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Mohamed Mahmoud, César Iván Torres, Bruce E Rittmann
When a mixed-culture microbial electrolysis cell (MEC) is fed with a fermentable substrate, such as glucose, a significant fraction of the substrate's electrons ends up as methane (CH4) through hydrogenotrophic methanogenesis, an outcome that is undesired. Here, we show that free ammonia-nitrogen (FAN, which is NH3) altered the glucose fermentation pathways in batch MECs, minimizing the production of H2, the "fuel" for hydrogenotrophic methanogens. Consequently, the Coulombic efficiency (CE) increased: 57% for 0...
October 17, 2017: Environmental Science & Technology
Anna Lange, Judith Becker, Dennis Schulze, Edern Cahoreau, Jean-Charles Portais, Stefan Haefner, Hartwig Schröder, Joanna Krawczyk, Oskar Zelder, Christoph Wittmann
Succinic acid is a platform chemical of recognized industrial value and accordingly faces a continuous challenge to enable manufacturing from most attractive raw materials. It is mainly produced from glucose, using microbial fermentation. Here, we explore and optimize succinate production from sucrose, a globally applied substrate in biotechnology, using the rumen bacterium Basfia succiniciproducens DD1. As basis of the strain optimization, the yet unknown sucrose metabolism of the microbe was studied, using (13)C metabolic flux analyses...
October 13, 2017: Metabolic Engineering
Zhiying Han, Shixia Chen, Xiaochang Lin, Hongjun Yu, Li'an Duan, Zhangying Ye, Yanbo Jia, Songming Zhu, Dezhao Liu
To identify the performance of step-fed submerged membrane sequencing batch reactor (SMSBR) treating swine biogas digestion slurry and to explore the correlation between microbial metabolites and membrane fouling within this novel reactor, a lab-scale step-fed SMSBR was operated under nitrogen loading rate of 0.026, 0.052 and 0.062 g NH4(+)-N (gVSS·d)(-1). Results show that the total removal efficiencies for NH4(+)-N, total nitrogen and chemical oxygen demand in the reactor (>94%, >89% and >97%, respectively) were high during the whole experiment...
October 16, 2017: Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering
Bekzod Khakimov, Lene D Christiansen, Anna-Lena Heins, Klavs M Sørensen, Charlotte Schöller, Anders Clausen, Thomas Skov, Krist V Gernaey, Søren B Engelsen
An industrial scale biomass production using batch or fed-batch fermentations usually optimized by selection of bacterial strains, tuning fermentation media, feeding strategy, and temperature. However, in-depth investigation of the biomass metabolome during the production may reveal new knowledge for better optimization. In this study, for the first time, the authors investigated seven fermentation batches performed on five Streptoccoccus thermophilus strains during the biomass production at Chr. Hansen (Denmark) in a real life large scale fermentation process...
October 16, 2017: Biotechnology Journal
Chengcheng Li, Fengming Lin, Le Zhou, Lei Qin, Bingzhi Li, Zhihua Zhou, Mingjie Jin, Zhan Chen
BACKGROUND: The induction of cellulase production by insoluble carbon source cellulose was a common and efficient strategy, but has some drawbacks, such as difficult fermentation operation, substantial cellulase loss, long fermentation time, and high energy-consumption, resulting in high cost of cellulase production in industry. These drawbacks can be overcome if soluble carbon sources are utilized as the inducers for cellulase production. However, until now the induction efficiency of most soluble carbon sources, especially lactose and glucose, is still inferior to cellulose despite extensive efforts have been made by either optimizing the fermentation process or constructing the recombinant strains...
2017: Biotechnology for Biofuels
L De Gelder, K Audenaert, B Willems, K Schelfhout, S De Saeger, M De Boevre
Food and feed stocks heavily contaminated with mycotoxins are rendered unfit for consumption and therefore discarded as waste. Due to the lack of guidelines and in accordance with the prudent avoidance principle, these waste streams are often incinerated. For better valorization, these streams could be used as input for anaerobic digestion. However, the degradation of multiple mycotoxins during anaerobic digestion and their effect on the methane production is currently unknown. In batch tests spiked with mycotoxins, aflatoxin B1, ochratoxin A, deoxynivalenol, zearalenone and T-2 toxin were degraded for more than 90%...
October 9, 2017: Waste Management
Jie Gao, Minh T Vo, Juliana A Ramsay, Bruce A Ramsay
Methods of producing medium-chain-length poly-3-hydroxyalkanoate (mcl-PHA) with high content of the dominant subunit, 3-hydroxydecanoate (HD), were examined with an emphasis on a high yield of polymer from decanoic acid. High HD content was achieved by using a β-oxidation knockout mutant of Pseudomonas putida KT2440 (designated as P. putida DBA-F1) or by inhibiting β-oxidation with addition of acrylic acid to wild type P. putida KT2440 in carbon-limited, fed-batch fermentations. At a substrate feed ratio of decanoic acid and acetic acid to glucose (DAA:G) of 6:4 g/g, P...
