Misting and nitrogen fertilization of shoots of a saltmarsh grass: effects upon fungal decay of leaf blades

We conducted a 12-week field manipulation experiment in which we raised the nitrogen availability (ammonium sulfate fertilization to roots) and/or water potential (freshwater misting) of decaying leaf blades of a saltmarsh grass (smooth cordgrass, Spartina alterniflora) in triplicate 11-m² plots, and compared the manipulated plots to unmanipulated, control plots. The ascomycetous fungi that dominate cordgrass leaf decomposition processes under natural conditions exhibited a boosting (>2-fold) of living standing crop (ergosterol content) by misting at the 1 st week after tagging of senescent leaves, but afterwards, living-fungal standing crop on misted blades was equivalent to that on control blades, confirming prior evidence that Spartina fungi are well adapted to natural, irregular wetting. Misting also caused 2-fold sharper temporal declines than control in instantaneous rates of fungal production (ergosterol synthesis), 5-fold declines in density of sexual reproductive structures that were not shown by controls, and 2-fold higher rates of loss of plant organic mass. Extra nitrogen gave a long-term boost to living-fungal standing crop (about 2-fold at 12 weeks), which was also reflected in rates of fungal production at 4 weeks, suggesting that saltmarsh fungal production is nitrogen-limited. Although bacterial and green-microalgal crops were boosted by manipulations of nitrogen and/or water, their maximal crops remained 0.3 or 2% (bacteria or green microalgae, respectively) of contemporaneous living-fungal crop. The fungal carbon-productivity values obtained, in conjunction with rates of loss of plant carbon, hinted that fungal yield can be high (>50%), and that it is boosted by high availability of nitrogen. We speculate that one partial cause of high fungal yield could be subsidy of fungal growth by dissolved organic carbon from outside decomposing leaves.     

Mass loss,fungal colonisation and nutrient dynamics of Phragmites australis leaves during senescence and early aerial decay

This study examined the mass loss, fungal biomass, and nutrient dynamics of standing Phragmites australis leaf blades during senescence and early decay in littoral reed stands of two hardwater lakes. Green living leaves were tagged at defined canopy heights in early autumn (late August or early September) and periodically collected until all leaf blades had fallen off the parent shoot. Samples were analysed for leaf dry mass remaining, fungal biomass associated with leaves (ergosterol concentrations), and nitrogen and phosphorus concentrations. Considerable mass loss of leaves occurred in the standing position (up to 28%). Nitrogen and phosphorus concentrations of leaves decreased substantially with time (by 39–77%), indicating that a major portion of these nutrients was translocated to the rhizome during senescence. Fungal biomass associated with leaves increased during the study period, reaching an estimated maximum of about 40 mg g⁻¹ of leaf dry mass. Fungal biomass was negatively correlated with leaf N and P concentrations. The observed patterns of leaf mass loss, nutrient dynamics, and fungal biomass were consistent with the successive senescence and death of leaves from the shoot base to its tip. The results of this study point to a notable mass loss of P. australis leaf blades in the standing position, which appears to be mediated by both plant and microbial processes. Nutrient dynamics, in contrast, appear to be largely governed by plant processes.     

Measuring summer patterns of ascospore release by saltmarsh fungi

One potentially important type of flux from standing-decaying marshgrass is the production and release of ascospores. The most extensive measurements of ascospore release from the principal marshgrass (Spartina alterniflora, smooth cordgrass) of saltmarshes of the eastern coastal United States involved an arbitrary, weeklong period of wet incubation of leaf-blade samples. We examined the possibility that shorter incubations would yield higher estimates of hourly rates of ascospore release, testing wet incubations of 3 to 71 h, using standing-decaying leaf blades of smooth cordgrass from low on living shoots and high on dead shoots. Incubations of 31 h appeared to be optimal. Species compositions of ascospores expelled from the two leaf types were distinctly different: high leaves yielded primarily aMycosphaerella species orPhaeosphaeria halima; low leaves yielded primarilyPhaeosphaeria spartinicola or theMycosphaerella species. All of these species consistently exhibited high coefficients of variation (>100%) for their mean rates of release of ascospores. Only theMycosphaerella species on high leaves gave evidence of a delayed onset of ascospore expulsion during incubation, and this evidence was equivocal. Grand mean rates of ascospore release forP. spartinicola and theMycosphaerella species were, respectively, 106 and 238 spores cm⁻² abaxial leaf area h⁻¹.     

