Effect of mixing on biogas production during mesophilic anaerobic digestion of screened dairy manure in a pilot plant

The effect of mixing on biogas production of a 1.5‐m³ pilot continuous stirred tank reactor (CSTR) processing screened dairy manure was evaluated. Mixing was carried out by recirculation of reactor content with a mono pump. The experiment was conducted at a controlled temperature of 37±1°C and hydraulic retention times (HRTs) of 20 and 10 days. The effect of continuous and intermittent operation of the recirculation pump on biogas production was studied. At 10 days of HRT, the results showed a minimal influence of recirculation rate on biogas production and that continuous recirculation did not improve reactor performance. At 20 days of HRT, the recirculation rate did not affect reactor performance. Combination of low solid content in feed animal slurry and long HRTs results in minimal mixing requirements for anaerobic digestion.     

Age-related dynamics of thalamic-cortical evoked potentials in the rabbit in the early period of life

Data have been obtained on development of evoked potentials in the sensorimotor cortex to electrical stimulation of the thalamic ventroposterolateral nucleus (VPL) in rabbits in early ontogeny. In 3-5 days rabbits, under four times increase of threshold electric stimulation of VPL the thalamocortical response (TCR) is presented by a positive-negative potential with a long latency and minimum amplitude parameters. Second and third TCR positive components to increasing of threshold value of electric stimulation 4 times, are differentiated from 7-8 days age. Age dynamics of TCR amplitude-temporal parameters is characterized by a shortening of latency and an increase of oscillations amplitude, most expressed at 2-3 weeks of postnatal life. TCR of one month rabbit to increased threshold electrical stimulation of VPL is presented by short-latency positive-negative oscillation with a positive phase consisting of three components with successively increasing amplitudes.     

Synthesis of lysogangliosides

The synthesis of gangliosides GM3, GM2, GM1, and GD1a solely lacking the fatty acid moiety, and thus called lysogangliosides in analogy to lysophospholipids, is described. Since a selective elimination of the fatty acid residue has not been achieved as yet, the gangliosides were first subjected to alkaline hydrolysis. By this procedure the fatty acyl as well as the acetyl groups of the sialic acid residue(s) were completely removed. The acetamido group of the N-acetylgalactosamine moiety of the gangliosides GM2, GM1, and GD1a was very little (congruent to 10%) hydrolyzed. In a two-phase system composed of water and ether, the selective protection of the sphingoid amino group was accomplished with a hydrophobic protective group (9-fluorenylmethoxycarbonyl). Lysogangliosides were obtained after re-N-acetylation of the sialooligosaccharide amino group(s) followed by removal of the protecting group. The overall yield was about 30%. The structures of the lysogangliosides were confirmed by chemical analysis as well as negative ion FAB mass spectrometry and 1H NMR spectroscopy. By simple re-N-acylation of lysogangliosides with any labeled fatty acid, labeled gangliosides are now obtainable that are identical with their parent gangliosides except for their labeled fatty acid residue. This has been demonstrated by the synthesis of GM1 with a [1-13C]palmitic acid moiety in its ceramide portion. If desired, double-labeled gangliosides may be obtained by use of labeled acetic anhydride in the synthesis of the lysogangliosides.     

Membrane lipid alterations and thermal stress in Salmonella typhimurium 7136

Salmonella typhimurium ATCC 7136 exhibited major changes in lipid composition when grown in the presence of either 0.15% sodium deoxycholate or 0.15% sodium benzoate. These lipophilic compounds had directly opposing effects on the lipid profile of the organism. The saturated/unsaturated ratio was markedly elevated in benzoate-grown cells. On the other hand, it was depressed by an even greater margin from the control after growth in the presence of deoxycholate. Adjustments in the phospholipid content of the cells were also recorded. Phosphatidylethanolamines decreased by 28 and 50% in the deoxycholate- and benzoate-grown cells, respectively. Compensatory increases in phosphatidylglycerols of 87.5 and 175% occurred, along with increases in cardiolipins of 12- and 22-fold, respectively. Deoxycholate or benzoate supplementation also altered the relative distribution of neutral lipids; again, benzoate stimulated the greater change. Compositional changes were accompanied in the organism by increased heat sensitivity, but the effect on the susceptibility of S. typhimurium to injury varied with the physical properties of the supplement used.