October 14, 2017: Biotechnology and Bioengineering
Chih-Jung Hsu, Harsh V Jain, Abasha Williams, Julie Wang, Scott C Lute, Serge L Beaucage, Kurt A Brorson
A rapid and cost-effective transient transfection method for mammalian cells is essential for screening biopharmaceuticals in early stages of development. A library of 25 amphipathic trans-acting oligodeoxythymidine phosphorothioate triester (dTtaPS) transfection reagents, carrying positively charged and lipophilic groups, has been constructed for this purpose. High-throughput screening of the library, using an imaging cytometer and an automated microbioreactor system, has led to the identification of dTtaPS(10+) as a potent transfection reagent...
October 10, 2017: Biotechnology and Applied Biochemistry
Marisol Belmonte, Chia-Fang Hsieh, José Luis Campos, Lorna Guerrero, Ramón Méndez, Anuska Mosquera-Corral, Gladys Vidal
The effect of free ammonia (NH3 or FA), free nitrous acid (HNO2 or FNA), and total alkalinity (TA) on the performance of a partial nitrification (PN) sequencing batch reactor (SBR) treating anaerobically pretreated pig slurry was studied. The SBR was operated under alternating oxic/anoxic (O/A) conditions and was fed during anoxic phases. This strategy allowed using organic matter to partially remove nitrite (NO2(-)) and nitrate (NO3(-)) generated during oxic phases. The desired NH4(+) to NO2(-) ratio of 1...
2017: BioMed Research International
G Kristin Jonsson, Jeanette Ulama, Malin Johansson, Malin Zackrisson Oskolkova, Johan Bergenholtz
Fluorinated spheres with grafted poly(ethylene glycol) (PEG) have been synthesized using a semi-batch emulsion polymerization in which the initiator is fed slowly to the reaction. In this way, PEG-grafted colloidal spheres can be fabricated with varying PEG chain length, different cores and varying degrees of crosslinking. The resulting batches have been characterized using disc centrifuge photosedimentometry and small-angle X-ray scattering. The size distribution is shown to be a sensitive function of the molar ratio of the reactive PEG macromonomer to fluorinated monomer, and with some optimization latices of very low polydispersity can be obtained with this simple synthesis method...
2017: Colloid and Polymer Science
Dominique Claveau-Mallet, Benoît Courcelles, Philippe Pasquier, Yves Comeau
The first version of the P-Hydroslag model for numerical simulations of steel slag filters is presented. This model main original feature is the implementation of slag exhaustion behavior, crystal growth and crystal size effect on crystal solubility, and crystal accumulation effect on slag dissolution. The model includes four mineral phases: calcite, monetite, homogeneous hydroxyapatite (constant size and solubility) and heterogeneous hydroxyapatite (increasing size and decreasing solubility). In the proposed model, slag behavior is represented by CaO dissolution kinetic rate and exhaustion equations; while slag dissolution is limited by a diffusion rate through a crystal layer...
September 19, 2017: Water Research
Yulong Tan, Matthias Leonhard, Berit Schneider-Stickler
Silicone is frequently used in clinical and medical fields for medical devices. Mixed biofilms composed of Candida and bacterial species causes frequently failure of medical silicone devices, In this in vitro study, we analyzed mixed biofilm formation of clinically isolated non-albicans Candida species and Staphylococcus epidermidis, including Candida tropicalis, Candida krusei and Candida parapsilosis under the influence of different growth media (RPMI 1640, BHI and TSB) and several culture variables (incubation period, feeding conditions and FBS)...
October 5, 2017: Microbial Pathogenesis
Sofia Esquivel-Elizondo, Joseph Miceli, Cesar I Torres, Rosa Krajmalnik-Brown
Medium-chain fatty acids (MCFA) are important biofuel precursors. Carbon monoxide (CO) is a sustainable electron and carbon donor for fatty acid elongation, since it is metabolized to MCFA precursors, it is toxic to most methanogens, and it is a waste product generated in the gasification of waste biomass. The main objective of this work was to determine if the inhibition of methanogenesis through the continuous addition of CO would lead to increased acetate or MCFA production during fermentation of ethanol...
