On 1^st May this year, Loughborough University, University of Bath and Perlemax Ltd, received funding from Innovate UK and BBSRC for a project, (supported from Industrial Strategy Challenge Fund), to investigate the continuous extraction capabilities of microbubbles in a fermentation reactor operated at 60-65 ^oC, to improve cellulosic biofuel production.

Cellulosic biofuels have attracted significant attention recently as a sustainable solution to the world’s growing energy demands.

One of the main issues pertaining to fermentation of sugars to alcohol is the decline in performance of fermentative organisms at high product concentrations, due to the inhibitory effects of the product on the producing organism. This is particularly true with thermophilic bacteria which grow at relatively high temperatures (50-70C). However, some of these bacteria are particularly well suited to grow on renewable, lignocellulosic feedstocks, so an effective way to continuously remove the alcohol from the fermentation broth would make the lignocellulose to ethanol process more economic.

When using a gas to strip material from a liquid, or to deliver material from a gas to a liquid the most important feature for determining the mass transfer rate is the ratio of bubble surface area to volume. For the same volume of gas, smaller bubbles will have a higher surface area than larger bubbles and should therefore be more effective at stripping ethanol from a solution.  However, smaller bubbles could potentially be more damaging to the bacteria, so their overall benefits cannot be assumed.

In this project we will be working collaboratively with University of Bath and Perlemax Ltd. To develop devices to allow continuous microbubble generation and extraction in a small-scale bioreactor, demonstrate its effectiveness in simulated mixtures containing ethanol but no cells and finally investigate its effectiveness for continuous ethanol extraction from fermentations containing bacteria growing at 60-65C.  The effects on the bacteria will be monitored and conditions modified to achieve optimal performance.

Dr Hemaka Bandulasena, Principal Investigator at Loughborough University, said:

“Depletion of fossil fuels and global warming have led to intense research on renewable energy sources that are sustainable and competitive. Biofuels produced from lignocellulosic biomass offer a promising solution, if costs can be reduced.”

For further information, please contact: Dr Hemaka Bandulasena

Top photograph: Joe Calverley (PhD researcher in Dr Bandulasena’s research group) working on the microbubble extraction rig at Loughborough University.

Left photograph: Experimental rig for continuous product removal from fermentation.