1,720,983 research outputs found
Cell wall engineering for better conversion of lignocellulosic biomass
Get PDFThe objective of our research was to use the flexibility of the cell wall to its extremes by modifying its composition while avoiding deleterious effects on plant physiology. One of the strategies to achieve this is the heterologous expression of genes coding for cell wall degrading (CWD) enzymes in plants. These can alter the cell wall structure during plant growth and might improve saccharification yield of the lignocellulosic biomass. In this PhD study 29 genes coding for cell wall degrading enzymes (66 different constructs) were introduced in Arabidopsis and one of the enzymes (a galactanase) was studied in detail. Interestingly, galactanase expression improved the saccharification efficiency without causing a dramatic yield penalty. In parallel, an attempt was made to modify cell wall properties by the expression of the A. caulinodans NodC gene in Arabidopsis. The obtained transgenic lines accumulated GlcNAc mono- and oligosaccharides in their apoplast, which influenced the overall cell wall architecture and modified the cell wall properties. Furthermore, since lignin is major limiting factor that affect saccharification yield, reducing lignin content became a potential strategy to improve the saccharification yield. Here, we have generated Arabidopsis lines with an altered PIRIN2 and PIRIN4 expression. The lines had an altered lignin composition, reduced lignin content and an improved saccharification yield. Despite their modified cell wall, no dramatic effect on plant growth and development was detected
Cell wall engineering by heterologous expression of cell wall-degrading enzymes for better conversion of lignocellulosic biomass into biofuels
No full textHuge energy demand with increasing population is addressing renewable and sustainable energy sources. A solu- tion to energy demand problem is to replace our current fossil fuel-based economy with alternative strategies that do not emit carbon dioxide. Plant biomass is one of the best candi- dates for this issue. Plants use solar power to convert carbon dioxide and water into sugars, which can be used in fermentation reactions to produce both energy and materials. However, the desired sugars are trapped in the highly recalci- trant cell wall as building blocks of cellulose chains. Moreover, the complexity of the plant cell wall structure hin- ders the hydrolysis of cellulose into fermentable sugar mono- mers. Although pretreatments are used to change the physical and chemical properties of the lignocellulosic biomass and improve hydrolysis rates, these pretreatments often use harsh and polluting chemicals and severely increase the cost of bio- fuel production. The goal of the review is to summarize recent researches, which describe generating plants with a modified cell wall and improve hydrolysis of cellulose without applying any or less pretreatment methods. Since pretreatment of lig- nocellulosic biomass is the most cost effective step in biofuel production, generating autodigestible plants could reduce the production cost of biofuels and bio-based biomaterials. One of the strategies to improve biomass conversion efficiency is the modification of the cell wall by heterologous expression of cell wall-modifying proteins. These cell wall-modifying proteins could alter the cell wall structure and reduce cell wall recalcitrance. The use of such transgenic technologies would consume less energy and chemicals when cellulose is more accessible for enzymatic hydrolysis
Investigation of combustion potential of tea pruning waste biomass mixed with lignite coal
Get PDFHayat standartlarının artmasına paralel olarak artan enerji gereksinimi enerjide dışa bağımlı olan
ülkeler için önemli bir sorundur. Artan enerji talebini karşılarken çevreye verilecek olan zararın en aza
indirgenmesi öncelikli hedefler arasında yer almaktadır. Kömür ile ile çalışan termik santrallerden elde
edilen enerji ülkemizin enerji ihtiyacının %32’sini karşılamaktadır. Kullanılan kömürün büyük bir kısmı
ithal kömür ve taşkömürüdür. Ülkemizde son yıllarda yapılan çalışmalar sonucunda linyit kömür
rezervimiz 16 milyar tonun üzerine çıkmıştır. Fakat bu linyit kömür çoğunlukla düşük kalorili olup,
yüksek oranda kükürt, nem ve kül içeriklidir. Bu tür ısıl değeri düşük çevresel etkisi fazla olan kömür
kaynaklarının verimli bir şekilde kullanımı için ileri teknolojilerin geliştirilmesi ulusal ve uluslararası
düzeyde bir gerekliliktir. Diğer yandan, ülkemizin sahip olduğu biyokütle enerjisi potansiyeli verimli bir
şekilde değerlendirilememektedir. Doğu Karadeniz bölgesinin önemli tarımsal atığı olan çay budama
atıkları linyit kömür ile belirli oranlarda harmanlanarak karışımın ısıl değeri, kül içeriği, kükürt ve uçucu
madde içeriği tespit edilmiştir. Çay budama atığının ısıl değeri linyit kömüründen yaklaşık olarak %30
az olmasına rağmen, linyit kömür ile %50 oranında harmanlandığında kül içeriği %12’lerden %6’lara,
kükürt içeriği ise %1.15’lerden %0.69’lara düşmüştür. Atık olarak kullanılan ve ekonomiye
kazandırılmayan bu tarımsal atıkların, linyit kömürü ile uygun karışım değerleri ile homojen şekilde
harmanlandığında enerji potansiyellerinin yüksek olduğu ve çevreci bir yakıt olduğu belirlenmiştir.The growing energy requirement in parallel with the increase in living standards is a major problem
for countries which are dependent on foreign sources for energy. Reducing the damage effect to the
environment while meeting increasing energy demand is among the priority targets. The energy
obtained from coal-fired thermal power plants accounts for 32%of our country's energy needs. Most
of the used coal are imported coal and hard coal in our country. The lignite reserves that have been
known in recent years by exploration studies have exceeded 16 billion tons in our country. However,
these lignite’s are generally low calorie, high sulfur, moisture and ash content. The development of
unique designs and / or technologies for the effective evaluation of such coal at national and
international level are needed. On the other hand, there is an important biomass potential in our
country; this potential is still not being assessed effectively and efficiently. Tea pruning wastes, which
are important agricultural wastes of the Eastern Black Sea region, were blended with lignite coal at
certain ratios and the content of the mixture was determined for colorimetric value, ash content,
sulfur content and volatile matter content. Although the tea pruning waste thermal value was
approximately 30% lower than the lignite, 50% blended biomass with lignite coal, ash content
decreased from 12% to 6% and sulfur content decreased from 1.15% to 0.69%. It was determined that
these agricultural wastes, which were used as waste and not used in industry, have a high energy
potential and an environmentally friendly fuel when they are homogeneously blended with lignite
coal
High-throughput screening of inhibitory effect of medicinal plants on bacterial DNA polymerases
No full textEuropean Biotechnology Conference -- MAY 05-07, 2016 -- LATVIAAntibiotic resistance is a serious and increasing problem in medicine. Particularly, pathogens are one of the most important public health issues at the 21st Century
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
