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1.
G. H. van Geel-Schutten F. Flesch B. ten Brink M. R. Smith L. Dijkhuizen 《Applied microbiology and biotechnology》1998,50(6):697-703
A total of 182 Lactobacillus strains were screened for production of extracellular polysaccharides (EPS) by a new method: growth in liquid media with
high sugar concentrations. Sixty EPS-positive strains were identified; 17 strains produced more than 100 mg/l soluble EPS.
Sucrose was an excellent substrate for abundant EPS synthesis. The ability to produce glucans appears to be widespread in
the genus Lactobacillus. The monosaccharide composition of EPS produced by Lactobacillus reuteri strain LB 121 varied with the growth conditions (solid compared to liquid medium) and the sugar substrates (sucrose or raffinose)
supplied in the medium. Strain LB 121 produced both a glucan and a fructan on sucrose, but only a fructan on raffinose. This
is the first report of fructan production by a Lactobacillus species. EPS production increased with increasing sucrose concentrations and involved extracellular sucrase-type enzymes.
Received: 20 March 1998 / Received revision: 12 August 1998 / Accepted: 12 August 1998 相似文献
2.
Regeneration of garlic callus as affected by clonal variation, plant growth regulators and culture conditions over time 总被引:3,自引:0,他引:3
A long-term regeneration system for garlic (Allium sativum L.) clones of diverse origin was developed. Callus was initiated on a modified Gamborg's B-5 medium supplemented with 4.5 μM 2,4-D and maintained on the same basal medium with 4.7 μM picloram+0.49 μM 2iP. Regeneration potential of callus after 5, 12 and 16 months on maintenance medium was measured using several plant growth
regulator treatments. The 1.4 μM picloram+13.3 μM BA treatment stimulated the highest rate of shoot production. Regeneration rate decreased as callus age increased, but healthy
plantlets from callus cultures up to 16-months-old were produced for all clones. Regeneration of long-term garlic callus cultures
could be useful for clonal propagation and transformation.
Received: 24 September 1998 / Revision received: 27 January 1999 / Accepted: 26 February 1999 相似文献
3.
Cryopreservation of shoot tips from in vitro plants of sweet potato [Ipomoea batatas (L.) Lam.] by vitrification 总被引:8,自引:0,他引:8
Routine cryopreservation of shoot tips from sweet potato [Ipomoea batatas (L.) Lam] has been hampered by their survival variability after cryogenic exposure. We examined the effects of light conditions
on stock plants, sucrose preculture and cryoprotectant loading on survival after vitrification using PVS2 solution. The survival
of vitrified sweet potato shoot tips cooled to approximately –208 °C was increased by preculturing with 0.3 M sucrose for 24 h at 22 °C. Survival was also enhanced by excising shoot tips immediately after the 8-h dark photoperiod.
The best survival after cryogenic exposure was obtained using 2 M glycerol +0.4 M sucrose for 1 h at 22 °C followed by dehydration with PVS2 for 16 min at 22 °C. Rapid cooling was used and achieved by
the immersion of foil strips into partially solidified nitrogen. Successfully vitrified and warmed shoot tips directly developed
shoots on a medium containing 1 μM NAA, 0.5 μM BA and 0.1 μM kinetin with only minimum callus formation. Shoot formation occurred in all surviving shoot tips. This procedure shows promise
for cryopreserving sweet potato shoot tips.
Received: 2 March 1999 / Revision received: 21 September 1999 / Accepted: 29 September 1999 相似文献
4.
Efficacy of silver thiosulfate (STS) in reducing ethylene-induced culture abnormalities during minimal growth conservation
of microplants was studied in seven potato (Solanum tuberosum L.) genotypes. Different concentrations of STS (0, 1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 μg ml–1) were tested in minimal growth medium based on MS medium supplemented with 20 g l–1 mannitol and 40 g l–1 sucrose. STS improved the microplant growth and reduced the culture abnormalities during prolonged maintenance of potato
shoot cultures in vitro. The beneficial effect of STS was most prominent for number of green leaves per microplant and leaf
senescence. After 16 months of storage, desirable microplant growth was observed in cultures conserved in medium containing
6.0–9.0 μg ml–1 STS. The profile of the peroxidase isozymes of conserved cultures did not show any apparent genetic variation due to the
presence of STS in the conservation medium.
