Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Negative effects of urbanization on agricultural soil easily oxidizable organic carbon down the profile of the Chengdu Plain, China
Luo, Youlin ; Li, Qiquan ; Wang, Changquan ; Li, Bing ; Stomph, Tjeerd Jan ; Yang, Juan ; Tao, Qi ; Yuan, Shu ; Tang, Xiaoyan ; Ge, Jinru ; Yu, Xuelian ; Peng, Yueyue ; Xu, Qiang ; Zheng, Gangxun - \ 2019
Land Degradation and Development (2019). - ISSN 1085-3278
easily oxidized organic carbon - impact factors - negative effects - rapid urbanization - soil profile

Soil easily oxidizable organic carbon (EOC) is directly related to CO2 density; dynamics in subsurface EOC have been observed globally in relation to rapid urbanization. However, in the context of rapid urbanization, the factors related to EOC and the response of the EOC pool to urbanization down the profile remain elusive. The aim of the current paper is to investigate possible changes in the distribution of EOC over the soil profile and the impact of land use, socioeconomic, and natural factors on these. The study used samples from 182 soil profiles (0–100 cm) taken in the peri-urban areas of the megacity Chengdu (a typical megacity with rapid urbanization). Main drivers of changes in soil EOC were analyzed by using spatial and regression analyses. Closer to the centre of the city, soil EOC levels were lower and land-use factors and socioeconomic factors contributed more to explaining variation in EOC levels in the 0–40-cm layer, whereas natural factors were most important at larger distance from the city. The effect of land-use factors and socioeconomic factors on EOC reached down to 60-cm depths. Moreover, an estimated 20% loss of EOC stock was observed close to the city in comparison with the surroundings, suggesting that the rapid process of urbanization was accompanied by a loss of EOC stock down the profile to depths of 60 cm, and the negative effects on EOC stock became more intensive as the distance to the city decreased.

ABA-mediated regulation of leaf and root hydraulic conductance in tomato grown at elevated CO2 is associated with altered gene expression of aquaporins
Fang, Liang ; Abdelhakim, Lamis Osama Anwar ; Hegelund, Josefine Nymark ; Li, Shenglan ; Liu, Jie ; Peng, Xiaoying ; Li, Xiangnan ; Wei, Zhenhua ; Liu, Fulai - \ 2019
Horticulture Research 6 (2019)1. - ISSN 2052-7276

Elevated CO2 concentration in the air (e[CO2]) decreases stomatal density (SD) and stomatal conductance (gs) where abscisic acid (ABA) may play a role, yet the underlying mechanism remains largely elusive. We investigated the effects of e[CO2] (800 ppm) on leaf gas exchange and water relations of two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (WT) and its ABA-deficient mutant (flacca). Compared to plants grown at ambient CO2 (400 ppm), e[CO2] stimulated photosynthetic rate in both genotypes, while depressed the gs only in WT. SD showed a similar response to e[CO2] as gs, although the change was not significant. e[CO2] increased leaf and xylem ABA concentrations and xylem sap pH, where the increases were larger in WT than in flacca. Although leaf water potential was unaffected by CO2 growth environment, e[CO2] lowered osmotic potential, hence tended to increase turgor pressure particularly for WT. e[CO2] reduced hydraulic conductance of leaf and root in WT but not in flacca, which was associated with downregulation of gene expression of aquaporins. It is concluded that ABA-mediated regulation of gs, SD, and gene expression of aquaporins coordinates the whole-plant hydraulics of tomato grown at different CO2 environments.

NSs Filament Formation Is Important but Not Sufficient for RVFV Virulence In Vivo
Li, Shufen ; Zhu, Xiangtao ; Guan, Zhenqiong ; Huang, Wenfeng ; Zhang, Yulan ; Kortekaas, Jeroen ; Lozach, Pierre Yves ; Peng, Ke - \ 2019
Viruses 11 (2019)9. - ISSN 1999-4915
filament - NSs - reverse genetics system - RVFV - virulence