Productivities of microbial decomposers during early stages of decomposition of leaves of a freshwater sedge

1. We examined standing-senescing, standing-dead and recently fallen leaf blades of Carex walteriana in fens of the Okefenokee Swamp to determine the nature of the microbial decomposers in the early stages of decomposition, measuring both standing crops and productivities ([³H]leucineprotein method for bacteria, [¹⁴C]acetateergosterol for fungi). 2. Fungal standing crops (ergosterol) became detectable at the mid-senescence stage (leaves about half yellow-brown) and rose to 14–31 mg living-fungal C g^?1 organic mass of the decaying system; bacterial standing crops (direct microscopy) were ± 0.2 mgC g^?1 until the fallen-leaf stage, when they rose to as high as 0.9 mgC g^?1. 3. Potential microbial specific growth rates were similar between fungi and bacteria, at about 0.03–0.06 day^?1, but potential production of fungal mass was 115–512 μgC g^?1 organic mass day^?1, compared with 0–22 μgC g^?1 day^?1 for bacteria. Rates of fungal production were about 6-fold lower on average than previously found for a saltmarsh grass, perhaps because much lower phosphorus concentratiofis in the freshwater fen limit fungal activity. 4. There was little change in lignocellulose (LC) percentage of decaying leaves, although net loss of organic mass at the fallen, broken stage was estimated to be 59%, suggesting that LC was lost at rates proportional to those for total organics during decay. Monomers of fungal-wall polymers (glucosamine and mannose) accumulated 2- to 4-fold during leaf decay. This may indicate that an increase found for proximate (acid-detergent) lignin could be at least partially due to accumulation of refractory fungal-wall material, including melanin. 5. A common sequence in decaying aquatic grasses is suggested: principally fungal alteration of LC during standing decay, followed by a trend toward bacterial decomposition of the LC after leaves fall and break into particles.     

Studies on cephalosporin-C production in an air lift reactor using different growth modes of Cephalosporium acremonium

This paper deals with the studies on Cephalosporin-C production in a lab-scale airlift reactor using Cephalosporium acremonium. Various growth modes, viz. pellets and Siran supported bioparticles were used to improve the process over conventional free mycelial fermentation. Cephalosporin-C production was significantly improved by using bioparticles over the free mycelial culture, probably due to the enhanced mass transfer in the fermentation broth. However, the biofilm of the bioparticles became unstable as the fermentation proceeded, and increase in the free cells in the broth occurs. The maximum specific growth rate of free cells, pellets and Siran carrier were observed to be 0·037, 0·033 and 0·045 h⁻¹, respectively. The oxygen transfer coefficient also improved for the immobilised modes (100 h⁻¹, 70 h⁻¹ for Siran carrier and pellets) and thereby enhanced specific antibiotic productivity, 18–28% were observed.     

Epiphytic survival of Pseudomonas viridiflava on tomato and selected weed species

A rifampicin-nalidixic acid mutant of Pseudomonas viridiflava (PV) was studied in the field and greenhouse with respect to its epiphytic survival on the roots and foliage of a susceptible (FM 6203) and resistant (Ontario 7710) tomato cultivar and 16 weed species. In the field, populations varied between years, which was attributed to differences in environmental conditions. Hot, dry conditions caused rapid decline or elimination of populations. Some hosts were more conducive than others in promoting epiphytic growth, and generally, roots were better survival sites than foliage. Some hosts such as johnsongrass, lambsquarters, pigweed, prickly sida, and red sorrel had no detectable populations of PV on foliage 2 weeks after inoculation. (Plants had been misted with a 10⁸ cfu/ml suspension until run off occurred.) PV was recovered at week 4 on the foliage of the two tomato cultivars, beggarweed, jimsonweed, morning glory, smooth vetch, and wild mustard, and was recovered until week 16 on roots of buckhorn plantain in the field and for the same period on the ground cherry in the field and greenhouse. In scanning electron microscopy studies, PV was observed to survive as microcolonies in depressions between epidermal cells, around trichomes, along veins, and sometimes around stomates of tomato and beggarweed. Bacterial cells sometimes were held together and to the leaf surface by fibril-like strands. These studies show that PV does have an epiphytic stage on both tomato and certain weed species. However, the epidemiological significance of the epiphytic stage is probably dependent on environmental conditions.     

