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1.
The use of silica gel prepared by sol-gel method and polyurethane foam as microbial carriers in the continuous degradation of phenol 总被引:5,自引:0,他引:5
A mixed microbial culture was immobilized by entrapment into silica gel (SG) and entrapment/ adsorption on polyurethane foam
(PU) and ceramic foam. The phenol degradation performance of the SG biocatalyst was studied in a packed-bed reactor (PBR),
packed-bed reactor with ceramic foam (PBRC) and fluidized-bed reactor (FBR). In continuous experiments the maximum degradation
rate of phenol (q
s
max) decreased in the order: PBRC (598 mg l−1 h−1) > PBR (PU, 471 mg l−1 h−1) > PBR (SG, 394 mg l−1 h−1) > FBR (PU, 161 mg l−1 h−1) > FBR (SG, 91 mg l−1 h−1). The long-term use of the SG biocatalyst in continuous phenol degradation resulted in the formation of a 100–200 μm thick
layer with a high cell density on the surface of the gel particles. The abrasion of the surface layer in the FBR contributed
to the poor degradation performance of this reactor configuration. Coating the ceramic foam with a layer of cells immobilized
in colloidal SiO2 enhanced the phenol degradation efficiency during the first 3 days of the PBRC operation, in comparison with untreated ceramic
packing.
Received: 2 December 1999 / Revision received: 2 February 2000 / Accepted: 4 February 2000 相似文献
2.
Biological treatment of drinking water is a cost-effective alternative to conventional physico/chemical processes. A new
concept was tested to overcome the main disadvantage of biological denitrification, the intensive post-treatment process to
remove microorganisms and remnant carbon source. The biological reaction zone and carbon supply were separated from the raw
water stream by a nitrate-permeable membrane. Denitrification takes place in a biofilm, which is immobilized at the membrane.
In a series of bench-scale runs, different types of membranes and reactor configurations were investigated. The best denitrification
rates achieved were 1230 mg NO3
−-N m−2 day−1. In one run, raw water containing 100 mg NO3
− l−1 was completely freed from nitrate. The membrane and the attached biofilm also represent a barrier against the passage of
the C source and nutrients into the raw water. At concentrations of 20 mg l−1 ethanol and 15 mg l−1 phosphate in the bioreactor no diffusion through the membrane into the treated water was observed. Without any post-treatment,
the effluent met nearly all the relevant criteria for drinking water; only the colony count was slightly increased.
Received: 18 December 1996 / Received last revision: 14 April 1997 / Accepted: 19 April 1997 相似文献
3.
Long-term performance and microbial dynamics of an up-flow fixed bed reactor established for the biodegradation of fluorobenzene 总被引:1,自引:0,他引:1
Carvalho MF Ferreira Jorge R Pacheco CC De Marco P Henriques IS Correia A Castro PM 《Applied microbiology and biotechnology》2006,71(4):555-562
An up-flow fixed bed reactor (UFBR) was established to investigate the biodegradation of fluorobenzene (FB) under a number of operating conditions, which included variation in the concentration of FB in the feed stream (up to 180 mg l−1) and temporary suspension of feeding. Degradation of FB was followed for a period of 8 months under a continuous flow regime. During the operation of the UFBR, FB was never detected in the reactor effluent, being biodegraded by the microbial biofilm or adsorbed to the granular activated carbon (GAC). Biodegradation of FB was observed from the beginning of the reactor operation, and overall, it accounted for 50% of the total amount fed to the bioreactor. High organic loads of FB (210–260 mg d−1 dm−3) were found to affect the biological removal efficiency, possibly due to an inhibitory effect caused by the higher FB concentrations fed to the bioreactor (149–179 mg l−1). When FB feeding was suspended for 1 month, biodegradation continued, indicating that the adsorbed FB became bioavailable. Biofilm bacterial dynamics were followed throughout the UFBR operation by denaturing gradient gel electrophoresis and plate-counting techniques, showing that a quite stable community was found in the bioreactor, and this was mainly attributed to the high selective pressure exerted by the presence of FB. 相似文献
4.
