Switchgrass storage effects on the recovery of carbohydrates after liquid hot water pretreatment and enzymatic hydrolysis

Perennial grasses that would be used for bioenergy and bioproducts production will need to be stored for various periods of time to ensure a continual feedstock supply to a bioprocessing facility. The effects of storage practices on grass composition and the response of grasses to subsequent bioprocesses such as pretreatment and enzymatic hydrolysis needs to be understood to develop the most efficient storage protocols. This study examined the effect of outdoor storage of round switchgrass bales on composition before and after liquid hot water pretreatment (LHW) and enzymatic hydrolysis. This study also examined the effect of washing LHW pretreated biomass prior to enzymatic hydrolysis. It was determined that switchgrass composition after baling was stable. As expected, glucan and lignin contents increased after LHW due to decreases in xylan and galactan. Washing biomass prior to enzymatic hydrolysis reduced saccharification, especially in samples from the interior of the bale, by at least 5%

Submicrometric Films of Surface-Attached Polymer Network with Temperature-Responsive Properties

International audienceTemperature-responsive properties of surface-attached poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled chemistry are investigated. The synthesis consists of cross-linking and grafting preformed ene-reactive polymer chains through thiol−ene click chemistry. The formation of surface-attached and cross-linked polymer films has the advantage of being wellcontrolled without any caution of no-oxygen atmosphere or addition of initiators. PNIPAM hydrogel films with same cross-link density are synthesized on a wide range of thickness, from nanometers to micrometers. The swelling-collapse transition with temperature is studied by using ellipsometry, neutron reflectivity, and atomic force microscopy as complementary surface-probing techniques. Sharp and high amplitude temperature-induced phase transition is observed for all submicrometric PNIPAM hydrogel films. For temperature above LCST, surface-attached PNIPAM hydrogels collapse similarly but without complete expulsion of water. For temperature below LCST, the swelling of PNIPAM hydrogels depends on the film thickness. It is shown that the swelling is strongly affected by the surface attachment for ultrathin films below ∼150 nm. For thicker films above 150 nm (to micrometers), surface-attached polymer networks with the same cross-link density swell equally. The density profile of the hydrogel films in the direction normal to the substrate is confronted with in-plane topography of the free surface. It results that the free interface width is much larger than the roughness of the hydrogel film, suggesting pendant chains at the free surface

Adding Value to Lignocellulosic Biorefinery: Efficient Process Development of Lignocellulosic Biomass Conversion into Polyhydroxybutyrate

Polyhydroxybutyrate (PHB) is bacteria synthesized polymer that has comparable mechanical properties as petroleum-based plastics and high biocompatibility. Current commercial PHB production process is not cost effective. Raw materials make up about 50% of the production cost. Lignocellulosic biomass are cheap, abundant feedstocks that can be converted into PHB to add profit and sustainability to lignocellulosic biorefinery. Lignocellulosic biorefinery upstream process produces polymeric sugar rich stream and lignin-enriched stream. Polymeric sugars are then hydrolyzed into a sugar stream with glucose, xyloseand arabinose mainly present. To the best of the author’s knowledge, limited studies have been done on sugar mixture conversion into PHB. For lignin, previous research achieved a PHB production ranging from 0.13 to 1 g/L, which is too low to be economical. The primary objectives of this research were twofold: (1) process development of polymeric sugars conversion into PHB, with a focus on sugar mixture conversion into PHB by Burkholderia sacchari DSM 17165, and (2) process development of lignin into PHB by Cupriavidus necator DSM 545, with a focus on enhancing PHB production using various types of supplements. For sugar mixture conversion into PHB, first, shake flask (250 mL) scale statistical experimental design and modeling were performed to optimize sugar mixture ratio and process variables for maximal PHB production; second, bioreactor scale (3L) fed-batch cultivation was conducted to produce PHB from simulated corn fiber sugar mixture. The highest PHB production reached 67 g/L for 4:2:1 (glucose:xylose:arabinose) mixture at 41 h corresponding to an accumulation of 77% of cell dry weight. Corresponding sugar conversion efficiency and productivity were 0.33 g PHB/g sugar consumed and 1.6 g/L/h, respectively, which are comparable to or higher than most previous studies. For lignin conversion into PHB, first, shake scale (250 mL) study achieved 10-fold increase (0.2 to 2.1 g/L) in PHB production by optimizing supplement formulations with Plackett-Burman and central composite designs. Second, fed-batch cultivation at bioreactor scale (1.7 L) were conducted to enhance PHB production to 4.5 g/L. This is the highest PHB production from lignin that the author has been aware of in the literature. Advisor: Mark R. Wilkin

