摘要 :
We investigated the influence of immobilization of bacterial cells and photocatalytic material TiO_2 on the degradation of phenol by conducting batch microcosm studies consisting of suspended, immobilized cells and immobilized TiO...
展开
We investigated the influence of immobilization of bacterial cells and photocatalytic material TiO_2 on the degradation of phenol by conducting batch microcosm studies consisting of suspended, immobilized cells and immobilized TiO_2 at various initial phenol concentrations (50-1,000 mgL~(-1)). Results showed that both suspended and immobilized cells were concentration-dependent, exhibiting the increasing degradation rate with the concentration of up to 500 mgL~(-1) above which it declined. The degradation rate of 0.39-3.47 mgL~(-1)h~(-1) by suspended cells was comparable with those of the literature. Comparison of the degradation rates between suspended, immobilized cells and immobilized TiO_2 revealed that immobilized cells achieved the highest degradation rate followed by immobilized TiO_2 and suspended cells due to the toxicity of phenol at the high concentration of 1,000 mgL~(-1). This indicates that immobilization of bacterial cells or photocatalytic materials can serve a better alternative to offer the higher degradation efficiency at high phenol concentrations.
收起
摘要 :
A novel biofiltration of pure culture was developed for H2S removal from synthetic biogas using Alcaligenes faecalis T307 immobilized on granular activated carbon (GAC) as packing materials. The effect of operating parameters, inc...
展开
A novel biofiltration of pure culture was developed for H2S removal from synthetic biogas using Alcaligenes faecalis T307 immobilized on granular activated carbon (GAC) as packing materials. The effect of operating parameters, including inlet H2S concentration, H2S flow rate, air flow rate, and height of media on the removal efficiency, was evaluated, together with a product analysis during long-term operation. Besides, the kinetics analysis of biofiltration was also studied. The experiment was performed in three biofilters. Biofilters A and B were packed with 20 and 40 cm of A. faecalis T307 immobilized GAC, respectively. Biofilter C as a control set was packed with 40 cm of the GAC without cell immobilization. The result showed that H2S removal efficiency of biofilters with A. faecalis T307 immobilized GAC was higher than 95% at high inlet concentrations (200-4000 ppm). Moreover, the complete H2S removal (100%) was found in biofilters A and B at H2S and air flow rate of 35 and 5.86 I h(-1), respectively. Product analysis of biofilters with A. faecalis T307 immobilized GAC was performed during the long-term operation (60 days). It was found that the major product was elemental sulfur and there was only a little of sulfate ions formed. In addition, the height of media did not significantly affect the H2S removal efficiency when the oxygen was sufficient at air flow rate of 5.8 I h(-1). Furthermore, in kinetic analysis, the maximum removal rate and saturation constant of H2S were calculated to be V-m = 1.1 kg m(-3) s(-1) and K-s = 5.2 g m(-3), respectively. (C) 2010 Elsevier Ltd. All rights reserved.
收起
摘要 :
A simple, rapid and reproducible procedure for the identification of extracellular cucumber (Cucumis sativus L.) alpha -galactosidase is described using callus cultures of seedlings from the tested plant, hairy roots of 2-day-old ...
展开
A simple, rapid and reproducible procedure for the identification of extracellular cucumber (Cucumis sativus L.) alpha -galactosidase is described using callus cultures of seedlings from the tested plant, hairy roots of 2-day-old seedlings of cucumber germinating on agar plates as well as cell suspension cultures derived from callus cultures. For the determination of the intracellular and extracellular activities of alpha -galactosidase, 6-bromo-2-naphthyl-alpha -D-galactopyranoside and p-nitrophenyl-alpha -D-galactopyranoside, respectively, were used as synthetic substrates.
收起
摘要 :
Gibberellic acid production was studied in different fermentation systems.Free and immobilized cells of Gibberella fujikuroi cultures in shake-flask,stirred and fixed-bed reactors were evaluated for the production of gibberellic a...
