The demand for bioactive secondary metabolites of natural origin is increasing every day. Micropropagation could be a strategy to respond more quickly to market demands, regardless of seasonality. This research aims to evaluate in vitro-grown plants of two hop varieties, namely Columbus and Magnum, as a potential source of bioactive compounds. The extracts were characterized in terms of total phenolic content by a Folin–Ciocalteu assay and antioxidant capacity by DPPH^•, ABTS⁺, and FRAP assays. The bioactive compound profile of the extracts from both varieties was determined by using UPLC-ESI-QqQ-MS/MS. The results confirmed richness in (poly)phenols and other secondary metabolites of the in vitro-grown hop plantlets. Thirty-two compounds belonging to the major families of phytochemicals characteristic of the species were identified, and twenty-six were quantified, mainly flavonoids, including xanthohumol and isoxanthohumol, phenolic acids, as well as α- and β-acids. This study confirms the validity of in vitro-derived hop plantlets as source of bioactive compounds to be used in the nutraceutical, pharmaceutical, and food industries.

(1) Background: Humulus lupulus L. plants constitute a rich source of bioactive compounds. The synthesis of bioactive compounds in plants is often triggered by the activation of secondary metabolism, which can be induced by biotic or abiotic elicitors. In vitro, the effect of the elicitors can be studied in a controlled environment and in a small space, independently of seasonal variations. Cytokinins are frequently used in plant tissue culture for bud regeneration, branching and shoot elongation due to their role in cell division enhancement. This study aimed to investigate the effects of different cytokinins on the growth parameters, total (poly)phenolic content and antioxidant capacity of in vitro-grown hop plants to evaluate hop vitro-derived biomass as a potential source of bioactive compounds. (2) Methods: unimodal hop (cvs. Cascade and Columbus) explants were cultured on media enriched with four cytokinins (kinetin, 6-benzylaminopurine, meta-topolin and 6-(γ,γ-dimethylallylamino)-purine) at four concentrations. (3) Results: A genotype-dependent response to different cytokinins was encountered. (4) Conclusions Columbus explants could root in culture media auxin-free, providing valuable opportunities for commercial nurseries. Moreover, cytokinins were confirmed to be valuable elicitors to stimulate the bioactive compound biosynthesis in micropropagated hop plants, making them a precious source for various industries.

(1) Background: Traditionally, hop is propagated using rhizome fragments or herbaceous stem cuttings. Micropropagation, therefore, offers a viable alternative for the large-scale production of healthy, genetically uniform plants, regardless of the season and within confined spaces. A temporary immersion system (TIS) facilitates plant propagation by alternating immersions of microcuttings in liquid culture medium with dry periods, preventing gas accumulation through forced ventilation. (2) Methods: In this study, the response of hop plantlets, cv. Columbus, cultured in media with and without sucrose, in solid and liquid culture systems (Plantform^TM bioreactor), was evaluated, considering its effect on morpho-physiological parameters, on the total phenolic content, and on antioxidant capacity. Moreover, to make the TIS more efficient, the effect of immersion duration (three and six minutes every twelve hours) was evaluated. (3) Results: The presence of sucrose in the culture medium improved plant proliferation in both culture systems tested: solid and liquid (particularly for explants immersed for three minutes). In the TIS, plantlets with a higher antioxidant capacity were obtained when sucrose-free culture medium was used. (4) Conclusions: This study confirms the efficacy of the TIS as a hop propagation method but also as a valid tool to produce biomass to be used as a source of bioactive compounds.

Nowadays, tomato, a commercially important crop, is increasingly cultivated in a soilless cultivation system to counteract climate change. Normally, this system uses cocopeat as a substrate, but its high cost and environmental impact have led to growing interest in alternatives like biochar (BC). In addition, biostimulants, such as wood distillate (WD), a pyrolysis by-product, are increasingly being used to improve fruit yield and quality. BC was used to partially replace (2% and 5%) cocopeat in growth bags for soilless tomato cultivation. Moreover, WD (3 mL/L) was distributed in the substrate every two weeks. The effect of BC and WD on tomato plant growth, fruit quality, and substrate microbial community was investigated. The integration of BC and WD into a soilless growing system for tomato cultivation can improve the fruit quality and influence the microbial activity of the substrate. Replacing part of the cocopeat in the substrate with BC and using an agri-waste-derived biostimulant represent a step forward in making agriculture more sustainable.

Food waste is a global concern, and its valorization through biostimulant production offers a sustainable and circular approach to agriculture. This study evaluated the effects of a novel fermented tomato-based biostimulant, obtained from unsold green and red tomatoes fermented with Weissella cibaria 4253, on the growth and fruit quality of indeterminate mini plum tomato plants (Solanum lycopersicum L., cv. Solarino) cultivated in a soilless greenhouse system. The biostimulant was applied weekly at three concentrations (100, 200, and 300 mL·L⁻¹) and compared to untreated controls during a 16-week experiment in a commercial greenhouse in Emilia-Romagna, Italy. Vegetative parameters, physiological traits, including chlorophyll content, SPAD, Fv/Fm, and fruit characteristics were monitored. Fruits from different truss positions (lower, medial, upper) were analyzed for morphological, physico-chemical, and biochemical traits, including firmness, total soluble solids, titratable acidity, total polyphenol content, antioxidant activity, and lycopene content. FTB application did not significantly affect vegetative growth, but improved several fruit quality parameters. The 100 mL·L⁻¹ dose increased total yield by 23 % and fruit weight by 8 %, while the 300 mL·L⁻¹ dose enhanced °Brix, sugar/acid ratio, antioxidant activity (up to 20 %), and improved fruit texture, particularly in upper trusses. Lycopene content increased in treated plants over the harvest season, while untreated plants showed a decline. Heatmap and BIOLOG analyses confirmed treatment-specific effects on fruit quality and substrate microbial activity. The potential of an experimental biostimulant derived from fermented unsold tomato fruits to enhance crop performance while reducing food waste was demonstrated, supporting circular agricultural practices.

Biostimulants boost plant growth, productivity, and nutrient retention, and can be produced from agri-food waste via microbial fermentation. In this study, undersized and unsold kiwifruits were fermented with Lactiplantibacillus plantarum to produce a fermented kiwifruit-based biostimulant (FKB). FKB was applied to soilless tomato plants (cv. Solarino) at two concentrations (50 and 100 mL L⁻¹) at the root level, every two weeks throughout the crop cycle. Fruits were analyzed for technological and chemical parameters, including color, texture, total soluble solids, titratable acidity, sugar/acid ratio, pH, electrical conductivity, total polyphenol content, antioxidant activity, and lycopene concentration. Additionally, metataxonomic analysis characterized the substrate microbial community at the beginning and the end of cultivation. Overall, the results indicate a dose-dependent effect of FKB on fruit quality parameters, with the highest concentration showing the most pronounced effects, specifically for the fruit firmness (8.02 N for FKB at 100 mL L⁻¹ vs. 7.25 N for the Control). Moreover, both tested concentrations were associated with increased antioxidant activity (on average +28%), and lycopene content (on average +57%) compared with the Control fruits. While overall microbial diversity remained largely unchanged, the relative abundance of bacterial taxa associated with nutrient cycling and plant–microbe interactions was modulated by the biostimulant, indicating subtle but potentially functionally relevant shifts in the rhizosphere microbiota. These findings suggest that fermented kiwifruit biomass can serve as an effective biostimulant, improving both fruit quality and the functional structure of the rhizosphere microbial community in soilless tomato cultivation.