Pollen Proteins Research Articles

Growing and Flowering in a Changing Climate: Effects of Higher Temperatures and Drought Stress on the Bee-Pollinated Species Impatiens glandulifera Royle.

Drought and higher temperatures caused by climate change are common stress conditions affecting plant growth and development. The reproductive phase is particularly sensitive to stress, but plants also need to allocate their limited resources to produce floral traits and resources to attract pollinators. We investigated the physiological and floral consequences of abiotic stress during the flowering period of Impatiens glandulifera, a bee-pollinated species. Plants were exposed to three temperatures (21, 24, 27 °C) and two watering regimes (well-watered, water stress) for 3 weeks. Not all parameters measured responded in the same manner to drought and/or heat stress. Drought stress induced leaf senescence, decreasing leaf number by 15–30% depending on growth temperature. Drought also reduced photosynthetic output, while temperature rise affected stomatal conductance. The number of flowers produced dropped 40–90% in response to drought stress, while higher temperatures shortened flower life span. Both stresses affected floral traits, but flower resources diminished in response to higher temperatures, with lower nectar volume and pollen protein content. We conclude that increased temperatures and drought stress, which are becoming more frequent with climate change, can negatively affect flowering, even if plants deploy physiological resistance strategies.

Pollen protein and lipid content influence resilience to insecticides in honey bees (Apis mellifera).

In honey bees (Apis mellifera), there is growing evidence that the impacts of multiple stressors can be mitigated by quality nutrition. Pollen, which is the primary source of protein and lipids in bees diets, is particularly critical for generating more resilient phenotypes. Here, we evaluate the relationship between pollen protein-to-lipid ratios (P:Ls) and honey bee insecticide resilience. We hypothesized that pollen diets richer in lipids would lead to increased survival in bees exposed to insecticides, as pollen-derived lipids have previously been shown to improve bee resilience to pathogens and parasites. Furthermore, lipid metabolic processes are altered in bees exposed to insecticides.We fed age-matched bees pollen diets of different P:Ls by altering a base pollen by either adding protein (casein powder) or lipids (canola oil) and simulating chronic insecticide exposure by feeding bees an organophosphate (Chlorpyrifos). We also tested pollen diets of naturally different P:Ls to determine if results are consistent. Linear regression analysis revealed that mean survival time for altered diets was best explained by protein concentration (p =0.04 , adjusted R2 =0.92), and that mean survival time for natural diets was best explained by P:L ratio (p =0.008 , adjusted R2 =0.93). Our results indicate that higher ratios of dietary protein to lipid has a negative effect on bee physiology when combined with insecticide exposure, while lower ratios have a positive effect. These results suggest that protein and lipid intake differentially influence insecticide response in bees, laying the groundwork for future studies of metabolic processes and development of improved diets.

Identification and characterization of an angiotensin-I converting enzyme inhibitory peptide from enzymatic hydrolysate of rape (Brassica napus L.) bee pollen

In this study, we identified a novel angiotensin-I converting enzyme (ACE) inhibitory peptide, His-Pro-Val-Thr-Gly-Leu (HPVTGL), derived from rape bee pollen (RBP) protein hydrolysate. HPVTGL was separated by ultrafiltration and purified using preparative high-performance liquid chromatography. The ACE inhibitory activity of HPVTGL was stable across a range of pH values (2.0–8.0) and temperatures (<100 °C) and retained after in vitro gastrointestinal digestion. A Lineweaver–Burk plot suggested that the inhibitory mode of HPVTGL was competitive. The molecular docking model revealed that HPVTGL can bind to important active pockets in the ACE active sites. Furthermore, the antihypertensive effects in spontaneously hypertensive rats (SHRs) also revealed that oral administration of HPVTGL can significantly decrease systolic blood pressure and diastolic blood pressure. These results suggest that HPVTGL has potential for use in functional foods or pharmaceutical agents against hypertension.

Impact of elevated air temperature and drought on pollen characteristics of major agricultural grass species.

