Evaluation of Halophyte Biopotential as an Unused Natural Resource: The Case of Lobularia maritima

Development of a marker-free engineered durum wheat overexpressing Lobularia maritima GASA1 with improved drought tolerance

Due to their fixed lifestyle, plants must adapt to abiotic or biotic stresses by orchestrating various responses, including protective and growth control measures. Growth arrest is provoked upon abiotic stress and can impair plant production. Members of the plant-specific GASA (gibberellic acid-stimulated Arabidopsis) gene family play crucial roles in phytohormone responses, abiotic and biotic stresses, and plant growth. Here, we recognized and examined the LmGASA1 gene from the halophyte plant Lobularia maritima and developed marker-free engineered durum wheat plants overexpressing the gene. The LmGASA1 transcript profile revealed that it's induced by stressful events as well as by phytohormones including GA3, MeJA, and ABA, suggesting that the LmGASA1 gene may contribute to these stress and hormone signal transduction pathways. Transient expression of GFP-LmGASA1 fusion in onion epidermal cells indicated that LmGASA1 is localized to the cell membrane. Further analysis showed that overexpression of LmGASA1 in durum wheat plants enhanced tolerance to drought stress compared with that in non-transgenic (NT) plants, imposing no yield penalty and enabling seed production even following drought stress at the vegetative stage. Altogether, our data indicate that LmGASA1 regulates both the scavenging capacity of the antioxidant enzymatic system and the activation of at least six stress-related genes that function as positive regulators of drought stress tolerance. LmGASA1 appears to be a novel gene useful for further functional analysis and potential engineering for drought stress tolerance in crops.

Mixture design of α-pinene, α-terpineol, and 1,8-cineole: A multiobjective response followed by chemometric approaches to optimize the antibacterial effect against various bacteria and antioxidant activity

α-Pinene, α-terpineol, and 1,8-cineole are compounds naturally present in essential oils, although their amounts vary from oil to oil. Although several studies have reported their antibacterial and antioxidant effects, there are few reports on the synergistic or antagonistic effects of their combinations. The objective of this study was to investigate the combined antibacterial effect of these three compounds. To our knowledge, this is the first report on the prediction of their optimal combination using the mixture design approach. The experimental antibacterial activity of the α-pinene, α-terpineol, and 1,8-cineole mixtures depended on the proportion of each compound in the mixture and the target strain, with minimum inhibitory concentrations (MIC) ranging from 0.31 to 1.85 mg/mL. Using the increased simplex-centroid mixture design, the mixture containing 0.33% of each molecule proved to be the most effective against Bacillus cereus and had the lowest MIC values. In addition, α-pinene, α-terpineol, and 1,8-cineole showed significant antioxidant activity against 2,2-picryl-1-hydrazyl radical (DPPH), with IC50 values of 24.53 ± 0.05, 65.63 ± 0.71, and 63.58 ± 0.01 μg/mL, respectively. Statistical planning and the development of utility profiles of the substance mixtures can predict the optimal composition that will exhibit the highest antibacterial activity against B. cereus as well as antioxidant properties. Furthermore, the synergistic effect of the mixtures can contribute significantly to their successful use as natural preservatives in various applications.

Salvia officinalis L. and Salvia sclarea Essential Oils: Chemical Composition, Biological Activities and Preservative Effects against Listeria monocytogenes Inoculated into Minced Beef Meat

In this study, Salvia officinalis L. and Salvia sclarea essential oils (EOs) were investigated using gas chromatography-mass spectrometry (GC-MS) to describe their chemical composition. The obtained results show, for both EOs, a profile rich in terpene metabolites, with monoterpenes predominating sesquiterpenes but with significant qualitative and quantitative differences. The main compound found in the Salvia officinalis EO (SOEO) was camphor (19.0%), while in Salvia sclarea EO (SCEO), it was linalyl acetate (59.3%). Subsequently, the in vitro antimicrobial activity of the EOs against eight pathogenic strains was evaluated. The disc diffusion method showed a significant lysis zone against Gram-positive bacteria. The minimum inhibitory concentrations (MICs) ranged from 3.7 mg/mL to 11.2 mg/mL, indicating that each EO has specific antimicrobial activity. Both EOs also showed significant antiradical activity against DPPH radicals and total antioxidant activity. In addition, the preservative effect of SOEO (9.2%) and SCEO (9.2%), alone or in combination, was tested in ground beef, and the inhibitory effect against Listeria monocytogenes inoculated into the raw ground beef during cold storage was evaluated. Although the effect of each individual EO improved the biochemical, microbiological, and sensory parameters of the samples, their combination was more effective and showed complete inhibition of L. monocytogenes after 7 days of storage at 4 °C. The results show that both EOs could be used as safe and natural preservatives in various food and/or pharmaceutical products.

