Initial Study of Fungal Bioconversion of guishe (Agave lechuguilla Residue) Juice for Bioherbicide Activity on Model Seeds

Abstract

In agriculture, weed management is a significant concern because their uncontrolled proliferation decreases soil quality for food crops. Allelopathy is a natural phenomenon in which the activity of allelochemical compounds inhibits the germination and growth of invasive plants as a defense mechanism. Among allelochemicals are polyphenols, which may affect genetic material or crucial enzyme activities for proper physiological function. Agroindustrial residues are a vast source of polyphenolic compounds with allelochemical activity. The bagasse of Agave Lechuguilla, known as guishe, is an abundant residue in México. The guishe has been characterized before by its polyphenolic content. Based on that, a fungal bioconversion process was developed to increase the availability of the allelochemicals in the guishe juice. First, guishe juice was obtained by mechanical pressed and characterized by spectrophotometric analysis. Results showed (g/L): 5.62 flavonoids, 0.64 of hydrolyzable polyphenols, 12.67 of reducing sugars, and 23.3 total sugars. The compounds detected by HPLC-ESI-MS were pterostilbene, hydroxycaffeic, caffeoyltartaric, and 4-O-glucoside coumaric acids, considered allelopathic. After the fungal bioprocess, (+)-gallocatechin and 3,7-Dimethyl quercetin were detected as additional compounds of interest. The flavonoid and hydrolyzable polyphenol content were modified to the highest accumulation of 1.57 and 14.9 g/L at 72 h, meaning a 2.45- and 2.22-fold increase. A bioprocess guishe juice (BGJ) was obtained at the compound accumulation peak of 72 h and evaluated in an allelopathic assay on model seeds (tomato and corn). Results show that BGJ inhibits up to 96.67% of corn seeds and up to 76.6% of tomato seeds compared to positive control.