An efficient Agrobacterium-mediated protocol for the stable genetic transformation of Eschscholzia californica Cham. (California poppy) via somatic embryogenesis is reported. Excised cotyledons were co-cultivated with A. tumefaciens strain GV3101 carrying the pBI121 binary vector. Except for the co-cultivation medium, all formulations included 50 mg l−1 paromomycin as the selective agent and 200 mg l−1 timentin to eliminate the Agrobacterium. Four to five weeks after infection, paromomycin-resistant calli grew on 80% of explants in the presence of 2.0 mg l−1 1-naphthaleneacetic acid (NAA) and 0.1 mg l−1 6-benzylaminopurine (BAP). Calli were cultured on somatic embryogenesis induction medium containing 1.0 mg l−1 NAA and 0.5 mg l−1 BAP, and somatic embryos were visible on 30% of the paromomycin-resistant calli within 3–4 weeks. Three to four weeks after
the somatic embryos were transferred to phytohormone-free plant regeneration medium, 32% converted to paromomycin-resistant
plants. Detection of the neomycin phosphotransferase gene and high levels of β-glucuronidase (GUS) mRNA and enzyme activity, and the cytohistochemical localization of GUS activity in all plant tissues
confirmed the integrative transformation of the regenerated plants. The normal alkaloid profile of California poppy was unaffected
by the transformation process; thus, the reported protocol could serve as a valuable tool to investigate the molecular and
metabolic regulation of the benzophenanthridine alkaloid pathway.
Received: 27 October 1999 / Revision received: 6 December 1999 / Accepted: 11 January 2000 相似文献
5.
Inhibition of methane production from whey by heavy metals – protective effect of sulfide 总被引:1,自引:0,他引:1
A whey solution was used as a substrate for methane production in an anaerobic fixed-bed reactor. At a hydraulic retention
time of 10 days, equivalent to a space loading of 3.3 kg (m3 day)−1, 90% of the chemical oxygen demand was converted to biogas. Only a little propionate remained in the effluent. Toxicity tests
with either copper chloride, zinc chloride or nickel chloride were performed on effluent from the reactor. Fifty per cent
inhibition of methanogenesis was observed in the presence of ≥10 mg CuCl2 l−1≥40 mg ZnCl2 l−1 and ≥60 mg NiCl2 l−1, respectively. After exposure to Cu2+, Zn2+ or Ni2+ ions for 12 days, complete recovery of methanogenesis by equimolar sulfide addition was possible upon prolonged incubation.
Recovery failed, however, for copper chloride concentrations ≥40 mg l−1. If the sulfide was added simultaneously with the three heavy metal salts, methanogenesis was only slightly retarded and
the same amount of methane as in non-inhibited controls was reached either 1 day (40 mg ZnCl2 l−1) or 2 days later (10 mg CuCl2 l−1). Up to 60 mg NiCl2 l−1 had no effect if sulfide was present. Sulfide presumably precipitated the heavy metals as metal sulfides and by this means
prevented heavy metal toxicity.
Received: 8 October 1999 / Received revision: 3 January 2000 / Accepted: 4 January 2000 相似文献
6.
The influence of ammonia on the anaerobic degradation of peptone by mesophilic and thermophilic populations of biowaste was
investigated. For peptone concentrations from 5 g l−1 to 20 g l−1 the mesophilic population revealed a higher rate of deamination than the thermophilic population, e.g. 552 mg l−1 day−1 compared to 320 mg l−1 day−1 at 10 g l−1 peptone. The final degree of deamination of the thermophilic population was, however, higher: 102 compared to 87 mg NH3/g peptone in the mesophilic cultures. If 0.5–6.5 g l−1 ammonia was added to the mesophilic biowaste cultures, deamination of peptone, degradation of its chemical oxygen demand
(COD) and formation of biogas were increasingly inhibited, but no hydrogen was formed. The thermophilic biowaste cultures
were most active if around 1 g ammonia l−1 was present. Deamination, COD degradation and biogas production decreased at lower and higher ammonia concentrations and
hydrogen was formed in addition to methane. Studies of the inhibition by ammonia of peptone deamination, COD degradation and
methane formation revealed a K
i (50%) for NH3 of 92, 95 and 88 mg l−1 at 37 °C and 251, 274 and 297 mg l−1 at 55 °C respectively. This indicated that the thermophilic flora tolerated significantly more NH3 than the mesophilic flora. In the mesophilic reactor effluent 4.6 × 108 peptone-degrading colony-forming units (cfu)/ml were culturable, whereas in the thermophilic reactor effluent growth of only
5.6 × 107 cfu/ml was observed.
