Growth Stimulation of Lactobacillus Species by Lactic Streptococci

Cell extracts of Streptococcus species important in cheese starters stimulated the growth of Lactobacillus species common to Cheddar cheese. All Lactobacillus strains employed, with the exception of a strain of L. casei, were significantly stimulated by a strain of S. diacetilactis. L. casei was highly stimulated by both a strain of S. lactis and a strain of S. diacetilactis. The stimulant(s) was dialyzable and was partially inactivated by heat. The stimulatory principle was active at 10 C, indicating that the stimulatory effect may be influencing the growth of lactobacilli in Cheddar cheese during curing. Viable Streptococcus cells did not inhibit the growth of Lactobacillus species.     

Predicting Growth in Stands of Mixed Species from that in Individual Species

The growth of spring cabbage (Brassica oleracea var. capitataL.) and carrot (Daucus carota L.) in mixed species stands iscompared with growth curves predicted by two forms of a dynamiccompetition model, which uses a conductance relationship (Aikmanand Scaife, 1993) to allow for the constraints on growth froma set of environmental variables. While a plant is isolated,light interception is assumed to occur within a zone whose areais a function of plant weight. Lateral foliage expansion isconstricted when the available space is filled. One form ofthe model assumes that all plants are of similar height (Aikmanand Benjamin, 1994). The second form assumes the crown zonesare in separate vertical layers, allowing greater lateral expansionin each layer but imposing shading on the underlayer. Parameter values of the model were estimated from the growthwithin even-aged monocrops. The first form of the model gavethe best prediction of growth in the intercrops, often producinga close agreement between observed and predicted weights. Onlyat the highest density used, 0·05 m spacing, did thedifferent height form of model give a better prediction of growth. Many mixed species stands may be approximated by one or otherof the forms of the model, and the relevant form can easilybe calibrated from the growth observed in monocrops. Hence,simple models may be sufficiently accurate to predict growthin mixed species systems such as intercrops, or crops and weeds.Copyright1995, 1999 Academic Press Cabbage, carrot, competition, intercrop, light, mechanistic model, temperature, canopy architecture     

Growth of Mixed Cultures on Mixed Substrates: I. Continuous Culture

Continuous culture on mixed glucose-lactose or glucose-butyrate media inoculated with river water led to a population composed of a pseudomonad and a coliform. The glucose was used preferentially to the other carbon source, and the utilization of the secondary carbon source was greatly reduced at high growth rates. Significant amounts of acetate were excreted even though the cultures were limited by the carbon source, rather than by oxygen or other nutrients. At high growth rates, the pseudomonad dominated the population, whereas at low and moderate growth rates the coliform was dominant. A syntrophic relationship was shown by the fact that the pseudomonad could not grow alone on the glucose-butyrate medium.     

Growth of Human Lymphoid Cells (Raji Strain) in a Five-Liter Fermentor

Procedures used to produce an established line of mammalian cells (L cell) in a New Brunswick fermentor were adapted to propagate human lymphoid cells in suspended culture. Control of pH within defined limits was more effective for regulation of cell metabolism than control of oxidation-reduction potential. An unusually high rate of agitation was required.     

Predicting the Growth Interactions between Plants in Mixed Species Stands using a Simple Mechanistic Model

The Conductance model is a simple mechanistic model used topredict the growth of species in monoculture or mixtures fromparameter values derived from plants grown in isolation. Incontrast to many mechanistic models that require extensive parameterization,the Conductance model is able to capture the growth of a broadrange of species using a few simplified assumptions regardingplant growth and easily derived species-specific parameter values.We examine the assumptions within the Conductance model thattotal leaf area per plant is proportional to total plant weight,and that an isolated plant has a projected crown zone area thatis proportional to the 2/3 power of its weight. Power ratherthan linear relations were found between weight and leaf areafor Brassica oleracea, Daucus carota, Matricaria inodora, Solanumnigrum,Stellaria media , Trifolium repens and Veronica persica.For all seven species, the value of the power was less thanunity. All species also exhibited a power relation between crownzone area and weight, with the slope of this relation beingless than 2/3 for B. oleracea, D. carota and S. media. Althoughmorphology type accounted for some of the variation in the parametervalues relating to light interception, there were considerabledifferences between species within upright or prostrate foliagespecies groups. The Conductance model was used to predict yieldsof B. oleracea, S. nigrum and V. persica grown in both monocultureand binary weed-crop mixtures over a range of temporal and spatialscales. After calibrating the model to non-competing plants,the model was used to predict growth of the weed and crop speciesin contrasting densities and stand types. In some crop-weedcombinations, predicted crop and weed weights were within 17%of observed values, with no systematic deviations. In others,systematic and large deviations occurred.Copyright 2001 Annalsof Botany Company Brassica oleracea L., Daucus carota L., Matricaria inodora L., Solanum nigrum L.,Stellaria media L., Trifolium repens L., Veronica persica L., competition, growth, leaf area, crown zone area, light, shoot morphology, canopy architecture     

Continuous Cultivation of Glucose-Limited Bean Cells (Phaseolus vulgaris L.) in a Modified Bacterial Fermentor

A commercially available bacterial fermentor was modified toallow the continuous cultivation of glucose-limited bean cells(Phaseolus vulgaris L.) at a defined pH. A steady state wasreached using a dilution rate of 0?004 h^–1 and was maintainedfor 4 months; during this period the dry weight and packed cellvolume of the culture remained constant; the yield for glucosewas 0?34 (dry wt./dry wt) and for carbon 0?27 (g atom/g atom).Glucose-limited cells had lower C/N ratios both for cytoplasmand cell walls than cells in the exponential phase of growthin batch cultures.     

