Airlift bioreactor for biological applications with microbubble mediated transport processes

Abstract

Microbubbles increase the mixing efficiency in airlift bioreactors. Dispersal of gas phase throughout the ALR occurs with decreasing the bubble size. Phase slip velocity decreases with smaller bubble size as gas rise rate decreases. a b s t r a c tAirlift bioreactors can provide an attractive alternative to stirred tanks, particularly for bioprocesses with gaseous reactants or products. Frequently, however, they are susceptible to being limited by gas-liquid mass transfer and by poor mixing of the liquid phase, particularly when they are operating at high cell densities. In this work we use CFD modelling to show that microbubbles generated by fluidic oscillation can provide an effective, low energy means of achieving high interfacial area for mass transfer and improved liquid circulation for mixing.The results show that when the diameter of the microbubbles exceeded 200 mm, the "downcomer" region, which is equivalent to about 60% of overall volume of the reactor, is free from gas bubbles. The results also demonstrate that the use of microbubbles not only increases surface area to volume ratio, but also increases mixing efficiency through increasing the liquid velocity circulation around the draft tube. In addition, the depth of downward penetration of the microbubbles into the downcomer increases with decreasing bubbles size due to a greater downward drag force compared to the buoyancy force. The simulated results indicate that the volume of dead zone increases as the height of diffuser location is increased. We therefore hypothesise that poor gas bubble distribution due to the improper location of the diffuser may have a markedly deleterious effect on the performance of the bioreactor used in this work.

Spatial and temporal scaling of unequal microbubble coalescence

“…In the environmental industry, the most common application of microbubbles is in the water and waste-water treatment [9][10][11][12][13] . Important micro/nano bubble technologies involved in lab-on-a-chip 14,15 , airlift bioreactor 16,17 , fluorinations 18 , hydrogenation 19,20 and DNA analysis 21 are attracting more and more attention. Bubble coalescence is a common phenomenon in different types of applications as the surface areas when bubbles are in touch tend to minimize.…”

Small-Scale Bioreactor for Sterile Hydroponics and Hairy Roots: Metabolic Diversity and Salicylic Acid Exudation by Hairy Roots of Hyoscyamus niger

“…The drawback of micro and nano bubble generators is that they require high-pressure pumps. Furthermore, in airlift mode the liquid velocity decreases with bubble radius for bubbles smaller than 100 µm [50]. Because micro bubbles are smaller than 50 µm and nano bubbles are smaller than 200 nm [49], micro bubbles and especially nano bubbles are less suitable to drive liquid transfer in airlift bioreactors.…”

Permissible parameters for the circulation rate of the sludge mixture in airlift reactor-clarifier with suspended layer

“…In recent years, airlift reactors are widely used for a variety of biological and chemical processes [1][2][3]. In particular, these facilities may contain activated sludge and serve for aerobic wastewater treatment [4,5].…”