Analysis of Mechanical Factors at Deep Cultivation

Abstract

Background. During the passage of technological processes, microorganisms are prone to the influence of various technological parameters, such as changes in temperature, pH of the culture medium, chemical, biological, and mechanical influences. To date, the degree of study of these effects is different. One is almost fully covered, while others are practically not studied at all. In some cases, the study of one factor leads to the emergence of new tasks and nuances in the study of others, since they are all inextricably interconnected. One of the least studied, but the most critical are mechanical effects. It has been unequivocally established that the rotation speed and the design of the mixing device affect the final product yield, but the nature and mechanisms of this effect remain unknown. Objective. The aim of the paper is to find out the effects of mechanical factors on microorganisms in the process of deep cultivation, in particular on recombinant bacteria and micelles, since they are the most sensitive to these factors, using literary data. And, on this basis, tasks for further research should be formulate. Methods. The research of scientists from different countries on the effects of the mechanical effects of mixing on microorganisms in the process of deep cultivation is studied and analyzed. Results. According to the literature data, dependencies of stirring rate on growth and microorganism status have been established, and recommendations for optimal mixer speeds for specific types of bacteria and micelles, which require further experimental confirmation, are provided. It has been found that increasing the size of cells increases their sensitivity to mechanical influences. The analysis of litera­ture has shown that viscosity decreases with increasing mixing intensity, which imposes a certain imprint on the kinetics of the process. It was detected that in conditions of deep cultivation with mechanical mixing the mycelial fungi, in contrast to bacterial organisms, is divided into relatively small segments that retain the ability to reproduce and accumulate biomass. Conclusions. The analysis of literature data showed that the mycelial fungi are the most sensitive to mechanical factors during deep cultivation. The optimum mixing speed for them is 120–150 rpm. It is necessary to modernize the design of the mixing device to optimize this process, to ensure the supply of nutrients and oxygen to all cells during deep cultivation in sufficient quantity for their development.

Keywords

• Microorganisms
• Deep cultivation
• Mechanical stress
• Shear stress
• Micromycetes
• Recombinant bacteria