Saccharification procedure

Grohmann and Bothast [119] used dilute acid to treat corn fiber at 100-160°C before subjecting the material to enzymatic hydrolysis (saccharification) with cellulase and glucoamylase at 45 °C. The saccharification procedure resulted in the conversion of 85% of corn fiber into simple sugars. The hydrolysate was then subjected to fermentation by E. coli KOll. After 72 h of fermentation, about 30 g/1 ethanol was obtained. The yield of ethanol was about 62% based on sugar consumed. 

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. 

In the preceding methods, the enzyme is confined to small droplets, capsules, or inert carrier. Enlargement of a capsule to the size of a fermenter is theoretically possible, and this principle has been applied with practical modifications. The enzyme is free in solution as in the batch procedures, but an ultrafilter serves to separate the reaction products from the enzyme and substrate. Substrate is continuously pumped into the system, and product is removed by ultrafiltration to provide a continuous system. This method is applicable only to systems where the substrate is a large or an insoluble substance, so that it - with the enzyme - are retained inside the membrane. Successful demonstration of experimental runs on cellulose saccharification (Chose and Kostick, 1969) and on starch hydrolysis (Butterworth et al., 1969) have been made. Success depends upon the availability of suitable membranes and practical application on their cost. 

The NMR analysis procedure discussed thus far provides a relative molar concentration of carbohydrates in the aqueous hydrolyzate resulting from the acidic saccharification of woody materials. In many cases, it is desirable to also determine the absolute concentration of sugars in a hydrolyzate, especially if the sugars are used for the production of chemicals or fuels in a subsequent process. 

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