Grass pollen allergens are known to be one of the major triggers of hay fever with an increasing number of humans affected by pollen associated health impacts. Climate change characterized by increasing air temperature and more frequent drought periods might affect plant development and pollen characteristics. In this study a one-year (2017) field experiment was conducted in Bavaria, Germany, simulating drought by excluding rain and elevated air temperature by installing a heating system to investigate their effects primarily on the allergenic potential of eight selected cultivars of the two grass species timothy and perennial ryegrass. It could be shown for timothy that especially under drought and heat conditions the allergen content is significantly lower accompanied by a decrease in pollen weight and protein content. In perennial ryegrass the response to drought and heat conditions in terms of allergen content, pollen weight, and protein content was more dependent on the respective cultivar probably due to varying requirements for their growth conditions and tolerance to drought and heat. Results support recommendations which cultivars should be grown preferentially. The optimal choice of grass species and respective cultivars under changing climate conditions should be a major key aspect for the public health sector in the future.

Pollen diversity and protein content in differentially degraded semi-arid landscapes in Kenya

In Africa there is a scarcity of information on how plant species that can provide forage for honey bees vary across differentially structured landscapes, and what are the implications of such variabilities on colony integrity. This research presents new insights into the diversity and richness of pollen collected by Apis mellifera scutellata, a subspecies of the Western honey bee native to sub-Saharan Africa, at six study sites of different degradation levels within a semi-arid landscape in Kenya. Ten colonies were established at each site and land cover characteristics were extracted using novel remote sensing methods. The sites differed by the proportions of natural vegetation, cropland, grassland and hedges within each site. Bee bread was collected five times, with three colonies in each of the six sites repeatedly sampled during the period from May 2017 to November 2018. Pollen identification and protein analysis within the study sites were thereafter conducted to establish the linkage between landscape degradation levels and abundance and diversity of pollen. Out of 124 plant species identified, Terminalia spp., Cleome spp. and Acacia spp. were identified as the most abundant species. Moreover, species richness and diversity were highest in the two sites located in moderately degraded landscapes. Pollen protein content showed statistically significant differences across season rather than geographical location. This study demonstrated that landscape degradation negatively affected the diversity and richness of pollen collected by honey bees. Consequently, this helps our understanding of native honey bees’ forage resource usage and plant species preferences in landscapes with varying degrees of degradation.

Changes in qualitative and quantitative traits of birch (Betula pendula) pollen allergenic proteins in relation to the pollution contamination

Birch (Betula pendula) pollen causes inhalant allergy in about 20% of human population in Europe, most of which is sensitive to the main birch allergen, Bet v1. The aim of the study was to find out (i) whether and how the analysed birch individuals differ in regard to composition of individual subunits of pollen proteins and to protein content in these subunits; (ii) whether the level of particulate matter relates to concentration of Bet v1 allergen. Study was performed in Southern Poland, in 2017–2019. Pollen material was collected at 20 sites, of highly or less polluted areas. Protein composition was analysed by SDS-PAGE, while the concentration of Bet v1 was evaluated by ELISA. The obtained results were estimated at the background of the particulate matter (PM10) level and the birch pollen seasons in Kraków. The electrophoregrams of pollen samples collected at different sites showed huge differences in staining intensities of individual protein subunits, also among important birch allergens: Bet v1, Bet v2, Bet v6 and Bet v7. The level of Bet v1 was significantly higher in the pollen samples collected at the more polluted sites. While the birch pollen allergenic potential is determined, the both pollen exposure and the content of the main allergenic components should be considered, as factors causing immunological response and clinical symptoms manifestation in sensitive individuals.