Received: 24 April 1998 / Received revision: 26 June 1998 / Accepted: 27 June 1998 相似文献
7.
Studies of microbial purification of a model waste water containing 4-nitrophenol were carried out in a continuously working
aerobic solid-bed reactor. The main emphasis was on the dynamic behaviour of the system after a sudden change in cultivation
conditions and on the steady-state performance of the reactor as a function of the pollution load. A change from ammonium-free
to ammonium-containing medium hardly influenced the nitrophenol degradation. The reactor responded differently to an increase
in pollutant load, which was brought about by increasing either the 4-nitrophenol content or the flow of the waste water.
Up to a load of 270 mg l−1 h−1 the pollutant was stably and almost completely degraded. At a higher load, only a partial 4-nitrophenol degradation took
place. A mathematical model was derived to describe the processes that occurred in the reactor. By segregation into two compartments
– the aqueous phase and the biofilm – account was taken of the fact that the pollutant is carried into the biofilm by diffusion
and is degraded there. The observed relations between the pollutant load, the pollutant concentration in the outlet of the
reactor and the reactor performance agreed with the simulated process behaviour. As the model simulation showed, the incomplete
pollutant degradation at a higher reactor load was caused by oxygen limitation.
Received: 5 August 1998 / Received revision: 22 October 1998 / Accepted: 24 October 1998 相似文献
8.
An extractive membrane biofilm reactor for degradation of 1,3-dichloropropene in industrial waste water 总被引:4,自引:0,他引:4
Katsivela E Bonse D Krüger A Strömpl C Livingston A Wittich RM 《Applied microbiology and biotechnology》1999,52(6):853-862
A bacterial biofilm, capable of mineralising a technical mixture of cis- and trans-1,3-dichloropropene (DCPE), was enriched on the biomedium side of an extractive membrane biofilm reactor (EMBR). The membrane
separates the biomedium from the industrial waste water, in terms of pH, ionic strength and the concentration of toxic chemicals.
The biofilm, attached to a silicone membrane, is able to mineralise DCPE after its diffusion through the membrane. Five bacterial
strains with degradation capabilities were isolated from the metabolically active biofilm and further investigated in batch
experiments. Two of them, Rhodococcus erythropolis strains EK2 and EK5, can grow with DCPE as the sole carbon source. Pseudomonas sp. EK1 utilises cis-3-chloroallylalcohol and cis-3-chloroacrylic acid, whereas the metabolite trans-3-chloroacrylic acid represents a dead-end product of the pathway of this strain. The other two strains, Delftia sp. EK3 and EK4, although unable to grow with DCPE as the carbon source, can transform DCPE and its upper-pathway intermediates
at reasonable conversion rates. They may represent helper functions of the biofilm consortium, which mineralised up to 12.5 mmol
DCPE per hour per gram of biomass protein. Higher feed rates in the EMBR (up to 15 mmol per hour per 100-l bioreactor volume)
and shock loads corresponding to concentrations up to 1.8 mmol l−1 led to a significant increase in the freely floating bacterial biomass in the reactor medium (OD546= 0.2). At the standard operating feed rate of 1.8 mmol h−1, the free biomass concentration was very low (OD546= 0.04).
Received: 23 April 1999 / Received revision: 1 July 1999 / Accepted: 5 July 1999 相似文献
9.