Received: 2 September 1998 / Revision received: 20 November 1998 / Accepted: 12 December 1998 相似文献
5.
A liquid culture protocol was developed to regenerate shoots from cotyledons of germinating seeds of jute (Corchorus capsularis L.). Reproducibility of the protocol was tested in three genotypes of jute. Highest bud differentiation rates into normal
shoots (via shoot-forming explants) were obtained on modified Murashige and Skoog's liquid medium containing 2.7 μM α-naphthaleneacetic acid and 4.4 μM benzylaminopurine. Regenerated shoots were excised, and the best root formation could be induced in medium with 2.5 μM indole-3-butyric acid and 1.5% sucrose. Bud primordia were formed directly on the cut surface of the cotyledons. Scanning
electron micrographs and histological studies confirmed the organogenic nature of the regenerated shoots. The physical condition
of the culture medium and the age of the explants played crucial roles in the induction of shoot development using shoots;
2-day-old explants being optimal. Approximately 70% of the shoots were successfully established in soil after hardening.
Received: 20 October 1997 / Revision received: 4 October 1998 / Accepted: 27 October 1998 相似文献
6.
Shoot tips from in vitro-grown, cold-hardened stock plants of white poplar (Populus alba L.) were successfully cryopreserved at –196 °C by one-step vitrification. After preculturing at 5 °C for 2 days on hormone-free
MS medium containing different sucrose concentrations, and loading for 20 min with 2 m glycerol and 0.4 m sucrose, shoot tips were treated with the PVS2 vitrification solution and plunged directly into liquid nitrogen. Best survival
rate (90%) was obtained when shoot tips were precultured on 0.09 m sucrose, hormone-free MS medium, vitrified by exposure to PVS2 solution for 60 min at 0 °C and, following cryopreservation,
rewarmed at 40 °C and washed in 1.2 m sucrose solution for 20 min. Regrowth was improved by plating shoot tips on a gelled MS medium containing 1.5 μm N6-benzyladenine plus 0.5 μm gibberellic acid, while shoot rooting was achieved on MS medium containing 3 μm indole-3-butyric acid. Following this procedure, almost 60% rooted shoots were obtained from cryopreserved shoot tips.
Received: 1 February 1999 / Revision received: 3 May 1999 · Accepted: 21 May 1999 相似文献
7.
Cryopreservation of apple (Malus×domestica Borkh.) shoot tips following encapsulation-dehydration or encapsulation-vitrification 总被引:1,自引:0,他引:1
Axillary shoot tips of apple cv. Golden Delicious isolated from shoot cultures were successfully cryopreserved using the
encapsulation-dehydration technique. After encapsulation in alginate gel, embedded shoot tips were dehydrated by exposure
to a sterile air flow before being frozen in liquid nitrogen and subsequent slow thawing. A preculture on modified MS medium
containing 0.75 M sucrose followed by 6 h of dehydration (21% residual water) led to the highest shoot regrowth of frozen, coated shoot tips
(83.7%). Among the sugars tested, sucrose and sorbitol presented the best cryoprotective effect. Four other scion apple varieties
and rootstocks were also successfully cryopreserved. Axillary shoot tips of five apple (Malus×domestica Borkh.) scion and rootstock cultivars were cryopreserved using the encapsulation-vitrification technique. Using a one-step
freezing method, we successfully cryopreserved axillary shoot tips without the requirement of a cold hardening pretreatment
of the shoot cultures. Cryopreserved shoot tips treated with aqueous cryoprotective mixture IV containing 180% (w/v) sucrose
and 120% (v/v) ethylene glycol showed the highest shoot regrowth rates, which varied from 64% to 77%, depending on the cultivar.
Received: 29 July 1999 / Revision received: 24 September 1999 / Accepted: 26 November 1999 相似文献
8.