Investigation of microwave drying on quality attributes, sensory properties and surface structure of bee pollen grains by scanning electron microscopy

The primary objective of this work was to investigate microwave drying behaviour of bee pollen grains, and study the effect of microwave drying on quality, physicochemical properties, sensory characteristics and morphological structure of the bee pollen. Bee pollen samples were dried at 180, 360, 540, 720 and 900 W microwave power levels. Drying kinetics of the bee pollen samples during microwave drying were investigated, and protein, fat, ash, carbohydrate, vitamin C, solubility and colour of dried bee pollen samples were evaluated. Scanning electron microscopy (SEM) images of fresh and microwave dried bee pollens were obtained, and their organoleptic properties were evaluated by panellists. Effective moisture diffusivity (Deff) values ranged from 0.04 × 10−8 to 1.14 × 10−8 m2/s, and the activation energy (Ea) was found to be 71.68 W/g. Drying time was shortened by 94% when the microwave power level was increased from 180 to 900 W. Protein, fat, total carbohydrates, vitamin C and colour values of bee pollen were affected by the microwave power level. Microwave power level was an important parameter for the colour change. The lowest ΔE value and the highest solubility (%) were obtained for bee pollen microwave dried at 180 W power level. Morphological changes were observed in microwave dried bee pollen grains. By comparing all the physicochemical properties and organoleptic characteristics of microwave dried bee pollens, the bee pollen dried at 180 W microwave power level was found to retain its quality attributes better than the other microwave dried bee pollens.

Flower Production, Headspace Volatiles, Pollen Nutrients, and Florivory in Tanacetum vulgare Chemotypes.

Floral volatiles and reward traits are major drivers for the behavior of mutualistic as well as antagonistic flower visitors, i.e., pollinators and florivores. These floral traits differ tremendously between species, but intraspecific differences and their consequences on organism interactions remain largely unknown. Floral volatile compounds, such as terpenoids, function as cues to advertise rewards to pollinators, but should at the same time also repel florivores. The reward composition, e.g., protein and lipid contents in pollen, differs between individuals of distinct plant families. Whether the nutritional value of rewards within the same plant species is linked to their chemotypes, which differ in their pattern of specialized metabolites, has yet not been investigated. In the present study, we compared Tanacetum vulgare plants of five terpenoid chemotypes with regard to flower production, floral headspace volatiles, pollen macronutrient and terpenoid content, and floral attractiveness to florivorous beetles. Our analyses revealed remarkable differences between the chemotypes in the amount and diameter of flower heads, duration of bloom period, and pollen nutritional quality. The floral headspace composition of pollen-producing mature flowers, but not of premature flowers, was correlated to that of pollen and leaves in the same plant individual. For two chemotypes, florivorous beetles discriminated between the scent of mature and premature flower heads and preferred the latter. In semi-field experiments, the abundance of florivorous beetles and flower tissue miners differed between T. vulgare chemotypes. Moreover, the scent environment affected the choice and beetles were more abundant in homogenous plots composed of one single chemotype than in plots with different neighboring chemotypes. In conclusion, flower production, floral metabolic composition and pollen quality varied to a remarkable extend within the species T. vulgare, and the attractiveness of floral scent differed also intra-individually with floral ontogeny. We found evidence for a trade-off between pollen lipid content and pollen amount on a per-plant-level. Our study highlights that chemotypes which are more susceptible to florivory are less attacked when they grow in the neighborhood of other chemotypes and thus gain a benefit from high overall chemodiversity.

Comparative proteomics of common allergenic tree pollens of birch, alder, and hazel.

BackgroundIn addition to known allergens, other proteins in pollen can aid the development of an immune response in allergic individuals. The contribution of the “unknown” protein allergens is apparent in phylogenetically related species where, despite of high homology of the lead allergens, the degree of allergenic potential can vary greatly. The aim of this study was to identify other potentially allergenic proteins in pollen of three common and highly related allergenic tree species: birch (Betula pendula), hazel (Corylus avellana) and alder (Alnus glutinosa).MethodsFor that purpose, we carried out a comprehensive, comparative proteomic screening of the pollen from the three species. In order to maximize protein recovery and coverage, different protein extraction and isolation strategies during sample preparation were employed.ResultsAs a result, we report 2500–3000 identified proteins per each of the pollen species. Identified proteins were further used for a number of annotation steps, providing insight into differential distribution of peptidases, peptidase inhibitors and other potential allergenic proteins across the three species. Moreover, we carried out functional enrichment analyses that, interestingly, corroborated high species similarity in spite of their relatively distinct protein profiles.ConclusionWe provide to our knowledge first insight into proteomes of two very important allergenic pollen types, hazel and alder, where not even transcriptomics data are available, and compared them to birch. Datasets from this study can be readily used as protein databases and as such serve as basis for further functional studies.

