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1.
The effects of initial culture pH ranging from 5.0 to 7.5 on biomass content, precursor 3-hydroxy-2-butanone (HB) accumulation,
and 2,3,5,6-tetramethylpyrazine (TTMP) formation by Bacillus subtilis CCTCC M 208157 were investigated in shake flask fermentation. Weak acidic conditions were found to favor cell growth and
precursor HB accumulation, while TTMP could be synthesized more efficiently in conditions with initial pH towards neutrality.
Batch bioprocess of TTMP fermentation by Bacillus subtilis CCTCC M 208157 at various controlled pH values ranging from 5.5 to 7.0 was then examined in 7.5-l fermentor. The results
suggested that optimum pH for cell growth and precursor HB accumulation was 5.5 with maximum cell growth rate (Q
x) and precursor HB accumulation rate (Q
HB) of 0.833 g l−1 h−1 and 1.118 g l−1 h−1, respectively, while optimum pH for TTMP formation was 7.0 with maximum TTMP formation rate (Q
TTMP) of 0.095 g l−1 h−1. A pH-shifted strategy was accordingly developed to improve TTMP production in bioreactor fermentation by shifting the culture
pH from 5.5 to 7.0 after 48 h of cultivation. By applying the strategy, final TTMP concentration of 7.43 g l−1 was obtained, being 22.2% greater than that of constant-pH fermentation. 相似文献
2.
Compared with steady state, oscillation in continuous very-high-gravity ethanol fermentation with Saccharomyces cerevisiae improved process productivity, which was thus introduced for the fermentation system composed of a tank fermentor followed
by four-stage packed tubular bioreactors. When the very-high-gravity medium containing 280 g l−1 glucose was fed at the dilution rate of 0.04 h−1, the average ethanol of 15.8% (v/v) and residual glucose of 1.5 g l−1 were achieved under the oscillatory state, with an average ethanol productivity of 2.14 g h−1 l−1. By contrast, only 14.8% (v/v) ethanol was achieved under the steady state at the same dilution rate, and the residual glucose was as high as 17.1 g l−1, with an ethanol productivity of 2.00 g h−1 l−1, indicating a 7% improvement under the oscillatory state. When the fermentation system was operated under the steady state
at the dilution rate of 0.027 h−1 to extend the average fermentation time to 88 h from 59 h, the ethanol concentration increased slightly to 15.4% (v/v) and residual glucose decreased to 7.3 g l−1, correspondingly, but the ethanol productivity was decreased drastically to 1.43 g h−1 l−1, indicating a 48% improvement under the oscillatory state at the dilution rate of 0.04 h−1. 相似文献
3.
Lakkana Laopaiboon Pornthap Thanonkeo Prasit Jaisil Pattana Laopaiboon 《World journal of microbiology & biotechnology》2007,23(10):1497-1501
Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations.
The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 108 cells ml−1 and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y
ps) and productivity (Q
p
) were 100 g l−1, 0.42 g g−1 and 1.67 g l−1 h−1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar
concentration of 24 °Bx was one-time substrate feeding, where P, Y
ps and Q
p
were 120 g l−1, 0.48 g g−1 and 1.11 g l−1 h−1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of
ethanol concentration and product yield. 相似文献
4.
Kamakshi Gupta P. K. Mishra Pradeep Srivastava 《Biotechnology and Bioprocess Engineering》2009,14(2):207-212
Lovastatin, a hypocholesterolemic agent, is a secondary metabolite produced by filamentous microorganism Aspergillus terreus in submerged batch cultivation. Lovastatin production by pellets and immobilized siran cells was investigated in an airlift
reactor. The process was carried out by submerged cultivation in continuous mode with the objective of increasing productivity
using pellet and siran supported growth of A terreus. The continuous mode of fermentation improves the rate of lovastatin production. The effect of dilution rate and aeration
rate were studied in continuous culture. The optimum dilution rate for pellet was 0.02 h−1 and for siran carrier was 0.025 h−1. Lovastatin productivity using immobilized siran carrier (0.0255 g/L/h) was found to be greater than pellets (0.022 g/L/h).
The productivity by both modes of fermentation was found higher than that of batch process which suggests that continuous
cultivation is a promising strategy for lovastatin production. 相似文献
5.
