Microfluidic bubbler facilitates near complete mass transfer for sustainable multiphase and microbial processing

Abstract

A microfluidic device (channels <70 μm) was utilized to create micro-scale bubbles to significantly increase mass transfer efficiency at low flow rates. The convergence of one gas and two liquid channels at a Y-junction generates bubbles via cyclic changes in pressure. At low flow rates, the bubbles had an average diameter of 110 μm, corresponding to a volumetric mass transfer KL a of 1.43 h(-1) . Values of KL a normalized per flow rate showed that the microbubbler had a 100-fold increased transfer efficiency compared to four other commonly used bubblers. The calculated percentage of oxygen transferred was approximately 90%, which was consistent with a separate off-gas analysis. The improved mass transfer was also tested in an algae bioreactor in which the microbubbler absorbed approximately 90% of the CO2 feed compared to 2% in the culture with an alternative needle bubbling method. The microbubbler yielded a cell density 82% of the cell density for the alternative needle tip with an 800-fold lower flow rate (0.5 mL/min versus 400 mL/min) and a 700-fold higher ratio of biomass to fed carbon dioxide. The application of microfluidics may transform interfacial processing in order to increase mass transfer efficiencies, minimize gas feeding, and provide for more sustainable multiphase processes. Biotechnol. Bioeng. 2016;113: 1924-1933. © 2016 Wiley Periodicals, Inc.

Bioreactor Operating Strategies for Improved Polyhydroxyalkanoate (PHA) Productivity

“…This is currently being addressed at the lab scale, and several promising high-productivity cultivation systems have been developed for both mcl-PHA and scl-PHA production that use only air [61,62,97,103,176] as well as in industrial-scale bioreactors [139,145]. Although other methods for increasing the driving force of oxygen transfer are available, including pressure [115], microbubble devices [118], and microfluidic devices [119], they have not yet been applied on a large scale.…”

“…Other approaches involve increasing a using microbubbler devices [118]. Although not used in a PHA production context, Baker et al (2016) used a microfluidic device to generate bubbles with an average diameter of around 110 μm, and obtained nearly ideal mass transfer (i.e., 90% of the oxygen in the gas phase was delivered to the liquid phase), which is a promising development for industrial biotechnology in general [119].…”

Three-Stage Shear-Serrated Aerator Broke CO2 Bubbles To Promote Mass Transfer and Microalgal Growth

“…A Y-junction microfluidic device was utilized to create microbubbles via cyclic changes in pressure. The microbubble absorbed approximately 90% of the CO 2 feed when the microfluidic device was installed in an algal bioreactor . Tesař et al developed a novel jet oscillator aerator, in which microbubbles were generated via pressure difference and gas reflux.…”