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Biotechnology for Biofuels

Clementine L Chambon, Thandeka Y Mkhize, Prashant Reddy, Agnieszka Brandt-Talbot, Nirmala Deenadayalu, Paul S Fennell, Jason P Hallett
Background: Sugarcane bagasse is an abundant and geographically widespread agro-industrial residue with high carbohydrate content, making it a strong candidate feedstock for the bio-based economy. This study examines the use of the low-cost protic ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4 ]) to fractionate a range of South African sugarcane bagasse preparations into a cellulose-rich pulp and lignin. The study seeks to optimize pretreatment conditions and examine the necessity of applying a depithing step on bagasse prior to pretreatment...
2018: Biotechnology for Biofuels
Sanchari Ghosh, Evert K Holwerda, Robert S Worthen, Lee R Lynd, Brenden P Epps
Background: Milling during fermentation, termed cotreatment, has recently been proposed as an alternative to thermochemical pretreatment as a means to increase the accessibility of lignocellulosic biomass to biological attack. A central premise of this approach is that partial solubilization of biomass changes the slurry's physical properties such that milling becomes more impactful and more feasible. A key uncertainty is the energy required to mill partially fermented biomass. To inform both of these issues, we report rheological characterization of small-particle, corn stover slurries undergoing fermentation by Clostridium thermocellum ...
2018: Biotechnology for Biofuels
Xianbo Su, Weizhong Zhao, Daping Xia
Background: Biogenic and biogenic-thermogenic coalbed methane (CBM) are important energy reserves for unconventional natural gas. Thus, to investigate biogenic gas formation mechanisms, a series of fresh coal samples from several representative areas of China were analyzed to detect hydrogen-producing bacteria and methanogens in an in situ coal seam. Complete microbial DNA sequences were extracted from enrichment cultures grown on coal using the Miseq high-throughput sequencing technique to study the diversity of microbial communities...
2018: Biotechnology for Biofuels
Sulin Lou, Ting Sun, Hui Li, Zhangli Hu
MicroRNAs are a class of endogenous non-coding RNAs that play a vital role in post-transcriptional gene regulation in eukaryotic cells. In plants and animals, miRNAs are implicated in diverse roles ranging from immunity against viral infections, developmental pathways, molecular pathology of cancer and regulation of protein expression. However, the role of miRNAs in the unicellular model green alga Chlamydomonas reinhardtii remains unclear. The mode of action of miRNA-induced gene silencing in C. reinhardtii is very similar to that of higher eukaryotes, in terms of the activation of the RNA-induced silencing complex and mRNA targeting...
2018: Biotechnology for Biofuels
Xiaoyu Liang, Jason M Whitham, Evert K Holwerda, Xiongjun Shao, Liang Tian, Yu-Wei Wu, Vincent Lombard, Bernard Henrissat, Dawn M Klingeman, Zamin K Yang, Mircea Podar, Tom L Richard, James G Elkins, Steven D Brown, Lee R Lynd
Background: Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Results: Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures...
2018: Biotechnology for Biofuels
Shuen Hon, Evert K Holwerda, Robert S Worthen, Marybeth I Maloney, Liang Tian, Jingxuan Cui, Paul P Lin, Lee R Lynd, Daniel G Olson
Background: Clostridium thermocellum has been the subject of multiple metabolic engineering strategies to improve its ability to ferment cellulose to ethanol, with varying degrees of success. For ethanol production in C. thermocellum , the conversion of pyruvate to acetyl-CoA is catalyzed primarily by the pyruvate ferredoxin oxidoreductase (PFOR) pathway. Thermoanaerobacterium saccharolyticum , which was previously engineered to produce ethanol of high yield (> 80%) and titer (70 g/L), also uses a pyruvate ferredoxin oxidoreductase, pforA , for ethanol production...
2018: Biotechnology for Biofuels
Juan D Tibocha-Bonilla, Cristal Zuñiga, Rubén D Godoy-Silva, Karsten Zengler
Production of biofuels and bioenergy precursors by phototrophic microorganisms, such as microalgae and cyanobacteria, is a promising alternative to conventional fuels obtained from non-renewable resources. Several species of microalgae have been investigated as potential candidates for the production of biofuels, for the most part due to their exceptional metabolic capability to accumulate large quantities of lipids. Constraint-based modeling, a systems biology approach that accurately predicts the metabolic phenotype of phototrophs, has been deployed to identify suitable culture conditions as well as to explore genetic enhancement strategies for bioproduction...
