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Abstract Background Simultaneous cofermentation of glucose and xylose mixtures would be a cost-effective solution for the conversion of cellulosic biomass to high-value products. However, most yeasts ferment glucose and xylose sequentially due to glucose catabolite repression. A well known thermotolerant yeast, Kluyveromyces marxianus, was selected for this work because it possesses cost-effective advantages over Saccharomyces cerevisiae for biofuel production from cellulosic biomass. Results In the present study, we employed a directed evolutionary approach using 2-deoxyglucose to develop a thermotolerant mutant capable of simultaneous cofermentation of glucose and xylose by alleviating catabolite repression. The selected mutant, K. marxianus SBK1, simultaneously cofermented 40 g/L glucose and 28 g/L xylose to produce 23.82 g/L ethanol at 40 °C. This outcome corresponded to a yield of 0.35 g/g and productivity of 0.33 g/L h, representing an 84% and 129% improvement, respectively, over the parental strain. Interestingly, following mutagenesis the overall transcriptome of the glycolysis pathway was highly downregulated in K. marxianus SBK1, except for glucokinase-1 (GLK1) which was 21-fold upregulated. Amino acid sequence of GLK1 from K. marxianus SBK1 revealed three amino acid mutations which led to more than 22-fold lower enzymatic activity compared to the parental strain. Conclusions We herein successfully demonstrated that the cofermentation of a sugar mixture is a promising strategy for the efficient utilization of cellulosic biomass by K. marxianus SBK1. Through introduction of additional biosynthetic pathways, K. marxianus SBK1 could become a chassis-type strain for the production of fuels and chemicals from cellulosic biomass.

It is well known that Phellinus linteus, which produces hispidin and its derivatives, possesses antioxidant activities. In this study, we investigated whether hispidin has protective effects on palmitate-induced oxidative stress in C2C12 skeletal muscle cells. Our results showed that palmitate treatment in C2C12 myotubes increased ROS generation and cell death as compared with the control. However, pretreatment of hispidin for 8 h improved the survival of C2C12 myotubes against palmitate-induced oxidative stress via inhibition of intracellular ROS production. Hispidin also inhibited palmitate-induced apoptotic nuclear condensation in C2C12 myotubes. In addition, we found that hispidin can suppress cleavage of caspase-3, expression of Bax, and NF-κB translocation. Therefore, these results suggest that hispidin is capable of protecting C2C12 myotubes against palmitate-induced oxidative stress.

Oxidative stress induced by reactive oxygen species (ROS) is the major cause of degenerative disorders including aging and disease. In this study, we investigated whether Cordyceps militaris extract (CME) has in vitro protective effects on hydrogen peroxide-induced oxidative stress in human dermal fibroblasts (HDFs). Our results showed that the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of CME was increased in a dose-dependent manner. We found that hydrogen peroxide treatment in HDFs increased ROS generation and cell death as compared with the control. However, CME improved the survival of HDFs against hydrogen peroxide-induced oxidative stress via inhibition of intracellular ROS production. CME treatment inhibited hydrogen peroxide-induced apoptotic cell death and apoptotic nuclear condensation in HDFs. In addition, CME prevented hydrogen peroxide-induced SA-β-gal-positive cells suggesting CME could inhibit oxidative stress-induced premature senescence. Therefore, these results suggest that CME might have protective effects against oxidative stress-induced premature senescence via scavenging ROS.

Among the many environmental stresses, excessive production of reactive oxygen species (ROS) and the ensuring oxidative stress are known to cause significant cellular damage. This has clinical implications in the onset of type 1 diabetes, which is triggered by the destruction of pancreatic β-cells and is associated with oxidative stress. In this study, we investigated the protective and antioxidative effects of mulberry extract (ME) in insulin-producing pancreatic β-cells. We found that ME protects pancreatic β-cells against hydrogen peroxide (H2O2)-induced oxidative stress and the associated apoptotic cell death. ME treatment significantly reduced the levels of H2O2-induced 2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and lipid peroxidation and intracellular ROS accumulation. In addition, ME inhibited DNA condensation and/or fragmentation induced by H2O2. These results suggest that ME protects pancreatic β-cells against hydrogen peroxide-induced oxidative stress.

