Investigation of polyhydroxyalkanoates (PHAs) biosynthesis from mixed culture enriched by valerate-dominant hydrolysate

The production of polyhydroxyalkanoates (PHAs) with a high fraction of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2MV) from mixed culture enriched by valerate-dominant hydrolysate was evaluated in this study. After long-term enrichment, the culture showed strong ability to synthesize 3HV and 3H2MV, even with acetate-dominant substrate. The ultilization of single or mixed iso-/n-valerate by the enriched culture showed that the mixture of iso-valerate and n-valerate was more efficient substrate than any single in terms of balancing microbial growth and PHAs synthesis. Besides, through comparing the kinetics and stoichiometry of the tests supplying valerate and propionate, the enriched culture with equivalent valerate and propionate (1:1 molar ratio) exhibited superior PHAs production performances to pure valerate or propionate, attaining more than 70 mol% of 3HVand 3H2MV. The above findings reveal that valerate-dominant hydrolysate is a kind of suitable substrate to enrich PHAs producing culture with great capability to synthesize 3HV and 3H2MV monomers, thus improving product properties than pure poly(3-hydroxybutyrate) (P3HB); also 3HV and 3H2MV production behaviors can be regulated by the type of odd-carbon VFAs in the substrate.

Open image in new window

     

The progress of interdisciplinarity in invasion science

Interdisciplinarity is needed to gain knowledge of the ecology of invasive species and invaded ecosystems, and of the human dimensions of biological invasions. We combine a quantitative literature review with a qualitative historical narrative to document the progress of interdisciplinarity in invasion science since 1950. Our review shows that 92.4% of interdisciplinary publications (out of 9192) focus on ecological questions, 4.4% on social ones, and 3.2% on social–ecological ones. The emergence of invasion science out of ecology might explain why interdisciplinarity has remained mostly within the natural sciences. Nevertheless, invasion science is attracting social–ecological collaborations to understand ecological challenges, and to develop novel approaches to address new ideas, concepts, and invasion-related questions between scholars and stakeholders. We discuss ways to reframe invasion science as a field centred on interlinked social–ecological dynamics to bring science, governance and society together in a common effort to deal with invasions.     

3种典型微生物农药对家蚕的毒性研究

苏云金芽孢杆菌、球孢白僵菌以及棉铃虫核型多角体病毒是细菌类、真菌类和病毒类微生物农药的典型代表。为了明确微生物农药对家蚕的毒性影响,选取以上3种典型微生物农药,分别探究其对家蚕的毒性。结果显示:苏云金杆菌原药对家蚕LC50值为1.33×105CFU·m L-1;球孢白僵菌原药对家蚕LC50值为1.14×106CFU·m L-1;棉铃虫核型多角体病毒母药对家蚕LC50值大于1.00×108PIB·m L-1。与此同时,通过进一步试验,明确了以上3种微生物农药对家蚕结茧率、死笼率、全茧量、茧层量等关键指标的影响。结果显示:除了棉铃虫核型多角体病毒母药,高浓度苏云金杆菌原药、球孢白僵菌原药对家蚕的结茧率和死笼率均具有显著影响;3种微生物农药对家蚕产茧能力指标全茧量、茧层量以及蛹重均无显著性影响。     

Impairments of cadmium on vitellogenin accumulation in the hepatopancreas of freshwater crab <Emphasis Type="Italic">Sinopotamon henanense</Emphasis>

During ovary maturation of crabs, vitellogenin (Vg), a precursor molecule of vitellin (Vn) needed for embryogenesis, can be produced in large quantities in the hepatopancreas and then transported to the ovary by the hemolymph. In the present study, effects of Cd on Vg accumulation in the hepatopancreas and Vg transportation of the freshwater crab Sinopotamon henanense were investigated. We also studied the impacts of Cd on the mRNA expression of genes involved in energy metabolism, protein metabolism, and metallothionein (MT) and glutathione (GSH) synthesis. After Cd treatment, the Vg concentration and the Vg mRNA expression in the hepatopancreas were downregulated. Pearson’s correlation coefficient showed that the Vg level in the hepatopancreas correlated positively with those of the ovary and hemolymph (correlation coefficients 0.844 and 0.749, respectively), suggesting that the Vg transport from the hepatopancreas to the ovary can be impaired by Cd. The levels of carbohydrate and protein in the hepatopancreas of Cd-exposed crabs were decreased, and an inhibited protein metabolism was also observed. Energy production related isocitrate dehydrogenase and cytochrome C oxidase mRNA expressions, and MT and GSH synthesis increased after 10 days of Cd treatment and decreased after 20 days. Cd also caused a time-dependent upregulation of malondialdehyde. Our findings showed that Cd decreased Vg accumulation in the hepatopancreas due to partially excessive energy consumption and an activated defense system in the hepatopancreas, suggesting a possible regulatory mechanism in S. henanense which is the competitive advantage of energy reserves in metabolic Cd stress responses over the high-energy flux during vitellogenesis to ensure a continuous supply of metabolic energy. Moreover, the damage of Vg accumulation in the hepatopancreas caused by Cd could lead to an insufficient accumulation of Vn in the ovary and cause a retardation of oocyte development.     

Spatial variation and toxicity assessment for heavy metals in sediments of intertidal zone in a typical subtropical estuary (Min River) of China

Environmental Science and Pollution Research - Sediment samples were collected in five marshes (C1, Phragmites australis marsh; C2, P. australis and Cyperus malaccensis marsh; C3, C. malaccensis...     