Rift Valley fever virus (RVFV) is a mosquito-borne phlebovirus that represents as a serious health threat to both domestic animals and humans. The viral protein NSs is the key virulence factor of RVFV, and has been proposed that NSs nuclear filament formation is critical for its virulence. However, the detailed mechanisms are currently unclear. Here, we generated a T7 RNA polymerase-driven RVFV reverse genetics system based on a strain imported into China (BJ01). Several NSs mutations (T1, T3 and T4) were introduced into the system for investigating the correlation between NSs filament formation and virulence in vivo. The NSs T1 mutant showed distinct NSs filament in the nuclei of infected cells, the T3 mutant diffusively localized in the cytoplasm and the T4 mutant showed fragmented nuclear filament formation. Infection of BALB/c mice with these NSs mutant viruses revealed that the in vivo virulence was severely compromised for all three NSs mutants, including the T1 mutant. This suggests that NSs filament formation is not directly correlated with RVFV virulence in vivo. Results from this study not only shed new light on the virulence mechanism of RVFV NSs but also provided tools for future in-depth investigations of RVFV pathogenesis and anti-RVFV drug screening.

Exploring near-surface ground ice distribution in patterned-ground tundracorrelations with topography, soil and vegetation: correlations with topography, soil and vegetation
Wang, Peng ; Jager, Judith de; Nauta, Ake ; Huissteden, Jacobus van; Trofim, Maximov C. ; Limpens, Juul - \ 2019
Plant and Soil (2019). - ISSN 0032-079X - 15 p.
Arctic tundra - Ground ice - Permafrost degradation - Polygon - Thaw depth - Vegetation

Aims: For informed predictions on the sensitivity of Arctic tundra landscape to permafrost thaw, we aimed to investigate the distribution pattern of near-surface ground ice and its influencing factors in Northeast Siberia. Methods: Near-surface permafrost cores (60 cm) were sampled along small-scale topographic gradients in two drained lakebeds. We investigated which factors (vegetation, hydrological and soil) correlated strongest with ice content and explored its spatial heterogeneity at different scales (1 to 100 m). Results: The ice content was highest in the depressions of the wet lakebed and lowest at the slopes of the dry lakebed. In the wet lakebed the ice content increased with depth, while in the dry lakebed the vertical distribution depended on topographical position. Spatial variability in ice content was similar at different scales, stressing strong influence of local drivers. 0–60 cm ice content correlated strongest with soil moisture of the overlying unfrozen soil, while 0–20 cm ice content correlated strongest with vegetation characteristics. Conclusions: Our study implies that vegetation effect on microclimate is strong enough to affect near-surface ice distribution, and that ice-rich tundra may be highly sensitive to thaw once climate warming offsets the protective impact of vegetation.

Microbial transformation of organic and inorganic halogen compounds
Peng, Peng - \ 2019
Wageningen University. Promotor(en): H. Smidt, co-promotor(en): S. Atashgahi. - Wageningen : Wageningen University - ISBN 9789463950190 - 182
A network approach to prioritize conservation efforts for migratory birds
Xu, Yanjie ; Si, Yali ; Takekawa, John ; Liu, Qiang ; Prins, Herbert H.T. ; Yin, Shenglai ; Prosser, Diann J. ; Gong, Peng ; Boer, Willem F. de - \ 2019
Conservation Biology (2019). - ISSN 0888-8892
bird migration - connectivity - conservation designation - habitat loss - network

Habitat loss can trigger migration network collapse by isolating migratory bird breeding grounds from nonbreeding grounds. Theoretically, habitat loss can have vastly different impacts depending on the site's importance within the migratory corridor. However, migration-network connectivity and the impacts of site loss are not completely understood. We used GPS tracking data on 4 bird species in the Asian flyways to construct migration networks and proposed a framework for assessing network connectivity for migratory species. We used a node-removal process to identify stopover sites with the highest impact on connectivity. In general, migration networks with fewer stopover sites were more vulnerable to habitat loss. Node removal in order from the highest to lowest degree of habitat loss yielded an increase of network resistance similar to random removal. In contrast, resistance increased more rapidly when removing nodes in order from the highest to lowest betweenness value (quantified by the number of shortest paths passing through the specific node). We quantified the risk of migration network collapse and identified crucial sites by first selecting sites with large contributions to network connectivity and then identifying which of those sites were likely to be removed from the network (i.e., sites with habitat loss). Among these crucial sites, 42% were not designated as protected areas. Setting priorities for site protection should account for a site's position in the migration network, rather than only site-specific characteristics. Our framework for assessing migration-network connectivity enables site prioritization for conservation of migratory species.

