1.0. Introduction 4044 2.0. Biomass Chemistry and Growth Rates 4047 2.1. Lignocellulose and Starch-Based Plants 4047 2.2. Triglyceride-Producing Plants 4049 2.3. Algae 4050 2.4. Terpenes and Rubber-Producing Plants 4052 3.0. Biomass Gasification 4052 3.1. Gasification Chemistry 4052 3.2. Gasification Reactors 4054 3.3. Supercritical Gasification 4054 3.4. Solar Gasification 4055 3.5. Gas Conditioning 4055 4.0. Syn-Gas Utilization 4056 4.1. Hydrogen Production by Water−Gas Shift Reaction 4056

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Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering.

Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

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Microbial cellulose utilization: fundamentals and biotechnology.

Lignocellulosic biomass has long been recognized as a potential sustainable source of mixed sugars for fermentation to biofuels and other biomaterials. Several technologies have been developed during the past 80 years that allow this conversion process to occur, and the clear objective now is to make this process cost-competitive in today's markets. Here, we consider the natural resistance of plant cell walls to microbial and enzymatic deconstruction, collectively known as "biomass recalcitrance." It is this property of plants that is largely responsible for the high cost of lignocellulose conversion. To achieve sustainable energy production, it will be necessary to overcome the chemical and structural properties that have evolved in biomass to prevent its disassembly.

http://science.sciencemag.org/content/sci/315/5813/804.full.pdf

Biomass recalcitrance: engineering plants and enzymes for biofuels production.

The End of History and the Last Man

Border Gateway Protocol (BGP) is the protocol backing the core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). Point of concern in BGP is its lack of effective security measures which makes Internet vulnerable to different forms of attacks. Many solutions have been proposed till date to combat BGP security issues but not a single one is deployable in practical scenario. Any security proposal with optimal solution should offer adequate security functions, performance overhead and deployment cost. This paper critically analyzes the deployment issues of best three proposals considering trade-off between security functions and performance overhead.

Comparative analysis of

The excessive use of pesticides to prevent the outbreak of plant diseases holds various disadvantages for the cost-effectiveness of agricultural production prac- tices, the quality of the end products, the environment and the labour force. The mount- ing public resistance to the use of hazardous pesticides on agricultural crops has hastened the search for natural antimicrobial peptides, enzymes and other types of biological con- trol agents. The objective of this study was to investigate the potential of the antifungal activity of a yeast-derived chitinase for possible future agricultural applications. When plants are exposed to fungal pathogens, they produce pathogenesis-related (PR) defence proteins, such as chitinases, in order to degrade the chitin in the cell walls of the attack- ing fungi, thereby inhibiting further fungal growth and the development of hyphae. We have cloned the Saccharomyces cerevisiae chitinase gene (CTS1-2) into a multicopy 2µ-based plasmid and overexpressed it under the control of the phosphoglycerate kinase I gene (PGK1) promoter (PGK1 P ) and terminator (PGK1 T ) sequences. Secretion of the recombinant CTS1-2-encoded chitinases was directed by the native leader peptide, or by the secretion signals of either the yeast mating pheromone α-factor (MFα1 S ) or the Tri- choderma reesei β-xylanase 2 (XYN2 S ). Northern blot analysis confirmed the PGK1 PT - directed expression of CTS1-2 and an indirect enzyme assay was used to compare the efficiency of secretion of the three different recombinant chitinases. These recombinant chitinases were also shown to effectively inhibit spore germination and hyphal growth of Botrytis cinerea, an economically important fungal pathogen of several agricultural crop plants, including grapevine. This study could lead to the development of yeast chitinases and/or chitinolytic yeasts as biocontrol agents to combat plant diseases and reduce the use of chemical pesticides in the agricultural industry.

Overexpression, secretion and antifungal activity of the Saccharomyces cerevisiae chitinase

Aims: The main objective of this study was to identify amino acid residues in the AGT1-encoded α-glucoside transporter (Agt1p) that are critical for efficient transport of maltotriose in the yeast Saccharomyces cerevisiae.



Methods and Results:  The sequences of two AGT1-encoded α-glucoside transporters with different efficiencies of maltotriose transport in two Saccharomyces strains (WH310 and WH314) were compared. The sequence variations and discrepancies between these two proteins (Agt1pWH310 and Agt1pWH314) were investigated for potential effects on the functionality and maltotriose transport efficiency of these two AGT1-encoded α-glucoside transporters. A 23-amino-acid C-terminal truncation proved not to be critical for maltotriose affinity. The identification of three amino acid differences, which potentially could have been instrumental in the transportation of maltotriose, were further investigated. Single mutations were created to restore the point mutations I505T, V549A and T557S one by one. The single site mutant V549A showed a decrease in maltotriose transport ability, and the I505T and T557S mutants showed complete reduction in maltotriose transport.