Recent Advances in the Incorporation of Polysaccharides with Antioxidant and Antibacterial Functions to Preserve the Quality and Shelf Life of Meat Products

Meat and meat products are susceptible to various types of natural processes such as oxidative degradation due to their high content of protein and essential amino acids. However, finding solutions to maintain the nutritional and sensory quality of meat and meat products is unavoidable. Hence, there is a pressing need to investigate alternatives to synthetic preservatives, focusing on active biomolecules of natural provenance. Polysaccharides are natural polymers of various sources that exhibit antibacterial and antioxidant properties via a variety of mechanisms, owing to their diversity and structural variation. For this reason, these biomolecules are widely studied in order to improve texture, inhibit the growth of pathogens, and improve the oxidative stability and sensory characteristics of meat products. However, the literature has not addressed their biological activity in meat and meat products. This review summarizes the various sources of polysaccharides, their antioxidant and antibacterial activities (mainly against pathogenic food strains), and their use as natural preservatives to replace synthetic additives in meat and meat products. Special attention is given to the use of polysaccharides to improve the nutritional value of meat, resulting in more nutrient-rich meat products with higher polysaccharide content and less salt, nitrites/nitrates, and cholesterol.

Assessment of Shoot Priming Efficiency to Counteract Complex Metal Stress in Halotolerant Lobularia maritima

The study investigated whether short-term priming supports plant defense against complex metal stress and multiple stress (metals and salinity) in halophyte Lobularia maritima (L.) Desv. Plants were pre-treated with ectoine (Ect), nitric oxide donor-sodium nitroprusside (SNP), or hydrogen sulfide donor-GYY4137 for 7 days, and were transferred onto medium containing a mixture of metal ions: Zn, Pb, and Cd. To test the effect of priming agents in multiple stress conditions, shoots were also subjected to low salinity (20 mM NaCl), applied alone, or combined with metals. Hydropriming was a control priming treatment. Stress impact was evaluated on a basis of growth parameters, whereas defense responses were on a basis of the detoxification activity of glutathione S-transferase (GST), radical scavenging activity, and accumulation of thiols and phenolic compounds. Exposure to metals reduced shoot biomass and height but had no impact on the formation of new shoots. Priming with nitric oxide annihilated the toxic effects of metals. It was related to a sharp increase in GST activity, glutathione accumulation, and boosted radical scavenging activity. In NO-treated shoots level of total phenolic compounds (TPC) and flavonoids remained unaffected, in contrast to other metal-treated shoots. Under combined metal stress and salinity, NO and H₂S were capable of restoring or improving growth parameters, as they stimulated radical scavenging activity. Ect and H₂S did not exert any effect on metal-treated shoots in comparison to hydropriming. The results revealed the stimulatory role of nitric oxide and low doses of NaCl in combating the toxic effects of complex metal stress in L. maritima. Both NO and NaCl interfered with thiol metabolism and antioxidant activity, whereas NaCl also contributed to the accumulation of phenolic compounds.

A New Approach in Meat Bio-Preservation through the Incorporation of a Heteropolysaccharide Isolated from Lobularia maritima L

In this study, a new heteropolysaccharide extracted from Lobularia maritima (L.) Desv. (LmPS), a halophyte harvested in Tunisia, was evaluated as an antioxidant and antibacterial additive in the bio-preservation of raw minced meat. For antibacterial testing, Gram-positive bacteria such as Staphylococcus aureus ATCC and Listeria monocytogenes ATCC 19,117 and Gram-negative bacteria such as Salmonella enterica ATCC 43,972 and Escherichia coli ATCC 25,922 were used. The results indicate that this polymer had a significant antibacterial activity against foodborne pathogens. Additionally, the effects of LmPS at 0.15, 0.3 and 0.6% on refrigerated raw ground beef were investigated from a microbiological, chemical, and sensory perspective. Microbiological analysis of the meat showed that treatment with LmPS significantly (p < 0.05) improved its shelf life, while the biochemical analysis evidenced a significant (p < 0.05) decrease in lipid oxidation. LmPS at 0.6% significantly reduced by 61% and 48% metmyoglobin accumulation at the end of the storage period when compared to BHT and control samples, respectively. The chemometric approach highlighted the relationships among the different meat quality parameters. LmPS can be introduced in the food industry as a powerful natural additive and could be an alternative to synthetic antioxidant compounds.