2018: Biotechnology for Biofuels
Krithika Ravi, Omar Y Abdelaziz, Matthias Nöbel, Javier García-Hidalgo, Marie F Gorwa-Grauslund, Christian P Hulteberg, Gunnar Lidén
Background: Lignin is a potential feedstock for microbial conversion into various chemicals. However, the degradation rate of native or technical lignin is low, and depolymerization is needed to obtain reasonable conversion rates. In the current study, base-catalyzed depolymerization-using NaOH (5 wt%)-of softwood Kraft lignin was conducted in a continuous-flow reactor system at temperatures in the range 190-240 °C and residence times of 1 or 2 min. The ability of growth of nine bacterial strains belonging to the genera Pseudomonas and Rhodococcus was tested using the alkaline-treated lignin as a sole carbon source...
2018: Biotechnology for Biofuels
María Santos-Merino, M Pilar Garcillán-Barcia, Fernando de la Cruz
Background: The microbial production of fatty acids has received great attention in the last few years as feedstock for the production of renewable energy. The main advantage of using cyanobacteria over other organisms is their ability to capture energy from sunlight and to transform CO2 into products of interest by photosynthesis, such as fatty acids. Fatty acid synthesis is a ubiquitous and well-characterized pathway in most bacteria. However, the activity of the enzymes involved in this pathway in cyanobacteria remains poorly explored...
2018: Biotechnology for Biofuels
Jonathan Herlet, Wolfgang H Schwarz, Vladimir V Zverlov, Wolfgang Liebl, Petra Kornberger
Background: Increasing the efficiency of enzymatic biomass degradation is crucial for a more economically feasible conversion of abundantly available plant feedstock. Synergistic effects between the enzymes deployed in the hydrolysis of various hemicelluloses have been demonstrated, which can reduce process costs by lowering the amount of enzyme required for the reaction. Xyloglucan is the only major hemicellulose for which no such effects have been described yet. Results: We report the beneficial combination of two enzymes for the degradation of the hemicellulose xyloglucan...
2018: Biotechnology for Biofuels
Fabian M Schwarz, Kai Schuchmann, Volker Müller
Background: Replacing fossil fuels as energy carrier requires alternatives that combine sustainable production, high volumetric energy density, easy and fast refueling for mobile applications, and preferably low risk of hazard. Molecular hydrogen (H2 ) has been considered as promising alternative; however, practical application is struggling because of the low volumetric energy density and the explosion hazard when stored in large amounts. One way to overcome these limitations is the transient conversion of H2 into other chemicals with increased volumetric energy density and lower risk hazard, for example so-called liquid organic hydrogen carriers such as formic acid/formate that is obtained by hydrogenation of CO2 ...
2018: Biotechnology for Biofuels
Chong Li, Shi Gao, Xiaotong Li, Xiaofeng Yang, Carol Sze Ki Lin
Background: Alkali used for pH control during fermentation and acidification for downstream recovery of succinic acid (SA) are the two largest cost contributors for bio-based SA production. To promote the commercialization process of fermentative SA, the development of industrially important microorganisms that can tolerate low pH has emerged as a crucial issue. Results: In this study, an in situ fibrous bed bioreactor (isFBB) was employed for the metabolic evolution for selection of Y...
2018: Biotechnology for Biofuels
James Wilson, Sarah Gering, Jessica Pinard, Ryan Lucas, Brandon R Briggs
To reduce emissions from petrochemical refinement, bio-production has been heralded as a way to create economically valuable compounds with fewer harmful effects. For example, gaseous alkenes are precursor molecules that can be polymerized into a variety of industrially significant compounds and have biological production pathways. Production levels, however, remain low, thus enhancing bio-production of gaseous petrochemicals for chemical precursors is critical. This review covers the metabolic pathways and production levels of the gaseous alkenes ethylene, isoprene, and isobutene...
2018: Biotechnology for Biofuels
Seyed Mostafa Hallaji, Ali Torabian, Behnoush Aminzadeh, Soraya Zahedi, Nicky Eshtiaghi
Background: Recently, it has been indicated that free nitrous acid (FNA) and Fenton pre-treatment of waste activated sludge can enhance methane production in anaerobic digestion of waste activated sludge. In addition, it has been revealed that the substances used in these pre-treatments are both eco-friendly and economically attractive because not only are they produced in anaerobic digestion, but they are also low priced. Since primary sludge and waste activated sludge are mixed prior to anaerobic digestion in the majority of wastewater treatment plants, this study aims to assess the influence of combined FNA and Fenton on the anaerobic digestion of mixed sludge...
