Fermentation profiles of the yeast Brettanomyces bruxellensis in d‐xylose and l‐arabinose aiming its application as a second‐generation ethanol producer

Abstract

The yeast Brettanomyces bruxellensis is able to ferment the main sugars used in firstgeneration ethanol production. However, its employment in this industry is prohibitive because the ethanol productivity reached is significantly lower than the observed for Saccharomyces cerevisiae. On the other hand, a possible application of B. bruxellensis in the second-generation ethanol production has been suggested because this yeast is also able to use D-xylose and L-arabinose, the major pentoses released from lignocellulosic material. Although the latter application seems to be reasonable, it has been poorly explored. Therefore, we aimed to evaluate whether or not different industrial strains of B. bruxellensis are able to ferment D-xylose and Larabinose, both in aerobiosis and oxygen-limited conditions. Three out of nine tested strains were able to assimilate those sugars. When in aerobiosis, B. bruxellensis cells exclusively used them to support biomass formation, and no ethanol was produced. Moreover, whereas L-arabinose was not consumed under oxygen limitation, D-xylose was only slightly used, which resulted in low ethanol yield and productivity. In conclusion, our results showed that D-xylose and L-arabinose are not efficiently converted to ethanol by B. bruxellensis, most likely due to a redox imbalance in the assimilatory pathways of these sugars. Therefore, despite presenting other industrially relevant traits, the employment of B. bruxellensis in second-generation ethanol production depends on the development of genetic engineering strategies to overcome this metabolic bottleneck.

A genome-informed higher rank classification of the biotechnologically important fungal subphylum Saccharomycotina

“…2015 , Tiukova et al 2019 ) and as a bioethanol producer ( Steensels et al . 2015 , da Silva et al 2020 ).…”