October 7, 2017: Biotechnology and Bioengineering
Macarena Larroude, Ewelina Celinska, Alexandre Back, Stephan Thomas, Jean-Marc Nicaud, Rodrigo Ledesma-Amaro
The increasing market demands of β-carotene as colorant, antioxidant and vitamin precursor, requires novel biotechnological production platforms. Yarrowia lipolytica, is an industrial organism unable to naturally synthesize carotenoids but with the ability to produce high amounts of the precursor Acetyl-CoA. We first found that a lipid overproducer strain was capable of producing more β-carotene than a wild type after expressing the heterologous pathway. Thereafter, we developed a combinatorial synthetic biology approach base on Golden Gate DNA assembly to screen the optimum promoter-gene pairs for each transcriptional unit expressed...
October 7, 2017: Biotechnology and Bioengineering
Benyamin Khoshnevisan, Panagiotis Tsapekos, Merlin Alvarado-Morales, Irini Angelidaki
Three distinctive start-up strategies of biogas reactors fed with source-sorted organic fraction of municipal solid waste were investigated to reveal the most reliable procedure for rapid process stabilization. Moreover, the experimental results were compared with mathematical modeling outputs. The initial inoculations to start-up the reactors were 10, 50 and 100% of the final working volume. While a constant feeding rate of 7.8gVS/d was considered for the control reactor, the organic loading rate for fed-batch reactors with 10 and 50% inoculation was progressively increased during a period of 60 and 13days, respectively...
September 20, 2017: Bioresource Technology
Minho Noh, Seung Min Yoo, Won Jun Kim, Sang Yup Lee
Escherichia coli gene expression knockdown using synthetic small RNA (sRNA) can be fine-tuned by altering sRNA sequences to modulate target mRNA-binding ability, but this requires thorough checking for off-target effects. Here, we present an sRNA gene expression knockdown system fine-tuned by using different promoters to modulate synthetic sRNA abundance. Our approach entails selecting knockdown target genes resulting from in silico flux response analysis and those related to product biosynthesis then screening strains transformed with a library of synthetic sRNA-promoter combinations for enhanced production...
September 26, 2017: Cell Systems
Gan Chin Heng, Mohamed Hasnain Isa, Jun-Wei Lim, Yeek-Chia Ho, Ali Akbar Lorestani Zinatizadeh
Biological treatments, such as activated sludge process, are common methods to treat municipal and industrial wastewaters. However, they produce huge amounts of waste activated sludge (WAS). The excess sludge treatment and disposal are a challenge for wastewater treatment plants due to economic, environmental, and regulatory factors. In this study, photo-Fenton pretreatment (oxidation using hydrogen peroxide and iron catalyst aided with UV light) was optimized using response surface methodology (RSM) and central composite design (CCD) to determine the effects of three operating parameters (H2O2 dosage, H2O2/Fe(2+) molar ratio, and irradiation time) on disintegration and dewaterability of WAS...
September 30, 2017: Environmental Science and Pollution Research International
Hang N Nguyen, Debora F Rodrigues
The present study investigates the chronic toxicity of graphene (G) and graphene oxide (GO) in activated sludge. Sequencing batch bioreactors were fed with influents containing 0, 1 and 5mgL(-1) of GO or G (12h cycles) for ten days. Reduction in performance of the bioreactors in relation to chemical oxygen demand, ammonia and phosphate removals was observed after three days in the bioreactors fed with 5mgL(-1) of nanomaterials. After about eight days, these reactors reached a steady state nutrient removal, which corresponded to recovery of certain groups of ammonia oxidizing bacteria and phosphate accumulating bacteria despite the increasing accumulation of nanomaterials in the sludge...
September 20, 2017: Journal of Hazardous Materials
Pinaki Dey, Vivek Rangarajan
Experimental investigations were carried out for Cupriavidus necator (MTCC 1472)-based improved production of poly-3 hydroxy butyrate (PHB) through induced nitrogen limiting fed-batch cultivation strategies. Initially Plackett-Burman design and response surface methodology were implemented to optimize most influencing process parameters. With optimized process parameter values, continuous feeding strategies ware applied in a 5-l fermenter with table sugar concentration of 100 g/l, nitrogen concentration of 0...
October 2017: 3 Biotech
U Rojas-Z, C Fajardo-O, I Moreno-Andrade, O Monroy
In order to have an efficient operation, sequencing batch reactors (SBR) must support granular biomass with high conversion rates, settling properties, and be able to deal with the inherent variability of the composition of real wastewaters. In this study, the effect of the influent composition and the specific organic loading rate (Bx) on the granulation process was evaluated in two SBRs, fed with greywater (GW) and a synthetic medium (SM). The feeding with SM led to the formation of compact granular biomass, with a sludge volume index (SVI) of 22...
September 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
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