Synthesis and characterization of a potential prebiotic trisaccharide from cheese whey permeate and sucrose by Leuconostoc mesenteroides dextransucrase

The production of new bioactive oligosaccharides is currently garnering much attention for their potential use as functional ingredients. This work addresses the enzymatic synthesis and NMR structural characterization of 2-α-D-glucopyranosyl-lactose derived from sucrose:lactose and sucrose:cheese whey permeate mixtures by using a Leuconostoc mesenteroides B-512F dextransucrase. The effect of synthesis conditions, including concentration of substrates, molar ratio of donor/acceptor, enzyme concentration, reaction time, and temperature, on the formation of transfer products is evaluated. Results indicated that cheese whey permeate is a suitable material for the synthesis of 2-α-D-glucopyranosyl-lactose, giving rise to yields around 50% (in weight respect to the initial amount of lactose) under the optimum reaction conditions. According to its structure, this trisaccharide is an excellent candidate for a new prebiotic ingredient, due to the reported high resistance of α-(1→2) linkages to the digestive enzymes in humans and animals, as well as to its potential selective stimulation of beneficial bacteria in the large intestine mainly attributed to the two linked glucose units located at the reducing end that reflects the disaccharide kojibiose (2-α-D-glucopyranosyl-D-glucose). These findings could contribute to broadening the use of important agricultural raw materials, such as sucrose or cheese whey permeates, as renewable substrates for enzymatic synthesis of oligosaccharides of nutritional interest.     

Preparation of Chitosan Nanocompositeswith a Macroporous Structure by Unidirectional Freezing and Subsequent Freeze-Drying

Chitosan is the N-deacetylated derivative of chitin, a naturally abundant mucopolysaccharide that consists of 2-acetamido-2-deoxy-β-d-glucose through a β (1→4) linkage and is found in nature as the supporting material of crustaceans, insects, etc. Chitosan has been strongly recommended as a suitable functional material because of its excellent biocompatibility, biodegradability, non-toxicity, and adsorption properties. Boosting all these excellent properties to obtain unprecedented performances requires the core competences of materials chemists to design and develop novel processing strategies that ultimately allow tailoring the structure and/or the composition of the resulting chitosan-based materials. For instance, the preparation of macroporous materials is challenging in catalysis, biocatalysis and biomedicine, because the resulting materials will offer a desirable combination of high internal reactive surface area and straightforward molecular transport through broad “highways” leading to such a surface. Moreover, chitosan-based composites made of two or more distinct components will produce structural or functional properties not present in materials composed of one single component. Our group has been working lately on cryogenic processes based on the unidirectional freezing of water slurries and/or hydrogels, the subsequent freeze-drying of which produce macroporous materials with a well-patterned structure. We have applied this process to different gels and colloidal suspensions of inorganic, organic, and hybrid materials. In this review, we will describe the application of the process to chitosan solutions and gels typically containing a second component (e.g., metal and ceramic nanoparticles, or carbon nanotubes) for the formation of chitosan nanocomposites with a macroporous structure. We will also discuss the role played by this tailored composition and structure in the ultimate performance of these materials.     

Evaluation of preflooding effects on iron extractability and phytoavailability in highly calcareous soil in containers

Previous pot cropping and laboratory incubation experiments were consistent with field observations showing that temporary flooding before cropping can increase the availability of soil Fe to plants. To study the effect of temporary flooding on changes in soil Fe phytoavailability we used 24 highly calcareous, Fe chlorosis–inducing soils to carry out a pot experiment where peanut and chickpea were successively grown after flooding for 30 d. At the end of the cropping experiment, the preflooded soil samples exhibited higher concentrations of acid oxalate‐, citrate/ascorbate‐ and diethylenetriaminepentacetic acid (DTPA)–extractable Fe (Fe_ox, Fe_ca, and Fe_DTPA, respectively) than the control (nonflooded) samples. Also, Fe_ox and Fe_ca exhibited no change by effect of reflooding of the cropped soils or three wetting–drying cycles in freeze‐dried slurries of soils previously incubated anaerobically for several weeks. Leaf chlorophyll concentration (LCC) in both peanut and chickpea was greatly increased by preflooding. The best predictor for LCC was Fe_ox, followed by Fe_ca and Fe_DTPA. The LCC–soil Fe relationships found suggest that the Fe species extracted by oxalate and citrate/ascorbate from preflooded soils were more phytoavailable than those extracted from control soils. However, the increased phytoavailability of extractable Fe forms was seemingly limited to the first crop (peanut). Flooding dramatically increased Fe_DTPA; however, high Fe_DTPA levels did not result in high LCC values, particularly in the second crop. Therefore, this test is a poor predictor of the severity of Fe chlorosis in preflooded soils.     

