Optimized Tip-Sonication Temperature and Mixing using Finite Element
Modeling for High-Yield Bacterial Cell-Free Extract
Abstract
Optimal tip sonication settings, namely tip position, input power, and
pulse durations, are necessary to ensure proper mixing and maintain
solution temperature below a critical temperature. This is significant
for temperature sensitive procedures like preparation of viable cell
extract for in vitro protein synthesis. In this paper, the optimum tip
immersion depth is estimated which ensures maximum mixing thereby
enhancing thermal dissipation of local cavitation hotspots inside the
sonication tube; from modeled velocity field streamlines this is found
at immersion depths between 20-30% height below the liquid surface. A
simplified finite element (FE) heat transfer model is presented and
validated experimentally with (R2 > 97%) which can predict
the temperature rise over time in a tip-sonicated vessel. This model is
used to observe the effect of temperature rise on cell extract
performance of E. coli BL21 DE3 star strain and estimate the temperature
threshold. From the combined heat map of yield and temperature it is
observed that yield is correlated with final steady state temperature.
Relative yields in the top 10% are observed for solution temperatures
maintained below 32°C; this reduces below 50% relative yield at
temperatures above 47°C. To extend utility of these finite element
models to other temperature sensitive sonication processes, we also
present a generalized workflow for direct simulation using the FE code
as well as master plots for estimation of sonication parameters (power
input and pulse settings) without need of running the code.