Bier ist ein komplexes Stoffgemisch aus Wasser, Ethanol und einer Vielzahl von flüchtigen und nichtflüchtigen geschmacksaktiven Verbindungen. Während der Lagerung kommt es zu chemischen Reaktionen, ...bei denen einige Bestandteile abgebaut und andere neu gebildet werden. Mit dem chemischen Profil verändert sich auch der Geschmack eines Bieres, was zur Alterung und schließlich zum Verderb führen kann. Den Einfluss der Verpackung auf die Lagerstabilität hat kürzlich ein US‐amerikanisches Forscherteam untersucht.
Due to increasing population and industrialization, the demand of energy is increasing day by day. Simultaneously, the worldwide bio-ethanol production is increasing constantly. The maize, sugarcane ...and sugar beets are major traditional agricultural crops used as bio-ethanol production but these crops are unable to meet the global demand of bio-ethanol production due to their primary value of food and feed. Hence, cellulosic materials such as agro-residues are attractive feedstock for bio-ethanol production. The cellulosic material is the most abundant biomass and agro-residues on the earth. Bio-ethanol from agro-residues could be a promising technology that involves four processes of pre-treatment, enzymatic hydrolysis, fermentation and distillation. These processes have several challenges and limitations such as biomass transport and handling, and efficient pre-treatment process for removing the lignin from the lignocellulosic agro-residues. Proper pre-treatment process may increase the concentrations of fermentable sugars after enzymatic hydrolysis, thereby improving the efficiency of the whole process. Others, efficient microbes and genetically modified microbes may also enhance the enzymatic hydrolysis. Conversion of cellulose to ethanol requires some new pre-treatment, enzymatic and fermentation technologies, to make the whole process cost effective. In this review, we have discussed about current technologies for sustainable bioethanol production from agro-residues.
To further improve the intrinsic reactivity of single-atom catalysts (SACs), the controllable modification of a single site by coordinating with a second neighboring metal atom, developing ...double-atom catalysts (DACs), affords new opportunities. Here we report a catalyst that features two bonded Fe–Co double atoms, which is well represented by an FeCoN6(OH) ensemble with 100% metal dispersion, that work together to switch the reaction mechanism in alcohol dehydrogenation under oxidant-free conditions. Compared with Fe-SAC and Co-SAC, FeCo-DAC displays higher activity performance, yielding the desired products in up to 98% yields. Moreover, a broad diversity of benzyl alcohols and aliphatic alcohols convert into the corresponding dehydrogenated products with excellent yields and high selectivity. The kinetic reaction results show that lower activation energy is obtained by FeCo-DAC than that by Fe-SAC and Co-SAC. Moreover, computational studies demonstrate that the reaction path by DACs is different from that by SACs, providing a rationale for the observed enhancements.
Yeast to directly convert cellulose and, especially, the microcrystalline cellulose into bioethanol, was engineered through display of minicellulosomes on the cell surface of Saccharomyces cerevisiae .... The construction and cell surface attachment of cellulosomes were accomplished with two individual miniscaffoldins to increase the display level. All of the cellulases including a celCCA (endoglucanase), a celCCE (cellobiohydrolase), and a Ccel_2454 (β-glucosidase) were cloned from Clostridium cellulolyticum , ensuring the thermal compatibility between cellulose hydrolysis and yeast fermentation. Cellulases and one of miniscaffoldins were secreted by α-factor; thus, the assembly and attachment to anchoring miniscaffoldin were accomplished extracellularly. Immunofluorescence microscopy, flow cytometric analysis (FACS), and cellulosic ethanol fermentation confirmed the successful display of such complex on the yeast surface. Enzyme–enzyme synergy, enzyme-proximity synergy, and cellulose–enzyme–cell synergy were analyzed, and the length of anchoring miniscaffoldin was optimized. The engineered S. cerevisiae was applied in fermentation of carboxymethyl cellulose (CMC), phosphoric acid-swollen cellulose (PASC), or Avicel. It showed a significant hydrolytic activity toward microcrystalline cellulose, with an ethanol titer of 1,412 mg/L. This indicates that simultaneous saccharification and fermentation of crystalline cellulose to ethanol can be accomplished by the yeast, engineered with minicellulosome.