Genetically transformed plants of a phalaenopsis orchid [Doritaenopsis Coral Fantasy×Phalaenopsis (Baby Hat×Ann Jessica)] were regenerated after cocultivation of cell clumps with Agrobacterium tumefaciens strains LBA4404 (pTOK233) and EHA101 (pIG121Hm) that harbored genes for β-glucuronidase (GUS) and hygromycin resistance.
The efficiency of transformation was markedly increased by 10 h cocultivation of cell clumps with A. tumefaciens that had been induced with 200 μm acetosyringone, and by inclusion of 500 μm acetosyringone in the cocultivation medium. Hygromycin-resistant cell clusters (0.5–3 mm in diameter) were selected from
the infected cell clumps after 4–6 weeks of culture on agar (8 g/l)-solidified new Dogashima medium (NDM) containing 20 g/l
sucrose, 0.1 mg/l naphthaleneacetic acid, 1.0 mg/l benzyladenine (BA), 50 mg/l hygromycin and 300 mg/l cefotaxime. The cell
clusters proliferated 4 weeks after transfer onto the same medium. To induce callus greening, the carbon source was changed
from sucrose to maltose. The green calli obtained produced protocorm-like bodies (PLBs) after 4 weeks of culture on phytohormone-free
NDM medium. Regeneration of transgenic plantlets was enhanced by incubating PLBs on NDM medium supplemented with 0.1 mg/l
abscisic acid, followed by partial desiccation for 10–30 min. Successful transformation was confirmed by histochemical GUS
assay, PCR analysis and Southern hybridization of transformants. With this transformation system, more than 100 hygromycin-resistant
phalaenopsis plantlets were produced about 7 months following infection of the cell aggregates.
Received: 10 November 1998 / Revision received: 4 June 1999 / Accepted: 22 June 1999 相似文献
9.
Indirect evidence has suggested that lignin peroxidase (LiP) of the white-rot fungus Phanerochaete chrysosporium catalyses oxidative decolourisation and depolymerisation of macromolecules from brown coal in vivo. In this study we show
that LiP catalyses these transformations in vitro. Unmethylated (USC45 coal) and methylated (MWSC6 coal) fractions of solubilised
macromolecules (M
r > 30 000) from a brown coal were treated with a semi-purified preparation of LiP isozymes from P. chrysosporium. Both coal fractions were decolourised, losing between 26% and 39% of their absorbance at both 280 nm and 400 nm, in reactions
that had an absolute requirement for H2O2 and veratryl alcohol. Neither coal fraction was transformed when the enzyme was heat-inactivated or in the presence of the
LiP inhibitor metavanadate. Gel-permeation chromatography showed that MWSC6 coal but not USC45 was depolymerised and yielded
low-molecular-mass (M
r < 30 000) fragments. Nine monomeric products were identified by GC-MS.
Received: 20 March 1998 / Received revision: 3 September 1998 / Accepted: 3 September 1998 相似文献
10.
Adventitious shoot buds were induced from leaf and stem explants of Bacopa monnieri on Murashige and Skoog medium supplemented with benzyladenine or kinetin. The source of the explants as well as different
gelling agents in the medium were found to influence shoot induction and eventual shoot growth. The best response was obtained
in leaf explants taken from shoot cultures grown in medium supplemented with 2 μM benzyladenine and gelled with 0.2% gelrite. A transverse section of the leaf explant incubated in this medium showed several
shoot primordia emerging from the leaf surface. This system exhibited a potential for repeated harvesting of the shoots from
the original leaf explant as the latter continued to expand and regenerate new shoots, upon repeated periodical subculturing
onto fresh medium. However, the callusing response of the plant was very low. Qualitative TLC studies of the regenerated shoots
revealed a phytochemical profile similar to that of the field grown-plants.
Received: 20 March 1998 / Revision received: 1 December 1998 / Accepted: 12 December 1998 相似文献
11.