Gas-phase degradation of VOCs using supported bacteria biofilms

Herein we report the use of Pseudomonas putida F1 biofilms grown on carbonized cellulosic fibers to achieve biodegradation of airborne volatile organic compounds (VOCs) in the absence of any bulk aqueous-phase media. It is believed that direct exposure of gaseous VOC substrates to biomass may eliminate aqueous-phase mass transfer resistance and facilitate VOC capture and degradation. When tested with toluene vapor as a model VOC, the supported biofilm could grow optimally at 300 p.p.m. toluene and 80% relative humidity, with a specific growth rate of 0.425 day⁻¹. During long-term VOC biodegradation tests in a tubular packed bed reactor, biofilms achieved a toluene degradation rate of 2.5 mg g_DCW⁻¹ h⁻¹ during the initial growth phase. Interestingly, the P. putida F1 film kept biodegrading activity even at the stationary nongrowth phase. The supported biofilms with a biomass loading of 20% (wt) could degrade toluene at a rate of 1.9 mg g_DCW⁻¹ h⁻¹ during the stationary phase, releasing CO₂ at a rate of 6.4 mg g_DCW⁻¹ h⁻¹ at the same time (indicating 100% conversion of substrate carbon to CO₂). All of these observations promised a new type of “dry” biofilm reactors for efficient degradation of toxic VOCs without involving a large amount of water.     

Isolation and growth characteristics of nitrilotriacetate-degrading bacteria

Two bacterial strains that degrade nitrilotriacetate (NTA) were isolated from NTA-acclimatized activated sludge. These bacteria grew well in NTA medium with optimal pH around 7. The growth rate constants of the bacteria, strains N-2 and N-5, were 0.046 h⁻¹ and 0.11 h⁻¹ at the concentration of 0.1% NTA (pH 7.0, 25°C), respectively.The growth of each bacterium was inhibited at high concentrations NTA. The growth rate decreased roughly linearly with increasing concentration of NTA. The strains N-2 and N-5 showed maximal cell growth at the concentrations of 0.2% and 0.25% NTA, respectively. The strain N-2 would not grow at the concentration of 0.5% NTA. On the other hand, the strain N-5 showed a little growth under the same conditions. Also, the bacterial growth was almost completely inhibited when divalent metal ions such as Mg⁺⁺, Ca⁺⁺, and Fe⁺⁺ were omitted from the culture medium, or slightly excess EDTA (1 mM) was added to the medium. These results suggest that the bacterial growth inhibition at high concentration of NTA is caused by the sequestration of metal ions in the medium.     

Secondary productivity (3H-Leucine and 3H-Thymidine incorporation), abundance and biomass of the epiphytic bacteria attached to detritus of Typha domingensis pers. in a tropical coastal lagoon

Senescent, naturally dried leaves of Typha domingensis were incubated inthe littoral region of a coastal lagoon and epiphytic bacterial volume,abundance, biomass and secondary productivity were measured during 127 daysof decomposition. The peak of cell abundance was registered at t =127 days when expressed per leaf surface area (10.07×10⁷cells cm^-2; 7.26 µgC cm^-2), and at t= 26 days when expressed per biofilm dry mass (38.10 ×10⁷ cells (mgDM biofilm)^-1, 30.52 µgC(mgDM biofilm)^-1). The highest values of bacterial biovolumesand lower turnover time were usually obtained in the beginning of thecolonization. Leu:Tdr ratios were also higher in the beginning of thecolonization, when bacterial community presented unbalanced metabolism.Consequently, the highest discrepancies between the bacterial secondaryproduction estimated by leu and Tdr incorporation were observed in the first2 days of decomposition. On average, the bacterial secondary productivityestimated by leu incorporation was 2.1 times higher than the valuesestimated by Tdr incorporation when the empirical factor for Tdr wasobtained from the relationship between Tdr and biomass increment. Thisdifference increased to 4.2 when the empirical factor was obtained from therelationship between Tdr and cell numbers increment. An average of bothmethods (0.0037 to 0.1397 µgC cm^-2 h^-1)produced results that fall within the range reported in the literature forepiphytic bacteria of freshwater ecosystems.     

