Multiple effects of swelling by sodium bicarbonate after delignification on enzymatic saccharification of rice straw.

The multiple effects of pretreatments by chemical delignification using acidified sodium chlorite (ASC) and swelling using sodium bicarbonate (SB) for enzymatic saccharification of rice straw in bioethanol production have been investigated in this study. The treatment with the combination of ASC three times (3× ASC) first and SB later resulted in the significant reduction in Klason lignin content up to 90% (wt./wt.). By the saccharification of the pretreated rice straw with cellulase enzymes, it was confirmed that SB treatment was an important step in the pretreatment process not only to disintegrate the cellulose structure but also to facilitate the amorphization of the crystalline cellulose as well as the extended removal of integrated lignin. Furthermore, FTIR analyses revealed that the crystal type of cellulose appeared to be changed from type I to type II by SB treatment, thereby increasing the cellulose surface area and making it more accessible to the cellulase enzyme. Conversion rate to sugar was remarkably increased when 3× ASC + SB treatments were applied to untreated rice straw, even though the saccharification of the treated rice straw was performed at a low enzyme loading (1/100, wt.-enzymes/wt.-substrate). Conclusively, rice straw could be saccharified at high yield in short time at low cellulase loading, enables the enzymatic saccharification to be more feasible for practical bioethanol production using rice straw as a substrate.

Enhancement of xylose uptake in 2-deoxyglucose tolerant mutant of Saccharomyces cerevisiae.

Chemical mutation of Saccharomyces cerevisiae using ethyl methane sulfonate was performed to enhance its ability of xylose uptake for ethanol production from lignocellulose under microaerobic condition. Among the appeared mutants, the mutant no. 2 (M2) strain screened using inhibitory effects of 2-deoxyglucose (DOG) showed more than 4-fold high ability in xylose uptake compared with the wild type strain, under the presence of glucose. The catabolite repression by glucose was sufficiently reduced in M2 strain due to its tolerance to the high concentration of DOG (0.5%, wt./vol.). Metabolomic analyses of various sugars in the cell revealed that some of xylose was reduced to xylitol in M2 cell, providing the concentration gradient of xylose and more uptake of xylose. Xylulose-5-phosphate was significantly detected in the crude cell extract from M2 strain, indicating higher metabolic activity in pentose phosphate pathway. This was also confirmed by in vitro analyses of key enzymes involved in glucose and xylose metabolism, such as hexokinase, glucose-6-phosphate dehydrogenase and xylose reductase. Glucose uptake was moderately suppressed in the presence of trehalose-6-phosphate inhibiting the activation of hexokinase, resulting in more uptake of xylose through hexose transport system. To our knowledge, this study is the first report verifying that the mutation technique successfully enhances the xylose uptake by S. cerevisiae, particularly under the presence of glucose.

Enzymatic digestion of corncobs pretreated with low strength of sulfuric acid for bioethanol production.

In this study, the effect and the optimum pretreatment condition of corncobs using low strength of H2SO4 were investigated, in which H2SO4 was used to improve the enzymatic digestibility of corncobs for saccharification without degradation of sugars released. The optimum pretreatment condition was found to be the addition of 0.5% (vol./vol.) H2SO4 and autoclaving at 122°C for 20 min. Under this condition, the structural integrity of corncob was altered to make cellulose microfibrils more accessible for cellulase enzymes, and the enzymatic digestion of corncobs could be significantly enhanced. A high yield of sugar, 80% (wt./wt.), could be obtained at a low enzyme dosage of 0.024 g enzymes/g cobs, when pretreated. As a result, the ethanol production was obviously improved by the pretreatment, i.e., the ethanol yield of 77% (wt./wt.) was obtained within 36 h in the SSF fermentation using Saccharomyces cerevisiae NBRC2114.

Assessment of heavy metal pollution in river water of Hanoi, Vietnam using multivariate analyses.

