Effect of Selenium Enrichment in a Sugarcane Hemicellulose Biorefinery Integrated into the First-generation Ethanol Process.

Integration of first- and second-generation ethanol production is a strategy to strengthen the economic viability of individual processes and the overall viability of biorefineries. The sharing of storage, fermentation, distillation, and energy infrastructure is an important advantage of process integration. Furthermore, integration contributes to the utilization and valorization of all products and by-products, which is key to the success of a biorefinery. Selenium-enriched yeasts have aroused great interest as mineral sources for their high bioavailability and low toxicity. This study aimed to evaluate the effect of selenium on yeast cell growth and production of ethanol and xylitol from hydrolyzed hemicellulosic biomass and sugarcane molasses. For this, cultures were enriched with sodium selenite at concentrations ranging from 1 to 20 mg/L. A miniaturization protocol was used to simulate biorefinery production of first-generation ethanol. The yeasts Spathaspora passalidarum and Kluyveromyces marxianus were able to grow under all tested conditions. The maximum specific growth rate, lag time, and biomass production were influenced by selenium concentration. S. passalidarum provided the best fermentation results, with 77.9% ethanol fermentation efficiency, 24.7% xylitol fermentation efficiency, 0.25 g/g glycerol yield, and 3.3 g cell biomass production. K. marxianus accumulated 122.92 mg selenium/kg biomass, whereas S. passalidarum had a maximum accumulation of 37.40 mg selenium/kg biomass. Yeasts also accumulated other minerals. Therefore, S. passalidarum has great potential as a biological platform and the results of this work could be useful for supporting the development of integrated processes to produce ethanol-, xylitol-, glycerol-, and selenium-enriched yeast products. [ABSTRACT FROM AUTHOR]