Biodegradation of radiolabelled synthetic lignin (14C-DHP) and mechanical pulp in a compost environment

Mineralization of radioactive synthetic lignin (14C-DHP) was studied in a compost environment at 35, 50 and 58 degrees C. Compost samples were successively extracted with water, dioxane and alkali, and the molecular weight distribution of some extracts was determined by gel permeation chromatography (GPC). Biodegradation of lignin-containing spruce groundwood (SGW) and pine sawdust was concurrently determined in controlled composting tests by measuring evolved CO2. The temperatures were the same as in the 14C-DHP mineralization experiment and bleached kraft paper, with a lignin content of 0.2%, was used as a reference. The mineralization of 14C-DHP was relatively high (23-24%) at 35 degrees C and 50 degrees C, although the mixed population of compost obviously lacks the most effective lignin degraders. At 58 degrees C the mineralization of 14C-DHP, as well as the biodegradation of SGW and sawdust, was very low, indicating that the lignin-degrading organisms of compost were inactivated at this temperature. SGW was poorly biodegradable (<40%) in controlled composting tests compared with kraft paper (77-86%) at all temperatures, which means that lignin inhibits the degradation of carbohydrates. During the incubation, water-soluble degradation products, mainly monomers and dimers, and the original 14C-DHP were either mineralized or bound to humic substances. A substantial fraction of 14C-DHP was incorporated into humin or other insolubles.     

Microbial d-xylonate production

D-Xylonic acid is a versatile platform chemical with reported applications as complexing agent or chelator, in dispersal of concrete, and as a precursor for compounds such as co-polyamides, polyesters, hydrogels and 1,2,4-butanetriol. With increasing glucose prices, D-xylonic acid may provide a cheap, non-food derived alternative for gluconic acid, which is widely used (about 80?kton/year) in pharmaceuticals, food products, solvents, adhesives, dyes, paints and polishes. Large-scale production has not been developed, reflecting the current limited market for D-xylonate. D-Xylonic acid occurs naturally, being formed in the first step of oxidative metabolism of D-xylose by some archaea and bacteria via the action of D-xylose or D-glucose dehydrogenases. High extracellular concentrations of D-xylonate have been reported for various bacteria, in particular Gluconobacter oxydans and Pseudomonas putida. High yields of D-xylonate from D-xylose make G. oxydans an attractive choice for biotechnical production. G. oxydans is able to produce D-xylonate directly from plant biomass hydrolysates, but rates and yields are reduced because of sensitivity to hydrolysate inhibitors. Recently, D-xylonate has been produced by the genetically modified bacterium Escherichia coli and yeast Saccharomyces cerevisiae and Kluyveromyces lactis. Expression of NAD(+)-dependent D-xylose dehydrogenase of Caulobacter crescentus in either E. coli or in a robust, hydrolysate-tolerant, industrial Saccharomyces cerevisiae strain has resulted in D-xylonate titres, which are comparable to those seen with G. oxydans, at a volumetric rate approximately 30?% of that observed with G. oxydans. With further development, genetically modified microbes may soon provide an alternative for production of D-xylonate at industrial scale.     

Water chemistry of Lake Ladoga and Russian-Finnish intercalibration of analyses

As part of the Russian-Finnish research studies on Lake Ladoga, joint expeditions were organized in 1992 and 1993. Water samples were collected for intercalibration of chemical analysis methods and to monitor the chemical quality of the lake water.In August of 1992 water samples were taken from northern Lake Ladoga for intercalibration of Russian and Finnish analysis methods. In August 1993 water samples were collected from 23 sampling stations in all parts of the lake; some of these were also used for intercalibration purposes.The oxygen, colour and COD_Mn results were at the same level in the intercalibration. In 1993, the P_tot results obtained were acceptable. In N_tot, Fe and Mn analysis there seemed to be systematic and random errors between some results.The Secchi depth ranged from 1.5 m to 3.3 m. The average concentrations for the total phosphorus ranged from 15 µg 1^–1 to 29 µg 1^–1. The total nitrogen values were from 620 µg 1^–1 to 690 µg 1^–1. The N:P ratio varied from 24 to 40. The concentration of phosphorus indicated mesotrophic or even eutrophic conditions in the lake. Phosphorus seemed to be the limiting nutrient to bacteria and algae.     

Variability of nutrient limitation in the Archipelago Sea,SW Finland

Over a two year study period, zooplankton was sampledin Gazi Bay, Kenya, using a 335 μm mesh size Bongonet. Two Way Indicator Species Analysis (TWINSPAN)classification technique demonstrated that rainfalland tidal regime had substantial influence on thezooplankton community structure. Samples collectedduring the rainy season months clustered together whentreated with TWINSPAN. Furthermore, theclustering was more pronounced for neap tidesamples than for spring tide ones. Samples obtainedduring spring tide did not give a clear cut pattern. Canonical Correspondence Analysis (C.C.A.) confirmedthese findings, a clustering together of rainy/neaptide samples; and little separation (based onenvironmental variables) between samplingstations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Polyamine flux analysis by determination of heavy isotope incorporation from 13C, 15N-enriched amino acids into polyamines by LC-MS/MS