Reductive dechlorination of 1,2-dichloroethane in the presence of chloroethenes and 1,2-dichloropropane as co-contaminants
Peng, Peng ; Schneidewind, Uwe ; Haest, Pieter Jan ; Bosma, Tom N.P. ; Danko, Anthony S. ; Smidt, Hauke ; Atashgahi, Siavash - \ 2019
Applied Microbiology and Biotechnology 103 (2019)16. - ISSN 0175-7598 - p. 6837 - 6849.
1,2-Dichloroethane - Co-contaminants - Dechlorination kinetics - Dehalococcoides - Dehalogenimonas

1,2-Dichloroethane (1,2-DCA) is one of the most abundant manmade chlorinated organic contaminants in the world. Reductive dechlorination of 1,2-DCA by organohalide-respiring bacteria (OHRB) can be impacted by other chlorinated contaminants such as chloroethenes and chloropropanes that can co-exist with 1,2-DCA at contaminated sites. The aim of this study was to evaluate the effect of chloroethenes and 1,2-dichloropropane (1,2-DCP) on 1,2-DCA dechlorination using sediment cultures enriched with 1,2-DCA as the sole chlorinated compound (EA culture) or with 1,2-DCA and tetrachloroethene (PCE) (EB culture), and to model dechlorination kinetics. Both cultures contained Dehalococcoides as most predominated OHRB, and Dehalogenimonas and Geobacter as other known OHRB. In sediment-free enrichments obtained from the EA and EB cultures, dechlorination of 1,2-DCA was inhibited in the presence of the same concentrations of either PCE, vinyl chloride (VC), or 1,2-DCP; however, concurrent dechlorination of dual chlorinated compounds was achieved. In contrast, 1,2-DCA dechlorination completely ceased in the presence of cis-dichloroethene (cDCE) and only occurred after cDCE was fully dechlorinated. In turn, 1,2-DCA did not affect dechlorination of PCE, cDCE, VC, and 1,2-DCP. In sediment-free enrichments obtained from the EA culture, Dehalogenimonas 16S rRNA gene copy numbers decreased 1–3 orders of magnitude likely due to an inhibitory effect of chloroethenes. Dechlorination with and without competitive inhibition fit Michaelis-Menten kinetics and confirmed the inhibitory effect of chloroethenes and 1,2-DCP on 1,2-DCA dechlorination. This study reinforces that the type of chlorinated substrate drives the selection of specific OHRB, and indicates that removal of chloroethenes and in particular cDCE might be necessary before effective removal of 1,2-DCA at sites contaminated with mixed chlorinated solvents.

Effects of iron, calcium, and organic matter on phosphorus behavior in fluvo-aquic soil: farmland investigation and aging experiments
Ma, Yuling ; Ma, Jie ; Peng, Hao ; Weng, Liping ; Chen, Yali ; Li, Yongtao - \ 2019
Journal of Soils and Sediments (2019). - ISSN 1439-0108
Calcium carbonate - Fe mineral - Fluvo-aquic soil - Organic fertilizer - Phosphorus fractions - Phosphorus immobilization

Purpose: Excessive fertilization has led to a high risk of phosphorus (P) leaching and related problems in the North China Plain, where the most typical cropland soil is fluvo-aquic soil. The main factors controlling environmental P behavior and the acting time sequence of these factors in soil after long-term P fertilizer application have not been well recognized. A clear understanding is essential for effective P management. Materials and methods: Effects of Fe minerals, calcium carbonate, and organic matter (OM) on P immobilization in fluvo-aquic soil were studied systematically through farmland investigation and aging experiments. Results and discussion: Phosphorus associated with Ca was the primary fraction in fluvo-aquic soil. Even though there was no significant correlation between the total contents of P and Ca in soils, formation of P-Ca phases facilitated by Ca2+ in soil solution was a mechanism of P retention when soil received excess P fertilizer. Positive correlations between the contents of P and Fe and total organic carbon (TOC) indicate that Fe minerals and OM have significant effects on P immobilization. Through the aging experiments, P was found to primarily adsorb on goethite and gradually forms Ca-P compounds. Organic fertilizer caused P release and inhibition of P adsorption in the initial stages; however, OM derived from organic fertilizer might facilitate P immobilization in the long term through the formation of a P-Ca-OM complex. Conclusions: Although superfluous application of P fertilizers leads to the gradual formation of Ca-P in fluvo-aquic soils, there is still a risk of P loss because P is not immediately adsorbed by Fe minerals. Moreover, application of organic fertilizers increases the risk of P loss. These results provide an important scientific basis for initiating P management policies for fluvo-aquic soils.