G. Zellner E. Feuerhake H. J. Jördening A. J. L. Macario E. Conway de Macario 《Applied microbiology and biotechnology》1995,43(3):566-571
A denitrifying bacterial biofilm population established on a polypropylene substratum of a fixed-film reactor was characterized
by microscopy, scanning electron microscopy and immunofluorescence after 120 days of operation. The reactor, operated at pH
7.0, 22°C, and −180 mV with synthetic wastewater containing methanol/nitrate, achieved a denitrification rate of 0.24 mol
NO-
3 l-1 day-1 with a removal efficiency for nitrate of 95%–99% at an organic loading rate of 0.325 mol methanol l-1 day-1. The gas produced contained 2%–3% (v/v) methane and 3%–4% (v/v) carbon dioxide in addition to nitrogen. The biofilm contained
mainly cells of Methanobrevibacter arboriphilus antigenically related to strain DC, short, flagellated, gram-negatively staining rods of Pseudomonas sp. antigenically related to Pseudomonas stutzeri strain AN11, non-identified pink-pigmented rods and small lemon-shaped cells with mono- and bipolar appendages resembling
prosthecate Hyphomicrobium sp. The biofilm analysis provided evidence for a syntrophy between the denitrifying, methylotrophic, bacterial consortium
and hydrogenotrophic methanogens, which were identified by antigenic fingerprinting with 17 antibody probes.
Received: 11 July 1994/Received revision: 23 September 1994/Accepted: 28 September 1994 相似文献
10.
Production of sophorolipids from whey 总被引:5,自引:0,他引:5
Otto RT Daniel HJ Pekin G Müller-Decker K Fürstenberger G Reuss M Syldatk C 《Applied microbiology and biotechnology》1999,52(4):495-501
Sophorolipids, obtained by a two-stage process starting from deproteinized whey concentrate using Cryptococcus curvatus ATCC 20509 and Candida bombicola ATCC 22214, were compared to products from one-stage processes, using different lipidic compounds as substrates. Results
showed that above all carbon source and not cultivation conditions had a distinct influence on the composition of the crude
product mixture and therefore on the physicochemical and biological properties of the sophorolipids, such as, for example,
surface activity, cytotoxicity and stability against hydrolases. The results were completed by corresponding data for purified
mono- and diacetylated (17-hydroxyoctadecenoic)-1′,4′′-lactonized sophorolipids. Crude sophorolipid mixtures showed moderate
to good surface active properties (SFTmin 39 mN m−1, CMC 130 mg l−1), water solubilities (2–3 g l−1) and low cytotoxicities (LC50 300–700 mg l−1). In contrast, purified sophorolipids were more surface active (SFTmin 36 mN m−1, CMC 10 mg l−1), less water soluble (max. 70 mg l−1) and showed stronger cytotoxic effects (LC50 15 mg l−1). Incubation of crude sophorolipid mixtures with different hydrolases demonstrated that treatment with commercially available
lipases such as from Candida rugosa and Mucor miehei distinctly reduced the surface active properties of the sophorolipids, while treatment with porcine liver esterase and glycosidases
had no effect.
Received: 23 February 1999 / Received revision: 27 May 1999 / Accepted: 28 May 1999 相似文献
11.
Thermophilic acidification of dairy wastewater 总被引:2,自引:0,他引:2
Acidification of simulated dairy wastewater was conducted in an upflow reactor at 55 °C. Results showed that the degree of
acidification decreased with the increase in chemical oxygen demand (COD) loading rate, from 60.8% at 4 g l−1 day−1 to 27.1% at 24 g l−1 day−1. Carbohydrate was readily degraded at all loading rates, but degradation of protein and lipid decreased with the increase
in loading rate. Most carbohydrate degradation occurred at the reactor bottom, whereas protein was degraded mainly after the
carbohydrate became depleted. The predominant acidification products were acetate, propionate, butyrate and ethanol, whereas
formate, i-butyrate, valerate, i-valerate, caproate, lactate, methanol, propanol and butanol were present in lesser quantities. The increase in loading rate
resulted in the increase of propionate and the decrease of acetate, but had little effect on ethanol and butyrate productions.
