Xylanase production from a Bacillus subtilis gene cloned into a strain of Escherichia coli was measured. Although this gene was expressed in E. coli at several temperatures, efficient normal xylanase secretion did not occur, the observed protein release apparently depending on cell leakage or lysis. Screening for a better microbial protein secretor free of cellulase selected B. cereus #259. The strain had wild plasmids that were hard to eliminate using acridine orange and elevated temperature curing techniques. While still bearing 5 wild plasmids, attempts to transform B. cereus #259 were unsuccessful using conventional methods and electroporation. Another strain, B. cereus #518, found to be free of wild plasmids, was then used. A bidirectional vector shuttle plasmid (pMK3) was employed to carry the cloned gene into this B. cereus strain. Transformation was carried out by high voltage electroporation. Xylanase production by the new B. cereus clone was similar to that from E. coli, but was shown to be continuously and normally secreted. The xylanase gene products from the E. coli and B. cereus hosts were shown to function identically. Both xylanases improved the delignification of unbleached softwood and hardwood kraft pulps, thus reducing the Cl$ sb2$ required to achieve a given degree of bleaching, without altering the physical properties of the fibers. Using a target kappa number lignin content) of 5, xylanase pretreatment of aspen kraft pulp led to a 22% saving of chlorine. Adsorbable organic halogens in the bleachery effluent were also lowered by more than 50%.

No description available.

Lignocellulose can become the best opportunity for the society to reduce its dependency on the harmful petroleum based products as well as to produce clean energy. In each part of the production cycle, biomass based products have a better environmental profiles than their petroleum based counterparts. Woody biomass has a vast availability, but it suffers from recalcitrance that is mostly caused by lignin that is functioning as a matrix, surrounding and binding the carbohydrates that are currently the most valuable of the wood components. Lignin-carbohydrate (LC) bonds are believed to be a key element in this recalcitrance and research has shown that these types of bonds are common in wood. These bonds are important in an economical point of view as well, as e.g. residual lignin structures in pulp (lignins bonded to the cellulose and hemicelluloses) require expensive bleaching sequences for their removal. The LC-structures can also be exploited technically as we now have demonstrated. We developed a method that utilizes phenolic end groups that are bonded to different hemicelluloses for cross-linking. The enzyme laccase was used for the cross-linking to create a cost-efficient processing scheme to both isolate and increase the molecular weight of the hemicelluloses. Membrane filtration was used as the key separation technique, which enables the establishment of industrial scale production. The final product had improved mechanical and thermal properties and could be used e.g. as barrier film component in renewable packaging. Nanocomposite formation with nanofibrillated cellulose was also studied. This improved the film properties further. The complexes are also possible to use as model compounds for lignin-carbohydrate complexes in wood. This technique can also be seen to mimick the lignification and lignin-carbohydrate network formation phenomena in plants enabling the formation of entire networks of wood components. Our results suggests that the side chains of hemicellulose might play an important role in network formation and that hemicellulose molecules can carry more than one lignin phenolic end group to fulfill this capability. / <p>QC 20140825</p>

The modern concept of “biorefinery” is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various bio-based products. It includes thermochemical processes such as gasification and fast pyrolysis. In thermo-mechanical pulp (TMP) mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, bio-sludges and other available fuels such as peat, recycled wood and paper products. On the other hand, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. The huge amount of purchased electricity can be compensated for by self-production of electricity from gasification, or the involved cost can be compensated for by extra revenue from bio-transport fuel production. This work is to study co-production of bio-automotive fuels, bio-power, and steam via gasification of the waste biomass streams in the context of the mechanical pulp industry. Ethanol and substitute natural gas (SNG) are chosen to be the bio-transport fuels in the study. The production processes of biomass-to-ethanol, SNG, together with heat and power, are simulated with Aspen Plus. Based on the model, the techno-economic analysis is made to evaluate the profitability of bio-transport fuel production when the process is integrated into a TMP mill.The mathematical modelling starts from biomass gasification. Dual fluidized bed gasifier (DFBG) is chosen for syngas production. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150 KWth Mid Sweden University (MIUN) DFBG. As a reasonable result, the tar content in the syngas decreases with the gasification temperature and the steam to biomass (S/B) ratio. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass or product gas needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming.For ethanol production, a stand-alone thermo-chemical process is designed and simulated. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost. The calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built over 200 MW.In TMP mills, wood and biomass residues are commonly utilized for electricity and steam production through an associated CHP plant. This CHP plant is here designed to be replaced by a biomass-integrated gasification combined cycle (BIGCC) plant or a biomass-to-SNG (BtSNG) plant including an associated heat &amp; power centre. Implementing BIGCC/BtSNG in a mechanical pulp production line might improve the profitability of a TMP mill and also help to commercialize the BIGCC/BtSNG technologies by taking into account of some key issues such as, biomass availability, heat utilization etc.. In this work, the mathematical models of TMP+BIGCC and TMP+BtSNG are respectively built up to study three cases: 1) scaling of the TMP+BtSNG mill (or adding more forest biomass logging residues in the gasifier for TMP+BIGCC); 2) adding the reject fibres in the gasifier; 3) decreasing the TMP SEC by up to 50%.The profitability from the TMP+BtSNG mill is analyzed in comparison with the TMP+BIGCC mill. As a major conclusion, the scale of the TMP+BIGCC/BtSNG mill, the prices of electricity and SNG are three strong factors for the implementation of BIGCC/BtSNG in a TMP mill. A BtSNG plant associated to a TMP mill should be built in a scale above 100 MW in biomass thermal input. Comparing to the case of TMP+BIGCC, the NR and IRR of TMP+BtSNG are much lower. Political instruments to support commercialization of bio-transport fuel are necessary. / Gasification-based Biorefinery for Mechanical Pulp Mills