Composite Gels Containing Whey Protein Fibrils and Bacterial Cellulose Microfibrils
Peng, Jinfeng ; Calabrese, Vincenzo ; Geurtz, Julia ; Velikov, Krassimir P. ; Venema, Paul ; Linden, Erik van der - \ 2019
Journal of Food Science 84 (2019)5. - ISSN 0022-1147 - p. 1094 - 1103.
bacterial cellulose microfibrils - fibrillar gel - microstructure - protein fibrils - whey protein isolate

In this study, we investigated the gelation of WPI fibrils in the presence of bacterial cellulose (BC) microfibrils at pH 2 upon prolonged heating. Rheology and microstructure were investigated as a function of BC microfibril concentration. The presence of BC microfibrils did not influence the gelation dynamics and resulting overall structure of the WPI fibrillar gel. The storage modulus and loss modulus of the mixed WPI-BC microfibril gels increased with increasing BC microfibril concentration, whereas the ratio between loss modulus and storage modulus remained constant. The WPI fibrils and BC microfibrils independently form two coexisting gel networks. Interestingly, near to the BC microfibrils more aligned WPI fibrils seemed to be formed, with individual WPI fibrils clearly distinguishable. The level of alignment of the WPI fibrils seemed to be dependent on the distance between BC microfibrils and WPI fibrils. This also is in line with our observation that with more BC microfibrils present, WPI fibrils are more aligned than in a WPI fibrillar gel without BC microfibrils. The large deformation response of the gels at different BC microfibril concentration and NaCl concentration is mainly influenced by the concentration of NaCl, which affects the WPI fibrillar gel structures, changing form linear fibrillar to a particulate gel. The WPI fibrillar gel yields the dominant contribution to the gel strength.

Airborne host–plant manipulation by whiteflies via an inducible blend of plant volatiles
Zhang, Peng Jun ; Wei, Jia Ning ; Zhao, Chan ; Zhang, Ya Fen ; Li, Chuan You ; Liu, Shu Sheng ; Dicke, Marcel ; Yu, Xiao Ping ; Turlings, Ted C.J. - \ 2019
Proceedings of the National Academy of Sciences of the United States of America 116 (2019)15. - ISSN 0027-8424 - p. 7387 - 7396.
Herbivore-induced plant volatiles - Jasmonic acid - Salicylic acid - Tomato - Whiteflies

The whitefly Bemisia tabaci is one of the world’s most important invasive crop pests, possibly because it manipulates plant defense signaling. Upon infestation by whiteflies, plants mobilize salicylic acid (SA)-dependent defenses, which mainly target pathogens. In contrast, jasmonic acid (JA)-dependent defenses are gradually suppressed in whitefly-infested plants. The down-regulation of JA defenses make plants more susceptible to insects, including whiteflies. Here, we report that this host–plant manipulation extends to neighboring plants via airborne signals. Plants respond to insect attack with the release of a blend of inducible volatiles. Perception of these volatiles by neighboring plants usually primes them to prepare for an imminent attack. Here, however, we show that whitefly-induced tomato plant volatiles prime SA-dependent defenses and suppress JA-dependent defenses, thus rendering neighboring tomato plants more susceptible to whiteflies. Experiments with volatiles from caterpillar-damaged and pathogen-infected plants, as well as with synthetic volatiles, confirm that whiteflies modify the quality of neighboring plants for their offspring via whitefly-inducible plant volatiles.

