Sugar conversions

It may be estimated that ethanol yields from lignocellulosics will range between 0.12 and 0.32 L kg-1 undried feedstock, depending upon the efficiency of five-carbon sugar conversion [26]. Other types of fermentation, including bacterial fermentation under aerobic and anaerobic conditions, can produce various other products from the sugar stream, including lactic acid. 

Recently, in another attempt to isolate an AGA biosynthetic gene cluster from S. sp. ( tenebrarius ) H6 an incomplete set of five putative sugar conversion... 

The sugar conversion and the monoethers/polyethers ratio (mono/poly ratio) were determined at 75°C for 140 min, using [Pd(acac)2/3PPh3] as the catalytic system with a sugar/butadiene/Pd ratio = 150 900 1 in DMF [28, 29]. Under these conditions, the conversions of 15 and 16 were 31 and 39% respectively with mono/ poly ratio = 5.2 and 8.1. Interestingly, the addition of triethylamine (20 equiv./Pd) increased the conversion and the selectivity towards the monoethers 51 and 56% conversions with mono/poly ratios = 9 and 19 for 15 and 16, respectively (Table 4). The conversion is also sensitive to the nature of the phosphane and to the Pd/ phosphane ratio. Indeed, variation of only the phosphane leads to conversions varying from less than 2 to 99%, alkyl phosphanes and sterically hindered aryl phosphanes being less effective. The selectivity also depends on the phosphane (Table 4) [29]. 

With 6 equiv. of 1, this selectivity was even increased because of the relative lower amount of the triether (Table 10). Nevertheless, experiments have been performed with 2-methoxyethanol, methylisobutylketone, and ethyl acetate as a supplementary co-solvent. While ethyl acetate is not suitable, good sugar conversion was achieved in the presence of the two other co-solvents, even using a low excess (3 equiv.) of 1. Switching to EtN(/-Pr)2 as the base reduced the sugar conversion but raised the monoether selectivity up to 97%. 

An alcohol content of about 14% is the highest, which can ordinarily be achieved directly by fermentation because at this concentration further sugar conversion by yeast is inhibited. Concentrations of up to about 18% by volume are possible with special strains of wine yeasts. A wine of higher alcohol content, however, is possible by the addition of brandy (distilled from wine) or fermentation alcohol to a natural wine. Wines where the natural alcohol content is supplemented to 14-20% by volume are referred to as fortified, or dessert wines, and include the varieties commonly known as sherries and ports. Fortification improves the keeping qualities for shipment and export by inhibiting further yeast action. Fortified wines are produced on about the same scale as natural wines. 

Clostridium butvricum(62). Maximum yields obtained were 1.2% in the medium representing a 40% sugar conversion. 

Glucose utilization was higher than 90% for all tested WEH suspensions, whereas xylose conversion remained lower, between 72 and 80%. The lowest sugar conversions of 90 and 72%, respectively, for glucose and xylose were seen at 40% WEH. This could be attributed to a technical problem with the pH control system because the pH value was maintained around 6.S-6.7 instead of pH 7, and the reactor operated under these conditions (pH 6.5-6.7) with 40% WEH until the end of the experiment. The overall sugar conversion efficiency to ethanol for all these experiments was in a range of 68-76% (Table 1). 

HRT (days) WEH (wt/v) % Influent Effluent Sugar conversion Yield- YEtOH" % CE % CR %... 

Place the following sugar conversions in the correct order used to regenerate starting material for the Calvin cycle, and name the enzyme that catalyzes each reaction ... 

The ethanol to sugar yield, R /s, was found to slightly increase during the fermentation as a result of the decrease of the growth yield. Based on a carbon balance of the sugar conversion into yeast, ethanol and CO2, the variation of R /s can be related to the previously expressed variation of Ry/s ss... 

In plant cell cultures, microencapsulation, by mimicking cell natural environment, improves efficiency in production of different metabolites used for medical, pharmacoIogicaL and cosmetic purposes. Human tissues are turned into bioartiflcial organs by encapsulation in natural polymers and transplanted to control hormone-deficient diseases such as diabetes and severe cases of hepatic failure. In continuous fermentation processes, immobilization is used to increase cell density, productivity and to avoid washout of the biological catalysts from the reactor. This has already been applied in ethanol and solvent production, sugar conversion, or wastewater treatment. 

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