The Strong and the Stronger: The Effects of Increasing Ozone and Nitrogen Dioxide Concentrations in Pollen of Different Forest Species

The knowledge of pollen sensitivity and tolerance to stress factors such as air pollution is important for forest sustainability, ensuring the most efficient production with the highest benefits and lowest resource losses. This study intended to evaluate the influence of common air pollutants in four forest trees species, Betula pendula Roth, Corylus avellana L., Acer negundo L. and Quercus robur L., through a comparative analysis at the same experimental conditions. We aimed to investigate the effect that may occur in pollen fertility, protein content, oxidative stress and wall composition after exposure in vitro to ozone and nitrogen dioxide at concentration levels for vegetation protection in Europe. Our results suggest changes in pollen viability, protein content and differential sensitivity related to ROS synthesis, NADPH oxidase activity, as well as in wall composition. The results indicate that NO2 exposure affected more the pollen species studied mostly at the highest concentration exposure. As for ozone, there were less significant differences between samples; however, a different behavior occurs in O3 expositions, where the most influence happens at the legal limit for vegetation protection in Europe. Our study showed that significant pollen functions could be compromised even at common air pollutant’s concentrations.

Molecular allergy diagnosis using pollen marker allergens and pollen panallergens: Five patterns seen in multiple test reactions topollen extracts.

Polysensitizations to tree, grass, and weed pollen are found in ~ 20% of pollen-allergic individuals. They are often based on broad IgE cross-reactivities to pollen panallergens belonging to highly conserved protein families: 1. profilins, 2. polcalcins (calcium-binding proteins in pollen), 3. cyclophilins. They represent highly conserved cross-reactive minor allergens present in all pollen species, but also in plant foods and other organisms. Despite being rarely clinically relevant they can hamper allergy diagnostic tests with extracts. In this situation, molecular allergy diagnosis is able to distinguish broad cross-reactivity due to allergen-specific IgE to pollen panallergens (i.e. profilins Bet v 2 or Phl p 12; polcalcins Bet v 4 or Phl p 7; and, in the future, cyclophilins Bet v 7 or Ole e 15) from primary IgE sensitizations to so-called marker allergens represented by important pollen major allergens: Bet v 1 for the birch and beech family (Fagales), Ole e 1 for olive and ash (Oleaceae), Phl p 1 for temperate climate grasses (Poaceae), Art v 1 for mugwort (Artemisia), Amb a 1 for Ambrosia species (Ambrosia). Five typical cases (A – E) with positive skin prick test results to tree, grass, and weed pollen extracts demonstrate typical patterns of IgE sensitization with a variable impact of pollen panallergens: A – profilins, B – polcalcins, C – profilins and polcalcins, D – presumably cyclophilins, E – primary polysensitization to tree, grass, and weed pollen without interference from profilins or polcalcins. Differences between pollen extract-based skin prick test diagnosis and molecular allergen-specific IgE testing are explained using the presented concept. This approach allows to reduce the number of allergen extracts – presuming they are also clinically relevant – for allergen immunotherapy (i.e., only tree and/or grass pollen extracts), particularly in pollen-polysensitized patients.

Effect of harvest season on the nutritional value of bee pollen protein.

