Inhibition of Mitochondrial Fission by Drp-1 Blockade by Short-Term Leptin and Mdivi-1 Treatment Improves White Adipose Tissue Abnormalities in Obesity and Diabetes

BACKGROUND

Obesity and type 2 diabetes are chronic diseases characterized by insulin resistance, mitochondrial dysfunction and morphological abnormalities.

OBJECTIVE

We have investigated if dysregulation of mitochondrial dynamics and biogenesis is involved in an animal model of obesity and diabetes.

METHODS

The effect of short-term leptin and mdivi-1 -a selective inhibitor of Drp-1 fission-protein- treatment on mitochondrial dynamics and biogenesis was evaluated in epididymal white adipose tissue (WAT) from male ob/ob mice.

RESULTS

An increase in Drp-1 protein levels and a decrease in Mfn2 and OPA-1 protein expression were observed with enhanced and sustained mitochondrial fragmentation in ob/ob mice compared to wt C57BL/6 animals (p<0.05). The content of mitochondrial DNA and PGC-1α mRNA expression -both parameters of mitochondrial biogenesis- were reduced in ob/ob mice (p<0.05). Treatment with leptin and mdivi-1 significantly increased mitochondrial biogenesis, improved fusion-to-fission balance and attenuated mitochondrial dysfunction, thus inducing white-to-beige adipocyte transdifferentiation. Measurements of glucose and lipid oxidation in adipocytes revealed that both leptin and mdivi-1 increase substrates oxidation while in vivo determination of blood glucose concentration showed decreased levels by 50% in ob/ob mice, almost to the wt level.

CONCLUSIONS

Pharmacological targeting of Drp-1 fission protein may be a potential novel therapeutic tool for obesity and type 2 diabetes.

Development of Microbiome Biobanks - Challenges and Opportunities

The microbiome research field is rapidly evolving, but the required biobanking infrastructure is currently fragmented and not prepared for the biobanking of microbiomes. The rapid advancement of technologies requires an urgent assessment of how biobanks can underpin research by preserving microbiome samples and their functional potential.

Fetal heart rate variability responsiveness to maternal stress, non-invasively detected from maternal transabdominal ECG

PURPOSE

Prenatal stress (PS) during pregnancy affects in utero- and postnatal child brain-development. Key systems affected are the hypothalamic-pituitary-adrenal axis and the autonomic nervous system (ANS). Maternal- and fetal ANS activity can be gauged non-invasively from transabdominal electrocardiogram (taECG). We propose a novel approach to assess couplings between maternal (mHR) and fetal heart rate (fHR) as a new biomarker for PS based on bivariate phase-rectified signal averaging (BPRSA). We hypothesized that PS exerts lasting impact on fHR.

METHODS

Prospective case-control study matched for maternal age, parity, and gestational age during the third trimester using the Cohen Perceived Stress Scale (PSS-10) questionnaire with PSS-10 over or equal 19 classified as stress group (SG). Women with PSS-10 < 19 served as control group (CG). Fetal electrocardiograms were recorded by a taECG. Coupling between mHR and fHR was analyzed by BPRSA resulting in fetal stress index (FSI). Maternal hair cortisol, a memory of chronic stress exposure for 2-3 months, was measured at birth.

RESULTS

538/1500 pregnant women returned the questionnaire, 55/538 (10.2%) mother-child pairs formed SG and were matched with 55/449 (12.2%) consecutive patients as CG. Maternal hair cortisol was 86.6 (48.0-169.2) versus 53.0 (34.4-105.9) pg/mg (p = 0.029). At 36 + 5 weeks, FSI was significantly higher in fetuses of stressed mothers when compared to controls [0.43 (0.18-0.85) versus 0.00 (- 0.49-0.18), p < 0.001].

CONCLUSION

Prenatal maternal stress affects the coupling between maternal and fetal heart rate detectable non-invasively a month prior to birth. Lasting effects on neurodevelopment of affected offspring should be studied.

TRIAL REGISTRATION

Clinical trial registration: NCT03389178.

P6297Genetic mutation of galectin-3 altered the temporal evolution of macrophage polarization and healing affecting the post myocardial infarct remodeling in mice

Background

Myocardial infarction (MI) is a dynamic process that leads to ventricular remodeling (VR) and largely to heart failure (HF). Previous studies established that Galectin-3 (Gal-3) is highly increased in the infarct zone from the beginning of MI and also that it is a prognostic marker of HF.