Only 2.5–8.8% of influent COD was converted to hydrogen and methane. The biomass yield was 0.30–0.43 mg VSS mg−1 COD.
Received: 8 December 1999 / Received revision: 14 February 2000 / Accepted: 25 February 2000 相似文献
12.
A novel method for the determination of microbial growth kinetics on hydrophobic volatile organic compounds (VOC) has been
developed. A stirred tank reactor was operated as a fed-batch system to which the VOC was continuously fed via the gas phase,
assuring a constant VOC concentration in the mineral medium. A flow of air was saturated with the VOC, and then mixed with
a further flow of air, to obtain a predetermined VOC concentration. Thus, different VOC concentrations in the mineral medium
could be obtained by altering the VOC concentration in the feed gas. The growth kinetics of Xanthobacter autotrophicus GJ10 on 1,2-dichloroethane (DCE) and of Pseudomonas sp. strain JS150 on MonoChloroBenzene (MCB) were assessed using this method. The growth of strain JS150 was strongly inhibited
at MCB concentrations higher than 160 mg l−1, and the results were fitted using a piecewise function. The growth kinetics of strain GJ10 were described by the Luong model
where maximum growth rate μmax = 0.12 h−1, substrate saturation constant K
S = 7.8 mg l−1, and maximum substrate concentration S
m (above which growth is completely inhibited) = 1080 mg l−1. Varying nitrogen and oxygen flows enabled the effect of oxygen concentration on the growth kinetics of Pseudomonas JS150 to be determined.
Received: 30 November 1998 / Received revision: 19 March 1999 / Accepted: 20 March 1999 相似文献
13.
Bioenergetics and RNA/DNA ratios in the common carp (Cyprinus carpio ) under hypoxia 总被引:2,自引:0,他引:2
Zhou BS Wu RS Randall DJ Lam PK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2001,171(1):49-57
Hypoxia caused by eutrophication occurs over large areas in aquatic systems worldwide. Common carp (Cyprinus carpio) exposed to hypoxia (1 mg · O2 · l−1 and 2 mg · O2 · l−1) for 1 week showed a significant reduction in feeding rate, respiration rate, faecal production and nitrogenous excretion
compared to those maintained at normoxia (7 mg · O2 · l−1). Fish exposed to hypoxia showed negative scope for growth (SfG), but no significant difference in the specific growth rate
was revealed after 1 week in both hypoxic groups. A significant reduction in RNA/DNA ratio was, however, clearly evident in
the white muscle of the 1 mg · O2 · l−1 treatment group, but not in the 2 mg · O2 · l−1 treatment group. Both specific growth rate and RNA/DNA ratio were significantly reduced when fish were exposed to severe
hypoxia (0.5 mg · O2 · l−1) for 4 weeks. At all levels of hypoxia, growth reduction was accompanied by a significant decrease in RNA/DNA ratio in white
muscle. Covariance analysis showed no significant difference between the slope of RNA/DNA ratio and growth rate under normoxic
conditions and 0.5 mg · O2 · l−1 for 4 weeks (F=1.036, P > 0.326), as well as 1.0 mg · O2 · l−1 and 2.0 mg · O2 · l−1 for 1 week (F = 0.457, P > 0.5), indicating that the RNA/DNA ratio serves as a biomarker of growth under all oxygen levels, at least under controlled
experimental conditions. SfG also appears to be more sensitive than the RNA/DNA ratio in responding to hypoxia in fish.
Accepted: 15 September 2000 相似文献
14.
In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal
amoA genes (5.70 × 106 ± 3.30 × 105 copies mg sludge−1) to bacterial amoA genes (8.60 × 106 ± 7.64 × 105 copies mg sludge−1) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations:
2, 10, and 30 mM NH4+–N (28, 140, and 420 mg N l−1). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying
activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation,
comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the
number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l−1), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l−1), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority
of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium
did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where
the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with
lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels. 相似文献
15.
