Pretreatment hydrolysis

Biocatalysts (of chemo/bio-catalysts working in tandem) able to fully convert the carbohydrates into ethanol and other fuels, and be robust and tolerant of the toxic compounds formed during the pretreatment (hydrolysis) process. 

To make Eq. 24 dimensionally consistent with Eq. 4, one can convert aH+ to mole fraction from molarity by dividing by the overall mole density of solution (also a function of temperature). One now has an expression that includes the effect of temperature and neutralization on added acid and can be used to predict pretreatment hydrolysis performance. 

Index Entries Carbonic acid pretreatment hydrolysis com stover aspen wood. 

A typical wood-to-ethanol bioconversion process consists of at least three major steps pretreatment, hydrolysis, and fermentation. The pretreatment stage has been shown to be the key step to providing a substrate susceptible to the subsequent hydrolysis. Steam explosion is one of the most intensively studied pretreatment methods for bioconversion of softwood materials (6-10). 

Figure 3.11 shows the chemical deposition process of GOx enzyme assembled 2-mercaptoethanol on gold that was previously modified by cobalt tetracarboxylic acid chloride phthalocyanine self-assembled monolayer gold. Electrochemical biosensor was introduced in the following steps pretreatment hydrolysis functionalized surface -> enzyme modification. Shervedani and his coworkers reported a similar... 

Keywords. Dilute acid. Pretreatment, Hydrolysis, Kinetics, Reactor design... 

The pretreated solid materials were hydrolyzed by commercial enzymes, with 20 g/1 substrate concentration at pH 4.8 and 50°C. It was found that the sugar content in the hydrolysate increased sharply in the first 12 h and reached stable levels after 72 h (data not shown). Therefore, the sugar released after 72 h of incubation was used for 3rield calculation. As shown in Fig. 2, the yields of glucose and xylose at both the hydrolysis stage and combined pretreatment/hydrolysis stages were maintained at stable levels due to the fact that the composition of the solid after pretreatment was almost constant (Table 1). 

Pretreatment Hyiirolysis Combined Preireatment Hydrolysis Combined Pretreatment Hydrolysis Combined... 

While there has been much progress in the study of cellulases, the applications of such technology have been limited by a lack of economical pretreatment of the lignocellulose. Without such pretreatment hydrolysis is slow and incomplete. The value of enhanced enzymatic attack on lignocellulose is not limited to the production of sugar and chemicals. The same procedures would be applicable to the increased digestibility of coarse fodder by ruminants. 

Wt% Pretreatment Hydrolysis ization ization with catalyst... 

Talebnia F, Karakashev D, Angelidaki I (2010) Production of bioethanol fiom wheat straw an overview on pretreatment, hydrolysis and fermentation. Bioresour Technol 101(13) 4744-4753. doi 10.1016/j.biortech.2009.11.080... 

The superstructure of the biochemical conversion platform of biomass (com stover) using biomass pretreatment, hydrolysis, and fermentation technologies was developed earlier to produce ethanol, butanol, succinic acid, and acetone with and without gasoline blend as presented in Figure 1.5 (Zondervan et al., 2011). Note that the short description of the processing blocks can be found in Zondervan et al. (2011) as well. 

Bioethanol production routes from different biomasses are show in Fig. 9.1. It typically contains foiu major steps, ie, feedstock pretreatment, hydrolysis (or saccharification). 

Waste treatment of fluoroborate solutions includes a pretreatment with aluminum sulfate to facditate hydrolysis, and final precipitation of fluoride with lime (18). The aluminum sulfate treatment can be avoided by hydrolyzing the fluoroborates at pH 2 in the presence of calcium chloride at this pH, hydrolysis is most rapid at elevated temperature (19). 

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). 

Applicahility/Limitations Hydrolysis is suitable for pretreating difflcult-to-treat wastes and for organics with substituents, such as phenols or chlorinated organics with reactive chlorine atoms. Hydrolysis is specific for only a limited number of contaminants. 

Several carbohydrates such as corn and potato starch, molasses and whey can be used to produce lactic acid. Starch must fust be hydrolysed to glucose by enzymatic hydrolysis then fermentation is performed in the second stage. The choice of carbohydrate material depends upon its availability, and pretreatment is required before fermentation. We shall describe the bioprocess for the production of lactic acid from whey. 

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... 

Cellulase and all chemicals used in this work were obtained from Sigma. Hydrolysis experiments were conducted by adding a fixed amount of 2 x 2 mm oflSce paper to flasks containing cellulase in 0.05 M acetate buffer (pH = 4.8). The flasks were placed in an incubator-shaker maintained at 50 °C and 100 rpm. A Box-Behnken design was used to assess the influence of four factors on the extent of sugar production. The four factors examined were (i) reaction time (h), (ii) enzyme to paper mass ratio (%), (iii) amount of surfactant added (Tween 80, g/L), and (iv) paper pretreatment condition (phosphoric add concentration, g/L), as shown in Table 1. Each factor is coded according to the equation... 

Cellulase enzyme complexes consist of three major types of proteins that synergistically catalyze the breakdown of a cellulosic substrate. Because the enzymes are strictly substrate-specific in their action, any change in the structure or accessibility of the substrate can have a considerable influence on the course of the hydrolysis reaction. A pretreatment method based on exposing cellulosic substrate to phosphoric acid solution [9] and addition of the nonionic... 

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