Ethanol production from Lycoris radiata Herbert (Amarylllidaceae) residues as a new resource

The large quantities of Lycoris radiata Herbert (Amarylllidaceae) residues, left after the extraction of alkaloids from the bulbs, could threaten the environment if not properly disposed. Therefore, the aim of this research is to investigate the feasibility of bioconversion of L. radiata Herbert residues to ethanol through batch fermentation. In L. radiata Herbert residues, the average contents (g kg−1) of non-structural carbohydrates, crude fiber, crude protein, ash, and lignin are 485.1, 177.3, 124.7, 108.9, and 91.0, respectively. Five commercial enzymes (β-glucanase, pectinase, xylanase, phytase and cellulase) were employed in pretreatment process and ethanol bioconversion was evaluated with three yeasts (Saccharomyces cerevisiae, osmotolerant S. cerevisiae and genetically engineered S. cerevisiae constructed to use cellobiose). The results showed that pretreament by β-glucanase successfully facilitated the penetration of α-amylase into ground material. After residues pretreatment by 10 g kg−1 of β-glucanase for 14 h at 50 °C, the viscosity decreased from 1135 to 59 Pa·s which was equivalent to that obtained by the combined whole five enzymes. Further experiments proved that osmotolerant S. cerevisiae was desirable for ethanol production from Lycoris radiate Herbert residues. The results are helpful to develop non-grain bioethanol production.

► The residuals from Lycoris radiata Herbert bulbs were able to generate 55% ethanol concentrations by yeast fermentation.
► Treatment with xylanase significantly reduced the viscosity more than 10-fold and improved fermentable sugars by ∼35%.
► An osmotolerant Saccharomyces cerevisiae strain that showed improved fermentation rates was identified.