponential feed at maximum specific growth rate, followed by a phase with linearly increasing feed rate and consequently steadily decreasing specific growth rate. The latter phase could be modeled also by exact mathematical treatment by the calculus of variations, yielding the explicit shape of the growth function, however, with certain indeterminate parameters. To evaluate the latter, one needs a numerical optimum search algorithm. The explicit shape of the growth function provides additional evidence that the Excel model results in correct data. Experimental evaluation in two independent fed batch cultures resulted in a good correlation to the optimized model data, and a 2.2 fold improvement of the volumetric productivity.Conclusion: The advantages of the procedure we describe here are the ease of use and the flexibility, applying software familiar to every scientist and engineer, and rapid calculation which makes predictions extremely easy, so that many options can be tested in silico quickly. Additional options like further biological and technological constraints or different functions for specific productivity and biomass yield can easily be integrated.