Sung Ok Han

The high price of petroleum-based diesel fuel has led to the development of alternative fuels, such as ethanol. Saccharomyces cerevisiae was metabolically engineered to utilize glycerol as a substrate for ethanol production. For the synthesis of fatty acid ethyl esters (FAEEs) by engineered S. cerevisiae that utilize glycerol as substrate, heterologous expression of an unspecific acyltransferase from Acinetobacter baylyi with glycerol utilizing genes was established. As a result, the engineered

Surfactin is a biological surfactant with numerous potential applications. In this study, Bacillus subtilis was engineered to improve surfactin production by the activation of two competence-stimulating pheromones, ComX and competence and sporulation factor (CSF) to stimulate the transcription of srfA operon. Both signaling factors, encoded by comX and phrC, were successfully overexpressed and subsequently increased surfactin production. Surfactin produced by engineered strains showed functional

The regulation of expression of the genes encoding the cellulases and hemicellulases of Clostridium cellulovorans was studied at the mRNA level with cells grown under various culture conditions. A basic pattern of gene expression and of relative expression levels was obtained from cells grown in media containing poly-, di- or monomeric sugars. The cellulase (cbpA and engE) and hemicellulase (xynA) genes were coordinately expressed in medium containing cellobiose or cellulose. Growth in the prese

In this study, Saccharomyces cerevisiae was engineered for simultaneous saccharification and fermentation of cellulose by the overexpression of the endoglucanase D (EngD) from Clostridium cellulovorans and the beta-glucosidase (Bgl1) from Saccharomycopsis fibuligera. To promote secretion of the two enzymes, the genes were fused to the secretion signal of the S. cerevisiaealpha mating factor gene. The recombinant developed yeast could produce ethanol through simultaneous production of sufficient

Cellulosomes and noncellulosomal (hemi)cellulolytic enzymes are produced by Clostridium cellulovorans to degrade plant cell walls. To understand their synergistic relationship, changes in mRNA and protein expression in cellulosomes and noncellulosomal (hemi)cellulolytic enzymes (hereafter called noncellulosomal enzymes) of cultures grown on cellobiose, cellulose, pectin, xylan, and corn fiber or mixtures thereof were examined. Cellulase expression, favored particularly by the presence of Avicel,

The effect of different carbon sources on the expression of tricarboxylic acid (TCA) cycle genes, along with glyoxylate bypass genes, in Corynebacterium glutamicum was determined. All TCA cycle genes were coordinately expressed in medium containing acetate. Growth in the presence of acetate gave rise to abundant expression of most TCA cycle genes, with the level of gltA transcript being the highest. However, when the cells entered the stationary phase triggered by acetate exhaustion, all genes w

The utilization of scaffolds for enzyme immobilization involves advanced bionanotechnology applications in biorefinery fields, which can be achieved by optimizing the function of various enzymes. This review presents various current scaffolding techniques based on proteins, microbes and nanomaterials for enzyme immobilization, as well as the impact of these techniques on the biorefinery of lignocellulosic materials. Among them, architectural scaffolds have applied to useful strategies for protei

A basic pattern of gene expression and of relative expression levels during different growth phases was obtained for Corynebacterium glutamicum R grown on different carbon sources. The gapA-pgk-tpi-ppc gene cluster was transcribed as a mono- or polycistronic mRNA, depending on the growth phase. The 1.4 kb (gapA) and 2.3 kb (pgk-tip) mRNAs were expressed in the early through late exponential phases, whereas the 3.7 kb (gapA-pgk-tpi) and 5.4 kb (pgk-tpi-ppc) mRNAs were only detected in the mid-exp