Continuous biogas production from fodder beet silage as sole substrate

Since April 2000 a two-step anaerobic plant with two subsequent 500 m3 reactors has been producing biogas from fodder beet silage (pH 3.4-4.1) as the sole substrate. The plant is located at Kirchlengern near Bielefeld, Germany. Initially the reactors were inoculated with swine manure at 37 degrees C. After a start-up phase the process was sustained at pH 7.5-8.0 by feeding the silage as sole substrate with an HRT of about 55 d twice a day. Parallel to the biogas plant at Kirchlengern four one-step laboratory reactors were continuously driven at temperatures of 37 degrees C, 45 degrees C, 60 degrees C and 65 degrees C. They were fed with the same silage, but only once per day (one impulse). The organic loading rate (OLR) was adjusted to 3.9 g volatile solids (VS)/(l*d) with a concomitant hydraulic retention time (HRT) of 27 d. There was no problem with starting the reactors, but after 86 days the volumetric gas production of the 65 degrees C reactor ceased and a high amount of approximately 65 mM propionate could be determined. By decreasing the temperature down to 60 degrees C a stable reactor performance was recovered for a period of at least 600 further days. Interestingly microscopic analyses revealed that the morphology of methanogenic bacteria in the 60 degrees C was quite different from the 37 and 45 degrees C reactor exhibiting only rodlike methanogens whereas at 37 degrees C coccoid morphotypes besides rodlike methanogens were dominant. In a 55 degrees C reactor (separate experiment) a mixture of coccoid and rodlike methanogens established. During impulse feeding with 3.9 g (VS)/(l*d) it was observed that the quickest recovery of gas production, the pH, CH4 and CO2 content as well as the redox value could be observed at 37 degrees C or at 45 degrees C. Recovery of 75% gas volume (related to the value before or after impulse feeding) was obtained after 5.5 and 7.5 h of feeding time point whereas the 60 degrees C reactor needed 16 h. Slight significant differences were seen in the spectrum of volatile fatty acids (VFA) reaching at 37 degrees or 45 degrees C its maximum with 10-30 mM total VFA at 2-3 h after feeding. After this the VFA level declined to nearly zero (except for the 60 degrees C reactor). Therefore the 37 degrees C reactor was favoured. A double experiment with a second 37 degrees C reactor was started by a somewhat different inoculation procedure from the remaining 3 reactors, but revealed similar results. An impulse feeding experiment with a very high OLR of 16.5 g (VS)/(l*d) lasting 1 week offered a stable reactor performance with a peak GPR of up to 24 l/(l reactor *d) and an HRT of 5.45d. Therefore a long term operation with an HRT of only 7.5 days and an OLR of 12 g (VS)/(l*d) should be possible. By increasing the temperature no significantly different specific gas production rates and methane yields could be observed, e.g. it gave 600-7001 biogas from 1 kg VS. The corresponding methane content ranged between 62-64%. With a methane content of 63 +/- 1% a yield of 40.1 +/- 2 m3 methane/ton fresh fodder beet silage was obtained.

Development of a methanogenic process to degrade exhaustively the organic fraction of municipal "grey waste" under thermophilic and hyperthermophilic conditions

Different laboratory-scale, continuously driven reactor concepts (up to 3 reactors in series, max. 70 degrees C) for anaerobic digestion of the organic fraction of municipal grey waste were investigated. Over a period of 2 1/2 years several setups of reactors being daily fed and held in steady state balance were investigated. The perferred variant was a 2-stage setup with a HRT of 4.3 d for the 1st and 14.2 d for the 2nd reactor. Removal efficiencies of VS obtained by comparing the organic loading rate (OLR, g VS/l/d) of the effluent with the OLR of the feed could reach 80%. Removal efficiencies determined indirectly by the combined biogas yield of the 1st and 2nd reactor stage revealed even up to 91.5% of the theoretical possible yield of 807 l/kg VS. The produced gas had a methane content of 60-65%. A completely distinct hydrolysis stage with a gas production of only 1.6-5.5% of the theoretical yield could be reached by hyperthermophilic conditions (60-70 degrees C) or by a HRT of 1.25 d. It also demonstrated that a stable methanogenesis was not possible at temperatures of 60-70 degrees C. Kinetic analyses of the 2nd reactor stage revealed that the degradation of VS fell from 80 to 40% with raising organic loading rate (OLR) from 3 to 11 g VS/l/d. In contrast to this the VS-removal of the first hydrolysis reactor stage increased linearily from 5 to 20% at raising OLR's from 12 to 26 g VS/l/d. The same kinetics with linear increase exhibited the specific cellulose degradation with conversion rates of 0.1-3 x 109 g cellulose/single bacterium (10(-12) g)/d. This was an indication for the cellulose degradation as a rate limiting step. Both reactor stages combined allowed an optimal VS removal efficiency at OLR of 10 g VS/l/d. Analysis of bacterial populations of 28 reactors were referred either to eubacteria utilizing different sugars or cellulose or acetate or H2-CO2 or archaea (plus antibiotics) with acetate or H2-CO2 as substrate. H2-CO2 utilizers with numbers of 10(8)-10(10)/g TS dominated obviously the acetotrophic methanogens by the factor 10-10,000. This explained the observed short HRTs being possible.

