Hydrolysis of cellulosic materials

Acid hydrolysis of cellulosic materials that include some hemicellulose, produces D-xylose, D-glucose, and cellobiose, as well as 11, 2-furalde-hyde (5), levulinic acid, formic acid, and acetic acid. In order to lessen the contamination due to hemicellulose, acid hydrolysis is generally performed in two steps dilute sulfuric acid (1%) at 80-120° followed by 5-20% sulfuric acid at 180°. The initial stage removes most of the pentogly-cans (pentosans). 

The advances made in enzymatic hydrolysis of cellulosic materials (14) are also of interest. This technology involves only moderate temperature processes in simple equipment which promises to be of significantly lower capital cost than the pressure equipment associated with conventional acid wood hydrolysis processes. All of these considerations combined to lead us to study processes for ethanol production from wood, especially in an effort to obtain data for material and energy balances, and possibly for the economics. 

Acid hydrolysis of cellulosic materials has been studied for many years (13,33). Although it is a relatively straightforward process, it has the problems of requiring acid-resistant equipment and yielding a poor grade of sugar (because the product contains many reaction product impurities). However, in terms of practical application, acid hydrolysis of cellulosic material is by far the most commonly used hydrolysis system. 

Influence of Fine Grinding on the Hydrolysis of Cellulosic Materials—Acid Vs. Enzymatic... 

Zheng and Tsao (1996) Batch Hydrolysis of cellulosic material to produce glucose Enzyme from cellulase... 

Hydrolysis of cellulosic materials from pulp and paper and municipal solid wastes to produce alcohol degradation of grain, fruit and vegetable wastes to produce glucose syrups [64]... 

Table VIII. Hydrolysis of Cellulose Materials by Trichoderma viride Cellulase ...

Viscose rayon is inherently a weak fibre, particularly when wet, therefore it is highly susceptible to damage if enzymatic hydrolysis is not controlled. The enzymatic hydrolysis of viscose fibres causes a decrease of the intrinsic viscosity from 250 to 140 ml/g and an increase in crystallinity from 29 to 39% after 44 h [34]. Strong changes of the structure, however, are not typical for the enzymatic hydrolysis of cellulosic materials. Neither cotton nor wood pulp show an essential decrease of the DP during enzymatic hydrolysis [35-37]. The kinetics of the enzymatic hydrolysis of regenerated cellulose fibres before and after acid prehydrolysis changes the kinetics from a monophasic to a biphasic first order reaction [38]. 

The most attractive features of solid-state fermentation include low capital investment and low operational costs. These features are favorable in the hydrolysis of cellulosic materials because the cost of cellulase is a key factor for commercial production. Currently, cellulase production by submerged culture has made great progress and been commercialized, while solid-state fermentation is only operated on a small scale in a few countries, such as China, and further efforts in research and development are still needed in order to improve the process and the equipment. 

Biological enzymatic conversion of glucose by fermentation also has been extensively studied for the production of many products one of the most important is bioethanol. Many bacteria and fungi could produce enzymes for the hydrolysis of cellulosic material. These microorganisms can be aerobic or anaerobic, mesophillic or thermophillic. ... 

Beltrame, P.L., Camitti, P., Forcher, B., 2001. Enzymatic hydrolysis of cellulosic materials a kinetic study. Biotechnology and Bioengineering 31, 160—167. 

Liu, L. Chen, H., Enzymatic hydrolysis of cellulose materials treated with ionic liquid... 

FIGURE 10.4 Summary of advantages and disadvantages of the different methods of pretreatment and hydrolysis of cellulosic material. 

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