Bee pollen is a natural product that has valuable nutritional and medicinal characteristics and has recently garnered increasing attention in the food industry due to its nutritive value. Here, we harvested pollen loads from the Al-Ahsa oasis in eastern Saudi Arabia during spring, summer, autumn, and winter in 2018/2019 to compare the nutritional value of bee pollen protein with the amino acid requirements of honeybees and adult humans. Based on the nutritional value of bee pollen protein, the optimal season for harvesting bee pollen was determined. The composition of the bee pollen showed the highest contents of crude protein, total amino acids, leucine, glutamic acid, valine, isoleucine, threonine, and glycine in samples collected in spring. The highest contents of lysine, phenylalanine, threonine, tryptophan, arginine, tyrosine, and cysteine were observed in samples collected in winter. The highest contents of histidine, methionine, and serine were in samples collected in autumn. Moreover, the highest levels of aspartic acid, proline, and alanine were in samples collected in summer. Leucine, valine, lysine, histidine, threonine, and phenylalanine (except in autumn bee pollen) contents in pollen from all four seasons were above the requirements of honeybees. Leucine, valine, histidine, isoleucine (except in autumn bee pollen), lysine (except in spring and summer bee pollen), and threonine (except in winter and spring bee pollen) in all tested samples were above the requirements of adult humans. In comparison with the minimal amino acid requirements of adult humans and honeybees, the 1st limiting amino acid in bee pollen collected during the different seasons was methionine. Bee pollen collected during spring (March-May) and winter (December-February) can be considered a nutritive food source for adult humans and honeybees.

Ambient particulate matter-associated autophagy alleviates pulmonary inflammation induced by Platanus pollen protein 3 (Pla3)

Subpollen particles (SPPs) with diameter less than 1 mm released from allergenic pollen grains contain allergens could trigger asthma and lung inflammation after being inhaled. In the meaning time, ambient fine particles attached on the pollen grains could have further effects on the inflammation. However, the mechanisms underlying these phenomena have not been fully elucidated. In this study, the effects of autophagy triggered by PM2.5 and Platanus SPPs were evaluated by using the A549 cell lines and a pollen sensitized rat model. First, autophagy in A549 cells was analyzed after exposure to PM2.5 using acridine orange staining, real-time quantitative PCR (qRT-PCR), and western blot (WB) assays. The increased levels of ROS, superoxide dismutase, and malonaldehyde in the lung homogenates of rats exposed to SPPs indicated that inflammatory response was triggered in the lungs. Treatment with autophagy-inhibiting drugs showed that autophagy suppressed ROS formation and decreased the production of thymic stromal lymphopoietin (TSLP), a critical pathway altering the inflammatory response. Although the effect was indirect, autophagy appeared to negatively regulate TSLP levels, resulting in a compromised immune response. These results suggested that SPPs promote ROS generation and increase TSLP levels, triggering downstream inflammation reactions. However, ambient PM2.5 could aggravate autophagy, which in turn effectively suppressed ROS and TSLP levels, leading to the alleviation of the immune response and pulmonary inflammation.

Nutritional and techno-functional properties of monofloral bee-collected sunflower (Helianthus annuus L.) pollen

The aim of this study was to examine nutritional (total lipid, carbohydrate, protein and ash content, fatty acids and protein profile) and techno-functional properties of monofloral bee-collected sunflower pollen (Helianthus annuus L.). The content of water, total protein, carbohydrate, lipid and ash was 24.99, 14.36, 82.01, 1.62 and 2.01 g/100g DW, respectively, with the total energy value of 400.06 kcal/100 g DW. The fatty acid profile revealed the presence of five fatty acids with the stearic acid as dominant one (31.4%) followed by α-linoleic (20.7%), pentadecanoic (18.2%), heneicosanoic (17.1%) and palmitic (12.5%) acids. FTIR analysis of bee pollen grains confirmed the presence of the main pollen chemical constituents such as proteins, water, carbohydrates and lipids, but also the presence of sporopollenin and polyphenols. Raman spectroscopy analysis indicated that the surface of pollen grains was rich in carotenoids. Low protein (3.64 g/100g DW) but high carbohydrate (77.09 g/100 g DW) solubility of bee pollen was observed. The good emulsifying properties (ESI, 19.98 min; EAI, 80.54 m2/g) and excellent oil (2.43 g/g DW) but poor water (0.87 g/g DW) absorption capacities were also registered. On the other hand, the sunflower bee pollen did not show foaming properties. These findings indicate to its applicability as useful nutritional, lipophilic and anti-foaming food ingredients.