Cryopreservation of in vitro-grown axillary shoot-tip meristems of mint (Mentha spicata L.) by encapsulation vitrification 总被引:1,自引:0,他引:1
Alginate-coated meristems from in vitro-grown axillary buds of mint (Mentha spicata L.) were successfully cryopreserved by vitrification. Excised meristems from nodal segments cold hardened at 4 °C for 3
weeks were encapsulated and osmoprotected by a mixture of 2 M glycerol plus 0.4 M sucrose. These meristems were dehydrated with a highly concentrated vitrification solution (PVS2 solution) for 3 h at 0 °C
prior to a plunge into liquid nitrogen. Successfully encapsulated vitrified meristems developed shoots within a week after
plating without intermediary callus formation. The average rate of shoot formation amounted to nearly 90%. This procedure
was successfully applied to other Mentha species. It was also confirmed that encapsulated vitrified meristems produced a much higher rate of shoot formation than
the encapsulated dried meristems. Thus, this revised encapsulation vitrification method appears promising for the cryopreservation
of mint and other germplasm.
Received: 24 November 1998 / Revision received: 8 February 1999 / Accepted: 26 February 1999 相似文献
12.
Pilot-scale production of butanol by Clostridium beijerinckii BA101 using a low-cost fermentation medium based on corn steep water 总被引:3,自引:0,他引:3
To improve the economic competitiveness of the acetone/butanol/ethanol fermentation process, glucose/corn steep water (CSW)
medium was used on a pilot scale for the production of solvents. The production of butanol by the Clostridium beijerinckii NCIMB 8052 parent strain and the solvent-hyperproducing BA101 mutant was compared. In a 20-l fermentation using 5% glucose/CSW
medium, C. beijerinckii 8052 produced 8.5 g butanol/l and 5 g acetone/l, while C. beijerinckii BA101 produced 16 g butanol/l and 7.5 g acetone/l. Further studies were carried out on a larger scale using an optimized
6% glucose/CSW medium. In a 200-l pilot-scale fermentor, C. beijerinckii 8052 produced 12.7 g butanol/l and 6 g acetone/l following 96 h of fermentation. C. beijerinckii BA101 produced 17.8 g/l and 5.5 g/l butanol and acetone respectively, following 130 h of fermentation. These results represent
a 40% increase in final butanol concentration by the C. beijerinckii BA101 mutant strain when compared to the 8052 parent strain. The total solvents (acetone, butanol, and ethanol) produced
by C. beijerinckii NCIMB 8052 and BA101 in a 200-l fermentation were 19.2 g/l and 23.6 g/l respectively. This is the first report of pilot-scale
butanol production by the solvent-hyperproducing C. beijerinckii BA101 mutant employing an inexpensive glucose/CSW medium.
Received: 26 May 1998 / Received revision: 21 September 1998 / Accepted: 11 October 1998 相似文献
13.
The time courses of growth and rosmarinic acid production by Lavandula vera MM cell suspension were investigated. The uptake of the main nutrients (sucrose, nitrogen, phosphorus, K, Ca, Mg) was followed
during cultivation and the data on the physiology of the L. vera MM cell culture are presented. It was established that the cell culture synthesizes rosmarinic acid during the linear phase
of growth for a relatively short period (between the 4th and 8th days of cultivation). The influence of sucrose concentration
in the nutrient medium on cell growth and accumulation of rosmarinic acid by L. vera MM cell culture was investigated. The results showed that 7% sucrose in the nutrient medium ensured a steady growth of the
cell suspension and increased the yield of rosmarinic acid (29.2 g/l dry biomass and 507.5 mg/l rosmarinic acid compared to
13.0 g/l dry biomass and 68.6 mg/l rosmarinic acid for the control cultivation with 3% sucrose).
Received: 17 September 1996 / Received revision: 31 January 1997 / Accepted: 1 February 1997 相似文献
14.
Cells of a suspension culture of Doritaenopsis cv. New Toyohashi were placed in a mixture of 2 M glycerol and 0.4 M sucrose for 15 min at room temperature and then dehydrated with a vitrification solution (PVS2) for 1–3 h on ice and plunged
into liquid nitrogen. The highest viability (64% by 2,3,5-triphenyltetrazolium chloride stainability) was obtained when the
cells were precultured in liquid New Dogashima medium with 0.1 M sucrose and 1.0 mg/l abscisic acid for 1 week at 25 °C in the light. Dehydration by PVS2 was important for the cryopreservation
of Doritaenopsis cells. Protocorm-like bodies were induced from cryopreserved cells without morphological variations.
