Mixed Culture System Research Articles

L‐Lactic acid production from starch by coimmobilized mixed culture system of Aspergillus awamori and Streptococcus lactis

<scp>L</scp>‐Lactic acid production from starch by coimmobilized mixed culture system of <i>Aspergillus awamori</i> and <i>Streptococcus lactis</i>

Effect of the solids retention time on the rate of biodegradation of organic compounds

AbstractThe paper studies the effect of the solids retention time (SRT) on the rate of biodegradation of morpholine (M), sulfanilic acid (SA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) in laboratory mixed culture systems, fed semicontinuously on a once‐a‐day feeding schedule. It has been found that the minimum values of SRT at which microorganisms degrading the above compounds were washed out from the cultivation systems were 3, 1, 1, and 20 days for M, SA, NTA, and EDTA systems, respectively. A critical value of SRT was defined as that below which the rate of substrate removal is lower than the rate of substrate application into the system. The critical values of SRT were found to be 8, 3, 2.5, and above 20 days for M, SA, NTA, and EDTA systems, respectively. In a range between the minimum and critical values of SRT the mixed culture system cannot give stable efficiency of a given compound removal and the effluent concentration can be expected to vary considerably. Above the critical value of SRT, every cultivation system has a potential capability of shock loading treatment.

Growth kinetics of top and bottom cultures of Saccharomyces spp. in a chemostat using sugarbeet molasses

AbstractGrowth kinetics were evaluated for three yeast strains of the genus Saccharomyces. Two topfloating strains, SF 115 and SF 116 and one flocculant yeast SF 104 were analyzed in pure and mixed cultures in 1‐liter continuous fermentation experiments in a chemostat. Growth was monitored for 72 h at 30°C in a medium containing sugarbeet molasses and 1.0 g/liter each of NH4H2PO4 and urea. SF 115 and SF 116 were found to have lower μmax values of 0.290 and 0.296 h−1, respectively, than SF 104, which had a μmax of 0.364 h−1. The two top‐floating yeasts (SF 115 and SF 116) demonstrated greater affinity for the substrate and utilized substrates at a greater rate. They have K8 values of 4.03 × 10−3 M and 3.798 × 10−3 M, respectively, compared to 9.06 × 10−3 M for SF 104. A mixed culture of SF 116 and SF and SF 104 was found to have a μmax of 0.426 h−1 with a Ks of 6.924 × 10−3 M. SF 115 grown in mixed culture with SF 104 exhibited a μmax of 0.473 h−1 with a Ks of 7.975 × 10−3 M. In both cases, the SF 104 was the dominant microbe in mixed culture systems.

Effect of Streptococcus parvulus and Peptostreptococcus magnus on cytotoxin levels of Clostridium difficile in anaerobic continuous flow culture.

An anaerobic continuous flow (CF) culture method was used in order to study the effect of Peptostreptococcus magnus and Streptococcus parvulus, anaerobic gram-positive cocci which are members of intestinal bacterial flora, on growth and cytotoxin-activity of Clostridium difficile. The growth- and the cytotoxin activity-patterns of C. difficile in an established CF culture of P. magnus were similar to those of C. difficile alone. On the other hand, in the mixed culture system of C. difficile and S. parvulus, the cytotoxin levels were significantly lower as compared with C. difficile alone in spite of the fact that no differences existed between growth of C. difficile in mixed and single culture systems. The culture filtrate of P. magnus did not influence the growth and cytotoxin production of C. difficile, nor did that of S. parvulus have any effect on growth of C. difficile in static culture. The cytotoxin activity of C. difficile was, however, suppressed by the culture filtrate of S. parvulus. Furthermore, when P. magnus or S. parvulus was statically cultured in a medium containing cytotoxic culture filtrate of C. difficile, the toxin in the medium was not inactivated.

Evaluation of Escherichia coli and Candida utilis as a model continuous, competitive mixed culture system

The yeast Candida utilis and the bacterium Escherichia coli B/r were evaluated as a candidate experimental, continous, competitive mixed culture system under ammonia-nitrogen limited conditions at 30 degrees C. High dilution rates favored yeast dominance, while low dilution rates favored bacterial dominance. The hydrogen ion concentration was also demonstrated to be an effective manipulative variable for control of the yeast-bacterial mixed culture. Through trial-and-error manipulation of the pH for the mixed culture operating at constant dilution rate, it was possible to locate a metastable equilibrium point and to operate in the vicinity of that point for more than 24h. The reproducible emergence of a variant E. coli was also noted in this study.