Fungal biomass and decomposition in Spartina maritima leaves in the Mondego salt marsh (Portugal)

Spartina maritima (Curtis) Fernald is a dominant species in the Mondego salt marsh on the western coast of Portugal, and it plays a significant role in estuarine productivity. In this work, leaf litter production dynamics and fungal importance for leaf decomposition processes in Spartina maritima were studied. Leaf fall was highly seasonal, being significantly higher during dry months. It ranged from 42 g m^-2 in June to less than 6 g m^-2 during the winter. Fungal biomass, measured as ergosterol content, did not differ significantly between standing-decaying leaves and naturally detached leaves. Fungal biomass increased in wet months, with a maximum of 614 g g^-1 of ergosterol in January in standing-decaying leaves, and 1077 g g^-1 in December, in naturally detached leaves, decreasing greatly in summer. Seasonal pattern of fungal colonization was similar in leaves placed in litterbags on the marsh-sediment surface. However, ergosterol concentrations associated with standing-decaying and naturally detached leaves were always much higher than in litterbagged leaves, suggesting that fungal activity was more important before leaf fall. Dry mass of litterbagged leaves declined rapidly after 1 month (about 50%), mostly due to leaching of soluble organic compounds. After 13 months, Spartina leaves had lost 88% of their original dry weight. The decomposition rate constant (k) for Spartina maritima leaves was 0.151 month^-1.     

Participation of a Specific Substrate Degrading Strain in a Mixed Bacteria Culture as a Result of Ciliate Grazing

Participation of nitrilotriacetic acid degrading bacterial strain NTA-1 in the continuous-cultivated mixed culture was studied under different conditions including predation pressure of the ciliate Dexiostoma campyla (STOKES , 1886). From the viewpoint of dispersed/flocculated biomass distribution, significant relationships between NTA-1 and total bacteria ratio, and dispersed and total biomass ratio were proved in the systems without high concentrations of ciliates. The ciliate concentrations reaching 10⁴ ml⁻¹ stabilized flocculated biomass growth without directly affecting NTA-1 portion. Using fluorescently labelled NTA-1 bacteria, filter feeding rates of ciliates were evaluated (maximum individual uptake rate upon NTA-1 bacteria as a number of bacteria per ciliate per hour being 120 h⁻¹ and 260 h⁻¹ under ciliate division rate of 0.3 day⁻¹ and 1 day⁻¹, respectively). Biomass balance showed that dispersed NTA-1 bacteria should not serve as the sole feeding source for these free-swimming ciliates. The role of diversity of mixed bacterial diet in ciliate growth and the role of ciliate predation in stabilizing bacterial assemblage structure was proved.     

Fungi on Leaf Blades of <Emphasis Type="Italic">Phragmites australis</Emphasis> in a Brackish Tidal Marsh: Diversity,Succession, and Leaf Decomposition

Although fungi are known to colonize and decompose plant tissues in various environments, there is scanty information on fungal communities on wetland plants, their relation to microhabitat conditions, and their link to plant litter decomposition. We examined fungal diversity and succession on Phragmites australis leaves both attached to standing shoots and decaying in the litter layer of a brackish tidal marsh. Additionally, we followed changes in fungal biomass (ergosterol), leaf nitrogen dynamics, and litter mass loss on the sediment surface of the marsh. Thirty-five fungal taxa were recorded by direct observation of sporulation structures. Detrended correspondence analysis and cluster analysis revealed distinct communities of fungi sporulating in the three microhabitats examined (middle canopy, top canopy, and litter layer), and indicator species analysis identified a total of seven taxa characteristic of the identified subcommunities. High fungal biomass developed in decaying leaf blades attached to standing shoots, with a maximum ergosterol concentration of 548 ± 83 μg g^–1 ash-free dry mass (AFDM; mean ± SD). When dead leaves were incorporated in the litter layer on the marsh surface, fungi experienced a sharp decline in biomass (to 191 ± 60 μg ergosterol g^–1 AFDM) and in the number of sporulation structures. Following a lag phase, species not previously detected began to sporulate. Leaves placed in litter bags on the sediment surface lost 50% of their initial AFDM within 7 months (k = −0.0035 day^–1) and only 21% of the original AFDM was left after 11 months. Fungal biomass accounted for up to 34 ± 7% of the total N in dead leaf blades on standing shoots, but to only 10 ± 4% in the litter layer. These data suggest that fungi are instrumental in N retention and leaf mass loss during leaf senescence and early aerial decay. However, during decomposition on the marsh surface, the importance of living fungal mass appears to diminish, particularly in N retention, although a significant fraction of total detrital N may remain associated with dead hyphae.     

