Sugar recovery

Figure 7. Process flow scheme for sugar recovery from citrus press liquors.

Griggs and coworkers studied hydrolysis with 3 M hydrochloric acid for 3 h at 100° of canine submaxillary mucin (CSM) and CSM mixed with a standard sugar mixture. Sugar recoveries were 76.0% for fucose, 76.6% for mannose, 84.3% for galactose, 82.5% for A -acetylglucosamine, and 87.7% for A -acetylgalactosamine. 

The high pentose yields obtained in the current study are favorable when compared to those previously reported for dilute-acid hydrolysis in batch processes (28-31). However, the hemicellulosic sugar yield reported in the literature is often expressed as xylose equivalents, which is difficult to compare to monosaccharide recovery. The highest monosaccharide recovery was obtained with low CS values, which is in agreement with previous findings for sulfuric acid-catalyzed steam explosion, in which also better hemicellulosic sugar recoveries were obtained at relatively low severities (28,32) of <2.2 (22). 

Ventre and co-workers,72-78 in later work, found that the addition of calcium chloride greatly increased the amount of aconitates thus recovered. The procedure used was as follows lime was added to a quantity of sorghum juice to adjust the pH value to approximately 6.9. The amount of lime required for this treatment was calculated as equivalents of aconitic acid and this portion of the aconitic acid in the original sample of juice was assumed to be free aconitic acid. The remaining aconitic acid was assumed to be bound in the form of a soluble aconitate. An amount of calcium chloride equivalent to the bound aconitate was then added to the juice for the precipitation. The insoluble aconitates which precipitated during the subsequent evaporation of the juices were removed by some appropriate means at a later point in the sugar recovery system. 

Neeser, J. R., and Schweizer, T. P. (1984). A quantitative determination by capillary gas—liquid chromatography of natural and amino-sugars (as o-mthyloxime acetates) and a study on hydrolytic conditions for glycoproteins and polysaccharides in order to increase sugar recoveries. Anal. Biochem. 142(1), 58-67. 

In the present study, pretreatment of whole-crop maize silage was studied with the aim of optimizing the bioethanol process. The influence of temperature, time, and pH on sugar recovery and yield after pretreatment and enzymatic hydrolysis was studied as well as the ethanol yield in simultaneous saccharification and fermentation (SSF) with S. cerevisiae. 

Maize silage was pretreated by wet oxidation and hydrothermal treatment as described in Table 1. The sugar recoveries based on analysis and overall mass balance of the pretreated fractions (solid fibers and liquid) and the raw material have been calculated according to Eq. 1, and the results are shown in Fig. 1. The total recovery of glucose was very close to a 100% in all experiments (not shown), while the recovery of hemicellulose sugars depended very much on pretreatment conditions. 

Wyman, C. E., Dale, B. E., Elander, R. T., Holtzapple, M, Ladisch, M. R., Lee, Y. Y. (2005). Comparative sugar recovery data from laboratory scale application of leading pretreatment technologies to com stover. Bioresource Technology, 96, 2026-2032. 

Yan LS, Zhang HM, Chen JW, Lin ZX, Jin Q, Jia HH, Huang H (2(X)9) Dilute sulfuric add cycle spray flow-through pretreatment of com stover for enhancement of sugar recovery. Bioresour Technol. 100 1803-1808... 

Perez JA, Ballesteros I, Ballesteros M, Sa z F, Negro Ml, Manzanares P. (2008). Optimizing liquid hot water pretreatment conditions to enhance sugar recovery from wheat straw for fuel-ethanol production. Fuel, 87, 3640-3647. 

Assuming that the lignin which is insoluble is poorly affected by the hydrolysis process, the lignin quantity (in weight) stays constant from the initial wheat straw to the LCFo i. Cellulose and hemicellulose contents have been decreased under the hydrolysis treatment. Around 40% of the total cellulose and 85% of the hemicellulose have been eliminated during the process and collected mostly in the soluble fraction (see Table 17.1). We can notice that the process yield of hemicellulose sugars recovery is not total. By HPLC analysis, the hemicellulose composition can be given. Hemicellulose is composed with 96% of xylose, 3% of arabinose, and 1% of mannose. 

Carbon dioxide explosion is a pre-treatment process that uses supercritical carbon dioxide to break down the biomass structure. In aqueous solution, carbon dioxide forms carbonic acid which depolymerizes lignocellulosic materials. As a small molecule, carbon dioxide can penetrate into the pores of the biomass better than ammonia. When carbon dioxide explodes due to the change of pressure, it breaks the cellulosic structure. This process is usually operated under high pressure but low temperature to prevent monosaccharide degradation. But in comparison to steam explosion and ammonia explosion processes, the sugar recovery yield from this process is... 

Maize juice produced from com starch, which has received considerable attention as a sucrose source, has been snccessfully deionized by conventional treatment with the result that improved sugar recoveries are possible. In the manufacture of dextrose, the organic acids and colored substances produced as degradation products during starch hydrolysis were eliminated economically by the use of the ion-exchange process to produce a high-quality sugar. 

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