Concentrations of heavy metals in water of the Nhue River (a suburban/rural river) and one of its tributaries, the To Lich River (an urban river), in Hanoi, Vietnam had been monitored, and spatial and seasonal variations in their composition were evaluated by means of principal component analysis and cluster analysis. Heavy metal concentrations in water of the two rivers were generally lower than the surface water quality standard in Vietnam, except for manganese in several sites, although they were higher than the median values in freshwater of the world by 0.42-43 times in Nhue and 0.13-32 times in To Lich. The two multivariate analyses represented that the composition of heavy metals in river water of To Lich was distinctly different from that of Nhue. It was also suggested that metal concentrations and their composition in Nhue river water would be affected by inflowing water of To Lich and wastewater discharged from the up- and middle-stream basin, and that they gradually recovered along the direction of water flow in the downstream area in rainy season.

Ethanol fermentation from biomass resources: current state and prospects.

In recent years, growing attention has been devoted to the conversion of biomass into fuel ethanol, considered the cleanest liquid fuel alternative to fossil fuels. Significant advances have been made towards the technology of ethanol fermentation. This review provides practical examples and gives a broad overview of the current status of ethanol fermentation including biomass resources, microorganisms, and technology. Also, the promising prospects of ethanol fermentation are especially introduced. The prospects included are fermentation technology converting xylose to ethanol, cellulase enzyme utilized in the hydrolysis of lignocellulosic materials, immobilization of the microorganism in large systems, simultaneous saccharification and fermentation, and sugar conversion into ethanol.

Isolation of a new heterotrophic nitrifying Bacillus sp. strain.

A heterotrophic nitrifier, named Bacillus sp. LY, was newly isolated from a membrane bioreactor (MBR). Bacillus sp. LY could utilize the organic carbon as the source of assimilation when it grew on glucose and ammonium chloride medium companying the formation of oxidized-nitrogen. It also could denitrify nitrate while nitrification. After 24 days incubation, the removal efficiencies of the COD and TN by Bacillus sp. LY were 71.7% and 61.2%, respectively. The phylogenetic analysis of Bacillus sp. LY was performed and the phylogenetic tree of Bacillus sp. LY and the neighbouring nitrifiers was given. Bacillus sp. LY could become a new bacterial resource for heterotrophic nitrification and might play a bioremediation role for nutrient removal.

Occurrence of estrogenic compounds in and removal by a swine farm waste treatment plant.

The total estrogenic activity of the wastewater from a swine farm in Japan was quantitatively characterized, and the compounds responsible for the estrogenic activity were identified and quantified. The wastewater treatment process consisted of a series of an up-flow anaerobic sludge blanket (UASB) and a trickling filter. Samples were collected at each treatment step, and the total estrogenic activity was determined by use of an in vitro gene expression assay (MVLN; MCF-7 human breast cancer cell stably transfected with the pVit-tk-LUC receptor plasmid). Individual estrogenic compounds were identified and quantified using liquid chromatography-mass spectrometry (LC/MS) and liquid chromatography-tandem mass spectrometry (LC/ MS/MS). To further identify the compounds contributing to the estrogenic activity in the wastewater, the sample extracts were fractionated into 12 fractions (fractions 1-12) by HPLC. The rate of removal of estrogenic activity between the effluent and the influent was greater than 97%. The trickling filter removed the majority of the estrogenic activity. The removal rates of specific estrogenic compounds ranged from 44 to 99%. Estrogenic activity was detected mainly in the fractions containing estrone (El), 17beta-estradiol (betaE2), 17alpha-estradiol (alpha E2), estriol (E3), bisphenol A (alphaPA), and equol (EQ0). The ratios of betaE2-EQc (betaE2 equivalents derived from chemical analysis) to betaE2-EQB (betaE2 equivalent derived from bioassay) in the 12 fractions collectively were contributed by El (17-30%), betaE2 (23-30%), acE2 (<1%), E3 (1-2%), BPA (<1%), and EQO (2-3%) in the influent and El (16-37%), PE2 (<1-7%), alphaE2 (<1%), E3 (<1-3%), BPA (<1%), and EQO (<1%) in the effluent. The compounds responsible for most of the estrogenic activity measured in the bioassay were natural estrogens such as El and betaE2.