Hydrolysis alkaline pretreatment

Table 2 Design matrix presenting TRS and glucose yields after hydrolysis of pretreated bagasse alkaline hydrogen peroxide (screened—S and nonscreened— NS).

Acid or alkaline treatments of particulate feeds have been shown to improve digester gas yields (17.22-25). Acid hydrolysis was not used in our work because severe reaction conditions are required, and there is considerable decomposition of the hydrolytic products under these conditions ( ). Dilute alkaline pretreatment was evaluated because alkali was shown to be more effective in promoting hydrolysis of cellulosic biomass than acid (17,26). It is postulated, for example, that sodium hydroxide breaks down the cross-linked lignin macro-molecules surrounding the cellulose fibers into alkali-soluble lower-molecular-weight units. In this way, the cellulose fibers are exposed for... 

The deterruination of amino acids in proteins requires pretreatment by either acid or alkaline hydrolysis. However, L-tryptophan is decomposed by acid, and the racemi2ation of several amino acids takes place during alkaline hydrolysis. Moreover, it is very difficult to confirm the presence of cysteine in either case. The use of methanesulfonic acid (18) and mercaptoethanesulfonic acid (19) as the protein hydroly2ing reagent to prevent decomposition of L-tryptophan and L-cysteine is recommended. En2ymatic hydrolysis of proteins has been studied (20). 

Hydrolysis, although a simple method in theory, yields terephthalic acid (TPA), which must be purified by several recrystallizations. The TPA must be specially pretreated to blend with ethylene glycol to form premixes and slurries of the right viscosities to be handled and conveyed in modern direct polyesterification plants. Hie product of the alkaline hydrolysis of PET includes TPA salts, which must be neutralized with a mineral acid in order to collect the TPA. That results in the formation of large amounts of inorganic salts for which commercial markets must be found in order to make the process economically feasible. There is also the possibility that the TPA will be contaminated with alkali metal ions. Hydrolysis of PET is also slow compared to methanolysis and glycolysis.1... 

Thioetherification of PECH is feasibly performed in DA-solvents as already described in the patent (20J. For example, the highest substitution was obtained by the reaction of P(ECH-EO)(1 1 copolymer of epichloro-hydrin and ethylene oxide) and equimolar thiophenoxide in HMPA at 100°C for 10 h as DS 83% for sodium and 93% for potassium salts. The DS in our nucleophilic substitution was estimated by the elemental analysis as well as the titration of liberated chloride ion with mercuric nitrate (21). In the latter method, reacted medium was pretreated with hydrogen peroxide when the reductive nucleophiles which can react with mercuric ion were used. As described before for PVC, thiolation was also achieved conveniently with iso-thiuronium salt followed by alkaline hydrolysis without the direct use of ill-smelling thiolate. The thiolated PECH obtained are rubbery solids, soluble in toluene, methylene chloride, ethyl methyl ketone and DMF and insoluble in water, acetone, dioxane and methanol. 

Semisolid samples, such as kidney, liver, and muscle, often require more intensive sample pretreatment. A favorite approach for tissue break-up appears to be tire homogenization in acetonitrile (519, 523, 524) or in an acetone-sulfuric acid mixture (521). Using chloroform for extraction of xylazine and its main metabolite from kidney tissue, high recovery values were attained (525). However, prior alkaline hydrolysis of the incurred samples at 95 C was considered essential when diethyl ether was used for extraction of the -blocker carazolol and seven sedatives from kidney tissue (526). 

M. Noami, M. Kataoka and Y. Seto, Improved tert-butyldimethylsilylation gas chromatographic/ mass spectrometric detection of nerve gas hydrolysis products from soils by pretreatment of aqueous alkaline extraction and strong anion-exchange solid-phase extraction, Anal. Chem., 74, 4709-4715 (2002). 

In alkaline hydrolysis, bases such as NaOH and NH3 are used for pretreatment The effects include increased porosity, larger internal surface area, a decrease of the degree of polymerization, separation of structural linkages between lignin and carbohydrates, and disruption of the lignin structure. 

Finally, a multianalyte, multimatrix method was developed for the routine determination of steroids in animal tissues (muscle, fat, and skin) (114). After the addition of internal standards and sample pretreatment, the analytes of interest were extracted from the matrix with unmodified CO2 and trapped on an alumina sorbent placed in the extraction vessel. After extraction, alkaline hydrolysis was performed and the analytes were derivatized. The samples were analyzed by GC-MS. The limit of detection for the different matrix-analyte combinations was 2 pg/kg, the repeatability ranged from 4% to 42% (nine replicates), and the reproducibility ranged from 2% to 39%. 

Com stover used for this study was harvested in 2003 at the Kramer Farm in Wray, Colorado. The stover was pretreated either in-house at the National Renewable Energy Laboratory or received via subcontract fiom the CAFI [12] pretreatment group members. The samples selected for this study were pietreated by alkaline peroxide (NREL), sulfite steam explosion (UBC), ammonia fiber explosion (MSU), and dilute sulfuric acid (NREL) methods. The composition of the pretreated stover was determined by a two-stage sulfuric acid hydrolysis treatment according to the NREL Laboratory Analytical Procedure titled Determination of Stmctural Carbohydrates and Lignin in Biomass [13]. The pretreatment conditions and compositional information for each substrate are listed in Table 2. 

Table 7 depicts the analysis of variance (ANOVA) for the model of glucose yield after hydrolysis for alkaline peroxide pretreatment of nonscreened bagasse when only the significant coefficients are taken into account. It can be seen that the model presents a high correlation coefficient and can be considered statistically significant with 90% of confidence according to the F test, as it presented a calculated value greater than the listed... 

The effectiveness of alkaline hydrogen peroxide and lime pretreatment in improving sugar cane bagasse susceptibility to enzymatic hydrolysis was evaluated. Two complete 2x2x2... 

For nonscreened bagasse, the best results are for alkaline peroxide pretreatment performed with 5% FI2O2 at ambient temperature for 24 h. Lime pretreatment with 0.40 g lime/g dry biomass at 70 °C for 36 h also leads to high glucose yield. The choice between alkaline peroxide and lime pretreatment in this case is not straightforward, and fermentation of the hydrolysis product to evaluate ethanol yields should help in the... 

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