Purpose

We aimed to study the effects of genetic deletion of Gal-3 on macrophage (MΦ) infiltration, cytokines expression, fibrosis and MMP-2 activity as well as VR and function after MI in mice.

Methods

Male C57BL/6J and Gal-3 KO mice were subjected to permanent coronary ligature or sham. At 1 week post-MI LV function and VR were studied by echocardiography. We also studied in the infarct zone: 1) F4/80+ MΦ infiltration by flow cytometry; 2) M2 macrophage polarization by detection of mannose receptor (MR) and chitinase-3-like protein-3 (YM1) phenotype markers by rt-qPCR; 3) mRNA expression of TNF-α, IL-6, IL-10 and TGF-β; 4) MMP-2 activity by zymography and 5) fibrosis by histology.

Results

Results are expressed as X±SEM; *p<0.05 C57 MI vs Gal-3 KO MI. After 1 week post-MI, the pulmonary congestion assessed by the lung weight/body weight ratio (mg/g) was 9±0.4, 8±0.5 and 9±0.4 in C57 sham, Gal-3 KO sham and C57 MI, respectively, nevertheless it was severely increased to 15±1.2* in infarcted Gal-3 KO mice. MΦ infiltration, cytokine expression and MMP-2 activity in the infarct zone are shown in the table.

Table 1 Groups F4/80+ MR YM1 TNF-α IL-6 IL-10 TGF-β MMP-2 MΦ (%) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) C57 MI 5.6±0.9 (8) 0.5±0.2 (3) 1.7±0.4 (3) 26±0.3 (3) 1.7±0.5 (3) 0.7±0.03 (3) 1.8±0.5 (3) 1±0.1 (5) Gal-3 KO MI 2.6±0.4* (8) 1.8±0.4*(8) 4.2±0.4* (8) 0.4±0.5* (8) 6.7±0.9 * (8) 2.8±0.3 * (8) 0.5±0.2 * (8) 2±0.4* (6) A.U.: Arbitrary units. In MR, YM1, TNF-α, IL-6, IL-10 and TGF-β represent mRNA expression. In MMP-2 represent gelatinolytic activity. Number of samples is shown between parentheses.

After 1 week post-MI, LV end diastolic dimension was increased from 4.4±0.1 to 4.8±0.2* at the same time that ejection fraction (%) was significantly reduced from 47±2 to 38±3* in C57+MI (13) and Gal-3 KO+MI (16) respectively. Collagen concentration in the infarct zone was significantly reduced from 30±1.2% (6) to 17±0.5* % (8) in C57 and Gal-3 KO respectively.

Conclusion(s)

Gal-3 is an essential regulatory factor for the early wound healing since it regulates the dynamics of the reparative process through the phenotypic profile of MΦ, the pro- and anti-inflammatory cytokines expression and fibrosis along the temporal evolution of MI in mice. The deficit of Gal-3 diminished the infiltration of MΦ altering its phenotypic polarization and consequently, the dynamics of the wound healing as well as aggravating the functional and structural evolution of cardiac remodeling.

Acknowledgement/Funding

Argentine Agency for Promotion of Science and Technology (PICT 2014-2320), University of Buenos Aires (UBACyT 20020170100619BA)

Low-molecular-weight-heparin increases Th1- and Th17-associated chemokine levels during pregnancy in women with unexplained recurrent pregnancy loss: a randomised controlled trial

Low-molecular-weight heparin (LMWH) is widely used to treat recurrent pregnancy loss (RPL) because of its anti-coagulant effects. Although in vitro studies have suggested additional immunological effects, these are debated. We therefore investigated whether LMWH could modulate immune responses in vivo during pregnancy of women with unexplained RPL. A Swedish open multi-centre randomised controlled trial included 45 women treated with tinzaparin and 42 untreated women. Longitudinally collected plasma samples were obtained at gestational weeks (gw) 6, 18, 28 and 34 and analysed by multiplex bead technology for levels of 11 cytokines and chemokines, chosen to represent inflammation and T-helper subset-associated immunity. Mixed linear models test on LMWH-treated and untreated women showed differences during pregnancy of the Th1-associated chemokines CXCL10 (p = 0.01), CXCL11 (p < 0.001) and the Th17-associated chemokine CCL20 (p = 0.04), while CCL2, CCL17, CCL22, CXCL1, CXCL8, CXCL12, CXCL13 and IL-6 did not differ. Subsequent Student's t-test showed significantly higher plasma levels of CXCL10 and CXCL11 in treated than untreated women at gw 28 and 34. The consistent increase in the two Th1-associated chemokines suggests a potential proinflammatory and unfavourable effect of LMWH treatment during later stages of pregnancy, when Th1 immunity is known to disrupt immunological tolerance.

