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Giordano Raquel L. C. Hirano Paulo C. Gonçalves Luciana R. B. Netto Willibaldo Schmidell 《Applied biochemistry and biotechnology》2000,84(1-9):643-654
This article presents a detailed study on the conditions for achieving a stable biocatalyst to be used in the production of
ethanol from starch. Different pellets were used depending on which characteristic of the biocatalyst was being studied: (a)
Saccharomyces cerevisiae entrapped in pectin or calcium alginate gel particles; (b) silica containing immobilized glucoamylase entrapped in pectin
gel particles; or (c) pectin gel particles, with the silicaenzyme derivative and yeast coimmobilized. The influence of several
variables on the mechanical resistance of the particle, on the viability of the microorganism, and on the rate of substrate
hydrolysis was studied with biocatalyst. The best conditions found were 6% pectin gel, 2-mm particle diameter, and curein
0.2 M CaCl2·2H2O/60 mM acetate buffer, pH 4.2, for gel preparation; and 6.0 g/L of CaCl2·2H2O in the fermentation medium. Biocatalyst (c) was successfully tested for the production of ethanol from liquefield manioc
flour syrup. 相似文献
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Marcio Luis Busi da Silva Hugo Moreira Soares Agenor Furigo Jr. Willibaldo Schmidell Henry Xavier Corseuil 《Applied biochemistry and biotechnology》2014,174(5):1810-1821
Column experiments were utilized to investigate the effects of nitrate injection on sulfate-reducing bacteria (SRB) inhibition and microbial enhanced oil recovery (MEOR). An indigenous microbial consortium collected from the produced water of a Brazilian offshore field was used as inoculum. The presence of 150 mg/L volatile fatty acids (VFA´s) in the injection water contributed to a high biological electron acceptors demand and the establishment of anaerobic sulfate-reducing conditions. Continuous injection of nitrate (up to 25 mg/L) for 90 days did not inhibit souring. Contrariwise, in nitrogen-limiting conditions, the addition of nitrate stimulated the proliferation of δ-Proteobacteria (including SRB) and the associated sulfide concentration. Denitrification-specific nirK or nirS genes were not detected. A sharp decrease in water interfacial tension (from 20.8 to 14.5 mN/m) observed concomitantly with nitrate consumption and increased oil recovery (4.3 % v/v) demonstrated the benefits of nitrate injection on MEOR. Overall, the results support the notion that the addition of nitrate, at this particular oil reservoir, can benefit MEOR by stimulating the proliferation of fortuitous biosurfactant-producing bacteria. Higher nitrate concentrations exceeding the stoichiometric volatile fatty acid (VFA) biodegradation demands and/or the use of alternative biogenic souring control strategies may be necessary to warrant effective SRB inhibition down gradient from the injection wells. 相似文献
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Continuous Production of Ethanol from Starch Using Glucoamylase and Yeast Co-Immobilized in Pectin Gel 总被引:1,自引:0,他引:1
This work presents a continuous simultaneous saccharification and fermentation (SSF) process to produce ethanol from starch
using glucoamylase and Saccharomyces cerevisiae co-immobilized in pectin gel. The enzyme was immobilized on macroporous silica, after silanization and activation of the
support with glutaraldehyde. The silica–enzyme derivative was co-immobilized with yeast in pectin gel. This biocatalyst was
used to produce ethanol from liquefied manioc root flour syrup, in three fixed bed reactors. The initial reactor yeast load
was 0.05 g wet yeast/ml of reactor (0.1 g wet yeast/g gel), used in all SSF experiments. The enzyme concentration in the reactor
was defined by running SSF batch assays, using different amount of silica–enzyme derivative, co-immobilized with yeast in
pectin gel. The chosen reactor enzyme concentration, 3.77 U/ml, allowed fermentation to be the rate-limiting step in the batch
experiment. In this condition, using initial substrate concentration of 166.0 g/l of total reducing sugars (TRS), 1 ml gel/1 ml
of medium, ethanol productivity of 8.3 g/l/h was achieved, for total conversion of starch to ethanol and 91% of the theoretical
yield. In the continuous runs, feeding 163.0 g/l of TRS and using the same enzyme and yeast concentrations used in the batch
run, ethanol productivity was 5.9 g ethanol/l/h, with 97% of substrate conversion and 81% of the ethanol theoretical yield.
Diffusion effects in the extra-biocatalyst film seemed to be reduced when operating at superficial velocities above 3.7 × 10−4 cm/s. 相似文献
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