We used commercial bakers' yeast (Saccharomyces cerevisiae) to study the conversion of D-xylulose to ethanol in the presence of D-xylose. The rate of ethanol production increased with an increase in yeast cell density. The optimal temperature for D-xylulose fermentation was 35°C, and the optimal pH range was 4 to 6. The fermentation of D-xylulose by yeast resulted in the production of ethanol as the major product; small amounts of xylitol and glycerol were also produced. The production of xylitol was influenced by pH as well as temperature. High pH values and low temperatures enhanced xylitol production. The rate of D-xylulose fermentation decreased when the production of ethanol yielded concentrations of 4% or more. The slow conversion rate of D-xylulose to ethanol was increased by increasing the yeast cell density. The overall production of ethanol from D-xylulose by yeast cells under optimal conditions was 90% of the theoretical yield. Previously, we described the production of ethanol from isomerized D-xylose (D-xylulose)

d -Xylulose, an intermediate of d -xylose catabolism, was observed to be fermentable to ethanol and carbon dioxide in a yield of greater than 80% by yeasts (including industrial bakers' yeast) under fermentative conditions. This conversion appears to be carried out by many yeasts known for d -glucose fermentation. In some yeasts, xylitol, in addition to ethanol, was produced from d -xylulose. Fermenting yeasts are also able to produce ethanol from d -xylose when d -xylose isomerizing enzyme is present. The results indicate that ethanol could be produced from d -xylose in a yield of greater than 80% by a two-step process. First, d -xylose is converted to d -xylulose by xylose isomerase. d -Xylulose is then fermented to ethanol by yeasts.

No abstract

We have developed a series of 4-amino-3,6-disulfonato-1,8-naphthalimide (ADSN) derivatives in an attempt to create nontoxic compounds effective against lentivirus infections. The ADSN derivative Lucifer Yellow CH ([N-(hydra zinocarbonyl)amino]-4-amino-3,6-disulfonato-1,8-naphthalimid e) (LYCH) was chosen as a parent compound because of its low toxicity in vivo and in vitro and its tendency to accumulate in monocyte/macrophages, a major reservoir for lentiviruses in vivo. Several ADSN derivatives inhibited reverse transcriptases (RTs) from human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV). Viral expression in HIV-infected human peripheral blood mononuclear cells was inhibited by noncytotoxic concentrations of two ADSN derivatives, designated A4 (biphenyl-4,4'-dicarboxaldehyde, Lucifer Yellow CH monohydrazone; EC50 = 29 microM after 6 days) and H4 (biphenyl-4,4'-dicarboxaldehyde, Lucifer Yellow CH dihydrazone; EC50 = 5.61 microM). A4 effectively suppressed the expression of FIV in infected Crandall feline kidney fibroblasts (CRFK) at 46.2 microM, reducing the RT levels by 97% after 19 days under conditions allowing direct cell-to-cell transmission of the virus. The viability of drug-treated FIV-infected CRFK cells increased significantly in the presence of A4 relative to the viability of untreated virus-infected cells. In contrast to A4 and H4, LYCH (which lacks the appended aromatic rings characteristic of A4 and H4) had no inhibitory effects on either virus and did not inhibit RT ex vivo. However, flow cytometry studies showed that both A4 and LYCH accumulate in two cell types that can support lentiviral infections: U937 human monocytic leukemic cells that have been induced to differentiate by using tetradecanoyl phorbol acetate, and CRFK cells.

A high-D-xylulose mixture (D-xylose-D-xylulose = 33:67) was prepared from the cold ethanol extract of preisomerized D-xylose solution (D-xylose-D-xylulose = 77: 23). Fusarium oxysporum f. sp. lini and Aspergillus niger were demonstrated to preferentially utilize D-xylose in the mixture of D-xylose and D-xylulose. Chromatographically pure D-xylulose was thus obtained in 90% yield. A high-D-xylulose mixture was also incubated with Rhodotorula toruloides, Klebsiellapneumoniae, Candida utilis, or Mucor rouxii. D-Xylose and D-xylulose were simultaneously consumed. When borate was added to the mixture, a D-xylulose-borate complex was formed, and it could be used to protect D-xylulose from being utilized.