Potential of Strawberry Leaves with Biostimulants: Repository of Metabolites and Bioethanol Production

To understand the potential uses of strawberry leaves and their application in the industrial sector, it is important to study their metabolic and lignocellulosic profile. The objective of the study was to characterize the metabolic profile of strawberry leaves grown with biostimulants and to verify whether this by-product can be utilized as a matrix for bioethanol production. The eight treatments studied were the absence and presence of biostimulants, as follows: arbuscular mycorrhizal fungi (AMF), Ascophyllum nodosum (AN), Trichoderma harzianum (TH), AMF + AN, AMF + TH, AN + TH, and AMF + AN + TH. Treatments were applied monthly, either manually (AMF) or with a micropipette (AN and TH), from June 2023 to March 2024. Hydrogen nuclear magnetic resonance (1H NMR) analysis identified 11 metabolites in the leaves, including 5 amino acids, 4 organic acids, and 2 carbohydrates, which may be of industrial interest. The leaves were used for bioethanol production through saccharification with cellulolytic enzymes, followed by fermentation with Saccharomyces cerevisiae. Enzymatic hydrolysis resulted in a total reducing sugar content of 21.12 g·L−1. Alcoholic fermentation yielded 8.97 g·L−1 of bioethanol in 12 h, which corresponds to 45.48 L·t−1 of dry leaves. In conclusion, regardless of biostimulation, strawberry leaves are an important repository of metabolites that can be used as raw material in different processes. Additionally, the leaves are suitable as raw material for bioethanol production in a biorefinery concept.