A number of polysaccharides exhibit pharmacological activities. Polysaccharides derived from Inonotus obliquus (PLIO) appear to have various potential pharmacological properties, including anti-tumor activity. However, the molecular mechanisms underlying these properties remain to be elucidated. The present study investigated the anti-metastatic potential of PLIO and the underlying signaling pathways in B16-F10 murine melanoma cells using the MTT colorimetric assay, in vitro migration and invasion assays, and flow cytometric and western blot analyses. PLIO inhibited the invasion of B16-F10 cells and suppressed the expression of matrix metalloproteinases. PLIO treatment inhibited nuclear factor-κB (NF-κB) nuclear translocation in B16-F10 cells. In addition, PLIO treatment inhibited the phosphorylation of c-Jun N-terminal kinases and AKT. These results suggest that PLIO may suppress the invasion of highly metastatic melanoma cells via inhibition of the AKT/NF-κB signaling pathways. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to elucidate the cytoprotective effects of polysaccharides isolated from Inonotus obliquus. The polysaccharides were extracted from the fruiting body of I. obliquus (PFIO) and the liquid culture broth of I. obliquus (PLIO). The effects of PFIO and PLIO on hydrogen peroxide (H2O2)-induced oxidative damage of RINm5F pancreatic β-cells were comparatively investigated using an MTT assay, immunofluorescent staining, flow cytometry, and western blot analyses in vitro. The results of the present study demonstrated that treatment with PFIO and PLIO decreased DNA fragmentation and the rate of apoptosis. In addition, pretreatment of cells with PFIO and PLIO prior to H2O2 exposure resulted in increased insulin secretion and scavenging activity for intracellular reactive oxygen species, as compared with treatment with H2O2 alone. The results of the present study suggested that PFIO and PLIO may exert protective effects against H2O2-induced oxidative stress via the regulation of mitogen-activated protein kinases, nuclear factor-κB and apoptotic proteins. Therefore, PFIO and PLIO may have potential merit as a medicinal food for the prevention of diabetes. [ABSTRACT FROM AUTHOR]

Background Cellobiose and xylose co-fermentation holds promise for efficiently producing biofuels from plant biomass. Cellobiose phosphorylase (CBP), an intracellular enzyme generally found in anaerobic bacteria, cleaves cellobiose to glucose and glucose-1-phosphate, providing energetic advantages under the anaerobic conditions required for large-scale biofuel production. However, the efficiency of CBP to cleave cellobiose in the presence of xylose is unknown. This study investigated the effect of xylose on anaerobic CBP-mediated cellobiose fermentation by Saccharomyces cerevisiae. Results Yeast capable of fermenting cellobiose by the CBP pathway consumed cellobiose and produced ethanol at rates 61% and 42% slower, respectively, in the presence of xylose than in its absence. The system generated significant amounts of the byproduct 4-O-β-Dglucopyranosyl- D-xylose (GX), produced by CBP from glucose-1-phosphate and xylose. In vitro competition assays identified xylose as a mixed-inhibitor for cellobiose phosphorylase activity. The negative effects of xylose were effectively relieved by efficient cellobiose and xylose co-utilization. GX was also shown to be a substrate for cleavage by an intracellular β- glucosidase. Conclusions Xylose exerted negative impacts on CBP-mediated cellobiose fermentation by acting as a substrate for GX byproduct formation and a mixed-inhibitor for cellobiose phosphorylase activity. Future efforts will require efficient xylose utilization, GX cleavage by a β- glucosidase, and/or a CBP with improved substrate specificity to overcome the negative impacts of xylose on CBP in cellobiose and xylose co-fermentation. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae cannot utilize cellobiose, but this yeast can be engineered to ferment cellobiose by introducing both cellodextrin transporter (cdt-1) and intracellular β-glucosidase (gh1-1) genes from Neurospora crassa. Here, we report that an engineered S. cerevisiae strain expressing the putative hexose transporter gene HXT2.4 from Scheffersomyces stipitis and gh1-1 can also ferment cellobiose. This result suggests that HXT2.4p may function as a cellobiose transporter when HXT2.4 is overexpressed in S. cerevisiae. However, cellobiose fermentation by the engineered strain expressing HXT2.4 and gh1-1was much slower and less efficient than that by an engineered strain that initially expressed cdt-1 and gh1-1. The rate of cellobiose fermentation by the HXT2.4-expressing strain increased drastically after serial subcultures on cellobiose. Sequencing and retransformation of the isolated plasmids from a single colony of the fast cellobiose-fermenting culture led to the identification of a mutation (A291D) in HXT2.4 that is responsible for improved cellobiose fermentation by the evolved S. cerevisiae strain. Substitutions for alanine (A291) of negatively charged amino acids (A291E and A291D) or positively charged amino acids (A291K and A291R) significantly improved cellobiose fermentation. The mutant HXT2.4(A291D) exhibited 1.5-fold higher Km and 4-fold higher Vmax values than those from wild-type HXT2.4, whereas the expression levels were the same. These results suggest that the kinetic properties of wild-type HXT2.4 expressed in S. cerevisiae are suboptimal, and mutations of A291 into bulky charged amino acids might transform HXT2.4p into an efficient transporter, enabling rapid cellobiose fermentation by engineered S. cerevisiae strains. [ABSTRACT FROM AUTHOR]

We demonstrate improved ethanol yield and productivity through cofermentation of cellobiose and galactose by an engineered Saccharomyces cerevisiae strain expressing genes coding for cellodextrin transporter (cdt-1) and intracellular β-glucosidase (gh1-1) from Neurospora crassa. Simultaneous fermentation of cellobiose and galactose can be applied to producing biofuels from hydrolysates of marine plant biomass. [ABSTRACT FROM AUTHOR]

The article reports on a study regarding the improved galactose fermentation of Saccharomyces cerevisiae through inverse metabolic engineering. The materials and methods utilized in the study were Saccharomyces cerevisiae that were used for galactose fermentation experiments. It concludes that the results of the study would be industrially useful in the biofuels area.

