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Lee R. Lynd – 1st expert on this subject based on the ideXlab platform

    Preparative Biochemistry & Biotechnology, 2013
    Co-Authors: Lois A. St Brice, Xiongjun Shao, Javier A. Izquierdo, Lee R. Lynd


    The affinity digestion process for cellulase purification consisting of binding to amorphous cellulose, and amorphous cellulose hydrolysis in the presence of dialysis (Morag et al., 1991), was optimized to obtain high activity recoveries and consistent protein recoveries in the isolation of Clostridium thermocellum cellulase. Experiments were conducted using crude supernatant prepared from C. thermocellum grown on either Avicel or cellobiose. While no difference was observed between Avicel-grown or cellobiose-grown cellulase in the adsorption step, differences were observed during the hydrolysis step. The optimal amorphous cellulose loading was found to be 3 mg amorphous cellulose per milligram supernatant protein. At this loading, 90–100% of activity in the crude supernatant was adsorbed. Twenty-four-hour incubation with the amorphous cellulose during the adsorption stage was found to result in maximal and stable adsorption of activity to the substrate. By fitting the adsorption data to the Langmuir mode…

  • testing alternative kinetic models for utilization of crystalline cellulose Avicel by batch cultures of clostridium thermocellum
    Biotechnology and Bioengineering, 2013
    Co-Authors: Evert K Holwerda, Lee R. Lynd


    Descriptive kinetics of batch cellulose (Avicel) and cellobiose fermentation by Clostridium thermocellum were examined with residual substrate and biosynthate concen- trations inferred based on elemental analysis. Biosynthate was formed in constant proportion to substrate consumption until substrate was exhausted for cellobiose fermentation, and until near the point of substrate exhaustion for cellulose fermentation. Cell yields (g pellet biosynthate carbon/ g substrate carbon) of 0.214 and 0.200 were obtained for cellulose and cellobiose, respectively. For cellulose fermenta- tion a sigmoidal curve fit was applied to substrate and biosynthate concentrations over time, which was then differentiated to calculate instantaneous rates of growth and substrate consumption. Three models were tested to describe the kinetics of Avicel utilization by C. thermocellum: (A) first order in cells, (B) first order in substrate, and (C) first order in cells and substrate, and second order overall. Models (A) and (B) have been proposed in the literature to describe cultures of cellulolytic microorganisms, whereas model (C) has not. Of the three models tested, model (c) provided by far the best fit to batch culture data. A second order rate constant equal to 0.735 L g C � 1 h � 1 was found for utilization of Avicel by C. thermocellum. Adding an endogenous metabolism term improved the descriptive quality of the model as substrate exhaustion was approached. Such rate constants may in the future find utility for describing and comparing cellulose fermentation involving other microbes and other substrates. Biotechnol. Bioeng. 2013;xxx: xx-xx.

  • conversion for Avicel and afex pretreated corn stover by clostridium thermocellum and simultaneous saccharification and fermentation insights into microbial conversion of pretreated cellulosic biomass
    Bioresource Technology, 2011
    Co-Authors: Xiongjun Shao, Lee R. Lynd, David A Hogsett, Anna Guseva, Venkatesh Balan, Bruce E Dale


    In this study, efforts were taken to compare solubilization of Avicel and AFEX pretreated corn stover (AFEX CS) by SSF and Clostridium thermocellum fermentation, with an aim to gain insights into microbial conversion of pretreated cellulosic biomass. Solubilization rates for AFEX CS are comparable for the two systems while solubilization of Avicel is much faster by C. thermocellum. Initial catalyst loading impacts final cellulose conversion for SSF but not for C. thermocellum. Hydrolysis of the two substrates using cellfree C. thermocellum fermentation broth revealed much smaller difference in cellulose conversion than the difference observed for growing cultures. Tests on hemicellulose removal and particle size reduction for AFEX CS indicated that substrate accessibility is very important for enhanced solubilization by C. thermocellum.

Antonio Aprigio Da Silva Curvelo – 2nd expert on this subject based on the ideXlab platform

  • characterization of depolymerized residues from extremely low acid hydrolysis ela of sugarcane bagasse cellulose effects of degree of polymerization crystallinity and crystallite size on thermal decomposition
    Industrial Crops and Products, 2012
    Co-Authors: Leandro Vinicius Alves Gurgel, Karen Marabezi, Luiz Antonio Ramos, Antonio Aprigio Da Silva Curvelo


    Sugarcane bagasse cellulose was subjected to the extremely low acid (ELA) hydrolysis in 0.07% H2SO4 at 190, 210 and 225 ◦ C for various times. The cellulose residues from this process were characterized by TGA, XRD, GPC, FTIR and SEM. A kinetic study of thermal decomposition of the residues was also carried out, using the ASTM and Kissinger methods. The thermal studies revealed that residues of cellulose hydrolyzed at 190, 210 and 225 ◦C for 80, 40 and 8 min have initial decomposition temperature and activation energy for the main decomposition step similar to those of Avicel PH-101. XRD studies confirmed this finding by showing that these cellulose residues are similar to Avicel in crystallinity index and crystallite size in relation to the 110 and 200 planes. FTIR spectra revealed no significant changes in the cellulose chemical structure and analysis of SEM micrographs demonstrated that the particle size of the cellulose residues hydrolyzed at 190 and 210 ◦C were similar to that of Avicel.

P Humbertdroz – 3rd expert on this subject based on the ideXlab platform

  • morphological packing flow and tableting properties of new Avicel types
    Drug Development and Industrial Pharmacy, 1995
    Co-Authors: Eric Doelker, Danielle Massuelle, Fabienne Veuillez, P Humbertdroz


    AbstractThe six Avicel products designed for compression – the classical grades PH-105, PH-103, PH-101 and PH-102, and the new Avicels PH-112 and PH-200 – have been submitted to a comparative investigation for both their basic and tableting properties. According to the manufacturer all these products differ by their nominal particle size and moisture content.Basic properties of the powders were first determined, namely moisture content (loss on drying and Karl Fischer titration), particle size and shape (sieving and image analysis), densities (true bulk and tap densities, Hausner ratio) and flow properties (vibratory hopper technique).As tableting properties, the compactibility of the powders and the effect of adding a hydrophobic lubricant (0.5% magnesium stearate) on the compact strength were evaluated by preparing compacts at a given applied pressure using a hydraulic press. Weight and dimensional variations were assessed by preparing tablets at a target crushing strength of 70 Newtons on a high speed …