Relationship of chemical structures of anthraquinones with their effects on the suppression of immune responses

A series of 37 anthraquinones were evaluated for their ability to inhibit the induction of cytolytic T-lymphocytes in a mixed lymphocyte culture system, useful as a preliminary screen for immunosuppressive agents. These compounds were also tested for their ability to prevent the production of antibody in mice. It was demonstrated that 1,4- bis [(2-aminoethyl)amino]-5, 8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD, 2) derived from mitoxantrone (MX, 1) by removing hydroxyethyl groups from both side chains was extremely active in depressing immune responses in vitro and in vivo. Four additional anthraquinones related to AEAD were also identified to share similar suppressive activity. They include a Schiff base, 1,4-dihydroxy-5,8- bis[[2-[3-pyridinylmethylene)amino]ethyl]amino]-9,10-antracenedione ( 25); a dimer with N-terminals methylated, 1,1-[ethylenebis (iminoethyleneimino)]- bis[5,8-dihydroxy-4-[(2-methylamino-ethyl)amino] anthraquinone tetrahydrochloride (35); an oxazolidine, 1,4-dihydroxy-5,8- dis [[2-(2-propyl-3-oxazolidinyl)ethyl]amino] anthraquinone (10); and its polymeric oxazolidine, poly [5,8-dihydroxy-1,4-anthraquinonyleneiminoethylene-3,2-oxazolidine-diyltrimethylene-2,3-oxazolidinediylethyleneimino] (36). These compounds may warrant further consideration as candidates for the treatment of refractory autoimmune diseases and in organ transplantation.

Ethanol production from starch by a coimmobilized mixed culture system of Aspergillus awamori and Zymomonas mobilis

The production of ethanol from starch by a coimmobilized mixed culture system of aerobic and anaerobic microorganisms in Ca-alginate gel beads was investigated. The mold Aspergillus awamori was used as an aerobic amylolytic microorganism and an anaerobic bacterium, Zymomonas mobilis, as an ethanol producer. By controlling the mixing ratio of the microorganisms in the inoculum size, a desirable coimmobilized mixed culture system, in which the aerobic mycelia grew on and near the oxygen-rich surface of the gel beads while the anaerobic bacterial cells mainly grew in the oxygen-deficient central part of the gel beads, was naturally established under the aerobic culture conditions, and ethanol could be directly produced from starch by the system. The ethanol productivity by the system in flask culture was particularly affected by the shear stress (dependent on the shaking speed) which controlled the mycelial growth on the surface of the gel beads. Under optimum culture conditions in the flask culture, the glucose produced was instantly consumed, and was not observed in the culture broth; the final concentration of ethanol produced from 100 g/L starch was 25 g/L and the yield coefficient for ethanol, Y(pls), was 0.38. The ethanol productivity by the coimmobilized mixed culture system was compared with those by other various culture systems and the advantages of the system were clarified.

Effect of pH oscillations on a competing mixed culture

Two microorganisms, E. coli and S. cerevisiae, competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a Chemostat. Pure culture experiments found S. cerevisiae to be insensitive to pH between 5 and 4.3 with a maximum specific growth rate (micro(max)) of 0.4/hr; while micro(max) of E. coli decreased from 0.6 h(-1) at pH 5 to 0.1 h(-1) at pH 4.3. Steady-state and cross-inoculation chemostat runs at a dilution rate of 0.17 h(-1) confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D =0.17 h(-1) with 1 g per liter glucose feed. The 16 h/16 h cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 h pH 5/14 h pH 4.3 cycle was found to be stable with smaller yeast concentrations. A 6 h/6 h cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus, varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.

THE CLOSTRIDIUM THERMOCELLUM-CLOSTRIDIUM THERMOSACCHAROLYTICUM ETHANOL PRODUCTION PROCESS: NUTRITIONAL STUDIES AND SCALE-DOWN

The Clostridium thermocellum-Clostridium thermosaccharolyticum mixed culture system has been scaled down into flasks in defined medium MJ with Solka Floe as carbon source. The best saccharolytic cu...

Bifurcations in a bang-bang controlled mixed culture system

A bang-bang controlled chemostat culture in which two microbial populations compete for the same nutrient was studied from the standpoint of bifurcation theory. The dilution rate was periodically switched between two fixed values. The bifurcations of periodic states due to changes in the control parameters, the period and the switching ratio were investigated and the region of co-existence in the control parameter plane was determined. The stability of each periodic state was determined by seeking the values of the corresponding characteristic multipliers. The bifurcations without any topological contradiction were determined by applying the index theory.