The production of cellulosic ethanol was carried out using samples of native (NCB) and ethanol-extracted (EECB) sugarcane bagasse. Autohydrolysis (AH) exhibited the best glucose recovery from both ...samples, compared to the use of both H3PO4 and H2SO4 catalysis at the same pretreatment time and temperature. All water-insoluble steam-exploded materials (SEB-WI) resulted in high glucose yields by enzymatic hydrolysis. SHF (separate hydrolysis and fermentation) gave ethanol yields higher than those obtained by SSF (simultaneous hydrolysis and fermentation) and pSSF (pre-hydrolysis followed by SSF). For instance, AH gave 25, 18 and 16 g L(-1) of ethanol by SHF, SSF and pSSF, respectively. However, when the total processing time was taken into account, pSSF provided the best overall ethanol volumetric productivity of 0.58 g L(-1) h(-1). Also, the removal of ethanol-extractable materials from cane bagasse had no influence on the cellulosic ethanol production of SEB-WI, regardless of the fermentation strategy used for conversion.
•Seven strategies were employed to produce ethanol from mixed CF and CS.•Three corn to CS ratios were applied for ethanol production from mixed CF and CS.•The performance of different integration ...methods varies with the ratio of CF to CS.•Highest ethanol titer of 99.3 g/L was obtained when the ratio of CF:CS was 20%:10%.•Mixing liquefied CF with 6 h hydrolyzed CS led to the highest ethanol productivity.
This work investigated all possible process integration strategies for ethanol production from corn and dilute acid pretreated corn stover (CS) as mixed substrates. Three corn to pretreated CS ratios (20%:10%, 10%:20% and 5%:25%) were examined. When the ratio of corn to pretreated CS was 20%:10%, the process integration strategy that mixed corn with CS hydrolysate for liquefaction followed by SSF resulted in the highest ethanol titer of 99.3 g/L. Mixing liquefied corn with pretreated CS for hydrolysis/saccharification followed by fermentation was the best strategy for the other two ratios. The strategy of mixing liquefied corn with pretreated CS for 6 h hydrolysis followed by fermentation showed the highest productivity for all the tested ratios.
The cost of biodiesels varies depending on the feedstock, geographic area, methanol prices, and seasonal variability in crop production. Most of the biodiesel is currently made from soybean, ...rapeseed, and palm oils. However, there are large amounts of low-cost oils and fats (e.g., restaurant waste, beef tallow, pork lard, and yellow grease) that could be converted to biodiesel. The crop types, agricultural practices, land and labor costs, plant sizes, processing technologies and government policies in different regions considerably vary ethanol production costs and prices by region. The cost of producing bioethanol in a dry mill plant currently totals US$1.65/galon. The largest ethanol cost component is the plant feedstock. It has been showed that plant size has a major effect on cost. The plant size can reduce operating costs by 15–20%, saving another $0.02–$0.03 per liter. Thus, a large plant with production costs of $0.29 per liter may be saving $0.05–$0.06 per liter over a smaller plant. Viscosity of biofuel and biocrude varies greatly with the liquefaction conditions. The high and increasing viscosity indicates a poor flow characteristic and stability. The increase in the viscosity can be attributed to the continuing polymerization and oxidative coupling reactions in the biocrude upon storage. Although stability of biocrude is typically better than that of bio-oil, the viscosity of biocrude is much higher. The bio-oil produced by flash pyrolysis is a highly oxygenated mixture of carbonyls, carboxyls, phenolics and water. It is acidic and potentially corrosive. Bio-oil can also be potentially upgraded by hydrodeoxygenation. The liquid, termed biocrude, contains 60% carbon, 10–20
wt.% oxygen and 30–36
MJ/kg heating value as opposed to <1
wt.% and 42–46
MJ/kg for petroleum.
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