Excess turbulence as a cause of turbohypobiosis in cultivation of microorganisms

Abstract

Abstract:The present review describes the influence of different types of mixing systems under excess turbulence conditions on microorganisms. Turbohypobiosis phenomena were described by applying a method for measurement of the kinetic energy of flow fluctuations based on the piezoeffect. It can be assumed that the shear stress effect (the state of turbohypobiosis) plays a role mainly when alternative mechanisms in cells cannot ensure a normal physiological state under stress conditions. Practically any system (inner construction of a bioreactor, culture and cultivation conditions, including mixing) requires its own optimisation to achieve the final goal, namely, the maximum product and/or biomass yields from substrate (Y P/S or/and Y X/S ), respectively. Data on the biotechnological performance of cultivation as well as power input, kinetic energy (e) of flow fluctuations, air consumption rate, rotational speed, tip speed, etc. do not correlate directly if the mixing systems (impellers-baffles) are dissimilar. Even the widely used specific power consumption cannot be relied upon for scaling up the cultivation performance using dissimilar mixing systems. A biochemical explanation for substrate and product transport via cell walls, carbon pathways, energy generation and utilisation, etc. furnishes insight into cellular interactions with turbulence of different origin for different types of microorganisms (single cells, mycelia forming cells, etc.

Effect of Turbulence on Nitrification Rate in Freshwater Column

“…At Re values greater than 4000 turbohypobiosis for Nitrobacter winogradskyi occurred. This relation between turbulent condition and microbial growth rate was also explained previously by Rikmanis et al (2007). Furthermore, a positive correlation between k and  was observed in this experimental series (r = 0.90, p = 0.014) ( Fig.5) which indicated turbulent effect on both k and  as they related to each other.…”

“…In contrast, strong turbulence can cause an adverse impact on microorganism by inhibiting microbial growth and metabolism, altering cell morphology, changing osmotic pressure, etc., which is known as turbohypobiosis. Such response of microbial cells to turbulence depends on the species 15) . In rivers, the degree of turbulence can range up to Re around 10 7…”

Sustainable Process for the Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Renewable Resources: A Simulation Study

“…The gas flow rate was continuously bubbled into the reactors at a superficial gas velocity ( U g ) under the limit for the transition from the homogeneous to the heterogeneous regime to avoid compromising the survival of the active biomass. , The transition superficial gas velocity ( U t ) was estimated according to Reilly’s eq U normalt = V small ε normalt ( 1 − ε t ) where V small [m s –1 ] is the velocity of small bubbles and ε t is the transition gas holdup, which can be estimated according to eqs and , respectively V small = 1 2.84 1 ρ normalg 0.04 σ 0.12 ε normalt = 0.59 B 1.15 ρ normalg 0.96 ρ normall σ 0.12 where ρ g [kg m –3 ] is the gas density, σ [N m –1 ] is the surface tension, B is determined experimentally, and ρ l [kg m –3 ] is the liquid density.…”

Critical analysis of engineering aspects of shaken flask bioreactors

“…The hyphae of fungi, due to long filaments, can be easily damaged by stirring, particularly in bioreactors with uneven stirring zones. The sensitivity of cells depends not only on stirring but also on the content of gas (aerated or nonaerated broth) and different liquid or solid dispersed components in liquid media (Rikmanis, Berzins, and Viesturs, 2007). Camacho et al (2007) used shaken flasks as model bioreactors to examine the effect of hydromechanical shear stress associated with intermittent fluid agitation on cell growth of red-tide Protoceratium reticulatum, a producer of yessotoxins.…”