Production and Characterization of First-Generation Bioethanol from Extracted Mesquite Pod (Prosopis juliflora (Sw.) DC.) Broth

The mesquite tree (Prosopis juliflora) is cultivated across 500,000 hectares in the semi-arid region of Brazil, primarily aimed at recovering degraded areas in the northeastern part of the country, which represents 15.7% of the national territory. However, its economic potential remains underutilized. Mesquite pods are particularly rich in carbohydrates, making them a promising raw material for bioethanol production. This study investigates the production of first-generation bioethanol from mesquite pods as feedstock. Mature pods were sourced from local producers in Sumé Town, located in the Cariri Paraibano microregion of Brazil. Sugar extraction from the mesquite pods involved hydration followed by pressing, with the extracted juice adjusted to a pH of 4.3 and soluble solids (°Brix) concentrations corrected to 20, 18, and 16. The juice was then subjected to fermentation using different yeast strains (fresh yeast, granular yeast, and FLNF CA-11) at a concentration of 25 g L−1. Alcoholic fermentation was carried out in a batch system, with measurements of cell concentration (biomass), soluble solids (°Brix), ethanol concentration (°GL), and pH taken at 2 h intervals over a 20 h period. The best physicochemical characterization of bioethanol was obtained using the LNF CA-11 yeast at 20 °Brix, producing a biofuel that met Brazilian legal standards set by the National Petroleum Agency (ANP). The bioethanol had a colorless appearance and was free of impurities, with a titratable acidity of 28.2 mg of acetic acid, electrical conductivity of 282.33 µS m−1, a specific mass of 809 kg m−3, an alcohol content of 95.5 °GL, a pH of 6.28, and no evaporation residue in 100 mL. Additionally, the highest bioethanol yield was achieved with broth fermented at 18 °Brix and LNF CA-11 yeast. These results highlight the potential of mesquite pods as a renewable energy alternative, especially relevant in the context of the global climate crisis; the growing need to reduce dependence on fossil fuels; and the need to reduce environmental problems; and they promote the added-value and use of this product.