Alfalfa fiber as a feedstock for ethanol and organic acids

Valuable co-products derived from fractionation of alfalfa herbage give the resulting fibrous fraction an economic advantage as a feed stock for ethanol or other organic products. Alfalfa fiber was saccharified and fermented with or without a liquid hot water (LHW) pretreatment. The LHW pretreatment hydrolyzed approximately 60% of the original fiber, yielding a high cellulose residue and aliquid extract. These yielded predominantly hexoses and pentoses, respectively, after enzymatic saccharification. Yields of ethanol and lactic acid resulting from fermentations are given.     

Modeling of a continuous pretreatment reactor using computational fluid dynamics

Computational fluid dynamic simulations are employed to predict flow characteristics in a continuous auger driven reactor designed for the dilure acid pretreatment of biomass. Slurry containing a high concentration of biomass solids exhibits a high viscosity, which poses unique mixing issues within the reactor. The viscosity increases significantly with a small increase in solids concentration and also varies with temperature. A well-mixed slurry is desirable to evenly distribute acid on biomass, prevent buildup on the walls of the reactor, and provides an uniform final product. Simulations provide flow patterns obtained over a wide range of viscosities and pressure distributions, which may affect reaction rates. Results provide a tool for analyzing sources of inconsistencies in product quality and insight into future design and operating parameters.     

Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.     

Determination of 5‐fluorocytosine, 5‐fluorouracil,and 5‐fluorouridine in hospital wastewater by liquid chromatography–mass spectrometry

Chemotherapeutics are pharmaceutical compounds the occurrence of which in the environment is of growing concern because of the increase in treatments against cancer diseases. They can reach the aquatic ecosystems after passing through wastewater treatment plants without complete removal. One of the most frequently used chemotherapeutics is 5‐fluorouracil which exhibits a strong cytostatic effect. In this paper, an analytical methodology was developed, validated, and applied to determine 5‐fluorouracil, its precursor, 5‐fluorocytosine, and its major active metabolite, 5‐fluorouridine, in hospital wastewater samples. Due to the expected low concentrations after dilution and interferences present in such a complex matrix, a very selective and sensitive detection method is required. Moreover, an extraction method must be implemented prior to the determination in order to purify the sample extract and preconcentrate the target analytes at micrograms per liter concentration levels. Solid‐phase extraction followed by liquid chromatography with tandem mass spectrometry was the combination of choice and all included parameters were studied. Under optimized conditions for wastewater samples analysis, recoveries from 63 to 108% were obtained, while intraday and interday relative standard deviations never exceeded 20 and 25%, respectively. Limits of detection between 61 and 620 ng/L were achieved. Finally, the optimized method was applied to samples from hospital wastewater effluents.     

水相识别分子印迹聚合物在样品预处理中的应用

分子印迹聚合物(MIPs)是模拟抗原-抗体识别机制,人工构筑的对目标物具有专一识别性的材料,构建具有优异水相识别能力的MIPs是分子印迹领域长期面临的挑战。近年来水相识别MIPs以其优异的抗基质干扰和水中识别能力,引起了分析化学家、材料学家和环境学家的广泛关注。本文综述了近年来水相识别MIPs在样品预处理中的应用研究。首先,简要介绍了MIPs的构筑原理、优势及面临水相识别困难的挑战。其次,介绍了样品前处理技术及其重要性。再次,结合各类新兴材料和MIPs制备技术,从样品前处理技术的角度(包括固相萃取、分散固相萃取、磁固相萃取、固相微萃取、管尖固相萃取和搅拌棒吸附萃取)全面总结了水相识别MIPs在含水样品分析中的应用,并结合材料性能和分析参数讨论了各类方法的分析优势。最后,分别从水相识别MIPs构建和预处理两方面提出了该领域面临的挑战和未来的发展趋势。     

Evaluation of three sorbent-phase extraction techniques based on hyper-crosslinked polymer for the extraction of five endocrine disrupters in water