Mashitha Pise Jaishree Rudra Sunita Bundale Deovrat Begde Nandita Nashikkar Avinash Upadhyay 《In vitro cellular & developmental biology. Plant》2012,48(1):85-91
Asparagus racemosus is an important monocot medicinal plant that is in great demand for its steroidal saponins called shatavarins. This study
was initiated to optimize the conditions for production of shatavarins in cell cultures of A. racemosus in a modified Murashige and Skoog (MS) medium supplemented with six different combinations of growth regulators. Biomass
accumulation was correlated with saponin production over a 30-d culture cycle. Biomass and saponin accumulation patterns were
dependent on combinations of growth regulators and the pH of the medium. Maximum levels of saponin and biomass accumulation
were recorded on day 25 of the culture cycle within a pH range of 3.4 to 5.6. Total saponin produced by the in vitro cultures was 20-fold higher than amounts produced by cultivated plants. Saponin accumulation was not a biomass-associated
phenomenon; cultures which showed the highest biomass accumulation were not the highest saponin accumulators. Maximum biomass
(28.30 ± 0.29 g l−1) and maximum levels of shatavarin IV(11.48 ± 0.61 mg g−1) accumulation was found using a medium containing 2.0 mg l−1 2,4-D, 2 g l−1 casein hydrolysate and 0.005% pectinase. The highest levels of sarsapogenin, secreted and intracellular (4.02 ± 0.09 mg g−1), accumulated using a medium containing 1.0 mg l−1 NAA, 1.0 mg l−1 2,4-D, 0.5 mg l−1 BAP, 2 g l−1 casein hydrolysate and 0.005% pectinase, after 25 d. Shatavarins were secreted into the medium and can be isolated easily
for further purification. 相似文献
16.
J. M. Obón J. R. Maiquez M. Cánovas H.-P. Kleber J. L. Iborra 《Applied microbiology and biotechnology》1999,51(6):760-764
The use of a biological procedure for l-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction
system. Continuous l-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst. This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was
able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g l-carnitine l−1 h−1). This process showed its feasibility for industrial l-carnitine production. In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium
component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this
particular method of cultivation was used.
Received: 10 December 1998 / Received revision: 19 February 1999 / Accepted: 20 February 1999 相似文献
17.
Jing Wang Hua Yang Hong Lu Jiti Zhou Jing Wang Chunli Zheng 《World journal of microbiology & biotechnology》2009,25(5):875-881
An aerobic microbial consortium constructed by the combination of Rhodotorula mucilaginosa Z1, Streptomyces albidoflavus Z2 and Micrococcus luteus Z3 was immobilized in polyurethane foam and its ability to degrade nitrobenzene was investigated. Batch experimental results
showed that polyurethane-foam-immobilized cells (PFIC) more efficiently degrade 200–400 mg l−1 nitrobenzene than freely suspended cells (FSC). Kinetics of nitrobenzene degradation by PFIC was well described by the Andrews
equation. Compared with FSC, PFIC exhibited better reusability (over 100 times) and tolerated higher shock-loadings of nitrobenzene
(1,000 mg l−1). Moreover, In the presence of salinity (≤5% NaCl, w/v), phenol (≤150 mg l−1) and aniline (≤50 mg l−1), respectively, degradation efficiency of nitrobenzene by PFIC reached over 95%. Even in the presence of both 100 mg l−1 phenol and 50 mg l−1 aniline, over 75% nitrobenzene was removed by PFIC in 36 h. Therefore, the immobilization of the defined consortium in polyurethane
foam has application potential for removing nitrobenzene in industrial wastewater treatment system. 相似文献
18.