Fermentative production of solvents (acetone, butanol, and ethanol) by Clostridium acetobutylicum is generally a biphasic process consisting of acidogenesis and solventogenesis. We report that the biphasic metabolism of
C. acetobutylicum could be changed by oxidoreduction potential (ORP) regulation. When using air to control the ORP of the fermentation broth
at −290 mV, an earlier initiation of solventogenesis was achieved. Solvent production reached 25.6 g l−1 (2.8 g acetone l−1, 16.8 g butanol l−1, 6.0 g ethanol l−1), a 35% increase compared with the ORP uncontrolled process. Metabolic flux analysis revealed that there was a general increase
of the central carbon flux in the first 24 h of fermentation when ORP was controlled at −290 mV, compared with the control.
Specifically, the solvent ratio (acetone:butanol:ethanol) was changed from 25:64:11 to 11:66:23 at ORP level of −290 mV, which
might have resulted from the rigidity at acetyl-CoA node and the flexibility at acetoacetyl-CoA and butyryl-CoA nodes in response
to ORP regulation. 相似文献
6.
Cui Fengjie Li Yin Liu Zhiqiang Zhao Hui Ping Lifeng Ping Liying Yang Yinan Xue Yaping Yan Lijiao 《World journal of microbiology & biotechnology》2009,25(4):721-725
The objective of this study was to maximize production of xylanase by a newly isolated strain Penicillium thiersii ZH-19. Response surface methodology was employed to study the effects of significant factors such as pH, temperature, xylan
concentration, and cultivation time, on the production of xylanase by Penicillium thiersii ZH-19. The optimal fermentation parameters for enhanced xylanase production were found to be pH 7.72, temperature 24.8°C, xylan
13.2 g l−1 and the fermentation time 125.8 h. The model predicted a xylanase activity of 75.24 U ml−1. Verification of the optimization showed that the maximum xylanase production reached 73.50 U mL−1 in the flask experiments and 80.23 U mL−1 in the scale of 15-L fermenter under the optimal condition. 相似文献
7.
Maltose and yeast extract were the most favourable carbon and nitrogen sources for exopolysaccharide production by submerged
culture of Shiraia bambusicola WZ-003, and initial maltose and yeast extract concentrations were at 30 and 3 g l−1, respectively. Plant oils could increase the mycelial growth and exopolysaccharide production in tested concentration. K+ and Mg2+ could enhance the mycelial growth and exopolysaccharide biosynthesis. The optimal cultivation temperature and initial pH
were found to be 26°C and 6.0, respectively. Exopolysaccharide concentration reached 0.53 g l−1 in 15-l fermenter under optimal nutritional conditions. 相似文献
8.
Anjali Madhavan Sriappareddy Tamalampudi Aradhana Srivastava Hideki Fukuda Virendra S. Bisaria Akihiko Kondo 《Applied microbiology and biotechnology》2009,82(6):1037-1047
Previously, a Saccharomyces cerevisiae strain was engineered for xylose assimilation by the constitutive overexpression of the Orpinomyces xylose isomerase, the S. cerevisiae xylulokinase, and the Pichia stipitis SUT1 sugar transporter genes. The recombinant strain exhibited growth on xylose, under aerobic conditions, with a specific growth
rate of 0.025 h−1, while ethanol production from xylose was achieved anaerobically. In the present study, the developed recombinant yeast was
adapted for enhanced growth on xylose by serial transfer in xylose-containing minimal medium under aerobic conditions. After
repeated batch cultivations, a strain was isolated which grew with a specific growth rate of 0.133 h−1. The adapted strain could ferment 20 g l−1 of xylose to ethanol with a yield of 0.37 g g−1 and production rate of 0.026 g l−1 h−1. Raising the fermentation temperature from 30°C to 35°C resulted in a substantial increase in the ethanol yield (0.43 g g−1) and production rate (0.07 g l−1 h−1) as well as a significant reduction in the xylitol yield. By the addition of a sugar complexing agent, such as sodium tetraborate,
significant improvement in ethanol production and reduction in xylitol accumulation was achieved. Furthermore, ethanol production
from xylose and a mixture of glucose and xylose was also demonstrated in complex medium containing yeast extract, peptone,
and borate with a considerably high yield of 0.48 g g−1. 相似文献
9.
Fermentation of high concentrations of lactose to ethanol by engineered flocculent Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
The development of microorganims that efficiently ferment lactose has a high biotechnological interest, particularly for cheese
whey bioremediation processes with simultaneous bio-ethanol production. The lactose fermentation performance of a recombinant
Saccharomyces cerevisiae flocculent strain was evaluated. The yeast consumed rapidly and completely lactose concentrations up to 150 g l−1 in either well- or micro-aerated batch fermentations. The maximum ethanol titre was 8% (v/v) and the highest ethanol productivity
was 1.5–2 g l−1 h−1, in micro-aerated fermentations. The results presented here emphasise that this strain is an interesting alternative for
the production of ethanol from lactose-based feedstocks. 相似文献
10.