A series of low-cost hyper-crosslinked polymers were prepared by an easy one-step Friedel-Crafts reaction. The synthesized hyper-crosslinked polymers exhibited remarkably porous structure, large surface area, and hydroxyl groups, which can be employed as an ideal adsorbent material for novel sorbent-phase extraction techniques. Based on this, using hyper-crosslinked polymers as sorbent and coating, three novel extraction methods, including micro-solid-phase extraction, dispersive solid-phase extraction, and solid-phase microextraction, were explored and evaluated for simultaneous measurement of five endocrine-disrupting compounds (triclosan and bisphenol A, tetrabromobisphenol A, tetrabromobisphenol A bisallylether, and tetrabromobisphenol A bis(2,3-dibromopropyl ether)) in environment water prior to high-performance liquid chromatography–ultraviolet. The influence of experimental parameters on three extraction techniques such as extraction time, the amount of hyper-crosslinked polymers, extraction temperature, ionic strength, and desorption conditions were optimized. Three previously mentioned methods provided limits of detection ranging from 0.01 to 0.05 μg/L, and high recoveries (85–99%) with relative standard deviations of 1.7–5.6%. This study presented the merits and disadvantages of three proposed extraction methods and their potential for effective monitoring of hazardous pollutants in real water samples.     

Pretreatment of corn stover by low-liquid ammonia recycle percolation process

A pretreatment method using aqueous ammonia was investigated with the intent of minimizing the liquid throughput. This process uses a flow-through packed column reactor (or percolation reactor). In comparison to the ammonia recycle percolation (ARP) process developed previously in our laboratory, this process significantly reduces the liquid throughput to one reactor void volume in packed bed (2.0–4.7 mL of liquid/g of corn stover) and, thus, is termed low-liquid ARP (LLARP). In addition to attaining short residence time and reduced energy input, this process achieves 59–70% of lignin removal and 48–57% of xylan retention. With optimum operation of the LLARP to corn stover, enzymatic digestibilities of 95, 90 and 86% were achieved with 60, 15, and 7.5 filter paper units/g of glucan, respectively. In the simultaneous saccharification and fermentation test of the LLARP samples using Saccharomyces cerevisiae (NREL-D₅A), an ethanol yield of 84% of the theoretical maximum was achieved with 6% (w/v) glucan loading. In the simultaneous saccharification and cofermentation (SSCF) test using recombinant Escherichia coli (KO11), both the glucan and xylan in the solid were effectively utilized, giving an overall ethanol yield of 109% of the theoretical maximum based on glucan, a clear indication that the xylan content was converted into ethanol. The xylooligomers existing in the LLARP effluent were not effectively hydrolyzed by cellulase enzyme, achieving only 60% of digestibility. SSCF of the treated corn stover was severely hampered when the substrate was supplemented with the LLARP effluent, giving only 56% the overall yield of ethanol. The effluent appears to significantly inhibit cellulase and microbial activities.     

On-Line Coupling of In-Tube Solid Phase Microextraction to Capillary Gas Chromatography for Trace Analysis of Aqueous Samples

Since the development of solid phase microextraction ( SPME ) method, many modifications have been made to improve the availability and application of the technique The in-tube SPME (ITSPME) was emerged and employed in high performance liquid chromatography (HPLC)     

Voltammetry determination of trace manganese with pretreatment glassy carbon electrode by linear sweep voltammetry

This paper described the determination of trace manganese using linear sweep voltammetry at a pretreatment glassy carbon electrode. The glassy carbon electrode pretreated by electrochemical method in the 0.1 mol l⁻¹ NaOH solution greatly improved the electrode responsibility in the determination of manganese(II). The barrier to the detection of low manganese concentration was overcome by means of autocatalytic effect of manganese oxide deposited on the electrode in advance. Under the optimum experiments condition (0.04 mol l⁻¹ NH₃-NH₄Cl buffer solution, pH 9.0), the linear range was 4×10⁻⁸ to 1×l0⁻⁶ mol l⁻¹ Mn(II) for linear sweep voltammetry and 1×10⁻⁹ to 4×10⁻⁸ mol l⁻¹ Mn(II) for convolution voltammetry. The relative standard deviation for 2×10⁻⁸ mol l⁻¹ Mn(II) is 3.4%. The proposed method is simple, rapid, sensitive and selective. It had been applied to the determination of trace manganese in samples with satisfactory results.