Enzymatic hydrolysis process

When autohydrolysed aspen was treated with cellulase enzyme, poor results were obtained. Based on a ton of dry wood, only about 300 lb of fermentable sugars were obtained, and the fermentation was very inefficient with low yields of ethanol. These results compare poorly with those shown in Figure 5 when autohy-drolysed-caustic extracted aspen was treated with cellulase enzyme, and then fermented. It would appear from these results that the caustic extraction step for lignin removal would be necessary if the enzymatic hydrolysis process were to be adopted and advisable when acid hydrolysis is used. 

The present results suggest that the enzymatic hydrolysis process is at least competitive with the acid hydrolysis process. The main difficulty with it is the long time required for the hydrolysis, compared with the acid process. The present work suggested a mechanism for overcoming this problem, which is to remove the sugars as formed, perhaps by combining the enzymatic hydrolysis and the fermentation in one vessel at the same time. 

Je, J. Y., Qian, Z. J., Byun, H. G., and Kim, S. K. (2007). Purification and characterization of an antioxidant peptide obtained from tuna backbone protein by enzymatic hydrolysis. Process Biochem. 42, 840-846. 

Figure 12. Relation of glucose selling price to delivered cellulose substrate costs for enzymatic hydrolysis process. Data for 250,000 t/yr plant 90% overall process efficiency, 50% enzyme recovery (reuse).

We have proposed that the normal enzymatic hydrolysis process also proceeds through such a phosphorane intermediate, but isomerization does not occur because pseudo-rotation is not permitted in the enzyme (22). Complete agreement does not exist with our proposal (23). In this case, the biomimetic model system was not based only on nature s enzyme, it pointed to possible aspects of the natural enzyme that had not been considered previously. Thus we had learned something from nature, and we returned the favor by learning something that could give insight into nature itself. 

The effect and action of enzymes seems to be very limited because ol the stronger conditions of alkali of mercerizing strength. Enzymatic hydrolysis is accelerated when mercerization is carried out without tension [44]. The greater accessibility and lower crystallinity of cellulose mercerized without tension is a decisive factor in the enzymatic hydrolysis process. Mercerized cotton is generally more prone to enzymatic modification than untreated cotton. 

Cooperative action, often designated synergy, of the three cellulolytic enzyme classes is essential for an efficient enzymatic hydrolysis process [181]. 

Aden A, Foust T. (2009). Technoeconomic analysis of the dilute sulfuric add and enzymatic hydrolysis process for the conversion of com stover to ethanol. Cellulose, 16(4), 535—545. 

Based on the cost of production, both the dilute acid and enzymatic hydrolysis process of com stover and the dry milling process of com are equally competitive. However, capital requirement for the biomass-based process has been a major research and development (R D) and engineering thrust of the biotechnology companies and research institutes. 

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