Fate and effects of triclosan in subtropical river biofilms
Zhang, Naisheng S. ; Peng, Feng-Jiao ; Ying, G.G. ; Brink, P.J. van den - \ 2019
Aquatic Toxicology 212 (2019). - ISSN 0166-445X - p. 11 - 19.
Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) is a broad-spectrum antimicrobial compound. Owing to its wide use, TCS has been frequently detected in river systems, especially in the (sub-)tropics. However, little information on its interaction with river biofilm in the (sub)tropics is currently available. In the present study, subtropical river biofilms were chronically exposed to TCS for 14 d at concentrations of 0.1–100 μg/L in artificial river water, which was followed by a 7 d recovery period. The results show that 100 μg/L TCS inhibited the growth of river biofilms and the no-observed-effect concentration (NOEC) of TCS on river biofilms was 10 μg/L. The affected biofilms did not completely recover within the 7 d of recovery period due to the adsorbed TCS which was not removed together with dissolved TCS. Exposure to TCS caused significant changes in prokaryotic species composition of river biofilms but no significant effects on eukaryotic species composition. In particular, the relative abundance of several TCS-tolerant bacterial species (e.g., Pseudoxanthomonas mexicana, Sphingopyxis alaskensis and Sphingomonas wittichii) in river biofilms increased following exposure to 10 and 100 μg/L TCS. River biofilm efficiently removed TCS from the liquid phase and the pH values of the aquatic system significantly affected the removal efficiency of TCS (from 36% at pH 6.5 to 60% at pH 8.5). No degradation products were detected in the liquid phase after 5 days of exposure, possibly due to strong adsorption of the hydrophobic degradation products to river biofilms and through biodegradation by bacteria utilizing TCS and its degradation products as source of carbon and energy for growth, such as Methyloversalitis universalis and Methylobacterium aquaticum.
Response of sediment bacterial community to triclosan in subtropical freshwater benthic microcosms
Peng, Feng Jiao ; Diepens, Noël J. ; Pan, Chang Gui ; Ying, Guang Guo ; Salvito, Daniel ; Selck, Henriette ; Brink, Paul J. Van den - \ 2019
Environmental Pollution 248 (2019). - ISSN 0269-7491 - p. 676 - 683.
Benthic macroinvertebrates - Microcosm - Sediment bacterial community - Toxicity - Triclosan

The response of sediment bacterial communities in subtropical freshwater benthic microcosms to sediment-associated triclosan (TCS; 28 d exposure) was analysed using Illumina high-throughput sequencing. This study highlights the interactive effects of TCS and the presence of benthic macroinvertebrates (Limnodrilus hoffmeisteri and Viviparidae bellamya) on sediment bacterial communities. Our results show that TCS alone significantly altered the taxonomic composition and decreased alpha diversity of sediment bacterial communities at concentrations ≥80 μg TCS/g dry weight (dw) sediment (sed). Regarding dominant phyla, TCS significantly reduced the relative abundance of Bacteroidetes and Firmicutes at these concentrations, whereas the relative abundance of Chloroflexi and Cyanobacteria increased. In the presence of benthic macroinvertebrates, the sediment bacterial community was affected by 8 μg TCS/g dw sed as well. However, the presence of benthic macroinvertebrates did not cause measurable changes to bacterial community in unspiked (i.e., control) sediment. These results indicate that TCS alone would not alter the sediment bacterial community at environmentally relevant concentrations (up till 8 μg/g dw sed), but may have an effect in combination with the presence of benthic macroinvertebrates. Therefore, we recommend to include benthic macroinvertebrates when assessing the response of sediment bacterial communities during exposure to environmental stress such as organic contaminants.

