Growth of immobilised plant cells in reticulate polyurethane foam matrices

Summary An inoculum of initially freely suspended cell aggregates ofCapsicum frutescens was immobilised in porous polyurethane foam matrices. Subsequent growth and substrate consumption of these immobilised cells in batch culture were measured and compared with those of suspension cultures. The results showed that the maximum specific growth rate of freely suspended cells was slightly higher than that of immobilised cells but the overall growth patterns and final cell yields were similar.     

Colonisation of polyurethane reticulated foam biomass support particle by methanogen species

Summary The ability of methanogen species to colonise reticulated polyurethane foam biomass support particles (BSP) in a continuous culture system using formate as carbon source was investigated. Scanning electron micrograph evidence and biomass measurements indicate that two methanogen species effectively colonised within the the matrix of the support particle.The freely suspended colonised BSP are resistant to washout, and a comparison of methane output of the immobilised culture and a liquid culture of the methanogens indicates the potential for process intensification of methane production.     

Retention of methanogens in colonised reticulated polyurethane foam biomass support particle

Summary Methanogens colonised on reticulated polyurethane foam BSP rapidly lost biomass when exposed to hydrodynamic stress. The loss was independent of the porosity of the BSP matrix. These findings indicate the binding forces between methanogen and particle surface is weak and may impose a limit on the potential for process intensification in fixed or fluidised bed methane digesters.     

Ferrous sulphate oxidation using Thiobacillus ferrooxidans cells immobilised in polyurethane foam support particles

Summary Oxidation of ferrous iron by Thiobacillus ferrooxidans cells passively immobilised in polyurethane foam particles, using both repeated batches and continuous operation, was studied in a laboratory-scale reactor. Repeated batches yielded complete oxidation at higher rates than single batches, providing resident inocula for subsequent batches. In continuous operation maximum ferric iron productivities were achieved at dilution rates well above theoretical washout values. At a dilution rate of 0.31 h^–1 [approximately three times the maximum specific growth rate (_max)], a productivity of 1.56 kg m^–3 h^–1, based on total ferric iron, or 1.0 kg m^–3 h^–1 based on dissolved ferric iron, was achieved. In addition, cells immobilised in the foam particles retained their oxidative ability for periods of up to 6 weeks when stored in the open air and could be reused immediately.     

Cultivation of animal cells in a reticulated vitreous carbon foam.

A reticulated vitreous carbon foam (RVCF) was used as a surface to cultivate a model anchorage-dependent animal cell line, 3T6 (mouse embryo fibroblast). This fixed-surface bioreactor provided a low-shear, chemically-inert, and reusable environment for cell growth. An external medium recirculation loop allowed aeration, nutrient monitoring, and medium replacement without disturbing the cells. Optimal flow rates for the attachment and growth phases were determined. Growth rates comparable to static (T-flask and petri dish) cultures and agitated microcarrier cultures were achieved with appropriately high medium recirculation rates. Metabolic parameters were shown to be useful indicators of cell mass, although specific glucose consumption rates were considerably higher for cultures in the RVCF reactor. Oxygen supply was shown to be the most likely limiting factor for scaleup.     

影响引人微生物根部定殖的因素

从外界引入的各类有益微生物如生防菌(BCA)和根际促生菌或增产菌(PGPR,YIB)到种子表面随其生根发芽而蔓延或直接到根表沿根分布定殖．外来微生物在根际定殖的过程为与根尖接触,沿根分布,最后在根际建立自己的种群．定殖的位点以PGPR为例,是表皮细胞间隙,或侧根、根毛基部．外来微生物在根际定殖动态变化的原因,由于根际生物的和非生物的因素引起的．生物因子除去外来微生物本身的生理特性,还有根际土著微生物与外来微生物的相互作用,更重要的是植物基因型对微生物定殖的影响．非生物因子包括土壤环境、土壤结构和含水量,土壤温度和土壤pH值均能影响外来微生物在根部的定殖．     

Factors affecting ice nucleation in plant tissues

Factors affecting the ice nucleation temperature of plants and plant tissues were examined. The mass of a sample had a marked effect on ice nucleation temperature. Small tissue samples supercooled to −10°C and were not accurate predictors of the nucleation temperature of intact plants in either laboratory or field experiments. This effect was not unique to plant tissues and was observed in autoclaved and control soil samples. Ice nucleation temperatures of bean, corn, cotton, and soybean seedlings were influenced by the length of subzero exposure, presence of ice nucleation active bacteria, and leaf surface wetness. The number of factors influencing ice nucleation temperature suggested that predicting the freezing behavior of plants in the field will be complex.     

