Centre of Biotechnology and Fine Chemistry

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Plant growth-promoting rhizobacteria (PGPR) improve the growth and nutrient use efficiency in maize (Zea mays L.) under water deficit conditions

Publication . Pereira, S. I. A.; Abreu, D.; Moreira, H.; Vega, A.; Castro, P. M. L.

Drought is one of the major abiotic stresses that affects crop yield worldwide. An eco-friendly tool that can broadly improve plants' tolerance to water stress is bioionocula comprising plant growth-promoting rhizobacteria (PGPR). In this study, the effect of two PGPR Cupriavidus necator 1C2 (B1) and Pseudomonas fluorescens S3X (B2), singly and/or co-inoculated at two inocula sizes (S1 - 3 × 103 cells g−1 dry weight (dw) soil and S2 - 3 × 106 cells g−1 dw soil), on growth, nutrient uptake, and use efficiency was assessed in maize (Zea mays L.) plants grown at three levels of irrigation (80% of water holding capacity (WHC) – well-watered, 60% of WHC - moderate water deficit stress, and 40% of WHC - severe water deficit stress) in a greenhouse experiment. The impact of water deficit and bioinoculants on soil microbial activity (fluorescein diacetate hydrolysis) was also evaluated. Moderate and severe water deficit negatively affected soil microbial activity, as well as, maize growth, by reducing plants' shoot biomass and increasing root/shoot ratio at 60 and 40% of WHC. Bioinoculants mitigated the negative effects on shoot biomass, especially when PGPR were co-inoculated, increasing up to 89% the aerial biomass of plants exposed to moderate water deficit. Bioinoculation also increased nitrogen (N) and phosphorous (P) use efficiency, which may have led to higher maize growth under water deficit conditions. The size of the inocula applied had marginal influence on biometric and nutrient parameters, although the higher concentration of the mixture of PGPR was the most effective in improving shoot biomass under moderate water deficit. This study shows that rhizobacterial strains are able to increase nutrient use efficiency and to alleviate water stress effects in crops with high water demands and have potential applications to keep up with productivity in water stress scenarios.

2020Journal article

Open access

Iron metabolism in soybean grown in calcareous soil is influenced by plant growth-promoting rhizobacteria: a functional analysis

Publication . Roriz, Mariana; Pereira, Sofia I.A.; Castro, Paula M.L.; Carvalho, Susana M.P.; Vasconcelos, Marta W.

Iron deficiency results in severe yield losses, particularly in calcareous soils. Recent evidences suggest that biofertilizers with plant growth-promoting rhizobacteria (PGPR) may be an efficient strategy for enhancing iron (Fe) nutrition in legumes. This work aimed at evaluating the capacity of PGPR strains to enhance Fe uptake-related processes in soybean grown in calcareous soil. From the studied 24 PGPR, Sphingobium fuliginis ZR 1–6 and Pseudomonas jessenni ZR 3–8 strains were selected for the inoculation experiment based on their in vitro ability to produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase, siderophores, and organic acids, to tolerate high pH, and to reduce Fe3+. The effect of bacterial inoculation on improving Fe uptake was tested using each isolate alone or combined and through the evaluation of several morphological, physiological, and molecular parameters. Inoculation with S. fuliginis showed beneficial effects particularly at the root level by the improvement of ferric chelate activity (111%) and FRO2 expression (646%), resulting in increased Fe root content (62%). Inoculation with P. jessenii increased Zn and Mn concentrations in the trifoliates (463% and 51%, respectively), decreased Zn concentration in the roots (88%), and increased the expression of FER4 in the trifoliates (5260%). Combined inoculation of both strains fostered Fe accumulation in the trifoliates and increased the expression of IRT1 and FER4 genes, indicating an improved capacity of Fe translocation to the shoots. These results suggest that inoculation with selected PGPR strains could be effective in improving Fe uptake and accumulation in soybean grown under Fe-deficient conditions.

2021Journal article

Restricted access

Potential biological properties of lycopene in a self-emulsifying drug delivery system

Publication . Báo, Sônia Nair; Machado, Manuela; Silva, Ana Luisa da; Melo, Adma; Cunha, Sara; Sousa, Sérgio S.; Malheiro, Ana Rita; Fernandes, Rui; Leite, José Roberto S. A.; Vasconcelos, Andreanne G.; Relvas, João; Pintado, Manuela

In recent years, lycopene has been highlighted due to its antioxidant and anti-inflammatory properties, associated with a beneficial effect on human health. The aim of this study was to advance the studies of antioxidant and anti-inflammatory mechanisms on human keratinocytes cells (HaCaT) of a self-emulsifying drug delivery system (SEDDS) loaded with lycopene purified from red guava (nanoLPG). The characteristics of nanoLPG were a hydrodynamic diameter of 205 nm, a polydispersity index of 0.21 and a zeta potential of −20.57, providing physical stability for the nanosystem. NanoLPG demonstrated antioxidant capacity, as shown using the ORAC methodology, and prevented DNA degradation (DNA agarose). Proinflammatory activity was evaluated by quantifying the cytokines TNF-α, IL-6 and IL-8, with only IL-8 showing a significant increase (p < 0.0001). NanoLPG showed greater inhibition of the tyrosinase and elastase enzymes, involved in the skin aging process, compared to purified lycopene (LPG). In vitro treatment for 24 h with 5.0 µg/mL of nanoLPG did not affect the viability of HaCaT cells. The ultrastructure of HaCaT cells demonstrated the maintenance of morphology. This contrasts with endoplasmic reticulum stresses and autophagic vacuoles when treated with LPG after stimulation or not with LPS. Therefore, the use of lycopene in a nanoemulsion may be beneficial in strategies and products associated with skin health.

2023-01Journal article

Open access

Factors influencing food waste during lunch of fourth-grade school children

Publication . Martins, Margarida Liz; Rodrigues, Sara S.P.; Cunha, Luís M.; Rocha, Ada

This study aims to explore the factors that influence plate waste at lunches served in primary schools. Data was collected for all fourth-grade children attending 21 primary schools from the city of Porto (Portugal) (n = 463). Plate waste was evaluated by the weighing method and factors influencing plate waste were collected by observation of menu and canteen characteristics and through the application of a questionnaire to children aiming to evaluate factors related to preferences and dietary patterns. Logistic regression was performed to identify predictors of plate waste. It was observed that fish menus and composed dishes showed a higher tendency for increased plate waste. However, this effect was not observed when adjusted for other variables. Soups without pulses and blended soups were less likely to be discarded by children. The presence of the teacher during meals and the possibility for children to leave the canteen whenever they wish, protected both the main dish and the soup from being wasted. A higher number of children in the canteen was associated with increased soup waste. As expected, children more pleased with the sensory characteristics of the main dish and soup were less likely to waste food. Children who consumed high-saturated fat content mid-morning snacks were more likely to waste soup. The main factors associated with plate waste were related to the presence of teachers during the mealtime, school meal policies and the meals’ sensory characteristics. Additionally, soup waste was determined by its composition, mid-morning snacks and the number of children in the canteen.

2020Journal article

Restricted access