Dilsen S Paul W Sandgathe A Tippe D Freudl R Thömmes J Kula MR Takors R Wandrey C Weuster-Botz D 《Applied microbiology and biotechnology》2000,54(3):361-369
A pH-auxostatic fed-batch process was developed for the secretory production of a fusion protein consisting of the pro-part
of Staphylococcus hyicus lipase and two synthetic human calcitonin (hCT) precursor repeats under the control of a xylose-inducible promotor from Staphylococcus xylosus. Using glycerol as the energy source and pH-controlled addition of yeast extract resulted in the production of 2000 mg l−1 of the fusion protein (420 mg l−1 of the recombinant hCT precursor) within 14 h, reaching 45 g l−1 cell dry mass with Staphylococcus carnosus in a stirred-tank reactor. Product titer and space-time yield (30 mg calcitonin precursor l−1 h−1) were thus improved by a factor of 2, and 4.5, respectively, compared to Escherichia coli expression-secretion systems for the production of calcitonin precursors. Two hundred grams of the fusion protein was secreted
by the recombinant S. carnosus on a 150-l scale (scale-up factor of 50) with a minimum use of technical-grade yeast extract (40 mg fusion protein g−1 yeast extract).
Received: 18 January 2000 / Received revision: 14 April 2000 / Accepted: 14 April 2000 相似文献
19.
During the process of producing cassava starch from Manihot esculenta roots, large amounts of cyanoglycosides were released, which rapidly decayed to CN− following enzymatic hydrolysis. Depending on the varying cyanoglycoside content of the cassava varieties, the cyanide concentration
in the wastewater was as high as 200 mg/l. To simulate anaerobic stabilization, a wastewater with a chemical oxygen demand
(COD) of about 20 g/l was prepared from cassava roots and was fermented in a fixed-bed methanogenic reactor. The start-up
phase for a 99% degradation of low concentrations of cyanide (10 mg/l) required about 6 months. After establishment of the
biofilm, a cyanide concentration of up to 150 mg CN−/l in the fresh wastewater was degraded during anaerobic treatment at a hydraulic retention time of 3 days. All nitrogen from
the degraded cyanide was converted to organic nitrogen by the biomass of the effluent. The cyanide-degrading biocoenosis of
the anaerobic reactor could tolerate shock concentrations of cyanide up to 240 mg CN−/l for a short time. Up to 5 mmol/l NH4Cl (i.e. 70 mg N/l = 265 mg NH4Cl/l) in the fresh wastewater did not affect cyanide degradation. The bleaching agent sulphite, however, had a negative effect
on COD and cyanide removal. For anaerobic treatment, the maximum COD space loading was 12 g l−1 day−1, equivalent to a hydraulic retention time of 1.8 days. The COD removal efficiency was around 90%. The maximum permanent cyanide
space loading was 50 mg CN− l−1 day−1, with tolerable shock loadings up to 75 mg CN− l−1 day−1. Under steady-state conditions, the cyanide concentration of the effluent was lower than 0.5 mg/l.
Received: 15 August 1997 / Received revision: 10 October 1997 / Accepted: 14 October 1997 相似文献
20.
Low-temperature bioremediation of a waste water contaminated with anionic surfactants and fuel oil 总被引:7,自引:0,他引:7
We conducted a laboratory study at 10 °C on the biological decontamination of the waste water from a garage and car-wash
that was contaminated with anionic surfactants (57 mg l−1) and fuel oil (184 mg hydrocarbons l−1). The indigenous microorganisms degraded both contaminants efficiently after biostimu- lation by an inorganic nutrient supply.
After 7 days at 10 °C, the residual contaminations were 11 mg anionic surfactants l−1 and 26 mg hydrocarbons l−1. After 35 days, only the anionic surfactants had been further reduced to 3 mg l−1. Bioaugmentation of the unfertilized waste water with a cold-adapted inoculum, able to degrade both hydrocarbons (diesel
oil) and anionic surfactants (sodium dodecyl sulphate), resulted in a significant increase of the hydrocarbon biodegradation
during the first 3 days of decontamination, whereas biodegradation of anionic surfactants was inhibited during the first 21 days
following inoculation. Bioaugmentation of the nutrient-amended waste water was without any effect.
Received: 14 November 1997 / Accepted: 29 November 1997 相似文献