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.

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Effects of pretreatment on the anaerobic digestion of waste activated sludge (WAS) were investigated in terms of VSS solubilization and methane production by batch experiments. The methods of pretreatment studied are NaOH addition (chemical), heating (thermal) and heating with NaOH addition (thermochemical) to the domestic WAS and to the combined WAS from domestic, commercial and industrial wastewaters. The thermochemical pretreatment gave the best result among three methods in the combined WAS, i.e., the VSS was solubilized by 40-50% and the methane production increased by more than 200% over the control when the WAS was heated at 130°C for 5 minutes with the dose 0.3 g NaOH/g VSS. In the domestic WAS, the VSS solubilization rate was 70-80% but the increase of the methane production was about 30% after thermochemically pretreated. The domestic WAS consists of 41% protein, 25% lipid and 14% carbohydrate on COD basis, and the solubilization rate of protein, which is the largest constituent of the WAS, was 63% in the thermochemical pretreatment. Although the effect of the thermochemical pretreatment on the methane production was higher to the combined WAS than to the domestic WAS, the methane production rate was 21.9 ml CH4/g VSSWAS·day in the domestic WAS and 12.8 ml CH4/g VSSWAS·day in the combined WAS.

Liquid-liquid phase separation and crystallization ͑or solid-liquid phase separation͒ both occur in protein solutions. By adopting egg-white lysozyme for a model system, we compared two types of diagrams, a phase diagram of the liquid-liquid phase separation and a morphological diagram of protein crystals. By superimposing these diagrams, we distinguished two types of white precipitates, urchinlike spherulites arising from the crystallization and protein-rich droplets from the liquid-liquid phase separation. Furthermore, we observed a transformation from the protein-rich droplets to the spherulites, and simultaneously an unusual pattern evolution of the protein-rich phase unlike the conventional phase separation of typical binary mixtures. This is understood in terms of the competition between the crystallization and the liquid-liquid phase separation.

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The phase behavior of apoferritin solutions induced by the addition of polyethylene glycol (PEG) was studied. The interaction between apoferritin molecules was determined by dynamic light scattering. The comparison of the experiments with the theoretical calculations showed that the addition of NaCl to the protein solution only screened the electrostatic repulsion and did not induce attraction. By the addition of PEG, on the other hand, significant attraction was induced and three types of precipitation (crystals, liquid domains, and random aggregates) appeared depending on the concentration of PEG and on its molecular weight. The strength of the attraction could be explained by the depletion mechanism, although there was slight discrepancy between the simple theory and the experiments. Superiority of PEG is thus demonstrated since the depletion mechanism does not depend on specific nature of proteins. From the phase diagram, we suggest that the control of the concentration and molecular weight of PEG are both needed for protein crystallization.

A batch fermentation utilizing Saccharomyces cerevisiae BY4742 was conducted to determine the inhibitory effects of highly concentrated substrate and product levels on yeast. Experiments were performed to determine the largest dosage of substrate and the largest product concentration that the yeast could tolerate in a very high gravity fermentation process. The yeast's growth and fermentation activities were characterized by changes in the biomass and ethanol yield under different substrate and product concentrations during fermentation. All of the experiments were performed at a pH of 5.0 and a temperature of 35°C with a stirring rate of 180 r/min and a fermentation time of 96 h. Furthermore, five cycles of acclimatization were conducted to improve the yeast's tolerance to ethanol. Ethanol yield was maximized at 95% with a product concentration of 39 g/L and substrate dosage of 80 g/L. The system exhibited an obvious increase in cell growth and ethanol production with increasing substrate dosage up to a critical point of 160 g/L glucose (53 g/L ethanol fermented and an ethanol yield of 65%). Above this point, cell growth and ethanol production were inhibited with the final product concentration increasing only slightly with an increase in the initial substrate concentration. The end product (ethanol) was shown to be the primary factor inhibiting yeast growth and fermentation activity because the yeast would completely stop growing and fermenting when the initial exogenous ethanol concentration exceeded 70 g/L. The endogenous ethanol exerted a greater impact on yeast performance during anaerobic fermentation than exogenous ethanol. Five cycles of acclimatization significantly improved the yeast density, cell morphology, and ethanol production during very high gravity fermentation. The ethanol yield increased from 6% to 30% under an initial exogenous ethanol concentration of 60 g/L.

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.