A recombinant putative β-galactosidase from Thermoplasma acidophilum was purified as a single 57 kDa band of 82 U mg−1. The molecular mass of the native enzyme was 114 kDa as a dimer. Maximum activity was observed at pH 6.0 and 90°C. The enzyme
was unstable below pH 6.0: at pH 6 its half-life at 75°C was 28 days but at pH 4.5 was only 13 h. Catalytic efficiencies decreased
as p-nitrophenyl(pNP)-β-d-fucopyranoside (1067) > pNP-β-d-glucopyranoside (381) > pNP-β-d-galactopyranoside (18) > pNP-β-d-mannopyranoside (11 s−1 mM−1), indicating that the enzyme was a β-glycosidase. 相似文献
11.
Butanol, a four-carbon primary alcohol (C4H10O), is an important industrial chemical and has a good potential to be used as a superior biofuel. Bio-based production of
butanol from renewable feedstock is a promising and sustainable alternative to substitute petroleum-based fuels. Here, we
report the development of a process for butanol production from glycerol, which is abundantly available as a byproduct of
biodiesel production. First, a hyper butanol producing strain of Clostridium pasteurianum was isolated by chemical mutagenesis. The best mutant strain, C. pasteurianum MBEL_GLY2, was able to produce 10.8 g l−1 butanol from 80 g l−1 glycerol as compared to 7.6 g l−1 butanol produced by the parent strain. Next, the process parameters were optimized to maximize butanol production from glycerol.
Under the optimized batch condition, the butanol concentration, yield, and productivity of 17.8 g l−1, 0.30 g g−1, and 0.43 g l−1 h−1 could be achieved. Finally, continuous fermentation of C. pasteurianum MBEL_GLY2 with cell recycling was carried out using glycerol as a major carbon source at several different dilution rates.
The continuous fermentation was run for 710 h without strain degeneration. The acetone–butanol–ethanol productivity and the
butanol productivity of 8.3 and 7.8 g l−1 h−1, respectively, could be achieved at the dilution rate of 0.9 h−1. This study reports continuous production of butanol with reduced byproducts formation from glycerol using C. pasteurianum, and thus could help design a bioprocess for the improved production of butanol. 相似文献
12.
An innovative consecutive batch fermentation process for very high gravity ethanol fermentation with self-flocculating yeast 总被引:1,自引:0,他引:1
An innovative consecutive batch fermentation process was developed for very high gravity (VHG) ethanol fermentation with the
self-flocculating yeast under high biomass concentration conditions. On the one hand, the high biomass concentration significantly
shortened the time required to complete the VHG fermentation and the duration of yeast cells suffering from strong ethanol
inhibition, preventing them from losing viability and making them suitable for being repeatedly used in the process. On the
other hand, the separation of yeast cells from the fermentation broth by sedimentation instead of centrifugation, making the
process economically more competitive. The VHG medium composed of 255 g L−1 glucose and 6.75 g L−1 each of yeast extract and peptone was fed into the fermentation system for nine consecutive batch fermentations, which were
completed within 8–14 h with an average ethanol concentration of 15% (v/v) and ethanol yield of 0.464, 90.8% of its theoretical value of 0.511. The average ethanol productivity that was calculated
with the inclusion of the downstream time for the yeast flocs to settle from the fermentation broth and the supernatant to
be removed from the fermentation system was 8.2 g L−1 h−1, much higher than those previously reported for VHG ethanol fermentation and regular ethanol fermentation with ethanol concentration
around 12% (v/v) as well. 相似文献
13.
