Filamentous fungi detecting and disarming furfural

Furfural is a small furan compound commonly found in lignocellulosic waste. Furfural greatly inhibits the growth of microorganisms, thus the presence of furfural makes it extremely cumbersome to utilize lignocellulosic waste as a renewable carbon source for production in biomanufacturing.

DTU BioBuilders are engineering a filamentous fungus to detect and convert furfural into harmless compounds. To detect furfural, we constructed a Synthetic Expression System (SES) containing a synthetic promoter and a synthetic transcription factor (sTF). In addition, we identified a promoter native to A. niger that is highly inducible in response to furfural and can serve as a furfural biosensor. With our engineered fungus, we aim to unlock the potential of lignocellulosic waste as a cheap and renewable carbon source in fermentation, thereby promoting sustainable production and responsible use of our shared resources on Earth.

The Problem

Depletion of resources and growing piles of waste

Detecting furfural by modifying synthetic transcription factors (sTFs)

As a starting point, we constructed sTFs with a corresponding synthetic promoter using the benzoic acid-sensing sTF, sBAD, which has been developed in yeast. Since the structure of benzoic acid resembles that of furfural, we anticipated sBAD could be used as a furfural-sensing biosensor. We introduced mutations in the sensing domain of sBAD, that we predicted would improve the binding affinity to furfural using Rosetta software. This system is one of very few reported SESs for filamentous fungi and the first in iGEM history!

Detecting furfural using a native promoter

We identified a gene in A. niger that is highly upregulated in response to furfural. We successfully constructed a plasmid expressing mCherry from the promoter of this upregulated gene and results indicate that mCherry expressed from the plasmid was also upregulated in response to furfural. Nonetheless, further investigations are needed to confirm that this is the first fully functional furfural biosensor.