The study of polyamine flux, i.e. the circulating flow of polyamines through the interconnected biosynthetic and catabolic pathways, is of considerable interest because of the established links between the polyamine metabolism and many diseases, such as cancer and diabetes. To study polyamine flux in detail, a novel method based on following the label incorporation from the (13)C, (15)N-labeled polyamine precursors, arginine, methionine and ornithine, into polyamines by LC-MS/MS was implemented. This methodology was tested on three distinct cell lines with different spermidine/spermine-N (1)-acetyltransferase (SSAT) expression levels, i.e. non-transgenic, transgenic and knockout. These trials allowed the identification of the critical conditions for the successful polyamine flux measurement, such as the functional time frame of label incorporation, until plateau phase with the selected precursor is reached. The novel LC-MS/MS-based method for polyamine flux overcame the limitations of previous existing methodologies, with baseline separation of the different polyamine species and the exact quantification of the incorporated label. Moreover, the obtained results clearly show that the increased SSAT expression is associated with accelerated polyamine flux.     

Estrogen regulates T helper 17 phenotype and localization in experimental autoimmune arthritis

IntroductionThe incidence and progression of many autoimmune diseases are sex-biased, which might be explained by the immunomodulating properties of endocrine hormones. Treatment with estradiol potently inhibits experimental autoimmune arthritis. Interleukin-17-producing T helper cells (Th17) are key players in several autoimmune diseases, particularly in rheumatoid arthritis. The aim of this study was to investigate the effects of estrogen on Th17 cells in experimental arthritis.MethodsOvariectomized DBA/1 mice treated with 17β-estradiol (E2) or placebo were subjected to collagen-induced arthritis (CIA), and arthritis development was assessed. Th17 cells in joints and lymph nodes were studied by flow cytometry. Lymph node Th17 cells were also examined in ovariectomized estrogen receptor α–knockout mice (ERα^−/−) and wild-type littermates, treated with E2 or placebo and subjected to antigen-induced arthritis.ResultsE2-treated mice with established CIA showed reduced severity of arthritis and fewer Th17 cells in joints compared with controls. Interestingly, E2-treated mice displayed increased Th17 cells in lymph nodes during the early phase of the disease, dependent on ERα. E2 increased the expression of C-C chemokine receptor 6 (CCR6) on lymph node Th17 cells as well as the expression of the corresponding C-C chemokine ligand 20 (CCL20) within lymph nodes.ConclusionsThis is the first study in which the effects of E2 on Th17 cells have been characterized in experimental autoimmune arthritis. We report that E2 treatment results in an increase of Th17 cells in lymph nodes during the early phase of arthritis development, but leads to a decrease of Th17 in joints during established arthritis. Our data suggest that this may be caused by interference with the CCR6-CCL20 pathway, which is important for Th17 cell migration. This study contributes to the understanding of the role of estrogen in the development of autoimmune arthritis and opens up new fields for research concerning the sex bias in autoimmune disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0548-y) contains supplementary material, which is available to authorized users.     

Engineering Filamentous Fungi for Conversion of d-Galacturonic Acid to l-Galactonic Acid

d-Galacturonic acid, the main monomer of pectin, is an attractive substrate for bioconversions, since pectin-rich biomass is abundantly available and pectin is easily hydrolyzed. l-Galactonic acid is an intermediate in the eukaryotic pathway for d-galacturonic acid catabolism, but extracellular accumulation of l-galactonic acid has not been reported. By deleting the gene encoding l-galactonic acid dehydratase (lgd1 or gaaB) in two filamentous fungi, strains were obtained that converted d-galacturonic acid to l-galactonic acid. Both Trichoderma reesei Δlgd1 and Aspergillus niger ΔgaaB strains produced l-galactonate at yields of 0.6 to 0.9 g per g of substrate consumed. Although T. reesei Δlgd1 could produce l-galactonate at pH 5.5, a lower pH was necessary for A. niger ΔgaaB. Provision of a cosubstrate improved the production rate and titer in both strains. Intracellular accumulation of l-galactonate (40 to 70 mg g biomass⁻¹) suggested that export may be limiting. Deletion of the l-galactonate dehydratase from A. niger was found to delay induction of d-galacturonate reductase and overexpression of the reductase improved initial production rates. Deletion of the l-galactonate dehydratase from A. niger also delayed or prevented induction of the putative d-galacturonate transporter An14g04280. In addition, A. niger ΔgaaB produced l-galactonate from polygalacturonate as efficiently as from the monomer.     

瑞氏木霉木糖醇脱氢酶基因的分离与鉴定

将在木聚糖上生长的瑞氏木霉(Trichoderma reesei)RutC-30的cDNA文库全部质粒转化已携带有毕赤氏酵(Pithia stipitis)木糖还原酶基因的重组酿酒酵母(Saccharomycescerevisiae)菌株H475,在H475中构建了瑞氏木霉的cDNA表达亚文库。在以木糖为唯一碳源的选择性酵母合成培养基上,从该亚文库中筛选到瑞氏木霉木糖醇脱氢酶cDNA基因．该基因片段长为1．3kb。Southern、Norhern印迹杂交分析和蛋白质凝胶电泳结果表明该基因确实来源于瑞氏木霉,所编码蛋白质分子量约为40kDa。携带有毕赤氏酵母木糖还原酶和瑞氏木霉木糖醇脱氢酶基因的重组酵母能够在以木糖为唯一碳源的培养基上生长,并能将90％以上的木糖转化为木糖醇、乙醇和其它副产品。