Development of a cascade production system finalized to the extraction of all-tomatine-rich fraction using the tomato cannery waste as feedstock

Tomato plants produce, among other defensive molecules, glycoalkaloides (i.e. all-tomatine). All-tomatine, found in highest concentrations in green fruits, leaves and stems, has demonstrated a wide variety of biological activities useful in fields such as agronomy and biopesticides. Despite the interest in its potential use, extraction methods for all-tomatine are few and mostly developed with an analytical scope. In analogy with other active principles (pyrethroids, nicotinoids), the all-tomatine can represent an alternative to the use of synthetic pesticides currently discouraged for their environmental persistence and progressive reduction of efficacy against target organisms. The aim of this work was to attempt the development of a process to extract all-tomatine based on the re-use of tomato waste industry residues as feedstock and to apply a cascade production approach. To do so, the lab-scale methods to extract all-tomatine were employed as a starting point and different tomato portions (green fruits, leaves, and stems) as feedstock. The best process in terms of feasibility and recovery was identified by mixing the extraction (acetic acid 5% v/v) and purification (ammonia 25% v/v precipitation) steps of different methods. The process was successively tested using the residues of the full-scale tomato cannery plant waste composed by stems + leaves (SL), and green fruits (GT) currently not valorized. The best recovery was obtained by the SL (yield of the extract: 10.8 mg g−1 dry matter (DM) of the starting biomass; all-tomatine pureness: 864 mg g−1 DM extract). The use of the acetic acid as extraction agent gave a solvent-free by-product (68% DM starting biomass), reusable as cultivation substrate. At the purification phase, the dialysis-treatment of the wastewater, recovered a solution rich in sugars and organic acid to get a full starting biomass recovery of 85.6% DM starting biomass.