产酸丙酸杆菌生长特性及5L罐发酵动力学研究

论文在摇瓶水平对产酸丙酸杆菌基本生长特性（温度、pH、摇床转速、接种量、种龄等）、碳源、氮源利用情况、产物抑制及5 L罐发酵动力学进行了研究。结果表明,该菌在32℃,初始pH 6．5,摇床转速150 r/min,接种24 h的种子液,接种量为5％条件下,产酸丙酸杆菌生长及产酸水平达最高值;该菌可利用碳源十分广泛,但对氮源要求比较高,只可利用有机氮源;在不同初始葡萄糖浓度下,产酸丙酸杆菌生长及产酸水平差异不大,无明显底物抑制现象;在2g/L的初始丙酸盐浓度下,该菌生长受到明显抑制;在5L发酵罐中,初始葡萄糖浓度为58．8 g/L,发酵72 h,葡萄糖消耗完全,丙酸终浓度达22．4 g/L,丙酸得率和产率分别达0．381 g/g和0．295 g/（L·h）,丙酸占总酸比例达72．10％。     

Continuous and Batch Production of Chloroperoxidase by Mycelial Pellets of Caldariomyces fumago in an Airlift Fermentor

Batch and continuous production of the extracellular heme glycoprotein chloroperoxidase (CPO) was studied with an airlift fermentor. We induced Caldariomyces fumago CMI 89362 to form pellets by transferring a small inoculum volume in preculture prior to growth in a 1-liter fermentor. Continuous replacement of the fructose-salts medium (dilution rate, 0.008 h⁻¹) supported continuous CPO formation at an average concentration of 128 ± 10 mg of CPO liter⁻¹ for 8 days. Optimum CPO production rates averaged 1.2 ± 0.1 mg of CPO h⁻¹ at dilution rates below 0.033 h⁻¹. Varying the carbohydrate content of the feed solution or the time of starting the feed did not significantly alter the amount of CPO produced. Batch fermentation in the airlift fermentor resulted in maximum CPO concentrations of 280 ± 80 mg of CPO liter⁻¹, although on two separate occasions CPO concentrations reached 400 to 450 mg liter⁻¹, which was double the amount obtained by free hyphae in shake flask culture.     

Microbial Ecophysiology of Whey Biomethanation: Comparison of Carbon Transformation Parameters, Species Composition, and Starter Culture Performance in Continuous Culture

Changes in lactose concentration and feed rate altered bacterial growth and population levels in a whey-processing chemostat. The bacterial population and methane production levels increased in relation to increased lactose concentrations comparable to those in raw whey (6%) and converted over 96% of the substrate to methane, carbon dioxide, and cells. Sequential increases in the chemostat dilution rate demonstrated excellent biomethanation performance at retention times as low as 25 h. Retention times shorter than 25 h caused prevalent bacterial populations and methane production to decrease, and intermediary carbon metabolites accumulated in the following order: acetate, butyrate, propionate, lactate, ethanol, and lactose. Bacterial species dominated in the chemostat as a function of their enhanced substrate uptake and growth kinetic properties. The substrate uptake kinetic properties displayed by the mixed chemostat population were equivalent to those of individual species measured in pure culture, whereas the growth kinetic properties of species in mixed culture were better than those measured in pure culture. A designed starter culture consisting of Leuconostoc mesenteroides, Desulfovibrio vulgaris, Methanosarcina barkeri, and Methanobacterium formicicum displayed biomethanation performance, which was similar to that of a diverse adapted mixed-culture inoculum, in a continuous contact digestor system to which 10 g of dry whey per liter was added. Preserved starter cultures were developed and used as inocula for the start-up of a continuous anaerobic digestion process that was effective for biomethanation of raw whey at a retention time of 100 h.     

Growth Response and Modifications of Organic Nitrogen Compounds in Pure and Mixed Cultures of Lactic Acid Bacteria from Wine

The interactions between the proteolytic X₂L strain of Oenococcus oeni and the non-proteolytic 12p strain of Pediococcus pentosaceus were assayed. The characteristics of cell growth, protein degradation, and amino acid production of both strains were determined in pure and mixed cultures. O. oeni showed poor cell growth and greater ability in the release of amino acids to the extracellular medium, whereas P. pentosaceus showed a higher yield in cell production with a decrease in the amino acid concentration in the medium. P. pentosaceus especially consumed essential amino acids for growth, and O. oeni released several of the essential amino acids important for growth of P. pentosaceus. In the mixed culture, mutualism was observed. The higher activity of the proteolytic system of O. oeni in mixed culture produced an increase in cell growth and in the amount of essential amino acids released. These findings provide new knowledge about the metabolic interactions between lactic acid bacteria isolated from wine when proteins are degraded in mixed bacterial populations.     