First estimates of productivity in Lessonia trabeculata and Lessonia nigrescens (Phaeophyceae, Laminariales) from the southeast Pacific

Lessonia is the main Laminariales found along the southeast Pacific coast. Lessonia nigrescens Bory de Saint‐Vincent in the intertidal and Lessonia trabeculata Villouta et Santelices in the subtidal, are the most important habitat constructors in rocky coastal communities in northern and central Chile. In both species, the seasonal production and erosion of distal tissue were estimated in biomass units using the Area of Constant Biomass Model that combined the individual blade elongation, obtained with the traditional hole‐punching method, with the blade length and biomass distribution along the blade. In austral late spring (December 96) and autumn (May 97), blade production and erosion were transformed to the level of population from standing stock measurements (number and biomass of blades and plants per substrate area), considering that previous blade weight analysis showed the highest and lowest values at these times, as well as the population parameter extremes that were expected to occur. Both species displayed a seasonal pattern, with a production increase in later winter and spring and decrease towards the end of summer that coincided with higher distal tissue erosion. At the level of individual blades, Lessonia trabeculata showed higher mean production (0.026 g dw d⁻¹) and erosion (0.01 g dw d⁻¹) than L. nigrescens (production 0.01 g dw d⁻¹ and loss 0.002 g dw d⁻¹). The standing stocks, with respect to density and biomass, were similar in spring and autumn for both populations. Nevertheless, the net productivity (production minus erosion) of the intertidal L. nigrescens showed greater values due to the greater density of blades (2112 ± 1360 (SE) blades m⁻²) compared with the subtidal L. trabeculata (527 ± 151 (SE) blades m⁻²). Spring net productivities of 42 g dw m⁻²d⁻¹ (254 g ww m⁻²d⁻¹; 11.46 gC m⁻²d⁻¹) for L. nigrescens and 11 g dw m⁻² d⁻¹ (64 g ww m⁻² d⁻¹; 2.46 gC m⁻²d⁻¹) for L. trabeculata were estimated. A preliminary model of production and biomass fate for Lessonia populations is proposed.     

Prodigiosin formation by Serratia marcescens in a chemostat

In a study of the control of metabolite formation, prodigiosin production by Serratia marcescens was used as a model. Specific production rates of prodigiosin formation were determined using batch culture technique. Sucrose as carbon source and NH₄NO₃ as nitrogen source resulted in a specific production rate of 0.476 mg prodigiosin (g cell dry weight)⁻¹ h⁻¹. Prodigiosin formation and productivity was inversely correlated to growth rate when the bacterium was grown under carbon limitation on a defined medium in a chemostat culture. The maximum specific growth rate (μ_max) was 0.54 h⁻¹ and prodigiosin was formed in amounts over 1 mg l⁻¹ up to a growth rate (μ) of 0.3 h⁻¹ at steady state conditions. At a dilution rate of 0.1 h⁻¹ growth at steady state with carbon and phosphate limitation supported prodigiosin formation giving a similar specific yield [1.17 mg prodigiosin (g cell dry weight)⁻¹ and 0.94 mg g⁻¹, respectively], however, cells grown with nitrogen limitation [(NH₄)₂SO₄] did not form prodigiosin. Productivity in batch culture was 1.33 mg l⁻¹ h⁻¹ as compared to 0.57 mg l⁻¹ h⁻¹ in the chemostat.     

Inoculum Density-Dependent Mortality and Colonization of the Phyllosphere by Pseudomonas syringae

Pseudomonas syringae inocula containing cell concentrations ranging from 10⁵ to 10⁹ cells per ml were applied to the primary leaves of bean plants. The plants were incubated under conditions of high temperature and illumination and low relative humidity. Bacterial mortality rates and the proportional population decline of the inoculum were lowest at the highest inoculum concentrations. Addition of a high concentration of heat-killed cells to the inoculum containing a low concentration of viable cells significantly reduced both the mortality rate and the proportional population decline of the viable cells. The mechanisms underlying this density-dependent mortality may include cooperative protective effects of extracellular factors, such as bacterial extracellular polysaccharides, and physical protection by neighboring cells. Although epiphytic populations derived from inoculum concentrations of 10⁸ or 10⁹ cells per ml tended toward 10⁶ CFU/g, the presumed carrying capacity of the leaf, populations derived from lower inoculum concentrations never achieved this carrying capacity. Assuming that epiphytic populations of P. syringae reside in discrete protected sites, our results suggest that at low inoculum concentrations, following a period of environmental stress, the number of viable cells may have dropped to zero in some sites; hence, the carrying capacity of the leaf could not be achieved.     

