Production of BioSNG from waste derived syngas: Pilot plant operation and preliminary assessment.

Bio-substitute natural gas (or BioSNG) produced from gasification of waste fuels and subsequent methanation of the product gas could play a crucial role in the decarbonisation of heating and transportation, and could be a vital part of the energy mix in the coming decades. The BioSNG demonstration plant described in this paper seeks to prove the technical feasibility of the thermal gasification of waste to renewable gas, through a preliminary experimental programme to take an existing stream of syngas, methanate it and show that it can be upgraded to gas grid quality requirements. The syngas used in the project is a waste-derived syngas from a two-stage fluidised bed - plasma pilot facility, which is then converted and upgraded in a new, dedicated conversion and clean up plant. Extensive trials were undertaken on methanation and gas upgrading units for over 60 h of continuous operation. The fundamentals of a once-through methanation process train have been established on the demonstration facility and a model built to extend the analysis over different operational parameters. Over the trials, methane outputs of greater than 50 kWth output were routinely produced from three methanation reactors in series, with a total CO conversion exceeding 90% at pressures as low as atmospheric, in line with kinetic model predictions. Retention of CO2 as well as adequate partial pressure of H2O in the process stream was important for process control. The plant provided demonstration of the efficacy of a PSA system for separation of CO2 (99% removal efficiency) as well as the potential to remove a proportion of residual H2, N2 and CO, although this was associated with appreciable CH4 slip. The process can be optimized primarily by reducing inlet temperature to methanation reactors, controlling syngas composition and using adequate steam to carbon ratio, depending on the type of waste. This information can be used to inform the design and economics of subsequent planned commercial plants that could significantly increase the potential of renewable gas in the UK and elsewhere in Europe, providing a low cost route to low carbon heat and transport.

Antigen presentation by human monocytes: effects of modifying major histocompatibility complex class II antigen expression and interleukin 1 production by using recombinant interferons and corticosteroids.

Lymphocyte proliferation in response to monocytes pulsed with an antigenic extract of Candida albicans was measured in vitro and the effects of modifying major histocompatibility complex (MHC) class II antigen expression at the surface of the antigen-presenting cells was investigated. The study shows that no simple correlation exists between changes in MHC class II antigen expression and changes in the effectiveness of antigen presentation. Recombinant interferon-alpha 1 (rIFN-alpha 1), rIFN-gamma and hydrocortisone were found to increase the expression of monocyte class II MHC antigens. In contrast, rIFN-alpha 2 did not increase class II antigen expression although it did increase MHC class I expression. Treatment of monocytes with rIFN-alpha 1, rIFN-alpha 2 or corticosteroids during antigen pulsing resulted in a reduction in the subsequent proliferative lymphocyte response. In all cases this inhibitory effect was restricted to antigen-specific proliferative responses since the polyclonal lymphocyte response to pokeweed mitogen-pulsed monocytes remained unaffected. Only rIFN-gamma treatment of antigen-pulsed monocytes resulted in enhancement of the subsequent specific lymphocyte proliferative response. The suppressive effects of hydrocortisone could not be attributed to its well documented inhibitory effects on arachidonic acid metabolism. The effect of C. albicans antigen, IFN and corticosteroids on interleukin 1 (IL 1) production by monocytes was also investigated. C. albicans antigen alone induced IL 1 production. So too did IFN-alpha 1 and IFN-gamma. IFN-alpha 2 did not induce IL 1 production. Addition of interferons together with C. albicans, however, resulted in the same level of IL 1 productions as with C. albicans antigen alone. Neither antigen nor IFN had any effect on IL 1 action in the thymocyte assay. Corticosteroids did not affect IL 1 production by monocytes but were potent antagonists of IL 1 in the thymocyte proliferation assay. Mitogen-induced thymocyte proliferation was also inhibited by corticosteroids. Pretreatment of monocytes with hydrocortisone followed by washing did not markedly affect their subsequent ability to produce IL 1 neither was it possible to reverse the inhibitory effects of hydrocortisone on antigen presentation by addition of exogenous IL 1. Thus, signals which alter class II MHC antigen expression influence the antigen-presenting capacity of monocytes by a mechanism independent of IL 1. No simple correlation exists between class II expression and antigen-presenting capacity.

Estrogen induces a demethylation at the 5' end region of the chicken vitellogenin gene.

The two isoschizomeric restriction endonucleases Msp I and Hpa II have been used to study changes in the methylation pattern of the vitellogenin gene after estrogen treatment. In the liver of the both estrogen-treated and nontreated chickens the vitellogenin gene is heavily methylated. However, estradiol causes a demethylation of a Hpa II site(s) at the 5' end region of the gene. The same Hpa II restriction site(s) is also unmethylated in the liver of egg laying hens but is methylated in the liver of roosters or in erythrocyte DNA. In the mature oviduct where no vitellogenin is synthesized but where several egg white proteins are under the control of estrogen, there is also a demethylation of the 5'end region of the vitellogenin gene. This demethylation does not precede the initiation of transcription of the gene but persists, and increases, even after vitellogenin transcription has ceased in the liver. Taken together, the results strongly suggest that in estrogen-responsive tissues the vitellogenin gene becomes demethylated at its 5' end region after estrogen stimulation whether the gene is expressed or not.