Interleukin-34 is present at the fetal-maternal interface and induces immunoregulatory macrophages of a decidual phenotype in vitro

STUDY QUESTION

Is the newly discovered cytokine interleukin (IL)-34 expressed at the human fetal-maternal interface in order to influence polarization of monocytes into macrophages of a decidual immunoregulatory phenotype?

SUMMARY ANSWER

IL-34 was found to be present at the fetal-maternal interface, in both fetal placenta and maternal decidua, and it was able to polarize monocytes into macrophages of a decidual phenotype.

WHAT IS KNOWN ALREADY

IL-34 was shown to bind to the same receptor as macrophage-colony stimulating factor (M-CSF), which has an important immunomodulatory role at the fetal-maternal interface, for example by polarizing decidual macrophages to an M2-like regulatory phenotype. IL-34 is known to regulate macrophage subsets, such as microglia and Langerhans cells, but its presence at the fetal-maternal interface is unknown.

STUDY DESIGN, SIZE, DURATION

The presence of IL-34 at the fetal-maternal interface was evaluated by immunohistochemistry (IHC) and ELISA in placental and decidual tissues as well as in isolated trophoblast cells and decidual stromal cells obtained from first trimester elective surgical terminations of pregnancy (n = 49). IL-34 expression was also assessed in third trimester placental biopsies from women with (n = 21) or without (n = 15) pre-eclampsia. The effect of IL-34 on macrophage polarization was evaluated in an in vitro model of blood monocytes obtained from healthy volunteers (n = 14). In this model, granulocyte macrophage-colony stimulating factor (GM-CSF) serves as a growth factor for M1-like polarization, and M-CSF as a growth factor for M2-like polarization.

PARTICIPANTS/MATERIALS, SETTING, METHODS

First trimester placental and decidual tissues were obtained from elective pregnancy terminations. Placental biopsies were obtained from women with pre-eclampsia and matched controls in the delivery ward. Polarization of macrophages in vitro was determined by flow-cytometric phenotyping and secretion of cytokines and chemokines in cell-free supernatants by multiplex bead assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Our study shows that IL-34 is produced at the fetal-maternal interface by both placental cyto- and syncytiotrophoblasts and decidual stromal cells. We also show that IL-34, in vitro, is able to polarize blood monocytes into macrophages with a phenotype (CD14highCD163+CD209+) and cytokine secretion pattern similar to that of decidual macrophages. The IL-34-induced phenotype was similar, but not identical to the phenotype induced by M-CSF, and both IL-34- and M-CSF-induced macrophages were significantly different (P < 0.05-0.0001 depending on marker) from GM-CSF-polarized M1-like macrophages. Our findings suggest that IL-34 is involved in the establishment of the tolerant milieu found at the fetal-maternal interface by skewing polarization of macrophages into a regulatory phenotype.

LIMITATIONS, REASONS FOR CAUTION

Although it is clear that IL-34 is present at the fetal-maternal interface and polarizes macrophages in vitro, its precise role in vivo remains to be established.

WIDER IMPLICATIONS OF THE FINDINGS

The recently discovered cytokine IL-34 is present at the fetal-maternal interface and has immunomodulatory properties with regard to induction of decidual macrophages, which are important for a healthy pregnancy. Knowledge of growth factors related to macrophage polarization can potentially be translated to treatment of pregnancy complications involving dysregulation of this process.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by grants from the Medical Research Council (Grant K2013-61X-22310-01-04), the Research Council of South-East Sweden (FORSS), and the County Council of Östergötland, Sweden. No author has any conflicts of interest to declare.

Effect of insulin-resistance on circulating and adipose tissue MMP-2 and MMP-9 activity in rats fed a sucrose-rich diet

BACKGROUND AND AIM

Adipose tissue produces different metalloproteinases (MMPs), involved in adipogenesis and angiogenesis. Different studies have shown that in obesity the behavior of different MMPs may be altered. However there are scarce data about the effect of insulin-resistance (IR) on MMP-2 and MMP-9 activity in adipose tissue. Our aim was to determine whether sucrose induced IR modifies MMP-2 and MMP-9 behavior in expanded visceral adipose tissue and the contribution of this tissue to circulating activity of these gelatinases.