Conclusions:  The amino acids Thr505 and Ser557, which are respectively located in the transmembrane (TM) segment TM11 and on the intracellular segment after TM12 of the AGT1-encoded α-glucoside transporters, are critical for efficient transport of maltotriose in S. cerevisiae.



Significance and Impact of the Study:  Improved fermentation of starch and its dextrin products, such as maltotriose and maltose, would benefit the brewing and whisky industries. This study could facilitate the development of engineered maltotriose transporters adapted to starch-efficient fermentation systems, and offers prospects for the development of yeast strains with improved maltose and maltotriose uptake capabilities that, in turn, could increase the overall fermentation efficiencies in the beer and whisky industries.

The Thr505 and Ser557 residues of the AGT1-encoded α-glucoside transporter are critical for maltotriose transport in Saccharomyces cerevisiae

Aims: The main objective of this study was to develop polysaccharide-degrading wine strains of Saccharomyces cerevisiae, which are able to improve aspects of wine processing and clarification, as well as colour extraction and stabilization during winemaking. Methods and Results: Two yeast expression ⁄secretion gene cassettes were constructed, namely (i) a pectinase gene cassette (pPPK) consisting of the endo-polygalacturonase gene (pelE) from Erwinia chrysanthemi and the pectate lyase gene (peh1) from Erwinia carotovora and (ii) a glucanase ⁄xylanase gene cassette (pEXS) containing the endo-b-1,4-glucanase gene (end1) from Butyrivibrio fibrisolvens and the endo-b-1,4-xylanase gene (xynC) from Aspergillus niger. The commercial wine yeast strain, VIN13, was transformed separately with these two gene cassettes and checked for the production of pectinase, glucanase and xylanase activities. Pinot Noir, Cinsaut and Muscat d’Alexandria grape juices were fermented using the VIN13[pPPK] pectinase- and the VIN13[pEXS] glucanase ⁄xylanase-producing transformants. Chemical analyses of the resultant wines indicated that (i) the pectinase-producing strain caused a decrease in the concentration of phenolic compounds in Pinot Noir whereas the glucanase ⁄xylanase-producing strain caused an increase in phenolic compounds presumably because of the degradation of the grape skins; (ii) the glucanase ⁄xylanase-producing strain caused a decrease in wine turbidity, especially in Pinot Noir wine, as well as a clear increase in colour intensity and (iii) in the Muscat d’Alexandria and Cinsaut wines, the differences between the control wines (fermented with the untransformed VIN3 strain) and the wines produced by the two transformed strains were less prominent showing that the effect of these polysaccharide-degrading enzymes is cultivar-dependent. Conclusions: The recombinant wine yeasts producing pectinase, glucanase and xylanase activities during the fermentation of Pinot Noir, Cinsaut and Muscat d’Alexandria grape juice altered the chemical composition of the resultant wines in a way that such yeasts could potentially be used to improve the clarity, colour intensity and stability and aroma of wine. Significance and Impact of the Study: Aspects of commercial-scale wine processing and clarification, colour extraction and stabilization, and aroma enhancement could potentially be improved by the use of polysaccharidedegrading wine yeasts without the addition of expensive commercial enzyme preparations. This offers the potential to further improve the price : quality ratio of wine according to consumer expectations.

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The heterologous expression of polysaccharidase-encoding genes with oenological relevance in Saccharomyces cerevisiae.

Objective measures of grape quality – are they achievable?

A total of 134 alpha-amylase producing Bacillus isolates and 21 reference strains were divided into 12 groups according to their similarities (% SSM). Phenotypic characteristics determined by the API 20E and API 50CHB galleries, other biochemical tests and morphological characteristics were used for the numerical analysis. The API Computer Service identified 45% of the isolates. The amylase yields of 16 alpha-amylase hyperproducing (AHP) isolates were compared with those of seven amylolytic reference and type strains. The AHP isolates were related to Bacillus subtilis, B. licheniformis and 'B. amyloliquefaciens'.

Isak S. Pretorius

Papers

Overexpression, secretion and antifungal activity of the Saccharomyces cerevisiae chitinase

The Thr505 and Ser557 residues of the AGT1-encoded α-glucoside transporter are critical for maltotriose transport in Saccharomyces cerevisiae

The heterologous expression of polysaccharidase-encoding genes with oenological relevance in Saccharomyces cerevisiae.

Objective measures of grape quality – are they achievable?

Numerical taxonomy of α-amylase producing Bacillus species