Species-dependent effects of habitat degradation in relation to seasonal distribution of migratory waterfowl in the East Asian–Australasian Flyway
Xu, Yanjie ; Si, Yali ; Yin, Shenglai ; Zhang, Wenyuan ; Grishchenko, Mikhail ; Prins, Herbert H.T. ; Gong, Peng ; Boer, Willem F. de - \ 2019
Landscape Ecology 34 (2019)2. - ISSN 0921-2973 - p. 243 - 257.
East Asian–Australasian Flyway - Fragmentation - Habitat loss - Isolation - Migratory connectivity - Migratory waterfowl - Seasonal distribution - Species trait - Wetland
Context: Migratory species’ resilience to landscape changes depends on spatial patterns of habitat degradation in relation to their migratory movements, such as the distance between breeding and non-breeding areas, and the location and width of migration corridors. Objectives: We investigated to what extent the impact of habitat degradation depended on the seasonal distributions of migratory waterfowl. Methods: Using logistic regression, we selected wetland sites for eight waterfowl species in the East Asian–Australasian Flyway (EAAF) by calculating the probabilities of species occurrence per wetland site in relation to environmental factors. We quantified landscape metrics related to habitat degradation within these wetland sites. We used general linear models to test for differences in the effects of habitat degradation on waterfowl species with different migration extents and at different latitudes. Results: The patterns of habitat degradation differed spatially across the EAAF and affected species to a different degree. Species with shorter and broader migration corridors (Anser cygnoid and A. anser) could benefit from improved habitat conditions in the west of the EAAF. Species with longer and narrower migration corridors (Cygnus columbianus, A. fabalis, A. albifrons, A. erythropus, Anas crecca, and Anas acuta) were under higher risk of habitat degradation in the coastal regions of China and Japan. Conclusions: Migratory species with longer and narrower migration corridors are more affected by habitat degradation, because they might have fewer alternative stopover sites at similar latitude. Our findings improve the understanding of species-specific effects of environmental changes on migratory species, and defines critical and endangered wetland sites, and vulnerable species.
Insights into the sediment toxicity of personal care products to freshwater oligochaete worms using Fourier transform infrared spectroscopy
Peng, Feng Jiao ; Hu, Li Xin ; Pan, Chang Gui ; Ying, Guang Guo ; Brink, Paul J. van den - \ 2019
Ecotoxicology and Environmental Safety 172 (2019). - ISSN 0147-6513 - p. 296 - 302.
Biochemical fingerprint - Deposit-feeder - FTIR spectroscopy - Microcosm - Musk - Triclosan

Personal care products (PCPs) are ubiquitous in the environment due to their wide use in daily life. However, there are insufficient sediment toxicity data of PCPs under ecologically relevant conditions. Here we used Fourier transform infrared spectroscopy (FTIR) to investigate the sediment toxicity of triclosan (TCS) and galaxolide (HHCB) to two freshwater benthic macroinvertebrates, Limnodrilus hoffmeisteri and Branchiura sowerbyi, in microcosms containing a diverse biological community. Exposure to 8 µg TCS/g and 100 µg HHCB/g dry weight (dw) sediment induced significant biochemical alterations in the L. hoffmeisteri tissue. 8 µg TCS/g primarily affected proteins and nucleic acid while 100 µg HHCB/g mainly affected proteins and lipids of L. hoffmeisteri. However, 0.8 µg TCS/g and 30 µg HHCB/g did not cause significant subcellular toxicity to L. hoffmeisteri. In contrast, exposure of B. sowerbyi to 30 µg HHCB/g led to significant biochemical changes, including proteins, polysaccharides and lipids. Therefore, B. sowerbyi was more sensitive to sediment-associated HHCB than L. hoffmeisteri. Such effects were significantly enhanced when the HHCB concentration increased to 100 µg/g dw where death of B. sowerbyi occurred. These results demonstrate the application of FTIR spectroscopy to sediment toxicity testing of chemicals to benthic invertebrates with biochemical alterations as endpoints that are more sensitive than standard toxic endpoints (e.g., survival and growth).

Mixed gels from whey protein isolate and cellulose microfibrils
Peng, Jinfeng ; Calabrese, Vincenzo ; Ainis, William Nicholas ; Scager, Ruben ; Velikov, Krassimir P. ; Venema, Paul ; Linden, Erik van der - \ 2019
International Journal of Biological Macromolecules 124 (2019). - ISSN 0141-8130 - p. 1094 - 1105.
Bacterial cellulose microfibrils - Mixed gel - Whey protein isolate