METHODS AND RESULTS

Male Wistar rats were fed with standard diet (Control) or standard diet plus 30% sucrose in the drinking water throughout 12 weeks (SRD). In epididymal adipose tissue vascular density, size and adipocyte density, PPARγ expression and MMP-2 and -9 were measured. Adipose tissue from SRD presented higher adipocyte size (6.32 ± 8.71 vs 4.33 ± 2.17 × 10(3) μm(2), p = 0.001) lower adipocyte density (164 (130-173) vs 190 (170-225) number/mm(2), p = 0.046) and lower vascular density (16.2 (12.8-23.5) vs 28.1 (22.3-46.5) blood vessels/mm(2), p = 0.002) than Control. MMP-2 and MMP-9 activity was decreased in SRD (1.93 ± 0.7 vs 3.92 ± 0.9 relative units, p = 0.048 and 1.80 ± 0.8 vs 5.13 ± 1.7 relative units, p = 0.004 respectively) in accordance with lower protein expression (0.35 ± 0.20 vs 2.71 ± 0.48 relative units, p = 0.004 and 1.12 ± 0.21 vs 1.52 ± 0.05 relative units, p = 0.036 respectively). There were no differences in PPARγ expression between groups.

CONCLUSION

Insulin resistance induced by SRD decreases MMP-2 and MMP-9 activity in adipose tissue which would not represent an important source for circulating MMP-2 and -9. In this state of IR, PPARγ would not be involved in the negative regulation of adipose tissue gelatinases.

[Can Peers Achieve Access to Socially Burdened Families? Evaluation Results of the Programme 'Community Mothers in Berlin-Kreuzberg']

This study evaluated a setting-based programme whose goal was to promote the healthy upbringing of children in a disadvantaged district through the empowerment of mothers. Women from the neighbourhood were trained as community mothers (CM) to impart their knowledge in home visitations to other mothers. 67 CMs were trained. They gained access to 118 families via home visits and to 191 families in single contacts. Information and support resulted in positive changes in all families available for interviews (n=44). The families also gained access to the professional help system.

Chrome Nitride Coatings for Applications in Plastics Processing

Coated moulds, especially cavity surfaces and ejection parts are state of the art in plastics processing. Regarding the plastification unit i.e. screws and barrels coatings are not well established. Wear in processing remains a problem, especially when no abrasion is permitted e.g. in manufacturing optical elements. The surfaces must resist the abrasion of hard glas fibres as well as the corrosive attack of the polymers. Electroplated chrome is one of the answers to these demands, because of its hardness and corrosion resistance. Another solution are thin hard coatings which are not yet well established. Titanium nitride produced by PVD technique was found to show excellent abrasion resistance but often not sufficient corrosion properties. Chrome nitride was found to have great hardness like TiN, corrosion resistance behaviour similar to electroplated chrome and in contrast to electroplated coatings no tensile internal stress.

The present study deals with the spectrum of characteristic properties of CrxN coatings like hardness, adhesion, internal stress, chemical composition and phases produced by PVD magnetron sputtering. The coatings were deposited on steel, described in characteristics and tested in a model wear test with plasticized moulding material (PA 66-GF50 and others) simulating the tribological situation between screw and barrel of extruders or injection moulds. The tribological behaviour was studied after the complex test procedure. The high temperature of the plasticized material, high abrasion by glas fibres and corrosive influence could only change the coatings properties of CrxN slightly.

Measurement of fasting salivary insulin and its relationship with serum insulin in children

BACKGROUND

Saliva is a useful sample as a source of hormones for the diagnosis of different diseases, particularly in pediatric patients and aged individuals, because saliva offers a noninvasive and stress-free alternative to serum collection. The aim of this study was to validate a salivary insulin method and to check its clinical application in pediatric patients.

METHODS

Saliva samples were collected from 130 boys and 147 girls aged 6-14 years. Salivary and serum insulin levels were measured with the chemiluminescent automated method Access (Beckman Coulter, Brea, CA, USA). Serum blood glucose levels were measured with the glucose oxidase method in an autoanalyzer.

