Biorefinery of Tomato Leaves by Integrated Extraction and Membrane Processes to Obtain Fractions That Enhance Induced Resistance against Pseudomonas syringae Infection

Abstract

Tomato leaves have been shown to contain significant amounts of important metabolites involved in protection against abiotic and biotic stress and/or possessing important therapeutic properties. In this work, a systematic study was carried out to evaluate the potential of a sustainable process for the fractionation of major biomolecules from tomato leaves, by combining aqueous extraction and membrane processes. The extraction parameters (temperature, pH, and liquid/solid ratio (L/S)) were optimized to obtain high amounts of biomolecules (proteins, carbohydrates, biophenols). Subsequently, the aqueous extract was processed by membrane processes, using 30–50 kDa and 1–5 kDa membranes for the first and second stage, respectively. The permeate from the first stage, which was used to remove proteins from the aqueous extract, was further fractionated in the second stage, where the appropriate membrane material was also selected. Of all the membranes tested in the first stage, regenerated cellulose membranes (RC) showed the best performance in terms of higher rejection of proteins (85%) and lower fouling index (less than 15% compared to 80% of the other membranes tested), indicating that they are suitable for fractionation of proteins from biophenols and carbohydrates. In the second stage, the best results were obtained by using polyethersulfone (PES) membranes with an NMWCO of 5 kDa, since the greatest difference between the rejection coefficients of carbohydrates and phenolic compounds was obtained. In vivo bioactivity tests confirmed that fractions obtained with PES 5 kDa membranes were able to induce plant defense against P. syringae.

Rhizobacterial Colonization and Management of Bacterial Speck Pathogen in Tomato by Pseudomonas spp.

“…tomato (Pst) DC3000 has gained notoriety as a model organism for investigating the complex relationships between plants and pathogens [ 24 ]. Pst is responsible for bacterial speck disease, which is one of the most serious foliar diseases of tomato due to the substantial losses it may cause when the temperature is low and moisture is high [ 25 ]. It is still difficult to manage this disease.…”

Membrane Cascade Fractionation of Tomato Leaf Extracts—Towards Bio-Based Crop Protection

“…Agriculture contributes a substantial role to humanity, as it provides food, feedstocks and covers other human needs, such as clothing and construction components. Plants are the main convertors of the sun's energy on earth, transforming and storing this energy chemically in plant biomass (~170 × 10 9 tons/year), mainly in the form of carbohydrates (~75% w/w) [1]. When the same plants are cultivated intensively in large areas, then these are called crops and are of paramount importance for the economy and societies.…”

“…The agricultural sector has realised that other solutions are required to minimise the environmental impacts of these materials and create additional valuable products when feasible [10]. Tomato leaf waste streams are a rich source of phytochemicals, such as biophenols [1,8,11,12], solanesol [5], alkaloids [11,12], proteins [1,8] and carbohydrates [1], that could be better exploited and could have applications in many industrial fields [5,9,11,12]. Unfortunately, often the chemistry and biological activities of natural products derived from biomass varies according to crop cultivated [11], batchto-batch variations, season and geographical location [13].…”

“…There are many efforts to use extracts that act as elicitors from various natural resources, such as seaweed [23,24], extract of liquid vermicompost [25], tomato leaf [1], liquorice (Glycyrrhiza glabra) leaf extract [18] and other plant resources [3,17]. The elicitor activity in these cases has been attributed to proteins [23], polysaccharides [1,24], fragmented DNA [16], peptides [16], humic acid [25], biophenols [12], cell-wall fragments [16,26], etc.…”

“…There are many efforts to use extracts that act as elicitors from various natural resources, such as seaweed [23,24], extract of liquid vermicompost [25], tomato leaf [1], liquorice (Glycyrrhiza glabra) leaf extract [18] and other plant resources [3,17]. The elicitor activity in these cases has been attributed to proteins [23], polysaccharides [1,24], fragmented DNA [16], peptides [16], humic acid [25], biophenols [12], cell-wall fragments [16,26], etc. As plant-based extracts contain a variety of different compounds, they can synergistically simultaneously induce a number of plant defence mechanisms, thus being more effective than synthetic crop protection products [17,24].…”