Isolation and fine structure organisation of an avian vitellogenin gene coding for the major estrogen-inducible mRNA.

Two phage lambda recombinant DNA clones covering the entire sequence of an avian vitellogenin gene, plus flanking regions, have been isolated from an erythrocyte DNA gene library and characterized by R-loop and restriction mapping. The total length of this avian vitellogenin gene is 23 kb. The cloned sequences flanking the gene at the 5' and 3' end are 7 and 3 kb, respectively. The total length of exons in the two clones is 6.7 kb (vitellogenin mRNA is 6.6 kb). The gene is interrupted by at least 25 introns with a mean intron length of 940 bp. Some 6--10 additional very small introns may also be present but they were not observed reproducibly. The mean exon length is 250 bp. Restriction endonuclease digests of total liver genomic DNA and lambda recombinant DNA were also analyzed by electrophoresis. Southern blotting and hybridization with cloned vitellogenin cDNA. The results show an identity of organisation of this vitellogenin in the DNA from the two sources, thus ruling out a possible cloning artifact. In contrast to Xenopus vitellogenin we have found no evidence to suggest that avian vitellogenin is encoded by a small family of related genes.

Characterization of cloned complementary DNA covering more than 6000 nucleotides (97%) of avian vitellogenin mRNA.

The messenger RNA coding for chicken vitellogenin, a precursor of the egg-yolk proteins lipovitellin and phosvitin, is synthesized in the liver following estrogen injection. This mRNA is 6600 nucleotides long. We have previously reported the cloning and preliminary characterization of some cDNA fragments representing portions of the vitellogenin mRNA [Biochem. Biophys. Acta, 606, 34--46 (1980)]. In this paper we report the full characterization of a larger series of such clones, representing almost the entire length of the mRNA, by restriction endonuclease mapping, R-loop mapping, RNA-DNA hybridization and by translation in vitro of the RNA which hybridizes to the cloned DNA. From the results we conclude that the chicken vitellogenin mRNA, unlike that of Xenopus laevis, does not vary in sequence over most of its length, although some variations in the cDNA sequences were detected particularly in clones derived from the 3' terminus of the RNA. All sequence variants appear to be present in RNA prepared from single animals. The possible origins of these minor species are discussed. Furthermore, we describe a cDNA clone complementary to an mRNA which is about the same size as vitellogenin mRNA and which codes for an egg yolk protein antigenically related to lipovitellin. This mRNA is synthesized constitutively.

Recombinant plasmids containing avian vitellogenin structural gene sequences derived from complementary DNA.

Purified mRNA coding for chicken vitellogenin, a precursor of egg yolk proteins, was transcribed to complementary DNA (cDNAvit) with avian myeloblastosis virus (AMV) reverse transcriptase. Double-stranded cDNA was synthesized with Escherichia coli DNA polymerase I (fragment A) using the self priming ability of the cDNA. Following S1 nuclease digestion the double-stranded cDNA was inserted into the Hind III site of plasmid pBR322 using the poly(dA) . poly(dT) tailing method, and the hybrid molecules were used to transform Escherichia coli chi 1776. Ampicillin-resistant colonies were screened by colony hybridization with 125I-labeled vitellogenen mRNA. Further screening of positive clones was done by agarose gel electrophoresis and in situ hybridization with 125I-labeled vitellogenin mRNA. In addition, plasmid DNA covalently bound to diazotized paper was used to select complementary mRNA sequences. The cloned vitellogenin sequences were shown to hybridize to a mRNA which directs the synthesis of immunoprecipitable vitellogenin when translated in a reticulocyte lysate cell-free system. The length of the inserted cDNA was determined by agarose gel electrophoresis and heteroduplex mapping. The largest insertion was about 2500 base pairs. Restriction mapping indicates that at least three plasmids out of four have different sequences.

Identification of a large precursor of vitellogenin mRNA in the liver of estradiol-treated chicks.

Studies were performed to determine whether vitellogenin mRNA from avian liver has a precursor molecule or not. Total cellular RNA was prepared from estradiol-treated chicken liver in the presence of 8 M guanidine HCl, 2-mercaptoethanol and aurintricarboxylic acid. After denaturation, RNA was fractionated on sodium dodecylsulfate-sucrose gradients and large size RNA was analyzed under stringent conditions on 85% formamide-sucrose gradients at 25 degrees C. RNA fractions collected from the gradients were hybridized with vitellogenin (3H)-cDNA. Besides mature vitellogenin mRNA (32S, 7,000 nucleotides) vitellogenin sequences were also found in RNA fractions ranging from 38-50S with a peak at 45-50S (12-15,000 nucleotides). Only 5-10% of the putative 38-50S pmRNA is polyadenylated. We calculated that the half-life of vitellogenin pmRNA is about 3-4 minutes. We conclude that vitellogenin mRNA has a precursor which is twice the size of the mature mRNA.