Improvement of nutritional quality of greenhouse-grown lettuce by arbuscular mycorrhizal fungi is conditioned by the source of phosphorus nutrition

The improvement of the nutritional quality of lettuce by its association with arbuscular mycorrhizal fungi (AMF) has been recently reported in a previous study. The aim of this research was to evaluate if the fertilization with three P sources differing in water solubility affects the effectiveness of AMF for improving lettuce growth and nutritional quality. The application of either water-soluble P sources (Hewitt's solution and single superphosphate) or the water-insoluble (WI) fraction of a "rhizosphere-controlled fertilizer" did not exert negative effects on the establishment of the mycorrhizal symbiosis. AMF improved lettuce growth and nutritional quality. Nevertheless, the effect was dependent on the source of P and cultivar. Batavia Rubia Munguía (green cultivar) benefited more than Maravilla de Verano (red cultivar) in terms of mineral nutrients, total soluble sugars, and ascorbate contents. The association of lettuce with AMF resulted in greater quantities of anthocyanins in plants fertilized with WI, carotenoids when plants received either Hewitt's solution or WI, and phenolics regardless of the P fertilizer applied.     

Bioavailability of β-cryptoxanthin in the presence of phytosterols: in vitro and in vivo studies

Bioactive compounds are used in the design and development of new food products with potential health benefits, although little is known regarding their bioavailability and interactions. This study assessed the stability, in vitro bioaccessibility, and human bioavailability of β-cryptoxanthin from β-cryptoxanthin-rich drinks with and without added phytosterols developed for this purpose. The developed drinks showed no difference in the content of β-cryptoxanthin, and they were stable over 6 months. In vitro, hydrolysis of β-cryptoxanthin esters and the amount of free β-cryptoxanthin at duodenal and micellar phases were similar regardless of the presence of phytosterols. In the human study, the daily intake provoked significant increments of β-cryptoxanthin in serum regardless of the type of the drink. In conclusion, in vitro and in vivo human studies have shown that the bioavailability of β-cryptoxanthin is not significantly affected by the presence of phytosterols when they are simultaneously supplied in a drink.     

Growth and development of pepper are affected by humic substances derived from composted sludge

A greenhouse experiment was conducted to evaluate the effects of humic substances extracted from composted sewage sludge on growth, phenological development, and photosynthetic activity of pepper (Capsicum annuum L. cv. Piquillo) plants. Humic substances derived from composted sludge (HSS) were compared with those derived from leonardite (HSL). Two doses of both humic substances were assayed (200 and 500 mg C [L substrate]^–1) and compared with a control (C). HSS showed higher nitrogen content and a higher percentage of aliphatic carbon, as well as a lower content of aromatic and phenolic carbon than HSL. HSS significantly increased plant dry‐matter production (up to 560%), plant height (86%–151%), and leaf area (436%–1397%) during the early stages of pepper development. Net photosynthesis and stomatal conductance increased in the treatments with HSS (up to 48% and 63%, respectively) at the vegetative stage. In addition, HSS accelerated the phenological development of pepper plants, reducing significantly the number of days to flowering and ripening, which occurred 12 and 14 d earlier than in control plants, respectively. In general, the treatments with HSS and HSL did not markedly affect chlorophyll and nutrient concentrations in the leaves. At maturity, only small differences in total fruit yield, number of fruits per plant, and fruit size were observed between amended and control plants. The results suggest that the mechanisms through which HSS affected plant growth and development were not associated with an improved nutrient uptake. Although the identity of the growth‐promoting factors remains to be found, the results suggest that they may be linked to the chemical structure of the humic substances.     