Received: 18 January 2000 / Revision received: 16 June 2000 / Accepted: 22 June 2000 相似文献
15.
Daniel HJ Otto RT Binder M Reuss M Syldatk C 《Applied microbiology and biotechnology》1999,51(1):40-45
In order to produce sophorolipids from whey, thereby lowering the lactose content and biological oxygen demand, a two-step
batch cultivation process was developed including medium sterilization by filtration. In the first step, whey was sterilized
by a combination of crossflow and sterile filtration. Because the sophorolipid-producing yeast Candida bombicola ATCC 22214 was not able to use lactose as a carbon source directly, the oleaginous yeast Cryptococcus curvatus ATCC 20509 was grown on deproteinized whey concentrates (DWC). With 1: 1 diluted DWC-20, lactose was consumed as the carbon
source and biomass (24 g/l dry weight content) as well as single-cell oil (SCO, 10 g/l) were produced. The cultivation broth
was disrupted with a glass bead mill and it served as medium for growth (29 g cell dry mass/l) and sophorolipid production
(12 g/l) of the yeast C. bombicola.
Received: 29 July 1998 / Received revision: 5 October 1998 / Accepted: 11 October 1998 相似文献
16.
Protoplasts were isolated from embryogenic suspension cultures derived from avocado (Persea americana Mill.) zygotic embryos and nucellus in an enzyme digestion solution consisting of 1% cellulase Onozuka RS, 1% Macerase R10,
0.2% Pectolyase Y-23, 0.7 M mannitol. 24.5 mM CaCl2, 0.92 mM NaH2PO4 and 6.25 2-[N-morpholino]ethanesulfonic acid (1.5 ml) mixed with 0.7 M MS–8P (2.5 ml). MS-8P medium consisted of Murashige and Skoog salts without NH4NO3, 1 mg l–1 thiamine HCl, 100 mg l–1 myo-inositol, 3.1 g l–1 glutamine and 8P organic addenda. Medium osmolarity was adjusted with 0.15 M sucrose and 0–0.55 M mannitol. Protoplast yields of 3.5×106 protoplasts g–1 were obtained. Growth and development of the protoplasts were significantly affected by osmolarity, nitrogen source, plating
density and culture medium dilution. Under optimum conditions, proembryos developed directly from embryogenic protoplasts
and subsequently into somatic embryos. Optimum conditions for somatic embryo development included the culture of protoplasts
at a density of 0.8–1.6×105 ml–1 in 0.4 M MS–8P for 2–3 weeks, followed by subculture in 0.15 M MS–8P at a diluted density of 20–40× for 1 month in darkness to obtain somatic embryos. Mature somatic embryos were recovered
on semisolid medium; however, a low frequency of plantlet recovery (≤1%) from protoplast-derived somatic embryos was observed.
Received: 9 February 1998 / Revision received: 4 May 1998 / Accepted: 15 May 1998 相似文献
17.
Morphogenesis and regeneration from stomatal guard cell complexes of cotton (Gossypium hirsutum L.) 总被引:1,自引:0,他引:1
The development of a regeneration system from cotton stomatal guard cells directly on epidermal strips is described. The
most important factors affecting embryogenic callus initiation in both of the varieties tested (Coker 312 and 315) were the
source of the epidermal tissue, including plant age (4–5 months old), the developmental stage of the flower (opening flower
stage) from which bracts were obtained, the composition of the culture medium and light irradiance. The flower developmental
stage was critical for callus formation, which was observed only from bracts obtained from opening flowers. In addition, epidermal
strips excised from the bract basal region were more responsive in culture than those obtained from the top region. Improved
callus initiation was obtained on epidermal strips which had their cuticle in contact with the culture medium. Light irradiance
was a limiting factor for embryogenic callus formation, which was observed only in calluses cultured under the lower light
irradiance (15.8 μmol m–2 s–1). Somatic embryogenesis was observed on callus cultures subcultured consecutively to a culture medium containing naphthalene
acetic acid (10.7 μM) and isopentenyladenine (4.9 μM). Histodifferentiation of somatic embryos was improved on a medium containing naphthaleneacetic acid (8.1 μM)+isopentenyladenine (2.5 μM) and abscisic acid (0.19–0.38 μM). Somatic embryo germination and plantlet development were obtained using established protocols with few modifications. On
average, one fully developed plant was obtained from the culture of circa 100 epidermal strips in both cultivars.