Whey proteins can form different gel structures ranging from fine-stranded to particulate when appropriate conditions are applied. By incorporating polysaccharides, the gelation of WPI can be influenced. We investigated the heat-induced gelation of whey protein isolate (WPI) in the presence of bacterial cellulose (BC) microfibrils at pH 7 at different concentrations of NaCl. Our results showed that WPI and BC microfibrils form a homogeneous dispersion at pH 7. Upon heating, the WPI gel was formed independently in the presence of the BC microfibril gel, resulting in the formation of a composite gel. The gel structure and gelation dynamics of WPI was not influenced by the presence of BC microfibrils. However, the presence of BC microfibrils increased the storage modulus of the WPI gel, with an increase being negligible when the strength of the WPI gel is above a certain value. With an increase of NaCl concentration, the WPI gel structure changes from fine-stranded to a particulate gel, while the BC microfibril gel structure remains unchanged. No macroscopic phase separation could be observed in the WPI-BC microfibril gels. Our results showed that the rheological properties and water holding capacity of the WPI-BC microfibril mixed gels are mainly dominated by the WPI.

Fate and effects of sediment-associated polycyclic musk HHCB in subtropical freshwater microcosms
Peng, Feng Jiao ; Kiggen, Fionne ; Pan, Chang Gui ; Bracewell, Sally A. ; Ying, Guang Guo ; Salvito, Daniel ; Selck, Henriette ; Brink, Paul J. Van den - \ 2019
Ecotoxicology and Environmental Safety 169 (2019). - ISSN 0147-6513 - p. 902 - 910.
Bacterial community - Benthic macroinvertebrates - Bioaccumulation - Dissipation - HHCB - Toxicity

Galaxolide (HHCB) is used as a fragrance ingredient in household and personal care products, and has been ubiquitously detected in the environment. Here we investigated the fate of HHCB in subtropical freshwater microcosms, and evaluated effects of sediment-associated HHCB on a biological community consisting of algae, Daphnia, benthic macroinvertebrates and bacteria. The concentrations of sediment-associated HHCB did not change significantly during a 28 days exposure period, but HHCB accumulated in worms with biota-sediment accumulation-factor (BSAF) values in the range of 0.29–0.66 for Branchiura sowerbyi and 0.94–2.11 for Limnodrilus hoffmeisteri. There was no significant effects of HHCB (30 μg/g dry weight (dw) sediment) on chlorophyll-a content, sediment bacterial community composition, and survival and growth of benthic macroinvertebrates. However, the presence of benthic macroinvertebrates altered the sediment bacterial community structure relative to microcosms without introduced organisms. The findings of this study suggest that a single high-dose of HHCB, over 28 days, at environmentally relevant concentrations would not impose direct toxicological risks to aquatic organisms such as benthic macroinvertebrates.

A new satellite-based indicator to identify spatiotemporal foraging areas for herbivorous waterfowl
Wei, Jie ; Xin, Qinchuan ; Ji, Luyan ; Gong, Peng ; Si, Yali - \ 2019
Ecological Indicators 99 (2019). - ISSN 1470-160X - p. 83 - 90.
Distribution - Geese - MODIS - Nutrient biomass - Plant phenology - Yangtze River floodplain

The distribution of food resources is a key factor in habitat selection. Herbivorous waterfowl prefer early-stage growing plants (from the onset of plant growth to the peak in nutrient biomass) as these offer higher energy intake rates. This plant development stage is not fully captured by commonly used satellite-derived vegetation indicators, which focus on plant biomass (e.g., Enhanced Vegetation Index, EVI) or active plant growth (e.g., the differential EVI between current and a previous date, diffEVI). To improve mapping suitable grazing areas for herbivorous waterfowl, we propose a new satellite-based plant growth indicator of early-stage plant growth (ESPG). We hypothesize that herbivorous waterfowl prefer plants at an early development stage during the growing season and select plants with a relatively later end of ESPG during the non-growing season. We use satellite tracking data of 20 greater white-fronted geese (Anser albifrons) wintering in the Yangtze River floodplain to validate our predictions. We build generalized linear models for goose distributions during the growing and non-growing seasons and compare the performance of ESPG to commonly used plant growth indictors (EVI and diffEVI). During the growing season, ESPG can explain 53% of variation in the goose distribution, outperforming EVI (27%) and diffEVI (34%). During the non-growing season, only the end of ESPG significantly influences goose distribution, explaining 25% of the variance (ESPG: AUC = 0.78; EVI: AUC = 0.58; diffEVI: AUC = 0.58). The newly-developed plant growth indicator ESPG could be used to improve models of herbivorous waterfowl distributions and hence support efforts toward waterfowl conservation and wetland management.