Stigma Receptivity Is Controlled by Functionally Redundant MAPK Pathway Components in Arabidopsis

In angiosperms, the process of pollination relies on species-specific interaction and signaling between the male (pollen) and female (pistil) counterparts where the interplay between several pollen and stigma proteins decides the fate of the pollen. In Brassicaceae, the dry stigmatic papillary cells control pollen germination by releasing resources only to compatible pollen thereby allowing pollen to hydrate and germinate. Despite the identification of a number of stigmatic proteins that facilitate pollination responses, the signaling mechanisms that regulate functions of these proteins have remained unknown. Here, we show that, in Arabidopsis, an extremely functionally redundant mitogen-activated protein kinase (MAPK) cascade is required for maintaining stigma receptivity to accept compatible pollen. Our genetic analyses demonstrate that in stigmas, five MAPK kinases (MKKs), MKK1/2/3/7/9 are required to transmit upstream signals to two MPKs, MPK3/4, to mediate compatible pollination. Compromised functions of these five MKKs in the quintuple mutant (mkk1/2/3RNAi/mkk7/9) phenocopied pollination defects observed in the mpk4RNAi/mpk3 double mutant. We further show that this MAPK nexus converges on Exo70A1, a previously identified stigma receptivity factor essential for pollination. Given that pollination is the crucial initial step during plant reproduction, understanding the mechanisms that govern successful pollination could lead to development of strategies to improve crop yield.

Identification of a 53 kDa protein, as a new high molecular weight allergen from Fraxinusexcelsior (Ash) pollen

Fraxinus excelsior (Ash) is a common tree and is important cause of winter–spring pollinosis in many temperate regions in the world. In this study, a high molecular weight allergen from ash pollen was identified. In all, 20 individuals allergic to ash participated in the study. Characterization and immunoreactivity of ash pollen proteins was performed using sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE), two-dimensional (2D) gel electrophoresis and immunoblotting. Immunoglobulin E (IgE)-binding proteins with apparent molecular mass ranging from 9 to 110 kDa were detected in ash pollen extract. Serum IgE of 7 (35%) patients reacted with a 53-kDa protein band. Analysis of 2D immunoblots showed several IgE-binding proteins. Moreover, mass spectrometry analysis indicated that the 53-kDa allergen was homologous to calreticulin. We defined a novel allergen from F. excelsior pollen with a molecular weight of about 53 kDa. This allergen could be considered as an important high molecular weight allergenic protein for further studies on cross-reactivity and development of diagnostic and therapeutic approaches.

Characterization of a 7 kDa pollen allergen belonging to the gibberellin‐regulated protein family from three Cupressaceae species

Severe allergy to fruits mediated by a 7kDa allergen belonging to the gibberellin-regulated protein (GRP) family is known to be associated with Cupressaceae pollinosis. To identify and characterize Cupressaceae pollen allergens involved in GRP-related fruit allergy. Pru p 7-related proteins from pollen of Cupressus sempervirens, Juniperus ashei and Cryptomeria japonica were identified using a rabbit anti-Pru p 7 antiserum, purified chromatographically and sequenced by mass spectrometry and bioinformatic comparisons. The Csempervirens protein was produced as a recombinant allergen in Pichia pastoris. IgE antibody binding to pollen GRP proteins was analysed in a peach allergic (n=54) and a cypress pollen allergic (n=88) patient population from southern France using ImmunoCAP. In each of the three Cupressaceae species studied, a 7kDa pollen protein related to Pru p 7 was identified and found to comprise an amino acid sequence of 63 residues in length, 92%-98% identical to each other and 67%-68% identical to Pru p 7. The Csempervirens, Jashei and Cjaponica GRP allergens have been officially recognized by the WHO/IUIS Allergen Nomenclature Sub-Committee and named Cup s 7, Jun a 7 and Cry j 7, respectively. Recombinant Cup s 7 showed IgE antibody binding capacity comparable to that of the purified natural allergen. Among 51 peach allergic subjects sensitized to Pru p 7, substantially higher levels of IgE to Cup s 7 than to Pru p 7 were found. Further, the pollen protein was able to completely outcompete IgE binding to Pru p 7, while the reverse competition effect was modest, consistent with primary sensitization by the pollen allergen. Pru p 7-related pollen allergens from three Cupressaceae species have been characterized and may become useful for the identification of pollinosis patients at risk of developing severe fruit allergy.

