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Crop Biotech Update

Discovery of Bacterial Mechanisms Leads to Cytotoxicity Tolerance in Biofuels

June 20, 2019

A team of scientists from the Lawrence Livermore National Laboratory (LLNL) and the Joint BioEnergy Institute published their new findings about identifying bacterial isolates and strains that are that are tolerant to high levels of two widely used Imidazolium ionic liquids or IILs. Specifically, they worked with two IIL tolerant Bacillus isolates and IIL tolerant E. coli laboratory strain. IILs are reagents that extract sugars from plants. In particular, a nearly limitless supply of sugar come from the plant cell walls. These are used to make biochemicals and biofuels. But during the treatment of biomass using IIL, residuals contaminate the sugar and bacterial and yeast growth are repressed. Bacterial and yeast growths are needed for the biochemical production of biofuels.

With the new discovery by the LLNL Team, a mechanism in the bacteria was found to withstand manipulation to promote IIL tolerance which resulted to a resistance to the cytotoxic effects of IIL. This involved an identified membrane transporter, or pump, in the bacteria responsible for exporting the toxic IIL. The scientists also identified two cases wherein this pump gene contained alterations in the RNA sequence of a regulatory guanidine riboswitch. Guanidine is a toxic byproduct of normal biological processes. The unmodified riboswitch was found to interact with guanidine, leading to conformational changes that cause the pump to switch on and make the bacterial cells IIL-resistant.

This may enable a more efficient biochemical production since, at an industrial level, it is essential to find less-harmful reagents and microbes that are resistant to cytotoxic effects. The results also overcome a key gap in biofuels and industrial biochemical production processes. Based on this new knowledge, new genetic engineering strategies can be proposed to improve the conversion of cellulosic sugars into biofuels and biochemicals in processes where a low concentration of ionic liquids exceed bacterial tolerance.

Read more from the Journal of Bacteriology.