The use of plant biomass for biofuel production will require efficient utilization of the sugars in lignocellulose. primarily glucose and xylose. However, strains of Saccharomyces cerevisiae presently used in bioethanol production ferment glucose but not xylose. Yeasts engineered to ferment xylose do so slowly, and cannot utilize xylose until glucose is completely consumed. To overcome these bottlenecks, we engineered yeasts to coferment mixtures of xylose and cellobiose. In these yeast strains, hydrolysis of cellobiose takes place inside yeast cells through the action of an intracellular β-glucosidase following import by a high-affinity cellodextrin transporter. Intracellular hydrolysis of cellobiose mini- mizes glucose repression of xylose fermentation allowing coconsumption of cellobiose and xylose. The resulting yeast strains, cofermented cellobiose and xylose simultaneously and exhibited improved ethanol yield when compared to fermentation with either cellobiose or xylose as sole carbon sources. We also observed improved yields and productivities from cofermentation experiments performed with simulated cellulosic hydrolyzates, suggesting this is a promising cofermentation strategy for cellulosic biofuel production. The successful integration of cellobiose and xylose fermentation pathways in yeast is a critical step towards enabling economic biofuel production. [ABSTRACT FROM AUTHOR]

The article presents a study on the presence of homolog amylosucrase in 12 Alteromonas and Pseudoalteromonas strains. It notes that amylosucrase is a glycosyltransferase that belongs to family 13 of the glycoside hydrolases which contains a variety of known polysaccharide-degrading enzymes. The results show that hydrolysis occurs predominant at higher temperatures, while transglycosylation occurs mainly at lower temperatures.

The production yield of Coenzyme Q10 (CoQ10) from the sucrose consumed by Agrobacterium tumefaciens KCCM 10413 decreased, and high levels of exopolysaccharide (EPS) accumulated after switching from batch culture to fed-batch culture. Therefore, we examined the effect of sucrose concentration on the fermentation profile by A. tumefaciens. In the continuous fed-batch culture with the sucrose concentration maintained constantly at 10, 20, 30, and 40 g l−1, the dry cell weight (DCW), specific CoQ10 content, CoQ10 production, and the production yield of CoQ10 from the sucrose consumed increased, whereas EPS production decreased as maintained sucrose concentration decreased. The pH-stat fed-batch culture system was adapted for CoQ10 production to minimize the concentration of the carbon source and osmotic stress from sucrose. Using the pH-stat fed-batch culture system, the DCW, specific CoQ10 content, CoQ10 production, and the product yield of CoQ10 from the sucrose consumed increased by 22.6, 13.7, 39.3, and 39.3%, respectively, whereas EPS production decreased by 30.7% compared to those of fed-batch culture in the previous report (Ha SJ, Kim SY, Seo JH, Oh DK, Lee JK, Appl Microbiol Biotechnol, 74:974–980, ). The pH-stat fed-batch culture system was scaled up to a pilot scale (300 l), and the CoQ10 production results obtained (626.5 mg l−1 of CoQ10 and 9.25 mg g DCW−1 of specific CoQ10 content) were similar to those obtained at the laboratory scale. Thus, an efficient and highly competitive process for microbial CoQ10 production is available. [ABSTRACT FROM AUTHOR]

This report describes the optimization of culture conditions for coenzyme Q10 (CoQ10) production by Agrobacterium tumefaciens KCCM 10413, an identified high-CoQ10-producing strain (Kim et al., Korean patent. 10-0458818, ). Among the conditions tested, the pH and the dissolved oxygen (DO) levels were the key factors affecting CoQ10 production. When the pH and DO levels were controlled at 7.0 and 0–10%, respectively, a dry cell weight (DCW) of 48.4 g l−1 and a CoQ10 production of 320 mg l−1 were obtained after 96 h of batch culture, corresponding to a specific CoQ10 content of 6.61 mg g-DCW−1. In a fed-batch culture of sucrose, the DCW, specific CoQ10 content, and CoQ10 production increased to 53.6 g l−1, 8.54 mg g-DCW−1, and 458 mg l−1, respectively. CoQ10 production was scaled up from a laboratory scale (5-l fermentor) to a pilot scale (300 l) and a plant scale (5,000 l) using the impeller tip velocity ( V tip) as a scale-up parameter. CoQ10 production at the laboratory scale was similar to those at the pilot and plant scales. This is the first report of pilot- and plant-scale productions of CoQ10 in A. tumefaciens. [ABSTRACT FROM AUTHOR]

Of the vitamins tested, inositol was the most effective for erythritol production. To increase erythritol production by Torula sp., inositol and a related compound, phytic acid (myoinositol hexaphosphate), were added to the culture media. Erythritol production in the presence of phytic acid was greater than that in the presence of inositol, due to the synergistic effects of phosphate and inositol. Supplementation with phosphate and inositol increased cell growth, erythritol production, and the activity of erythrose reductase in cells. Inositol was a more effective stimulator of cell growth and erythritol production than was phosphate. [ABSTRACT FROM AUTHOR]