Effect of succinylation on the secondary structures, surface, and thermal properties of date palm pollen protein concentrate.

The present study was attempted to investigate the effect of succinylation, as chemical modification, on the functionality of male date palm pollen protein concentrate (MDPPPC). Succinylation was applied at two levels, 4 and 8mol of succinic acid per mole of lysine. 4M and 8M were compared to the native MDPPPC. Findings proved that succinylation improved the surface properties of pollen protein including solubility and surfactant activity. Increased solubility of succinylated MDPPPC has been noticed especially in pH superior to pHi. The results from the differential scanning calorimetry showed a significant decrease (P < 0.05) of the denaturation temperature and the heat enthalpy for succinylated MDPPPC. β turn of succinylated MDPPPC increased significantly (P < 0.05) at the expense of β sheet indicating that the protein gained more mobility after succinylation which explains the enhancement of the functional properties and promotes the use of succinylated protein as a techno-functional ingredient.

Competitive pressure by territorials promotes the utilization of unusual food source by subordinate ants in temperate European woodlands

In the presence of territorial dominant ant species, lower-ranked ants change their foraging strategy by shifting their activity in time and space and by switching to suboptimal food sources. Although important for many insect species, pollen is a rarely used food source by ants. Occasional pollen consumption was demonstrated only in a handful of ant species that are mainly lower-ranked in the competitive hierarchy. We hypothesized that the consumption of pollen by subordinate ants might be enhanced by competitive pressure exerted by dominant species. In the frame of the current study, we assessed the food preference of ant species within a supercolony of the territorial wood ant Formica polyctena by offering them pollen and animal protein baits. Subordinate ant species, especially Myrmica ants, exploited both pollen and animal protein, while F. polyctena foraged only for animal protein. The Myrmica ants exploited pollen sources more intensively on plots where F. polyctena dominated animal protein baits, thus interspecific competition was stronger. As suggested by our study, under suboptimal conditions, where food availability is hindered, e.g. by the presence of superior competitors, pollen can, indeed, be used as a food source by subordinate ants.

Stability and structural properties of bee pollen protein hydrolysate microencapsulated using maltodextrin and whey protein concentrate

In this research, the bee pollen protein hydrolysate was microencapsulated by spray drying using maltodextrin (MD), whey protein concentrate (WPC) and a mixture of both compounds. For this purpose, the bee pollen was hydrolysed by alcalase (enzyme concentration of 1.5%) at 50 °C and pH 8 during 3.95 h, and then freeze-dried. The hydrolysed protein and wall materials were used in ratio of 1:10 (w/w). The wall materials included maltodextrin 2%, WPC 2%, as well as maltodextrin and WPC mixtures with 3:1 ratio. The resulting capsules were exposed to UV radiation for 48 h to accelerate the oxidation. The results showed that the capsule prepared using maltodextrin and WPC mixture showed the highest DPPH radical scavenging during exposure to UV radiation. Based on the FTIR spectroscopy results, the wall containing maltodextrin and WPC mixture showed the best performance in maintaining the chemical structure of hydrolysed protein. The SEM results indicated that the microcapsules prepared with WPC and maltodextrin mixture as wall material showed uniform and smoother wall than those prepared with maltodextrin alone. Finally, it was found that the maltodextrin and WPC mixture was the best wall with an appropriate protective capability for the microencapsulation of hydrolysed proteins and their protection against UV radiation.