Enzymatic hydrolysis pretreatment

This session deals with recent progress on pretreatment of lignocellu-losic biomass, the peripheral reactions associated with pretreatment, and assessment of the effectiveness of pretreatment by enzymatic hydrolysis. Pretreatment is an essential element of the integral bioconversion process, and its objective is to enhance the susceptibility of cellulosic substrates to the action of cellulase enzymes. 

Figure 1 shows the experimental procedure used to evaluate the hydrolysis methods of SFF. First, the SFF material was subjected to saccharification with amyloglucosidase to determine the amount of starch available in the material. Second, the material was subjected to pretreatment in either a steam pretreatment unit or a microwave oven, followed by enzymatic hydrolysis. Pretreatment in a microwave oven was performed both with and without the addition of acid. Direct enzymatic hydrolysis was also performed. 

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. 

Error 1 CRMs completely or partly not identical with the matrix to be analyzed Ber-mejo-Barrera et al. (1999) studied enzymatic hydrolysis procedures using pronase E as sample pretreatment for multi-element - Cu, Fe, Mg, Zn, Ag, As, Cd, and Pb -determination in biological materials, mussel samples and human hair. 

Bioconversion platforms for lignocellulosics-to-ethanol are beginning to become commercially viable, but the effectiveness of the pretreatment stage should still be improved, the cost of the enzymatic hydrolysis stage decreased, and overall process efficiencies improved by better synergies between various process stages. There is also a need to improve process economics by creating co-products that can add revenue to the process. 

The effective pretreatments for enzymatic hydrolysis of cellulose in hardwoods and agricultural residues have been developed over the past 90 years and new or improved ones are still being developed. The initial impetus for pretreatment research was the expansion of a feed base for ruminants (i.e., cattle and sheep). The concentration of pretreatment research on animal feed preparation placed an additional burden on researchers, because the product must be not only fully convertible to animal live-weight, but also nontoxic and palatable. Early feeding trials of pretreated fine sawdust to cattle produced very dismal results (55). This may be the reason, besides the... 

Wood pretreated by autohydrolysis and extraction is necessary for successful enzymatic hydrolysis, and advantageous for acid hydrolysis. 

Chum, H. L. Black, S. Johnson, D. K. Sarkanen, K. V. Robert, D. Organosolv Pretreatment for the Enzymatic Hydrolysis of Poplars. II. Isolation and Quantitative Structural Studies of Lignins. Submitted. 

C. Pena-Farfal, A. Moreda-Pineiro, A. Bermejo-Barrera, P. Bermejo-Barrera, H. Pinochet-Cancino and I. De-Gregori-Henriquez, Ultrasound bath-assisted enzymatic hydrolysis procedures as sample pretreatment for multielement determination in mussels by inductively coupled plasma atomic emission spectrometry, Anal. Chem., 76(13), 2004, 3541-3547. 

The production of fuel ethanol from renewable lignocellulosic material ("bioethanol") has the potential to reduce world dependence on petroleum and to decrease net emissions of carbon dioxide. The lignin-hemicellulose network of biomass retards cellulose biodegradationby cellulolytic enzymes. To remove the protecting shield of lignin-hemicellulose and make the cellulose more readily available for enzymatic hydrolysis, biomass must be pretreated (1). 

Corn stover, like lignocellulosic materials in general, is resistant to enzymatic hydrolysis, because of both the tight network in the lignocellulose complex and the crystalline structure of the native cellulose. These difficulties can be overcome by employing a suitable pretreatment (7). 

The amount of mono- and disaccharides released (glucose, xylose, cellobiose, and arabinose) by pretreatment utilizing acid and enzymatic hydrolysis was analyzed by high-performance liquid chromatography (HPLC) (Shimadzu, Kyoto, Japan), using an Aminex HPX-87H column with a matching precolumn (Bio-Rad, Hercules, CA) at 65°C. The eluent was 5 mM H2S04 at a flow rate of 0.5 mL/min with detection by refractive index. 

ECC% Conversion After 48 h of Enzymatic Hydrolysis and Amounts of Released Glucose (g) from 100 g of Untreated Material (DM) During Pretreatment and Hydrolysis... 

Although most cellulase enzyme complexes, including Celluclast, contain xylanase activity (data not shown), the amount of released xylose after enzymatic hydrolysis was negligible, especially compared with the amount of released xylose after pretreatment. 

The highest overall sugar yield after both pretreatment and enzymatic hydrolysis, 56.1 g/100 g of DM, was also obtained at 190°C, for 5 min with 2% H2S04. 

A major problem in the commercialization of this potential is the inherent resistance of lignocellulosic materials toward conversion to fermentable sugars (4). To improve the efficiency of enzymatic hydrolysis, a pretreatment step is necessary to make the cellulose fraction accessible to cellulase enzymes. Delignification, removal of hemicellulose, and decreasing the crystallinity of cellulose produce more accessible surface area for cellulase enzymes to react with cellulose (5). 

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