Liu Y Sha Q Wu S Wang J Yang L Sun W 《Journal of industrial microbiology & biotechnology》2006,33(4):274-282
A microorganism with the ability to catalyze the resolution of racemic phenyloxirane was isolated and identified as Aspergillus niger SQ-6. Chiral capillary electrophoresis was successfully applied to separate both phenyloxirane and phenylethanediol. The
epoxide hydrolase (EH) involved in this resolution process was (R)-stereospecific and constitutively expressed. When whole cells were used during the biotransformation process, the optimum
temperature and pH for stereospecific vicinal diol production were 35°C and 7.0, respectively. After a 24-h conversion, the
enantiomer excess of (R)-phenylethanediol produced was found to be >99%, with a conversion rate of 56%. In fed-batch fermentations at 30°C for 44 h,
glycerol (20 g L−1) and corn steep liquor (CSL) (30 g L−1) were chosen as the best initial carbon and nitrogen sources, and EH production was markedly improved by pulsed feeding of
sucrose (2 g L−1 h−1) and continuous feeding of CSL (1 g L−1 h−1) at a fermentation time of 28 h. After optimization, the maximum dry cell weight achieved was 24.5±0.8 g L−1; maximum EH production was 351.2±13.1 U L−1 with a specific activity of 14.3±0.5 U g−1. Partially purified EH exhibited a temperature optimum at 37°C and pH optimum at 7.5 in 0.1 M phosphate buffer. This study
presents the first evidence for the existence of a predicted epoxide racemase, which might be important in the synthesis of
epoxide intermediates. 相似文献
14.
Liu S Skinner-Nemec KA Leathers TD 《Journal of industrial microbiology & biotechnology》2008,35(2):75-81
Lactobacillus buchneri strain NRRL B-30929 was isolated from a fuel ethanol production facility. This heterofermentative, facultative anaerobe can
utilize xylose as a sole carbon source and tolerates up to 12% ethanol. Carbohydrate utilization (API, Biomerieux) and Phenotype
Microarrays™ (PM, Biolog) analyses indicated that the strain is able to metabolize a broad spectrum of carbon sources including
various monosaccharides (C5 and C6), disaccharides and oligosaccharides, with better rates under anaerobic conditions. In
pH-controlled bioreactors, the bacterium consumed xylose and glucose simultaneously at high concentrations (125 g L−1, pH 6.0). The major fermentation products were lactate (52 g L−1), acetate (26 g L−1) and ethanol (12 g L−1). The strain ferments glucose alone (pH 4.0) into lactate and ethanol with a molar ratio of 1.03:1. This strain will be further
explored via genetic engineering for potential applications in biomass conversion.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the names by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
15.
Yin Li Zhiqiang Liu Fengjie Cui Yingying Xu Hui Zhao 《World journal of microbiology & biotechnology》2007,23(6):837-843
A new strain of Penicillium sp. ZH-30 that produces xylanase was isolated from soil. According to the morphology and comparison of internal transcribed
spacer (ITS) rDNA gene sequence, the strain Penicillium sp. ZH-30 was identified as a strain of Penicillium oxalicum. When xylan or wheat bran was used as substrate at 30°C for 3 days under submerged cultivation, xylanase production was 5.3
and 13.3 U ml−1, respectively. The temperature and pH for optimum activity were 50°C and 5.0–6.0, respectively. 相似文献
16.
Chen XS Li S Liao LJ Ren XD Li F Tang L Zhang JH Mao ZG 《Bioprocess and biosystems engineering》2011,34(5):561-567
The production of ε-poly-l-lysine (ε-PL) by Streptomyces sp. M-Z18 from glycerol was investigated in a 5-L jar-fermenter. Batch fermentations by Streptomyces sp. M-Z18 at various pH values ranging from 3.5 to 4.5 were studied. Based on the analysis of the time course of specific
cell growth rate and specific ε-PL formation rate, a novel two-stage pH control strategy was developed to improve ε-PL production
by shifting the culture pH from 3.5 to 3.8 after 36 h of cultivation. By applying the strategy, the maximal ε-PL concentration
and productivity had a significant improvement and reached 9.13 g L−1 and 4.76 g L−1 day−1, respectively, compared with those in one-stage pH control process where the pH value is controlled at 3.5 (7.83 g L−1 and 3.13 g L−1 day−1). Fed-batch fermentation with two-stage pH control strategy was also applied to produce ε-PL; final ε-PL concentration of
30.11 g L−1 was obtained, being 3.3-fold greater than that of batch fermentation. To our knowledge, it is the first report on production
of ε-PL from glycerol in fermenter scale and achievement of high ε-PL production with two-stage pH control strategy. 相似文献
17.
Mahapatra P Kumari A Garlapati VK Banerjee R Nag A 《Indian journal of microbiology》2010,50(4):396-403
Extracellular lipase was produced from Rhizopus oligosporus NRRL 5905 through solid state fermentation (SSF). To provide an optimum fermentation conditions for maximum lipase yield,
five process variables (temperature, liquid–solid ratio, pH, incubation period and spore concentration) were optimized using
evolutionary operation (EVOP) factorial design technique taking into account the interaction between the process variables.