展开
Gibberellic acid production was studied in different fermentation systems.Free and immobilized cells of Gibberella fujikuroi cultures in shake-flask,stirred and fixed-bed reactors were evaluated for the production of gibberellic acid (GA3).Gibberellic acid production with free cells cultured in a stirred reactor reached 0.206 g/L and a yield of 0.078 g of GA3/g biomass.
收起
摘要 :
In recent years immobilized cells have commonly been used for various biotechnological applications, e.g., antibiotic production, soil bioremediation, biodegradation and biotransformation of xenobiotics in wastewater treatment pla...
展开
In recent years immobilized cells have commonly been used for various biotechnological applications, e.g., antibiotic production, soil bioremediation, biodegradation and biotransformation of xenobiotics in wastewater treatment plants. Although the literature data on the physiological changes and behaviour of cells in the immobilized state remain fragmentary, it is well documented that in natural settings microorganisms are mainly found in association with surfaces, which results in biofilm formation. Biofilms are characterized by genetic and physiological heterogeneity and the occurrence of altered microenvironments within the matrix. Microbial cells in communities display a variety of metabolic differences as compared to their free-living counterparts. Immobilization of bacteria can occur either as a natural phenomenon or as an artificial process. The majority of changes observed in immobilized cells result from protection provided by the supports. Knowledge about the main physiological responses occurring in immobilized cells may contribute to improving the efficiency of immobilization techniques. This paper reviews the main metabolic changes exhibited by immobilized bacterial cells, including growth rate, biodegradation capabilities, biocatalytic efficiency and plasmid stability.
收起
摘要 :
The nitrilase from Alcaligenes faecalis ECU0401 belongs to the category of arylacetonitrilase, which could hydrolyze 2-chloromandelonitrile, 3,4-dimethoxyphenylacetonitrile, mandelonitrile, and phenylacetonitrile into the correspo...
展开
The nitrilase from Alcaligenes faecalis ECU0401 belongs to the category of arylacetonitrilase, which could hydrolyze 2-chloromandelonitrile, 3,4-dimethoxyphenylacetonitrile, mandelonitrile, and phenylacetonitrile into the corresponding arylacetic acids. To overcome the permeability barrier and prepare whole cell biocatalysts with high activities, permeabilization of Alcaligenes faecalis ECU0401 in relation to nitrilase activity was optimized by using cetyltrimethylammonium bromide (CTAB) as permeabilizing agent. The nitrilase activity from Alcaligenes faecalis ECU0401 increased 4.5-fold when the cells were permeabilized with 0.3% (w/v) CTAB for 20 min at 25A degrees C and pH 6.5. Consequently, almost all the mandelonitrile was consumed and converted to (R)-(-)-mandelic acid with greater than 99.9% enantiomeric excess (e.e.) by the CTAB-permeabilized cells. The permeability barrier has been significantly reduced in the hydrolysis of mandelonitrile by using CTAB-permeabilized cells and a dynamic resolution was successfully achieved, giving a 100% theoretical yield of (R)-(-)-mandelic acid. Efficient biocatalyst recycling was achieved as a result of cell immobilization in calcium alginate, with a product-to-biocatalyst ratio of 3.82 g (R)-(-)-mandelic acid g(-1) dry cell weight (dcw) cell after 20 cycles of repeated use.
收起
摘要 :
Petroleum contamination of marine environments due to exploitation and accidental spills causes serious harm to ecosystems. Bioremediation with immobilized microorganisms is an environmentally friendly and cost-effective emerging ...