RESULTS

The precision profile of the method was determined for six aliquots of different concentrations from pools of saliva, and the coefficients of variation (CV) were 2.4% for 1 μUI/ml, 4% for 0.5, 8.9% for 0.25, 19% for 0.12, 28% for 0.06, and 38% for 0.03 μUI/ml, being the functional sensibility (concentration corresponding to a 20% CV) 0.12 μUI/ml. Insulin recovery was 100.13%. Salivary insulin levels diminished 29.8% in samples stored during 7 days at 2-8 °C. Differences in insulin values were not observed when samples were stored at -20 °C during 7 days. The methods used to measure salivary and serum insulin correlated significantly (r=0.92, P<0.001). However, at levels of serum insulin >20 μUI/ml, this correlation declined (r=0.57, P=0.083).

CONCLUSION

The proposed method for salivary insulin measurement showed convenient analytical characteristics.

Hepatic lipase activity is increased in non-alcoholic fatty liver disease beyond insulin resistance

BACKGROUND AND OBJECTIVE

Hepatic lipase is a lipolytic enzyme mostly synthesized and localized at the surface of liver sinusoidal capillaries, which hydrolyses triglycerides and phospholipids of intermediate density, large low density (LDL) and high density lipoproteins. Hepatic lipase activity is increased in insulin resistant states. Non-alcoholic fatty liver disease (NAFLD) is characterized by insulin resistance. However, at present, no data are available regarding the behaviour of hepatic lipase with regard to the degree of hepatic steatosis. Our aim was to evaluate hepatic lipase activity in NAFLD patients and its relationship to the severity of hepatic steatosis.

DESIGN AND PATIENTS

We studied 48 patients with NAFLD (diagnosed by ultrasonography and confirmed by liver biopsy) and 30 controls. Steatosis was semi-quantitatively assessed and considered as mild or grade 1, moderate or grade 2 and severe or grade 3.

MEASUREMENTS

hepatic lipase activity, lipid and lipoprotein profile (including intermediate density lipoproteins and dense LDL), adiponectin, insulin, glucose and high sensitivity C-reactive protein were measured. Homeostasis model assessment for insulin resistance (HOMA) index was calculated.

RESULTS

Patients with hepatic steatosis presented with higher hepatic lipase activity, HOMA and dense LDL and lower levels of adiponectin, high density lipoproteins, cholesterol and apoA-I. Hepatic lipase activity positively correlated significantly with the severity of hepatic steatosis. Hepatic lipase correlated with a more atherogenic profile and persisted higher in patients even after corrected for age, gender, body mass index, HOMA and adiponectin.

CONCLUSION

The higher hepatic lipase activity in NAFLD patients contributes to a more atherogenic profile linked to increased cardiovascular risk, beyond the insulin resistance and the reduction in adiponectin.

Increase in MMP-2 activity in overweight and obese women is associated with menopausal status

BACKGROUND

Metalloproteinases (MMPs) are synthesized in the subendothelium and are involved in the atherosclerosis and cardiovascular disease process because of their major significance in vascular remodeling and plaque rupture. MMPs are also synthesized in adipose tissue during angiogenesis; however, the role of these enzymes in obesity and insulin-resistant states is still controversial.

OBJECTIVE

To evaluate MMP-2 activity in the circulation of overweight and obese women and in normal-weight controls, and to associate the levels of these factors with metabolic, adipose tissue and inflammation biomarkers.

METHODS

Plasma MMP-2 activity, adiponectin and C-reactive protein concentration, lipoprotein profile and HOMA were determined in 39 healthy women (13 normal weight and 26 overweight/obese).

RESULTS

Overweight/obese women were older (p < 0.001) than normal-weight women; 20/26 of overweight/obese women were postmenopausal compared with 4/13 of normal-weight women. Overweight/obese women had significantly higher plasma activity of MMP-2 than controls (mean relative area: 0.81 (range 0.4-1.92) vs. 1.33 (range 0.4-3.1); p < 0.005); this difference was lost after adjusting for menopausal status. MMP-2 activity positively correlated with waist circumference (p < 0.002), HOMA (p < 0.003), and high-sensitivity C-reactive protein (p < 0.05), apolipoprotein B (p = 0.006) and triglyceride/high density lipoprotein (HDL) cholesterol index (p < 0.001), and negatively with HDL cholesterol (p < 0.001), HDL2 cholesterol (p < 0.008), HDL3 cholesterol (p < 0.05) and adiponectin (p < 0.05). The association with HOMA and adiponectin persisted even after adjusting for menopausal status.