Factors affecting the rate of T-DNA transfer from Agrobacterium tumefaciens to Nicotiana glauca plant cells

Different factors involved in the early steps of the T-DNA transfer process were studied by using a -glucuronidase gene (gusA) as a reporter in Nicotiana glauca leaf disc transformation experiments. The levels of transient expression of the gusA gene in leaf discs infected with several strains or vir mutants correlated well with their virulence phenotype, except for virC mutants. The rate of T-DNA transfer was shown to be stimulated in the case of non-oncogenic strains by the co-transfer of small amounts of oncogenic genes. It was found that the location of the T-DNA in the Agrobacterium genome affected the T-DNA transfer rate especially in virC mutants. The virC mutants transferred the gusA-containing T-DNA located on a binary vector more efficiently than the oncogenic T-DNA of the Ti plasmid. Although wild-type strains induced high levels of gusA expression early after infection, the gusA expression appeared to be lost late after infection in the infected leaf discs. In contrast, in leaf discs infected by virC mutants the level of gusA expression increased steadily in time. A model explaining these results is presented.     

影响引入微生物根部定殖的因素

从外界引入的各类有益微生物如生防菌（ＢＣＡ）和根际促生菌或增产菌（ＰＧＰＲ,ＹＩＢ）到种子表面随其生根发芽而蔓延或直接到根表沿根分布定殖。外来微生物在根际定殖的过程为与根尖接触,沿根分布,最后在根际建立自己的种群。定殖的位点以ＰＧＰＲ为例,是表皮细胞间隙,或侧根、根毛基部。外来微生物在根际定殖动态变化的原因,由于根际生物的和非生物的因素引起的。生物因子除去外来微生物本身的生理特性,还有根际土著微生     

Factors affecting growth and product formation in plant cells grown in continuous culture

In the present work we examined the potential benefits of the continuous culture (chemostat) technique at improving biomass yields of Mentha and Dioscorea cells and product formation (diosgenin) by Dioscorea cells. In contrast to Mentha cells, Dioscorea cells were sensitive to mechanical agitation in the exponential growth phase and could only be grown in a bubble column type fermentor. Maximal biomass yield of 0.5 and 0.4 g cell dry weight g^?1sucrose were obtained for Mentha and Dioscorea cells, respectively. When the phosphate concentration during the growth phase of Dioscorea was increased, a maximal concentration of 7.8% diosgenin (of dry weight) was obtained. Productivity of diosgenin was 12 mg 1^?1 day^?1 in a two-stage continuous process as compared to 7.3 mg 1^?1 day^?1 in a batch culture.     

Methanogenesis by methanogen species immobilised on reticulated foam biomass support particles. Inhibition of methane production at high substrate concentrations

Summary The rate of methanogenesis by a substrate depleted methanogenic culture immobilised on reticulated polyurethane foam particles became increasingly inhibited at –S>300 mM. (–S=Reactor substrate concentration). Inhibition was duplicated by the sequential addition of metabolically inert sorbitol to cultures 40–60 mins after initiating methane production with formate (–S<300 mM).     

Ethanol production from sucrose by immobilizedZymomonas mobilis cells in polyurethane foam

Summary The possibility of using polyurethane foam as a support for the immobilization ofZymomonas mobilis cells to carry out sucrose conversion to ethanol was investigated. Sucrose hydrolysis efficiencies of 90% and higher, volumetric reactor productivity of 20 gL^–1h^–1 and final ethanol concentration of 6.3% (v/v) at a dilution rate of 0.4 h^–1 show the good performance of polyurethane foams for whole cell immobilization.     

Use of polyurethane foam for the biodegradation of n-alkanes by immobilised cells of Pseudomonas

Pseudomonas strains C12B and A3 were separately immobilised in polyurethane foam and their ability to biodegrade n-decane or n-hexadecane tested and compared with that of freely suspended cells. In the presence of immobilised Pseudomonas C12B or A3 cells about 90% of n-alkane, originally present in liquid medium, was removed, 25%-40% of which was due to biodegradation.     

Immobilisation of anchorage-independent animal cells using reticulated polyvinyl formal resin biomass support particles

Summary Immobilisation of anchorage-independent animal cells using Biomas Support Particles (BSPs) was investigated. Mouse myeloma MPC-11 cells were physically entrapped in three-dimensional reticulated polyvinyl formal (PVF) resin PSPs (3×3×3 mm) with matrices of relatively small pores (30–100 m) by filtering medium containing cells or incubating in a shake flask for inoculation. Physically entrapped cells became immobilised in the BSPs by forming aggregates within the matrices of the reticulated PVF resin, and cell density in the BSPs reached at least 10⁷ cells/cm³ BSP. Immobilised cells in the BSPs were successfully cultivated in static and/or shake-flask cultures with regular replacement of medium for a long period.     

Effects of jet-fuel microbial isolates on a polyurethane foam

Jet-fuel microbial isolates were studied for effects on a polyurethane foam material that has been proposed as a baffling material for use in aircraft fuel tanks. Evidence was found that a polyesterurethane foam gave increased cell counts and oxygen uptake with a bacterial isolate, and extensive matting with fragmentation and decreases in tensile strength of the foam with a fungal isolate. The polyurethane foam was affected by activity of the jet-fuel microbial isolates to an extent that would cause serious microbiological problems in the fuel tanks of jet aircraft.