Summary of findings from the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI): corn stover pretreatment

The Biomass Refining Consortium for Applied Fundamentals and Innovation, with members from Auburn University, Dartmouth College, Michigan State University, the National Renewable Energy Laboratory, Purdue University, Texas A&M University, the University of British Columbia, and the University of California at Riverside, has developed comparative data on the conversion of corn stover to sugars by several leading pretreatment technologies. These technologies include ammonia fiber expansion pretreatment, ammonia recycle percolation pretreatment, dilute sulfuric acid pretreatment, flowthrough pretreatment (hot water or dilute acid), lime pretreatment, controlled pH hot water pretreatment, and sulfur dioxide steam explosion pretreatment. Over the course of two separate USDA- and DOE-funded projects, these pretreatment technologies were applied to two different corn stover batches, followed by enzymatic hydrolysis of the remaining solids from each pretreatment technology using identical enzyme preparations, enzyme loadings, and enzymatic hydrolysis assays. Identical analytical methods and a consistent material balance methodology were employed to develop comparative sugar yield data for each pretreatment and subsequent enzymatic hydrolysis. Although there were differences in the profiles of sugar release, with the more acidic pretreatments releasing more xylose directly in the pretreatment step than the alkaline pretreatments, the overall glucose and xylose yields (monomers + oligomers) from combined pretreatment and enzymatic hydrolysis process steps were very similar for all of these leading pretreatment technologies. Some of the water-only and alkaline pretreatment technologies resulted in significant amounts of residual xylose oligomers still remaining after enzymatic hydrolysis that may require specialized enzyme preparations to fully convert xylose oligomers to monomers.     

Model-based fed-batch for high-solids enzymatic cellulose hydrolysis

While many kinetic models have been developed for the enzymatic hydrolysis of cellulose, few have been extensively applied for process design, optimization, or control. High-solids operation of the enzymatic hydrolysis of lignocellulose is motivated by both its operation decreasing capital costs and increasing product concentration and hence separation costs. This work utilizes both insights obtained from experimental work and kinetic modeling to develop an optimization strategy for cellulose saccharification at insoluble solids levels greater than 15% (w/w), where mixing in stirred tank reactors (STRs) becomes problematic. A previously developed model for batch enzymatic hydrolysis of cellulose was modified to consider the effects of feeding in the context of fed-batch operation. By solving the set of model differential equations, a feeding profile was developed to maintain the insoluble solids concentration at a constant or manageable level throughout the course of the reaction. Using this approach, a stream of relatively concentrated solids (and cellulase enzymes) can be used to increase the final sugar concentration within the reactor without requiring the high initial levels of insoluble solids that would be required if the operation were performed in batch mode. Experimental application in bench-scale STRs using a feed stream of dilute acid-pretreated corn stover solids and cellulase enzymes resulted in similar cellulose conversion profiles to those achieved in batch shake-flask reactors where temperature control issues are mitigated. Final cellulose conversions reached approximately 80% of theoretical for fed-batch STRs fed to reach a cumulative solids level of 25% (w/w) initial insoluble solids.     

Microstructure and properties of polyurethanes derived from castor oil

The goal of this work was the synthesis of novel segmented polyurethanes with a high percentage of components derived from renewable sources. The soft segment was a polyol derived from castor oil and the hard segment structure was varied by means of different chain extenders, petrochemical-based 1,4-butanediol (BD) and corn sugar-based 1,3-propanediol (PD). The synthesis was carried out in bulk and without catalyst via a two-step polymerization varying hard segment ratio. Physico-chemical, mechanical and morphological characterization was performed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), atomic force microscopy (AFM), mechanical testing and termogravimetric analysis (TGA). Properties have been discussed from the viewpoint of hard/soft microdomain phase separation and also the hard segment nature and formed structure. An increase in hard segment content was accompanied by an increase in hard domain order, crystallinity, and stiffness. The hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to impart properties ranging from elastomeric to rigid behaviour with the increase of hard segment content. Polyurethanes synthesized from bio-based chain extender showed a slightly lower crystallinity in the hard segment structure than that synthesized from BD as the chain extender. This lower crystallinity avoids strength concentrations at the soft/crystalline hard segment interface, thus improving the mechanical properties at high hard segment content. The slightly higher thermal stability observed for BD based polyurethanes is related with their more packed structures and crystallinity observed in the hard segment structure.     

Sorption of ofloxacin and chrysoidine by grape stalk. A representative case of biomass removal of emerging pollutants from wastewater

Emerging pollutants, as antibiotics or dyes, in aquatic ecosystems are a crucial concern and numerous techniques have been developed for their removal. Efficiency, cost effectiveness, and biodegradability reveal biomass sorption as one of the most appealing methods. This study aims to evaluate the effectiveness of grape stalk as a sorbent for ofloxacin (a fluoroquinolone antibiotic) and chrysoidine (an azo-dye). The kinetic and the thermodynamic aspects of the sorption were studied. A pseudo first-order kinetic behavior is shown by both substances, though the kinetic constants of ofloxacin are almost double than those of chrysoidine. The sorption isotherms, which strictly follow the Langmuir model, show remarkable differences as a function of pH and of biomass size. The trend of Langmuir parameters, Q_max and K, as a function of pH and size, is discussed, and different binding mechanisms are proposed. Kinetic and thermodynamic parameters prefigure grape stalk as a potential biomass for scavenging toxic substances from wastewater.     