CONCLUSION

Our finding of increased plasma activity of MMP-2 in overweight/obese women, associated with menopausal status, is important given that it fits in with an early stage of cardiovascular disease; the association of MMP-2 activity with obesity markers may be a link between adipose tissue and risk for cardiovascular disease.

Destruction by anaerobic mesophilic and thermophilic digestion of viruses and indicator bacteria indigenous to domestic sludges

In raw sludges and in mesophilically and thermophilically digested anaerobic sludges, large variations in numbers of viruses occurred over narrow ranges of numbers of fecal coliforms, total coliforms, and fecal streptococci, demonstrating that the bacteria were poor quantitative reflectors of the numbers of the viruses detected. Mesophilic and thermophilic digestion of anaerobic sludges destroyed all three indicator bacteria more rapidly than such digestion destroyed the viruses. The relative rates for the destruction of viruses, fecal coliforms, and fecal streptococci in the digested sludges were consistent over the 17-month study. Fecal coliforms were 7 to 8 times more sensitive than the viruses to mesophilic digestion and 9 to 10 times more sensitive to thermophilic digestion. Total coliforms were even more sensitive. The rates at which fecal streptococci were destroyed by mesophilic and thermophilic digestion of anaerobic sludges approached those at which the viruses were destroyed by those processes; this suggested that the rates at which fecal streptococci in sludges are destroyed by those processes may serve as useful indicators for the rates at which viruses in sludges are destroyed by those processes.

[Involvement of the global regulators GrrS, RpoS, and SplIR in formation of biofilms in Serratia plymuthica]

Most bacteria exist in the natural environment as biofilms, multicellular communities attached to hard surfaces. Biofilms have a characteristic architecture and are enclosed in the exopolymer matrix. Bacterial cells in biofilms are extremely resistant to antibacterial factors. It was shown in this work that the GrrA/GrrS system of global regulators of gene expression and the sigma S subunit of RNA polymerase (RpoS) play a significant role in positive regulation of biofilm formation in the rhizospheric bacterium Serratia plymuthica IC1270. Inactivation of grrS and rpoS genes resulted in an up to six-to-sevenfold and four-to-fivefold reduction in biofilm formation, respectively. Mutations in the grrS gene decreased the capacity of the bacterium for swarming motility. The splIR Quorum Sensing (QS) system was shown to negatively influence the biofilm formation. Transfer of the recombinant plasmid containing cloned genes splI/splR of S. plymuthica HRO-C48 into S. plymuthica IC1270 cells led to a twofold decrease of their ability to form biofilms. Inactivation of the splI gene coding for the synthase of N-acyl-homoserine lactones in S. plymuthica HRO-C48 resulted in a 2-2.5-fold increase in the level of biofilm formation, whereas the inclusion of plasmid carrying the cloned splI/splR genes into these mutant cells restored the biofilm formation to the normal level. The results obtained demonstrate that the formation of biofilms in S. plymuthica is positively regulated by the GrrA/GrrS and RpoS global regulators and is negatively regulated by the SplIR QS system.

Enhancement of biogas production by addition of hemicellulolytic bacteria immobilised on activated zeolite

Biogas from agricultural biomass and residues is a valuable source of renewable energy. However, recalcitrant plant cell structures represent a barrier in the fermentative biodegradation process in single- and two-stage reactors. Therefore, approaches concerning a more efficient de-polymerisation of cellulose and hemicellulose to monomeric sugars are required amongst others in order to optimise the fermentation efficiency and to increase methane yields. Here we show a new strategy for the enhancement of biogas production from hemicellulose-rich substrates. Hemicellulolytic populations from a common biogas fermenter consortium were successively enriched in batch-cultures using a synthetic medium containing xylan powder as single carbon source under anaerobic mesophilic conditions. Enriched hemicellulolytic bacteria were immobilised on trace metal activated zeolite to ensure a stable storage and easy application. Xylanase activity increased continuously during subsequent enrichment cycles by up to 162%. In batch-culture experiments we were able to observe an increase of methane by 53% compared to controls without additionally introduced microorganisms immobilised on zeolite. Specific enrichment of hemicellulolytic bacteria during the process was confirmed by using single strand conformation polymorphism (SSCP) analysis based on amplification of the eubacterial 16S rDNA fragments. Using sequence analysis conspicuous bands from SSCP patterns could be identified as belonging to the groups Bacteroides sp., Azospira oryzae (Dechlorosoma sp.) as well as to a wide spectrum of diverse species within the order of Clostridiales (Firmicutes).