AhaP,A Quorum Quenching Acylase from Psychrobacter sp. M9-54-1 That Attenuates Pseudomonas aeruginosa and Vibrio coralliilyticus Virulence

Although Psychrobacter strain M9-54-1 had been previously isolated from the microbiota of holothurians and shown to degrade quorum sensing (QS) signal molecules C6 and C10-homoserine lactone (HSL), little was known about the gene responsible for this activity. In this study, we determined the whole genome sequence of this strain and found that the full 16S rRNA sequence shares 99.78–99.66% identity with Psychrobacter pulmonis CECT 5989^T and P. faecalis ISO-46^T. M9-54-1, evaluated using the agar well diffusion assay method, showed high quorum quenching (QQ) activity against a wide range of synthetic N-acylhomoserine lactone (AHLs) at 4, 15, and 28 °C. High-performance liquid chromatography-mass-spectrometry (HPLC-MS) confirmed that QQ activity was due to an AHL-acylase. The gene encoding for QQ activity in strain M9-54-1 was identified from its genome sequence whose gene product was named AhaP. Purified AhaP degraded substituted and unsubstituted AHLs from C4- to C14-HSL. Furthermore, heterologous expression of ahaP in the opportunistic pathogen Pseudomonas aeruginosa PAO1 reduced the expression of the QS-controlled gene lecA, encoding for a cytotoxic galactophilic lectin and swarming motility protein. Strain M9-54-1 also reduced brine shrimp mortality caused by Vibrio coralliilyticus VibC-Oc-193, showing potential as a biocontrol agent in aquaculture.     

Nitrate uptake by Vicia faba L. Plants: A physiological approach 1

This study was conducted to obtain information on the properties of the nitrate (NO₃ ^‐) uptake system in Vicia faba. The results showed that in plants grown in the absence of NO₃ ^‐, they cannot absorb it upon initial exposure to this anion. When this plant makes contact with environmental NO₃ ^‐, NO₃ ^‐uptake by the roots is progressively induced. However, in NO₃ ^‐‐grown plants, the uptake system is yet induced so they had the ability to take up NO₃ ^‐ at high rates from the beginning. The Michaelis’ constant (K,_M) and maximum uptake rate (V_max) were estimated from measurements of NO₃ ^‐ depletion in the uptake medium. The apparent K_M value for net NO₃ ^‐ uptake in induced V. faba plants was 60 μM and the corresponding V_max 0.44 umol NO₃ ^‐ (g FW)^‐1 h^‐1. This last value was low compared with that of other species, while K_M is in the range for other higher plants. From the results of our experiments at low and high NO₃ ^‐ concentrations, we discuss the possibility of the existence of two NO₃ ^‐ uptake systems, one of a high affinity (functioning at low NO₃ ^‐concentrations) and another of low affinity (operative at high NO₃ ^‐ level in the medium).     

INTERRELATION BETWEEN FRUIT MINERAL CONTENT AND PRE-HARVEST CALCIUM TREATMENTS ON ‘GOLDEN SMOOTHEE’ APPLE QUALITY

The effects of different pre-harvest calcium treatments and their interrelation with other nutrients in apples (Malus domestica Borkh, ‘Golden Smoothee’) on quality attributes at harvest and after cold storage and on relation between calcium (Ca) and other nutrients were investigated. Calcium sprays were applied during three-seasons beginning 60 days after full bloom (DAFB), with 6 or 12 applications in the second part of the growing season. It was confirmed that calcium treatments generally resulted in increased flesh firmness at harvest but not sufficient to maintain during storage. Treatments reduced bitter pit and lenticel blotch pit after cold storage, but these disorders were not totally eliminated. The treatments did not influence evolution of titratable acidity and soluble solids. Total fruit calcium increased with number of applications, but this increase was not proportional with number of applications. The beneficial effect of calcium treatments was reflected in the nitrogen/Calcium (N/Ca), potassium/calcium (K/Ca), and (K+Mg)/Ca ratios.