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DESCRIPTION OF PREFERRED EMBODIMENTS
The following Examples 1 to 4 show the use of succinic acid to hydrolyze sucrose to glucose and fructose in high yields.
EXAMPLE I
Effect of Catalyst Concentration at Low Temperatures.
Sucrose and water are mixed in E-flasks in ratio liquid:solid 10:1. Temperature is kept constant at 60° C. in an oven equipped with a shake table. Succinic acid(cas:110-15-6) is added to the flasks to give concentrations of 1, 3, and 5% acid by weight. The data is shown in Tables 5 to 7. An increase in the catalyst loading increases the rate of hydrolysis significantly at low temperatures. Yields after ten (10) hours hydrolysis for glucose and fructose are summarized in Table 1. The yields are based on the amount of glucose or fructose formed divided by the amount of sucrose hydrolyzed. For glucose at higher acid concentrations some product degradation takes place. For fructose some degradation is evident at all acid concentrations.
TABLE 1
Yield of fermentable sugars in weight-%.
Yield (weight-%)
Fructose Glucose
1% SA 88.4 99.3
3% SA 86.5 95
5% SA 87.2 94.9
EXAMPLE 2
Effect of Catalyst Concentration at Elevated Temperatures
Sucrose and water were mixed in E-flasks in ratio liquid:solid 10:1. Temperature was kept constant by heating on a heating plate. Agitation was obtained from a magnetic stirrer. Temperatures investigated were 80° C. and 100° C. The catalyst loading (succinic acid(cas:110-15-6) added) corresponds to 0.5, 1, 3, and 5% by weight as in Example 1. Sucrose hydrolysis as a function of time for the different catalyst loadings at 80° C. and at 100° C. The data is shown in Tables 5 to 7. At higher temperatures the hydrolysis rate was greatly increased. At 80° C. acid concentrations above 1% resulted in almost complete hydrolysis after two hours. A concentration of 1% needed three hours to complete the hydrolysis and 0.5% was not finished until after six hours. At 100° C. the hydrolysis was completed in one hour for all acid concentrations. Hydrolysis products were formed in yields 95-100% based on the sucrose hydrolyzed with less degradation of fructose.
EXAMPLE 3
Hydrolysis of Liquid:Solid Ratios 10:4
To produce a media with high enough sugar concentration for fermentation purposes higher liquid:solid ratios (higher percentages of sucrose) must be used. Using the same experimental setup as in Example 2, but with liquid:solid ratio 10:4, acid concentrations of 1%, and 5% were investigated at 80° C. and 100° C. Sucrose hydrolysis results are presented in Table 14. Yields after finished hydrolysis are shown in Table 2. The yields are expressed on a weight basis as the mass of produced monosaccharides per mass of hydrolyzed sucrose. From the yields it can be seen that the best results are achieved by low acid loadings and high temperatures. After one hour the yields were close to 100%, and heating for another hour did not generate any significant sugar degradation.
TABLE 2
Yield of fermentable sugars in weight-%.
Yield (weight-%)
Glucose Fructose
80° C., 1% SA 81.8 86.2
80° C., 5% SA 82.3 86.2
100° C., 1% SA 95.9 99.4
100° C., 5% SA 88.8 92.3
EXAMPLE 4
Fermentation of Glucose-Fructose Mixture in Ratio 50-50
A 12 L fermenter was used. A media constituted by the substances given in Table 3 was mixed and sterilized in the fermenter. 0.5 L inoculum of a pure AFP184 (an E. coli mutant described in U.S. published application 200300/7559 to Donnelly et al), grown for 16 hours in sterile Tryptic Soy Broth, was added together with a 2 L solution with a concentration of 400 g/L of glucose and fructose in ratio 1:1. The total starting volume of the fermentation was 8 L. The fermentation was aerated for eight hours with filter sterilized air. After eight hours a high cell density was achieved and the fermentation conditions were changed to anaerobic by cutting of air and adding carbon dioxide. This then proceeds for 16 hours producing succinic acid(cas:110-15-6). The final succinic acid(cas:110-15-6) concentration, yield per gram and mole consumed sugar during the anaerobic phase and the productivity per gram, litre and hour is shown in Table 4. The sugar concentration change during the fermentation is presented in Table 15. E. coli mutant AFP184 can ferment mixtures of glucose and fructose as produced in Examples 1 to 3.
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