No description available.

No description available.

Eucalypts are a major forest resource globally and the area of eucalypt plantations for pulp and paper production is expanding rapidly in Australia. Consequently, there is an increasing need to breed eucalypts with improved wood properties. Since many high value wood traits are under strong genetic control, identification of DNA markers linked to these traits will have application in breeding programs. In recent years there has been a shift in marker strategy away from QTL mapping in pedigrees to association studies in unrelated populations. In the latter approach, single nucleotide polymorphisms (SNPs) in candidate genes are screened to identify SNPs that significantly associate with wood traits. Significant SNPs could be used for marker-assisted selection (MAS) in breeding programs. The objectives of this study were to identify candidate genes that may influence pulp yield in eucalypts and to identify SNP variants in those genes that associate with superior wood and pulp traits. / Approximately 300 trees from a full-sib Eucalyptus nitens progeny derived from a wide intra specific cross were used for gene discovery. DNA microarrays containing ~5800 young xylem of cDNAs Eucalyptus grandis were screened with probes synthesised from RNA isolated from trees with either high or low pulp yield. Forty-six transcripts were differentially regulated, of which 27 were more abundant in high pulp trees and 19 were more abundant in low pulp trees. All differentially expressed cDNAs were partially sequenced and searched against existing gene databases. Six genes were selected as putative pulp yield candidate genes based on their significant similarity to genes with known function and were named EgrCesA3 (cellulose synthase), EgrNAM1 (NAM family protein), EgrXET (xyloglucan endotransglycosylase), EgrGalk (galactokinase), EgrHB1 (class III homeodomain leucine zipper protein) and EgrZnf1 (C3HC4 type zinc finger protein). / Real-Time PCR was carried out on selected genes to confirm the accuracy of the microarray results. Full length cDNAs were obtained for EgrCesA3, EgrHB1 and EgrZnf1 and the candidate genes were partially characterised. An additional candidate gene, the novel gene EgrPAAPA, was selected based on previous research due to its high expression in the cambium and its expression in eucalypt branches. EgrPAAPA was cloned by screening an E. grandis cDNA library and fully sequenced. The full length EgrPAAPA encodes a short 172 amino acid protein rich in alanine, glutamic acid and proline residues. The EgrPAAPA protein appears to be a hydroxyproline-rich glycoprotein (HRGP) and the repetitive ‘PAAPA’ motif suggests that it might play a structural role in cell wall development. Southern blot analysis revealed that E. grandis has a single copy of the EgrPAAPA gene and northern blot analysis revealed that EgrPAAPA is most strongly expressed in xylem tissues. / Allelic variation in EnCesA3, EnNAM1, EnPAAPA and EnHB1 was examined by sequencing each gene in 16 to 24 unrelated E. nitens individuals. SNPs were identified by sequence analysis and patterns of nucleotide diversity, linkage disequilibrium and the selection of suitable polymorphisms were estimated. A moderate level of nucleotide diversity (θw = 0.0056 and π = 0.0039) was observed and linkage disequilibrium was generally low, extending only a few hundred base pairs in each gene. Negative selection has been operating in EnHB1. Selected TagSNPs from EnNAM1, EnHB1 and EnPAAPA were genotyped across 300 unrelated E. nitens trees which had been phenotyped for six wood quality traits including pulp yield, cellulose, lignin, Klason lignin, microfibril angle (MFA) and density. Five highly significant genetic associations (p<0.01) were detected between several SNPs in EnHB1 and all wood quality traits except density. A significant association was also found between EnPAAPA and MFA (p<0.05). No significant associations were found with any of the EnNAM1 SNPs. The strong genetic associations between SNPs in EnHB1 and a range of wood traits is consistent with this gene’s known role as a transcription factor controlling vascular development. Validation of these associations in different populations will be necessary in order to confirm these results. Alternatively, QTL mapping can be performed in order to confirm whether QTL for wood property traits can be detected at the EnHB1 and EnPAAPA loci.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.93-94).

Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 1988. / Includes bibliography.

Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 2001. / Includes bibliography.