Effect of Lignocellulose Waste-Biomass Pretreatment of the Peels of Musa acuminata (Banana) and Ananas comosus (Pineapple) on the Production of Bioethanol via Solid-State Fermentation

The use of fruits both domestically and industrially generates waste from their discarded peels which may lead to environmental pollution and contamination. This work aims at evaluating the effects of chemical pre-treatment of biomass on the physicochemical properties and the effects of process parameters on the production of ethanol via solid-state fermentation. The biomass was dried, ground and subjected to chemical pretreatment using H₂SO₄ and NaOH. pH, total Titratable acidity (TTA), total soluble sugar (TSS), specific gravity (SG), and total reducing sugars (TRS) were carried out before and after the pretreatment of biomass. Acid hydrolysis and neutralisation of the biomass were then carried out before solid-state fermentation. A central composite design (CCD) was used to evaluate the effects of process parameters; fermentation time (X₁), pH (X₂), and biomass load (X₃) on the physicochemical and functional properties of the bioethanol produced. Before pretreatment, the TRS and TSS of pineapple and banana peel biomass were observed to be 16.67 & 5.36% and 8 & 5%Bx respectively. For acid pretreatment, pineapple peel biomass had higher TRS and TSS ranging from 20.69% - 30.0% and 10% - 21%Bx compared to banana peel biomass with TRS and TSS ranging from 14.39% - 21.8% and 9.9% - 14.9%Bx respectively. Whereas, for alkaline pretreatment, pineapple biomass had TRS and TSS ranging from 13.71% - 19.35% and 10% - 17.5%Bx while banana biomass had higher yields of TSS ranging from 10% - 16.5%Bx and TRS ranging from 10.79% - 19.98%. The optimum fermentation conditions for Banana Peel Biomass were fermentation time (48.88 h), pH (6.11), and biomass load (21.96 g/ml); with ethanol conc., density, TRS, and TSS of 2.56%, 1.025 g/ml, 13.93% and 2.59%Bx respectively from Banana biomass pretreated with acid. While for Pineapple Peel Biomass, the optimum conditions were; fermentation time (34.51 h), pH (4.82), and biomass load (24.0 g/ml) with ethanol conc., density, TRS and TSS of 2.42%, 1.015 g/ml, 37.72% and 5.61%Bx respectively from Pineapple biomass pretreated with acid. This study showed that chemical pretreatment has a positive impact on the physicochemical properties of fruit biomass with acid pretreatment being the most effective in the release of sugars and production of bioethanol.