Ulnar lengthening and radial recession procedures for Kienböck's disease. Long-term clinical and radiographic follow-up

Twenty patients with Kienböck's disease who had undergone a joint levelling procedure, were reviewed at a mean of 11 years following surgery. Clinical and radiological evaluation revealed good long-term results with all patients complaining of less pain than before surgery and with statistically significant increases in range of motion and grip strength. Radiologically a significant number of patients were found still to have lunate fractures and fragmentation. In addition, 13 patients have developed new bone formation in the lunate fossa, and 12 show osteoarthritic changes, particularly at the radioscaphoid interface. Radial shortening was felt to be superior to ulnar lengthening in that there were fewer problems with bone union.

Molecular genetics of human androgen insensitivity

Androgen insensitivity syndromes represent one cause of human male pseudohermaphroditism related to defects in the androgen receptor. The formation of a biologically active androgen receptor complex with testosterone and 5 alpha-dihydrotestosterone is required for normal androgen action during fetal development and differentiation of the internal accessory sex glands and external genitalia. Cloning of the human androgen receptor complementary DNA and genetic screening of human subjects with the clinical and biochemical features of androgen insensitivity using the polymerase chain reaction, denaturing gradient gel electrophoresis and nucleotide sequencing techniques have led to the identification of molecular defects in the androgen receptor. The complexity of phenotypic presentation by affected subjects with the complete or partial forms of androgen insensitivity is represented by the heterogeneity of androgen receptor gene mutations which include deletions and point mutations, with the latter causing inappropriate splicing of RNA, premature termination of transcription and amino acid substitutions. The naturally occurring mutations in the androgen receptor of subjects with androgen insensitivity represent a base upon which we can increase our understanding of the structure and function of the androgen receptor in normal physiology and disease.

Flocculation in methanogens, a comparative study of Methanosarcina barken strains Jülich and Fusaro

Two strains of Methanosarcina barkeri grown on methanol as substrate were investigated for their ability to aggregate: the new, flocculent strain Jülich formed stable flocs of several millimetres in diameter during rapid growth on a methanol-containing medium ("bread-crumb growth"). When observed with an electron microscope, the Jülich strain showed a unique parenchymatic texture with thick-walled cells inside a floc, and coccoidlike cells on the periphery. In contrast to the Jülich strain, the strain Fusaro grew on methanol in dispersed form, and generated macroscopically visible clumps only under poor growth conditions, induced, for example, by calcium deficiency. The formation of large cell aggregations of the Fusaro strain could also be induced during growth in the presence of 0.01% of the stain Calcofluor which is known to interact specifically with β-1,4 and β-1,3 glucan moieties. Sugar analyses revealed a different pattern for both strains: the exopolymer of the flocculent strain Jülich contained half the rhamnose, a third the fucose, equal amounts of mannose and glucose, but four times more glucuronic acid and arabinose than the strain Fusaro grown in the dispersed form. The high proportion of glucuronic acid in the exopolymer of the flocculating form is of particular interest because of the role of uronic acids in adhesion.

Ultrastructural investigation of 12 Methanosarcinae and related species grown on methanol for occurrence of polyphosphatelike inclusions

A comparative investigation by electron microscopy of 12 strains and species belonging to the Methanosarcinaceae family of methanogenic bacteria revealed the existence of polyphosphatelike bodies during growth on methanol in an optimized medium. The Methanosarcina barkeri strains Fusaro, 227, and Wiesmoor, and M. vacuolata were found to contain smoothly marginated, polyphosphatelike inclusions. They were identified by a positive Neisser stain, by the absence of a boundary membrane, and by X-ray microanalysis in situ. They had a diameter of 0.15–0.25 µm and contained the elements Ca, P, and Fe, and sometimes Mg, S, and Cl. In addition to the polyphosphatelike bodies, coarse-looking electron-dense "granula" were observed in the cytoplasm of most of the strains. They had an average diameter of 30 nm and the same elemental composition as the polyphosphatelike bodies. As demonstrated for M. barkeri Fusaro, the "granula" were also present in cells grown in acetate and H2–CO2.