Physicochemical characterization of residual biomass (seed and fiber) from açaí (Euterpe oleracea) processing and assessment of the potential for energy production and bioproducts

Acai residual biomass can be a potential source for a wide range of applications, especially biotechnological, such as solid-state fermentation processes and production of fermentable sugars (mannose), such as raw material for food, pharmaceutical, and other industries. Fiber and seed of acai fruit (Euterpe oleracea) were characterized, after pulp extraction, in samples collected at different maturation stages (seasonality). The seed contained a remarkable amount of mannose (75%) followed by glucose (6%) and galactose (2%), with mannan as the main polysaccharide. The fiber was a lignocellulosic biomass containing glucose (30%) and xylose (19%). Mannan and cellulose in the seed and fiber, respectively, were the polysaccharide responsible for the crystallinity of both materials, with the seed showing higher values. The period of fruit harvesting (winter or summer crops) influenced the maturity and chemical composition of the residues, which had higher crystallinity in the summer season. Hydrothermal treatment was very efficient for fiber but failed for seed, indicating a high recalcitrance of mannan in acai seed.