Discovering novel hydrolases from hot environments
Wohlgemuth, Roland ; Littlechild, Jennifer ; Monti, Daniela ; Schnorr, Kirk ; Rossum, Teunke van; Siebers, Bettina ; Menzel, Peter ; Kublanov, Ilya V. ; Rike, Anne Gunn ; Skretas, Georgios ; Szabo, Zalan ; Peng, Xu ; Young, Mark J. - \ 2018
Biotechnology Advances 36 (2018)8. - ISSN 0734-9750 - p. 2077 - 2100.
Biocatalysis - Enrichment - Enzyme characterization - Enzyme screening - Gene expression - Genomics - Hydrolases - Metagenomics - Sequencing - Thermophiles

Novel hydrolases from hot and other extreme environments showing appropriate performance and/or novel functionalities and new approaches for their systematic screening are of great interest for developing new processes, for improving safety, health and environment issues. Existing processes could benefit as well from their properties. The workflow, based on the HotZyme project, describes a multitude of technologies and their integration from discovery to application, providing new tools for discovering, identifying and characterizing more novel thermostable hydrolases with desired functions from hot terrestrial and marine environments. To this end, hot springs worldwide were mined, resulting in hundreds of environmental samples and thousands of enrichment cultures growing on polymeric substrates of industrial interest. Using high-throughput sequencing and bioinformatics, 15 hot spring metagenomes, as well as several sequenced isolate genomes and transcriptomes were obtained. To facilitate the discovery of novel hydrolases, the annotation platform Anastasia and a whole-cell bioreporter-based functional screening method were developed. Sequence-based screening and functional screening together resulted in about 100 potentially new hydrolases of which more than a dozen have been characterized comprehensively from a biochemical and structural perspective. The characterized hydrolases include thermostable carboxylesterases, enol lactonases, quorum sensing lactonases, gluconolactonases, epoxide hydrolases, and cellulases. Apart from these novel thermostable hydrolases, the project generated an enormous amount of samples and data, thereby allowing the future discovery of even more novel enzymes.

Bioaccumulation and Biotransformation of Triclosan and Galaxolide in the Freshwater Oligochaete Limnodrilus hoffmeisteri in a Water/Sediment Microcosm
Peng, Feng-Jiao ; Ying, Guang Guo ; Pan, Chang Gui ; Selck, Henriette ; Salvito, Daniel ; Brink, Paul J. van den - \ 2018
Environmental Science and Technology 52 (2018)15. - ISSN 0013-936X - p. 8390 - 8398.

Personal care products are widely used in our daily life in considerable quantities and discharged via the down-the-drain route to aquatic environments, resulting in potential risks to aquatic organisms. We investigated bioaccumulation and biotransformation of two widely used personal care products, triclosan (TCS) and galaxolide (HHCB) spiked to sediment, in the oligochaete worm Limnodrilus hoffmeisteri in water/sediment microcosms. After 7 days of sediment exposure to 3.1 μg of TCS or HHCB/g of dry weight sediment, the accumulation of TCS and HHCB in L. hoffmeisteri reached equilibrium, at which point the biota-sediment accumulation factors (BSAFs) were 2.07 and 2.50 for TCS and HHCB, respectively. The presence of L. hoffmeisteri significantly accelerated the dissipation of the levels of TCS and HHCB in the microcosms, with approximately 9.03 and 2.90% of TCS and HHCB, respectively, eliminated from the water/sediment systems after exposure for 14 days in the presence of worms. Two biotransformation products, methyl triclosan and triclosan O-sulfate, were identified for TCS in worm tissue, whereas only methyl triclosan was identified in the sediment. Unlike TCS, no evidence of biotransformation products was found for HHCB in either worm tissue or sediment. These experiments demonstrate that L. hoffmeisteri biotransformed TCS through methylation and sulfation, whereas HHCB biotransformation was undetectable.

Ecological risks of personal care ingredients for subtropical benthic communities
Peng, Fenjiao - \ 2018
Wageningen University. Promotor(en): P.J. Brink, co-promotor(en): Guang-Guo Ying. - Wageningen : Wageningen University - ISBN 9789463433129 - 211
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