Distribution and controls of heavy metals and organic matter in the surface sediments of the Southern Yellow Sea,China

Environmental Science and Pollution Research - Accurate and effective determination of the source of heavy metals is essential for the treatment of marine ecological environments. This article...     

基于手机APP的便携式智能无线FDR传感器系统的设计

设计了一种基于频域反射法(FDR)且具有充电功能的无线便携式传感器,能够实现自动采集、无线传输、便携充电等功能。该采集单元以单片机为核心,采用MC9S082AW60进行数据采集,通过无线传输技术进行实时传输,实现了FDR传感器的高精度、实时性强、携带方便等优点。该传感器使用简单,携带方便,适合操作人员在现场随时进行采集。     

Effect of copper(II) on biodegradation of benzo[a]pyrene by Stenotrophomonas maltophilia

Benzo[a]pyrene (BaP) biodegradation by Stenotrophomonas maltophilia was studied under the influence of co-existed Cu(II) ions. About 45% degradation was achieved within 3 d when dealing with 1 mg L^?1 BaP under initial natural pH at 30 °C; degradation reached 48% in 2 d at 35 °C. Efficacy of BaP biodegradation reached the highest point at pH 4. In the presence of 10 mg L^?1 Cu(II) ions, the BaP removal ratio was 45% on 7th day, and maintained stable from 7 to 14 d at 30 °C under natural pH. The favorable temperature and pH for BaP removal was 25 °C and 6.0 respectively, when Cu(II) ions coexisted in the solutions. Experiments on cometabolism indicated that S. maltophilia performed best when sucrose was used as an additional carbon source. GC–MS analysis revealed that the five rings of BaP opened, producing compounds with one or two rings which were more bioavailable.     

Removal of sulfamethoxazole and sulfapyridine by carbon nanotubes in fixed-bed columns

Sulfamethoxazole (SMX) and sulfapyridine (SPY), two representative sulfonamide antibiotics, have gained increasing attention because of the ecological risks these substances pose to plants, animals, and humans. This work systematically investigated the removal of SMX and SPY by carbon nanotubes (CNTs) in fixed-bed columns under a broad range of conditions including: CNT incorporation method, solution pH, bed depth, adsorbent dosage, adsorbate initial concentration, and flow rate. Fixed-bed experiments showed that pH is a key factor that affects the adsorption capacity of antibiotics to CNTs. The Bed Depth Service Time model describes well the relationship between service time and bed depth and can be used to design appropriate column parameters. During fixed-bed regeneration, small amounts of SMX (3%) and SPY (9%) were irreversibly bonded to the CNT/sand porous media, thus reducing the column capacity for subsequent reuse from 67.9 to 50.4 mg g^?1 for SMX and from 91.9 to 72.9 mg g^?1 for SPY. The reduced column capacity resulted from the decrease in available adsorption sites and resulting repulsion (i.e., blocking) of incoming antibiotics from those previously adsorbed. Findings from this study demonstrate that fixed-bed columns packed with CNTs can be efficiently used and regenerated to remove antibiotics from water.     

Fate in soil of 14C-sulfadiazine residues contained in the manure of young pigs treated with a veterinary antibiotic

The fate of ¹⁴C-labeled sulfadiazine (¹⁴C-SDZ) residues was studied in time-course experiments for 218 days of incubation using two soils (A_p horizon of loamy sand, orthic luvisol; A_p horizon of silt loam, cambisol) amended with fresh and aged (6 months) ¹⁴C-manure [40 g kg^?1 of soil; 6.36 mg of sulfadiazine (SDZ) equivalents per kg of soil], which was derived from two shoats treated with ¹⁴C-SDZ. Mineralization of ¹⁴C-SDZ residues was below 2% after 218 days depending little on soil type. Portions of extractable ¹⁴C (ethanol-water, 9:1, v/v) decreased with time to 4–13% after 218 days of incubation with fresh and aged ¹⁴C-manure and both soils. Non-extractable residues were the main route of the fate of the ¹⁴C-SDZ residues (above 90% of total recovered ¹⁴C after 218 days). These residues were high immediately after amendment depending on soil type and aging of the ¹⁴C-manure, and were stable and not remobilized throughout 218 days of incubation. Bioavailable portions (extraction using CaCl₂ solution) also decreased with increasing incubation period (5–7% after 218 days). Due to thin-layer chromatography (TLC), 500 μg of ¹⁴C-SDZ per kg soil were found in the ethanol-water extracts immediately after amendment with fresh ¹⁴C-manure, and about 50 μg kg^?1 after 218 days. Bioavailable ¹⁴C-SDZ portions present in the CaCl₂ extracts were about 350 μg kg^?1 with amendment. Higher concentrations were initially detected with aged ¹⁴C-manure (ethanol-water extracts: 1,920 μg kg^?1; CaCl₂ extracts: 1,020 μg kg^?1), probably due to release of ¹⁴C-SDZ from bound forms during storage. Consistent results were obtained by extraction of the ¹⁴C-manure-soil samples with ethyl acetate; portions of N-acetylated SDZ were additionally determined. All soluble ¹⁴C-SDZ residues contained in ¹⁴C-manure contributed to the formation of non-extractable residues; a tendency for persistence or accumulation was not observed. SDZ's non-extractable soil residues were associated with the soluble HCl, fulvic acids and humic acids fractions, and the insoluble humin fraction. The majority of the non-extractable residues appeared to be due to stable covalent binding to soil organic matter.