酸奶发酵剂和乳酸菌生物技术育种

由新鲜牛奶制成的酸奶由于其丰富的营养、特殊的风味、爽滑的质构和良好的生理功能 ,倍受人们青睐。对酸奶乳酸菌的微生物种类、功能及其组成的酸奶发酵剂进行了综述 ,并简要介绍了乳酸菌生物工程育种方面的研究进展及酸奶乳酸菌研究领域一些令人感兴趣的课题。     

Growth of an Ethane-utilizing Mixed Culture in a Chemostat

Bacteria capable of utilizing ethane as their sole source of carbon and energy at 42° were readily isolated from soil samples obtained from Brunei with batch culture enrichment techniques. No ethane utilizers capable of growth at 42° were isolated, however, from soil samples obtained from Britain. An ethane-utilizing mixed culture was grown under ammonia limitation in chemostat culture. The lipid content of the culture was inversely proportional to the dilution rate. Similarly, the amount of organic carbon excreted into the culture supernatant was inversely proportional to the growth rate and could be accounted for mainly as carbohydrate. The specific rates of ethane and oxygen consumption, carbon dioxide production and yield from ethane were directly proportional to the dilution rate.     

Polyalcohol Production by Pichia miso in a Jar Fermentor

Cultural conditions for polyalcohol production by Pichia miso were examined in Waldhof type 20 liter-fermentor scale. The best result was obtained under conditions where the aeration rate was 1 volume per volume of the medium per minute with the stirring rate of 500r.p.m., (Kd=5×l0^-6 [g-mol of O₂/atm. min. ml.]); in 5 days incubation, Pichia miso completely dissimilated the glucose of a high concentration, 30%, and produced glycerol, D-arabitol and erythritol in a very high yield, 50% of sugar consumed. The greatest advantage compared with the shake flask culture is that the required fermentation time is shortened to half.     

Growth of Facultatively Heterofermentative Lactobacilli on Starter Cell Suspensions

The growth of facultatively heterofermentative lactobacilli (FHL) on cell suspensions of the homofermentative Lactobacillus helveticus was investigated. Osmotic lysis of L. helveticus led to a significant increase of ribose. It decreased steadily in parallel with the growth of FHL, strongly suggesting that the bacteria used ribose as a growth substrate.     

Energetics of Growth of a Defined Mixed Culture of Desulfovibrio vulgaris and Methanosarcina barkeri: Interspecies Hydrogen Transfer in Batch and Continuous Cultures

Interspecies hydrogen transfer was studied in Desulfovibrio vulgaris-Methanosarcina barkeri mixed cultures. Experiments were performed under batch and continuous growth culture conditions. Lactate or pyruvate was used as an energy source. In batch culture and after 30 days of simultaneous incubation, these organisms were found to yield 1.5 mol of methane and 1.5 mol of carbon dioxide per mol of lactate fermented. When M. barkeri served as the hydrogen acceptor, growth yields of D. vulgaris were higher compared with those obtained on pyruvate without any electron acceptor other than protons. In continuous culture, all of the carbon derived from the oxidation of lactate was recovered as methane and carbon dioxide, provided the dilution rate was minimal. Increasing the dilution rate induced a gradual accumulation of acetate, causing acetate metabolism to cease at above μ = 0.05 h⁻¹. Under these conditions all of the methane produced originated from carbon dioxide. The growth yields of D. vulgaris were measured when sulfate or M. barkeri was the electron acceptor. Two key observations resulted from the present study. First, although sulfate was substituted by M. barkeri, metabolism of D. vulgaris was only slightly modified. The coculture-fermented lactate produced equimolar quantities of carbon dioxide and methane. Second, acetogenesis and methane formation from acetate were completely separable.     

Continuous Removal of Lactic Acid from Wastewater by Candida utilis

Under steady-state conditions, the maximum rate of lactic acid removal was found to be 588 mg/h per liter of continuous culture.     

Inhibition of Lipid Peroxidation of Lecithin Liposomes Kept in a pH-Stat System Near Neutral pH

During 5 days of autoxidation of egg lecithin liposomes in nonbuffered saline pH dropped from an initial value of 7.4 to 4.5. A linear relationship between oxidation index and pH was obtained. Lipid peroxidation, monitored as conjugated diene and TBA-reactive products, was inhibited significantly by keep ing the samples under pH-controlled conditions (7.4 plusmn; 0.5), compared to controls. Obtained results indicate that the buffering capacity of Tris and Hepes buffers may play a role in their recently reported (D. Fiorentini et al. (1989) Free Radical Res. Commun., 6, 243) inhibitory action against lipid peroxidation of lecithin liposomes.