2018: Biotechnology for Biofuels
Guokun Wang, Wendi Jia, Na Chen, Ke Zhang, Lixian Wang, Pin Lv, Ronglin He, Min Wang, Dongyuan Zhang
Background: The filamentous fungus Trichoderma reesei , the most widely used cellulase producer, also has promising applications in lignocellulose-based biorefinery: consolidated bioprocessing for the production of high value-added products. However, such applications are thwarted by the time-consuming metabolic engineering processes (design-build-test-learn cycle) for T. reesei , resulted from (i) the spore separation-mediated purification as the multinucleate hyphae, (ii) transformant screening for high expression levels since unavailable of episomal expression system, and (iii) cases of inexpressible heterologous proteins...
2018: Biotechnology for Biofuels
Verena Oehling, Paul Klaassen, Oliver Frick, Christian Dusny, Andreas Schmid
Bioethanol production processes with Saccharomyces cerevisiae using lignocellulosic biomass as feedstock are challenged by the simultaneous utilization of pentose and hexose sugars from biomass hydrolysates. The pentose uptake into the cell represents a crucial role for the efficiency of the process. The focus of the here presented study was to understand the uptake and conversion of the pentose l-arabinose in S. cerevisiae and reveal its regulation by d-glucose and d-galactose. Gal2p-the most prominent transporter enabling l-arabinose uptake in S...
2018: Biotechnology for Biofuels
Jin Jin, Ying Wang, Mingdong Yao, Xiaoli Gu, Bo Li, Hong Liu, Mingzhu Ding, Wenhai Xiao, Yingjin Yuan
Background: Astaxanthin is a natural carotenoid pigment with tremendous antioxidant activity and great commercial value. Microbial production of astaxanthin via metabolic engineering has become a promising alternative. Although great efforts have been conducted by tuning the heterologous modules and precursor pools, the astaxanthin yields in these non-carotenogenic microorganisms were still unsatisfactory for commercialization, indicating that in addition to targeted tailoring limited targets guided by rationally metabolic design, combining more globe disturbances in astaxanthin biosynthesis system and uncovering new molecular mechanisms seem to be much more crucial for further development...
2018: Biotechnology for Biofuels
Jannis Broeker, Matthias Mechelke, Melanie Baudrexl, Denise Mennerich, Daniel Hornburg, Matthias Mann, Wolfgang H Schwarz, Wolfgang Liebl, Vladimir V Zverlov
Background: The bioconversion of lignocellulosic biomass in various industrial processes, such as the production of biofuels, requires the degradation of hemicellulose. Clostridium stercorarium is a thermophilic bacterium, well known for its outstanding hemicellulose-degrading capability. Its genome comprises about 50 genes for partially still uncharacterised thermostable hemicellulolytic enzymes. These are promising candidates for industrial applications. Results: To reveal the hemicellulose-degrading potential of 50 glycoside hydrolases, they were recombinantly produced and characterised...
2018: Biotechnology for Biofuels
Tapio Lehtinen, Henri Virtanen, Suvi Santala, Ville Santala
Background: Microbial biosynthesis of alkanes is considered a promising method for the sustainable production of drop-in fuels and chemicals. Carbon dioxide would be an ideal carbon source for these production systems, but efficient production of long carbon chains from CO2 is difficult to achieve in a single organism. A potential solution is to employ acetogenic bacteria for the reduction of CO2 to acetate, and engineer a second organism to convert the acetate into long-chain hydrocarbons...
2018: Biotechnology for Biofuels
Han Sun, Weiyang Zhao, Xuemei Mao, Yuelian Li, Tao Wu, Feng Chen
Microalgae are capable of producing sustainable bioproducts and biofuels by using carbon dioxide or other carbon substances in various cultivation modes. It is of great significance to exploit microalgae for the economical viability of biofuels and the revenues from high-value bioproducts. However, the industrial performance of microalgae is still challenged with potential conflict between cost of microalgae cultivation and revenues from them, which is mainly ascribed to the lack of comprehensive understanding of carbon metabolism and energy conversion...
2018: Biotechnology for Biofuels
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