Chemical Analysis and Antioxidant Capacity of the Stages of Lignocellulosic Ethanol Production from Amazonian Fruit Industrial Waste

Abstract: The production of ethanol from wastes resulting from the process of growing Amazonian fruit is a little-explored approach, in which unknown chemical compounds are released with potential for industrial application. This work aimed to produce lignocellulosic ethanol from waste from Amazonian fruit farming and to chemically characterize the stages of the process. The wastes (açaí seeds, mango peel, and peach palm peel) were pretreated with 1% to 5% H2SO4 and 15% solids; the resulting solid fraction was enzymatically hydrolyzed with cellulase at 20 FPU, and the liquid fraction (liqueurs) and enzymatic and fermented hydrolysates produced were chemically characterized. Via HPLC for sugars and fermentation inhibitors, we determined the antioxidant capacities and total phenolic compounds. The liquors from the pretreatment of açaí seeds released the most significant amount of glucose, while in the hydrolyzed solid fractions, the mango peel produced the highest glucose content. Among the fermented liquors, the highest ethanol content was the açaí seed at 15 and 5% (0.183–0.276 g/L). High glucose levels were produced (0.09–25.05 g/L) and provided ethanol levels that can be improved (0.061–10.62 g/L), in addition to liquors and hydrolysates with interesting amounts of phenolic compounds (14.04–131.87 mg EAG/g DM) and high antioxidant capacities (417.78–2774.07 mmol TEAC/g), demonstrating that these wastes can have other applications in addition to ethanol production.