Protein Metabolism in Cultured Plant Tissues

Rates of protein synthesis in normal callus tissues (either tight or loose morphological form), in crown gall callus tissues and in cultured pith cells were measured for both the lower surface cells (those in contact with the original growth medium) and upper surface cells (those never in contact with the growth medium until labeling). Cells of both surfaces of loose and crown gall callus and the upper-surface cells of tight callus had similar rates of protein synthesis, 29–31 mg of protein synthesized × (g protein)⁻¹× h⁻¹. The lower surface cells of tight callus had a 35% lower rate of synthesis, 20 mg × g⁻¹× h⁻¹. Pulse-chase experiments suggested that rates of protein degradation for all tissues were the same, 21–23 mg protein × (g protein)⁻¹× h⁻¹. Thus, there probably was no accumulation of protein in the lower surface cells of tight callus tissue, but the other tissues had rates of accumulation equaling 10 mg × (g protein)⁻¹× h⁻¹. Autoradiography and electron-microscopic examination of cells in tight callus labeled with ³H-leucine show that: (a) the lower-surface cells were more degenerate than cells within the callus or on the upper surface; and (b) the first few cell layers nearest the medium were preferentially labeled. Pulse-chase experiments were also used to quantitate the nonprecursor pool (defined as that tritium in the soluble amino acid pool that does not equilibrate with protein during a pulse-chase experiment). The nonprecursor pool increased linearly with time at the same rate as incorporation of ³H-leucine into protein. Furthermore, the nonprecursor pool copurified with leucine and was probably either D- or L-leucine.     

Enclosure experiment on the control mechanism of planktonic bacterial standing stock

In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the different enclosures ranged from 1.2 to 2.7×10⁷ cells mL⁻¹ throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was 6.3×10⁵ cells mL⁻¹ h⁻¹. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already stocked in the water column, though it is not known whether the dominant bacteria were the same.     

Physiological and morphological study of encapsulated Saccharomyces cerevisiae

The impact of encapsulation on the anaerobic growth pattern of S. cerevisiae CBS 8066 in a defined synthetic medium over 20 consecutive batch cultivations was investigated. In this period, the ethanol yield increased from 0.43 to 0.46 g/g, while the biomass and glycerol yields decreased by 58 and 23%, respectively. The growth rate of the encapsulated cells in the first batch was 0.13 h⁻¹, but decreased gradually to 0.01 h⁻¹ within the 20 sequential batch cultivations. Total RNA content of these yeast cells decreased by 39% from 90.3 to 55 mg/g, while the total protein content decreased by 24% from 460 to 350 mg/g. On the other hand, the stored carbohydrates, that is, glycogen and trehalose content, increased by factors of 4.5 and 4 within 20 batch cultivations, respectively. Higher biomass concentrations inside capsules led to a lower glucose diffusion rate through the membrane, and volumetric mass transfer coefficient for glucose was drastically decreased from 6.28 to 1.24 (cm³/min) by continuing the experiments. Most of the encapsulated yeast existed in the form of single and non-budding cells after long-term application.     

Production of l-Methionine-enriched cells of a mutant derived from a methylotrophic yeast,Candida boidinii

l-Methionine-enriched cells production of an ethionine-resistant mutant of Candida boidinii no. 2201 was greatly improved by the control of pH and by feeding of methanol and other medium components during cultivation in a jar fermentor. Under the optimal conditions, 38.5 g (as dry weight)_of cells abd 282 mg of pool methionine (intracellular pool of free l-methionine) per l of culture broth were obtained after 11 d of cultivation.The culture conditions for production of l-methionine-enriched cells in continuous culture were investigated. With limited methanol in continuous cultivation, pool methionine productivity reached a maximum value of 1.14 mg·l⁻¹·h⁻¹ at a dilution rate of 0.05·h⁻¹. During methanol-limited growth in continuous cultivation, the pool methionine content of the mutant was about 20–35% higher than that in batch cultivation.