Optimization through EVOP resulted in around 3 fold increase in lipase activity (77 U gds−1) at a liquid–solid ratio of 1.5:1, fermentation temperature of 35°C, initial fermentation pH 6, incubation period 5 days
and a spore concentration of 108 spores ml−1. 相似文献
18.
Gonzalez-Contreras P Weijma J Buisman CJ 《Applied microbiology and biotechnology》2012,93(3):1295-1303
The extreme acid conditions required for scorodite (FeAsO4·2H2O) biomineralization (pH below 1.3) are suboptimal for growth of most thermoacidophilic Archaea. With the objective to develop
a continuous process suitable for biomineral production, this research focuses on growth kinetics of thermoacidophilic Archaea
at low pH conditions. Ferrous iron oxidation rates were determined in batch-cultures at pH 1.3 and a temperature of 75°C for
Acidianus sulfidivorans, Metallosphaera prunea and a mixed Sulfolobus culture. Ferrous iron and CO2 in air were added as sole energy and carbon source. The highest growth rate (0.066 h−1) was found with the mixed Sulfolobus culture. Therefore, this culture was selected for further experiments. Growth was not stimulated by increase of the CO2 concentration or by addition of sulphur as an additional energy source. In a CSTR operated at the suboptimal pH of 1.1, the
maximum specific growth rate of the mixed culture was 0.022 h−1, with ferrous iron oxidation rates of 1.5 g L−1 d−1. Compared to pH 1.3, growth rates were strongly reduced but the ferrous iron oxidation rate remained unaffected. Influent
ferrous iron concentrations above 6 g L−1 caused instability of Fe2+ oxidation, probably due to product (Fe3+) inhibition. Ferric-containing, nano-sized precipitates of K-jarosite were found on the cell surface. Continuous cultivation
stimulated the formation of an exopolysaccharide-like substance. This indicates that biofilm formation may provide a means
of biomass retention. Our findings showed that stable continuous cultivation of a mixed iron-oxidizing culture is feasible
at the extreme conditions required for continuous biomineral formation. 相似文献
19.
Biofilms formed by the green alga Trentepohlia aurea could be a useful tool in the removal of nitrate and phosphate from water. When a prepared biofilter was dampened with medium
and incubated under low light intensity (10 μmol photons m−2 s−1) between 5 and 50 μmol photons m−2 s−1, the efficiency of removal of inorganic compounds from water was higher without the decomposition of chlorophylls in the
cells. Algal cells immobilized on a glass fiber filter could be kept for 12 weeks under dark conditions at 4°C in the refrigerator.
We tried to construct a laboratory-scale photobioreactor for the removal of inorganic nitrogen and phosphate from water by
the biofilm. In this study, the synthetic wastewater was prepared by diluting 18-fold Bold’s basal medium with deionized water.
The photobioreactor could efficiently remove nitrate and phosphate from the synthetic wastewater under continuous illumination.
The removal ability of nitrate and phosphate per sheet of the biofilter in the photobioreactor exhibited about an 8- and 16-fold
increase, respectively, in 3 days, compared with the bath experimental results. This study showed that the cycling of wastewater
in the reactor by the pump led to a significant improvement in the efficiency of the inorganic ion uptake from water. 相似文献
20.
Yue Shi Xiu-tao Zhao Peng Cao Yinyin Hu Liang Zhang Yan Jia Zeqi Lu 《Biotechnology letters》2009,31(9):1327-1333
In order to treat the kitchen wastes and produce hydrogen, anaerobic fermentation technology was used in this experiment.
The results showed that the fermentation type changed from mixed acid fermentation to ethanol fermentation in a continuous
stirred tank reactor (CSTR) 22 days after start-up. The maximum efficiency of hydrogen bio-production in the CSTR was 4.77 LH2/(L reactor d) under the following conditions: organic loading rate (OLR) of 32–50 kg COD/(m3 d), oxidation reduction potential (ORP) of −450 to −400 mV, influent pH value of 5.0–6.0, effluent pH value of 4.0–4.5, influent
alkalinity of 300–600 mg/l, temperature of 35 ± 1°C and hydraulic retention time (HRT) of 7 h. An artificial neural network
(ANN) model was established, and each parameter influencing the performance of the reactor was compared using the method of
partitioning connection weights (PCW). The results showed that OLR, pH, ORP and alkalinity could influence the fermentation
characteristics and hydrogen yield of the anaerobic activated sludge; with an influence hierarchy: OLR > pH values > ORP > alkalinity.
An economic analysis showed that the cost of producing hydrogen in this experiment was less than the cost of electrolysis
of water. 相似文献