Graduate Program of Chemical Engineering, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil.
Graduate Program of Chemical Engineering, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil; Federal Institute of Education, Science and Technology of São Paulo, Campus Capivari, Capivari, SP, 13360-000, Brazil.
Enzyme Microb Technol. 2020 Sep;139:109587. doi: 10.1016/j.enzmictec.2020.109587. Epub 2020 Apr 30.
The hydrodynamic environment in bioreactors affects the oxygen transfer rate and the shear conditions during microbial cultivations. Therefore, assessment of the effect of the hydrodynamic environment on cellular morphology can contribute to favoring the production of metabolites of interest. The aim of this work was to use image analysis in order to quantify the fragmentation of Aspergillus niger pellets in a conventional bioreactor operated using different impeller speeds, air flow rates, and impeller configurations including Rushton turbines and Elephant Ear impellers, with evaluation of the influence of the hydrodynamic environment on the production of cellulolytic enzymes. An empirical kinetic model was proposed to describe the dynamics of pellet fragmentation and quantify the shear conditions. The results showed that the agitation speed affected the dynamics of pellet fragmentation in two ways, by accelerating the damage process and by increasing the magnitude of the fragmentation. Both endoglucanase and β-glucosidase production exhibited a linear relationship with the pellet fragmentation percentage, which was directly related to the shear conditions. Interestingly, β-glucosidase production was favored under high shear conditions, while the highest endoglucanase production occurred under low shear conditions. These findings may be useful for defining suitable systems and operating conditions for the production of metabolites including enzymes in bioreactors, as well as defining conditions that favour a specific pre-determined enzyme cocktail.
生物反应器中的流体动力学环境会影响微生物培养过程中的氧传递速率和剪切条件。因此，评估流体动力学环境对细胞形态的影响有助于促进感兴趣代谢产物的生产。本工作旨在使用图像分析来量化黑曲霉颗粒在使用不同搅拌速度、空气流量和搅拌器配置（包括 Rushton 涡轮和象耳叶轮）的传统生物反应器中的破碎情况，评估流体动力学环境对纤维素酶生产的影响。提出了一个经验动力学模型来描述颗粒破碎的动力学，并量化剪切条件。结果表明，搅拌速度通过加速颗粒损伤过程和增加破碎程度来影响颗粒破碎动力学。内切葡聚糖酶和β-葡萄糖苷酶的生产均与颗粒破碎百分比呈线性关系，而颗粒破碎百分比与剪切条件直接相关。有趣的是，β-葡萄糖苷酶的生产在高剪切条件下得到促进，而内切葡聚糖酶的最大生产则发生在低剪切条件下。这些发现对于在生物反应器中定义适合的系统和操作条件以生产包括酶在内的代谢产物，以及定义有利于特定预定酶混合物的条件可能是有用的。
