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L F Chen

Publications and source records attributed to L F Chen.

At least 55 records · Page 3Linked to original sources
PubMed1985

Alpha-1-antitrypsin types in five Chinese national minorities.

The frequencies of alpha-1-antitrypsin alleles were determined for five Chinese national minorities: Uigur, Korean, Mongolian, Chuang, and Li. PI S and PI Z alleles are not found in the five populations studied. PI ETOK allele is present in Korean, Mongolian, and Chuang populations, and Etokyo is a very common alpha-1-antitrypsin variant in Chinese. Other alleles which occur in more than one of the minorities are PI X (Mongolian and Chuang) and PI M4 (Korean and Uigur). The high frequency of PI M4 in the Uigur population suggests a probably Occidental origin of this nationality.

Alleles↗
PubMed1985

Geographical variability of alpha-1-antitrypsin alleles in China: a study on six Chinese populations.

Alpha-1-antitrypsin phenotypes of six Chinese Han populations (20 degrees-45 degrees N. latitude) were determined. The frequency of allele M2 increases from North to South China. The north-south change of M2 appears to be mainly at the expense of alleles M1 and M3. Geographical variability of other variants was also observed. In the northern populations, the most common variants are M4 and Etokyo; in the southern populations, Pweishi, a variant which can not be distinguished electrophoretically from Pyasugi. These results form a distribution pattern of alpha-1-antitrypsin alleles in China.

Alleles↗
PubMed1981

Production of Ethanol from d-Xylose by Using d-Xylose Isomerase and Yeasts.

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.

Journal Article↗
PubMed1981

d-Xylulose Fermentation to Ethanol by Saccharomyces cerevisiae.

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 degrees 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.

Journal Article↗
PubMed1979

Affinity chromatography of endoglucanase of Trichoderma viride by concanavalin A-agarose.

Endoglucanase (C kappa cellulase) and cellobiase are often cross-contaminated in separation procedures by ion-exchange chromatography such as DEAE-cellulose. By using concanavalian A (Con A)-agarose chromatography, C kappa cellulase and cellobiase from Trichoderma virde can be separated. C kappa cellulase showed affinity toward Con A. indicating a glycoprotein containing alpha-D-mannopyransyl and alpha-D-glucopyranosyl end groups or internal 2-O-D-mannopyranosyl residues in sugar moieties. This method provides a way to estimate the quantities of C kappa enzyme produced by T. viride and possibly by other organisms.

Binding Sites↗
PubMed1977

Characteristics of yeast invertase immobilized on porous cellulose beads.

Invertase from Candida utilis was immobilized on porous cellulose beads by an ionic-quanidino bond. The immobilized invertase showed optimum activity between pH 4.0 and 5.4, while the free enzyme had a sharp optimum at pH 4.1. Both temperature profiles were fairly similar up to 55 degrees C. However, above this temperature the immobilized enzyme was more stable than the free enzyme. From the temperature data, the activation energies were found to be 7,322 and 4,052 cal/g mol for the free and the immobilized enzyme, respectively. Candida invertase shows characteristics of substrate inhibition. Both the Km and Ki for the free and the immobilized enzymes were determined. The apparent Ki for the immobilized invertase was much higher than the Ki of the free enzyme, suggesting a diffusion effect. Immobilized invertase molecules deep in the pores only see sucrose concentrations much less than the bulk concentrations. Immobilization, thus, offers certain processing advantages in this regard.

Candida↗
PubMed1977

Chemical procedures for enzyme immobilization on porous cellulose beads.

In a previous article, the method of preparation and the physical properties of porous (75 to 80% porosity) cellulose beads were described (Biotechnol. Bioeng., 18, 1057 (1976). The present article reports that the chemical procedures employed for immobilizing enzymes on ordinary cellulose can be applied to the porous cellulose beads. The results showed more enzyme loading on the beads than ordinary cellulose. The choice of the procedures might also affect the mechanical strength of the cellulose beads.

Carbohydrate Epimerases↗