In-situ assessment of concrete bridge decks and pavements using stress-wave based methods

Concrete infrastructure of United States is aging and deteriorating. Accurate assessment the condition of concrete infrastructure is critical for its maintenance and rehabilitation. Stress-wave based methods, including ultrasonic surface wave (USW) and impact echo (IE), are becoming popular for characterizing defects and mechanical properties of concrete infrastructures. In this dissertation, a comprehensive literature review of seismic wave theory and common types of defects identified in concrete infrastructures, as well as stress-wave based methods used for concrete infrastructure monitoring and characterizing on a selected concrete bridge deck and two concrete pavement segments are present. The utility and reliability of both methods were carefully evaluated and validated based on the comparison analysis with other destructive or non-destructive testing (NDT) methods carried out in the field or laboratory for the same bridge decks and pavement segments, such as the concrete hydro-demolition, drilling, static modulus of elasticity of concrete specimens in compression and ground penetrating radar (GPR). Detailed investigation of the sensitivity and limitation of stress-wave based methods for different types of defects identified in concrete bridge decks and pavements has been performed and presented. The outcome of this study is to expand the knowledge of stress-wave based methods, to better understand their strengths and limitations, to evaluate the reliability and utility of both the USW and IE test results in characterizing and monitoring defects and mechanical properties of concrete infrastructures. The result of this study is most beneficial for transportation agencies and researchers to use stress-wave based methods properly and effectively for further feasibility studies or monitoring of concrete infrastructures --Abstract, page iv

Adding Value to Lignocellulosic Biorefinery: Efficient Process Development of Lignocellulosic Biomass Conversion into Polyhydroxybutyrate

Polyhydroxybutyrate (PHB) is bacteria synthesized polymer that has comparable mechanical properties as petroleum-based plastics and high biocompatibility. Current commercial PHB production process is not cost effective. Raw materials make up about 50% of the production cost. Lignocellulosic biomass are cheap, abundant feedstocks that can be converted into PHB to add profit and sustainability to lignocellulosic biorefinery. Lignocellulosic biorefinery upstream process produces polymeric sugar rich stream and lignin-enriched stream. Polymeric sugars are then hydrolyzed into a sugar stream with glucose, xyloseand arabinose mainly present. To the best of the author’s knowledge, limited studies have been done on sugar mixture conversion into PHB. For lignin, previous research achieved a PHB production ranging from 0.13 to 1 g/L, which is too low to be economical. The primary objectives of this research were twofold: (1) process development of polymeric sugars conversion into PHB, with a focus on sugar mixture conversion into PHB by Burkholderia sacchari DSM 17165, and (2) process development of lignin into PHB by Cupriavidus necator DSM 545, with a focus on enhancing PHB production using various types of supplements. For sugar mixture conversion into PHB, first, shake flask (250 mL) scale statistical experimental design and modeling were performed to optimize sugar mixture ratio and process variables for maximal PHB production; second, bioreactor scale (3L) fed-batch cultivation was conducted to produce PHB from simulated corn fiber sugar mixture. The highest PHB production reached 67 g/L for 4:2:1 (glucose:xylose:arabinose) mixture at 41 h corresponding to an accumulation of 77% of cell dry weight. Corresponding sugar conversion efficiency and productivity were 0.33 g PHB/g sugar consumed and 1.6 g/L/h, respectively, which are comparable to or higher than most previous studies. For lignin conversion into PHB, first, shake scale (250 mL) study achieved 10-fold increase (0.2 to 2.1 g/L) in PHB production by optimizing supplement formulations with Plackett-Burman and central composite designs. Second, fed-batch cultivation at bioreactor scale (1.7 L) were conducted to enhance PHB production to 4.5 g/L. This is the highest PHB production from lignin that the author has been aware of in the literature. Advisor: Mark R. Wilkin