CONICET | Buscador de Institutos y Recursos Humanos

Lignocellulosic biomasses, such as agricultural and forest residues, represent an abundant, renewable, and low-cost resources to produce biofuels, chemicals, and polymers. The recalcitrant nature of lignocellulosic biomass is the major issue for its exploitation in biotechnological processes. Physicochemical pretreatments are used to improve the bioconversion of this type of biomass, but they could generate toxic by-products, as furan and phenols, that could inhibit several biological processes. In this study, 40 fungal strains were analyzed for their capability to grow with different concentrations of furfural (F) derived from dehydration of hemicellulosic carbohydrates, and the lignin derivatives vanillin (V), 4-hydroxybenzaldehyde (H), and syringaldehyde (S). Growth performance of fungal strains was analyzed at different concentrations of the inhibitors, as single molecules or mixes of them. The high-throughput screening performed with the 40 fungal strains confirmed the strong toxicity of phenolic aldehydes and furfural. Furthermore, results showed that in the presence of single molecule solutions, the growth inhibition depends not only on the nature and concentration of the assayed compounds but also on the presence of glucose as co-substrate. Byssochlamys nivea MUT 6321 showed promising growth performance when the inhibitors were used as single molecules and it was the only fungus that could grow when the four molecules were simultaneously present in culture media. The capacity of B. nivea to degrade F and the phenolic aldehydes was analyzed by monitoring the residual concentration of each compound in the media using HPLC. B. nivea was able to completely degrade furfural in 24 h. As regards the phenolic aldehydes, results showed that 99 % of H, S, and V were transformed after 4, 9, and 11 days, respectively. B. nivea completely degraded V, H, and S present in the mix of the three molecules (MP mix). However, when F was present in the mix (MPF), a faster and preferential consumption of F instead of phenolic aldehydes was observed. Furthermore, V, H, and S in the MPF mix showed a delay in their transformation in comparison to MP mix. This finding could be explained considering that F and the phenolic aldehydes are molecules with different chemical structures and may then require the activation of different catabolic mechanisms, demanding time and resources to accomplish it. This preference in toxic molecules transformation is a promising feature of B. nivea, considering that phenolic compounds, such as S and V, were reported to have less impact than F on biotechnological processes. In conclusion, this study highlights the importance to explore fungal biodiversity to discover new strains for future biotechnological applications and provides important information for the use of B. nivea to remove toxic compounds present in pretreated lignocellulosic biomass that could potentially lead to the enhancement of biofuels and chemicals production.

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