Received: 19 May 2000 / Revision received: 25 August 2000 / Accepted: 29 August 2000 相似文献
18.
Regeneration of Acacia mangium through somatic embryogenesis 总被引:2,自引:0,他引:2
Somatic embryogenesis and whole plant regeneration were achieved in callus cultures derived from immature zygotic embryos
of Acacia mangium. Embryogenic callus was induced on MS medium containing combinations of TDZ (1–2 mg/l), IAA (0.25–2 mg/l) and a mixture of
amino acids. Globular embryos developed on embryogenic callus cultured on the induction medium. Nearly 42% of embryogenic
cultures with globular embryos produced torpedo- and cotyledonary-stage embryos by a two-step maturation phase. The first
stage occurred on 1/2-strength MS basal medium containing 30 g/l sucrose and 5 mg/l GA3 followed by the second stage on 1/2-strength MS basal medium containing 50 g/l sucrose. Of the cotyledonary-stage somatic
embryos, 11% germinated into seedlings that could be successfully transferred to pots. Light- and scanning electron microscopy
showed that the somatic embryos originated from single cells of the embryogenic callus. Further, a single cell layer could
be detected beneath the developing somatic embryos that appeared to be a demarcation layer isolating the somatic proembryonic
structure from the rest of the maternal callus. A suspensor-like structure connected the globular embryos to the demarcation
layer. This is the first successful report of plant regeneration through somatic embryogenesis for this economically important
tropical forest species.
Received: 20 January 2000 / Revision received: 28 September 2000 / Accepted: 29 September 相似文献
19.
Poly(hydroxybutyric acid) (PHB) was produced by a selectant of Azotobacter beijerinckii in media containing only organic nitrogen sources such as N substrates. The chosen compounds were casein peptone, yeast extract,
casamino acids and urea, each combined with carbon substrates glucose or sucrose. The PHB was synthesized under growth-associated
conditions. The concentrations amounted to more than 50% of cell dry mass on casein peptone/glucose as well as urea/glucose
medium within 45 h fermentation time. Corresponding to these yields, productivities of about 0.8 g PHB l−1 h−1 were discovered. The highest values increased to 1.06 g PHB l−1 h−1 on casein peptone/glucose medium and 1.1 g PHB l−1 h−1 on yeast extract/glucose medium after a period of 20 h. It was found that oxygen limitation was essential for successful
product formation, as demonstrated earlier. These data from basic research may support further investigations into the use
of technical proteins from renewable sources as substrates for PHB production by a strain of A. beijerinckii.
Received: 3 June 1997 / Received revision: 29 August 1997 / Accepted: 15 September 1997 相似文献
20.
Barley microspore-derived doubled-haploid embryos have been produced in vitro. The development of embryo desiccation technology will allow long-term storage, germplasm preservation and low delivery cost.
Treatment of the microspore-derived embryos was essential to induce desiccation tolerance and to arrest further development
and plant regeneration. At the concentrations used, a treatment with trehalose was more efficient than with sucrose, and mannitol
was harmful to the embryos. Up to 80% of the desiccated embryos produced complete green plants when transferred to regeneration
medium, by the application of a 0.6 m trehalose or a 10–5 m abscisic acid treatment to the embryos in the culture induction medium. The morphology of these plants was similar to plants
produced directly from non-desiccated embryos.
Received: 28 September 1998 / Revision received: 27 November 1998 / Accepted: 5 January 1999 相似文献