Hβ分子筛催化甜高粱秆汁转化制呋喃类化合物

以γ-丁内酯为溶剂,研究了Hβ分子筛催化富含蔗糖、葡萄糖和果糖的甜高粱秆汁转化制呋喃类化合物（5-羟甲基糠醛或糠醛）的性能。结果表明,甜高粱秆汁在Hβ分子筛上主要转化为5-羟甲基糠醛,而含糖量相同的模型甜高粱秆汁在相同的反应条件下,主要产物却是糠醛。²⁷Al 固体核磁结果表明,甜高粱秆汁中的微量碱性金属钾等能与Hβ分子筛发生离子交换,导致Hβ分子筛上六配位铝转变为四配位铝;因为六碳糖生成糠醛需要Hβ分子筛上具备合适的铝配位环境,而离子交换引起铝配位状态的变化,导致了甜高粱秆汁在Hβ分子筛上的主要产物是5-羟甲基糠醛。     

A simple HPLC column-switching technique for the determination of deoxynivalenol (vomitoxin) in maize and corn silage

Summary A method is described for the determination of deoxynivalenol (DON) in maize and corn silage with a detection limit by UV of 0.2 ppm after a simple separation by means of connected reversed-phase columns.     

Mechanism of the Adsorption Process: Cu2+ Adsorpted by Ramie Stalk

Agriculture wastes, ramie stalk, was used to adsorb Cu²⁺ ion from the aqueous solutions. Adsorption behaviors and mechanism involved in were systematically explored and discussed. A better fitting result of adsorption isotherms of Cu²⁺ to ramie stalk was obtained from the Langmuir model. This suggested the surface of ramie stalk is rather homogeneous, which is supported by a better fitting result of the adsorption kinetic by using a pseudo‐first‐order kinetic model. Following surface complexation modeling suggested Cu²⁺ uptake is driven by water‐associated adsorption along with the precipitated CuO species. This is attributed to the low dissociation constant of ramie stalk and thus there was only around one quarter of sur‐ face adsorption sites participating Cu²⁺ uptake at acidic environment.     

Removal of copper(II) from aqueous solution with rape stalk modified by citric acid

In this paper, rape stalk was modified with citric acid (CA) to prepare copper ion biosorbent. The modified rape stalk (MRS) was characterized by Fourier transforms infrared (FTIR), zeta potential, and thermogravimetric analysis (TGA). The effects of various parameters like initial Cu²⁺ concentration, contact time, initial pH, and temperature on adsorption capacity were studied. The adsorption capacity of MRS at 298 K was 69.84 mg/g, far higher than 18.24 mg/g for native rape stalk (NRS). The adsorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and endothermic nature of the adsorption process. The ion exchange of the adsorption mechanism was affirmed. MRS could be a potentially low-cost and green adsorbent for removal of Cu²⁺ from aqueous solution.     

Industrial scale-up of pH-controlled liquid hot water pretreatment of corn fiber for fuel ethanol production

The pretreatment of cellulose in corn fiber by liquid hot water at 160°C and a pH above 4.0 dissolved 50% of the fiber in 20 min. The pretreatment also enabled the subsequent complete enzymatic hydrolysis of the remaining polysaccharides to monosaccharides. The carbohydrates dissolved by the pretreatment were 80% soluble oligosaccharides and 20% monosaccharides with o1% of the carbohydrates lost to degradation products. Only a minimal amount of protein was dissolved, thus enriching the protein content of the un dissolved material. Replication of laboratory results in an industrial trial at 43 gallons per minute (163 L/min) of fiber slurry with a residence time of 20 min illustrates the utility and practicality of this approach for pretreating corn fiber. The added costs owing to pretreatment, fiber, and hydrolysis are equivalent to less than $0.84/gal of ethanol produced from the fiber. Minimizing monosaccharide formation during pretreatment minimized the formation of degradation products; hence, the resulting sugars were readily fermentable to ethanol by the recombinant hexose and by pentose-fermenting Saccharomyces cerevisiae 424A (LNH-ST) and ethanologenic Escherichia coli at yields >90% of theoretical based on the starting fiber. this cooperative effort and first successful trial opens the door for examining the robustness of the pretreatment system under extended run conditions as well as pretreatment of other cellulose-containing materials using water at controlled pH.     

HPLC法检测玉米中痕量单端孢霉烯属族毒素

以对酞内酰胺苯甲酰氨（４－（２－ｐｈｔｈａｌｉｍｉｄｙ１）ｂｅｎｚｏｙ１ ｃｈｌｏｒｉｄｅ，简称ＰＩＢ－ＣＩ）为衍生试剂，建立了一种快速、灵敏分析单端孢霉烯属族毒素中脱氧雪腐镰刀菌烯醇的新方法，对衍生反应条件，衍生物分离及定量检测条件都进行了研究，衍生物用ＯＤＳ柱分离，紫外检测器检测（λ＝３００ｎｍ）乙腈＋水（５８＋４２Ｖ＋Ｖ）作流动相，检出限为６ｐｍｏｌ。用于分析玉米中的痕量ＤＯＮ，简化了样品处