展开
Petroleum contamination of marine environments due to exploitation and accidental spills causes serious harm to ecosystems. Bioremediation with immobilized microorganisms is an environmentally friendly and cost-effective emerging technology for treating oil-polluted environments. In this study, Bacillus licheniformis was entrapped in Ca alginate beads using the electrospray technique for light crude oil biodegradation. Three important process variables, including inoculum size (5–15% v/v), initial oil concentration (1500–3500 ppm), and NaCl concentration (0–30 g/L), were optimized to obtain the best response of crude oil removal using response surface methodology (RSM) and Box–Behnken design (BBD). The highest crude oil removal of 79.58% was obtained for 1500 ppm of crude oil after 14 days using immobilized cells, and it was lower for freely suspended cells (64.77%). Our result showed similar trends in the effect of variables on the oil biodegradation rate in both free cell (FC) and immobilized cell (IC) systems. However, according to the analysis of variance (ANOVA) results, the extent of the variables’ effectiveness was different in FC and IC systems. In the immobilized cell system, all variables had a greater effect on the rate of light crude oil degradation. Moreover, to evaluate the effectiveness of free and immobilized B. licheniformis in bioremediation of an actual polluted site, the crude oil spill in natural seawater was investigated. The results suggested the stability of beads in the seawater, as well as high degradation of petroleum hydrocarbons by free and immobilized cells in the presence of indigenous microorganisms.
收起
摘要 :
Surface-engineered yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis α-amylase on the cell surface was used for direct production of ethanol from uncooked raw starch. By using 50 g/L...
展开
Surface-engineered yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis α-amylase on the cell surface was used for direct production of ethanol from uncooked raw starch. By using 50 g/L cells during batch fermentation, ethanol concentration could reach 53 g/L in 7 days. During repeated batch fermentation, the production of ethanol could be maintained for seven consecutive cycles. For cells immobilized in loofa sponge, the concentration of ethanol could reach 42 g/L in 3 days in a circulating packed-bed bioreactor. However, the production of ethanol stopped thereafter because of limited contact between cells and starch. The bioreactor could be operated for repeated batch production of ethanol, but ethanol concentration dropped to 55% of its initial value after five cycles because of a decrease in cell mass and cell viability in the bioreactor. Adding cells to the bioreactor could partially restore ethanol production to 75% of its initial value.
收起
摘要 :
Surface-engineered yeast Saccharomyces cerevisiae codisplaying Rhizopusoryzae glucoamylase and Streptococcus bovis a-amylase on the cell surface was used fordirect production of ethanol from uncooked raw starch. By using 50 g/L ce...
展开
Surface-engineered yeast Saccharomyces cerevisiae codisplaying Rhizopusoryzae glucoamylase and Streptococcus bovis a-amylase on the cell surface was used fordirect production of ethanol from uncooked raw starch. By using 50 g/L cells during batchfermentation, ethanol concentration could reach 53 g/L in 7 days. During repeated batchfermentation, the production of ethanol could be maintained for seven consecutive cycles.For cells immobilized in loofa sponge, the concentration of ethanol could reach 42 g/L in3 days in a circulating packed-bed bioreactor. However, the production of ethanol stoppedthereafter because of limited contact between cells and starch. The bioreactor could beoperated for repeated batch production of ethanol, but ethanol concentration dropped to55% of its initial value after five cycles because of a decrease in cell mass and cell viabilityin the bioreactor. Adding cells to the bioreactor could partially restore ethanol production to75% of its initial value.
收起
摘要 :
A cell suspension culture of Citrullus vulgaris Schrad cv. "Samara" ℃ was permeabilized by Tween 80 and immobilized by glutaraldehyde. The highest lactase activity was achieved at pH 4.3, the temperature optimum for cell suspensi...
展开
A cell suspension culture of Citrullus vulgaris Schrad cv. "Samara" ℃ was permeabilized by Tween 80 and immobilized by glutaraldehyde. The highest lactase activity was achieved at pH 4.3, the temperature optimum for cell suspension was at 50, while for the immobilized cells the optimum was at 58 ℃. The hydrolysis of substrate was linear for 3 h, reaching 60-67% conversion rate. The cells were characterized by high enzyme activity. The stability of the enzyme showed convenient physico-mechanical properties (physical protection from shear forces and easy separation of product from biocatalysts) in long-term storage.
收起
原文获取