Influence of dietary alfalfa:orchardgrass hay and lasalocid on in vitro estimates of dry matter digestibility and volatile fatty acid concentrations of cecal contents and rate of digesta passage in sows.

Four mature crossbred sows were fistulated in the cecum, with two sows fed a corn-alfalfa:orchardgrass hay (46%) diet (CH) and two fed a corn-soybean meal diet (CS). Four experiments were conducted to evaluate buffers, incubation times, buffer pH and substrate and inocula sources in an in vitro, anaerobic, mixed-culture system. In vitro dry matter digestibility (IVDMD) and substrate solubility in buffer (SS) were determined. In Exp. 1, substrates were CH and CS diets with cecal inocula obtained from CH- and CS-fed sows. The bicarbonate (B) buffer resulted in lower (P less than .01) and less variable SS for all treatments. In vitro dry matter digestibility was higher (P less than .01) for the CS diet at both 24 and 48 h incubation. Use of the B buffer also resulted in higher (P less than .001) IVDMD values. In Exp. 2, substrates were either as in Exp. 1 or were freeze-dried cecal contents (CC) from CH- or CS-fed sows. In vitro dry matter digestibility of CC was lower (P less than .006) than IVDMD of diet, while IVDMD was higher (P less than .02) with cecal inocula than fecal inocula. In Exp. 3, substrate-inocula treatments were CH-CH, CH-CS, CS-CH and CS-CS. Substrate solubility was lower (P less than .05) at pH 5.8 than at pH 6.8. In vitro dry matter digestibility was higher when substrate and inocula were from the same source and at pH 5.8. In Exp. 4, CC and inocula were from sows fed CH and CS diets with or without lasalocid. In vitro dry matter digestibility was higher with CC from lasalocid-fed sows and inocula from sows fed no lasalocid. The CH diet resulted in higher acetate (Ac) and lower propionate (Pr) molar proportions than did the CS diet, while lasalocid increased molar proportion Pr and decreased molar proportion Ac in cecal contents from sows fed either diet. Corn-alfalfa:orchardgrass hay-fed sows had a faster rate of digesta passage and shorter cecal retention time than did CS-fed sows.

Synergistic anti-suppressor effect of mini cells prepared from Salmonella typhimurium and mitomycin C in EL 4-bearing mice.

The subcutaneous growth of EL4 cells was significantly accelerated when they were injected together with spleen cells collected from mice which had received EL4 cells SC 14 days previously, and all mice died within 18 days after receiving this mixture; 80% of mice which received a mixture of EL4 and spleen cells collected immediately after EL4 graft survived over 40 days. Spleen cells collected 14 days after EL4 graft suppressed the blastogenic responses of normal spleen lymphocytes to concanavalin A, pokeweed mitogen, and lipopolysaccharide of Escherichia coli in a mixed culture system. Acceleration of tumor growth was retarded when EL4 cells were injected together with spleen cells from EL4-bearing mice treated with both Salmonella typhimurium mini-cells and mitomycin C, and 60% of mice survived over 40 days. Blastogenic responses of normal spleen lymphocytes mixed with spleen cells from EL4-bearing mice treated with both mini-cells and mitomycin C were restored almost to control levels. The results suggest that combination treatment with mini-cells and mitomycin C synergistically inhibits the induction of suppressor cells in EL4-bearing mice.

Model system of bulking and flocculation in mixed culture of Sphaerotilus sp. and Pseudomonas sp. for dissolved oxygen deficiency and high loading

A mixed continuous culture system was made up as a model for bulking and flocculation phenomena of the activated sludge to study the effect of dissolved oxygen (DO) deficiency and the effect of high organic loading. The system consisted of a floc forming bacterium and a filamentous bacterium which were isolated from the activated sludge and were identified as Pseudomonas sp. and Sphaerotilus sp., respectively. Sphaerotilus sp. had potential to cause a filamentous bulking phenomenon on the activated sludge. It was observed that the filamentous microorganism showed three kinds of growth form, filamentous form, pellet form and dispersed form, and that the floc former showed two kinds of growth form, good floc form and dispersed form. In the model system, these changes of growth form of two microorganisms, which could be thought as the cause of settling characteristics changes, depended on the DO level and the dilution rate (as a substitution for organic loading). The DO level also influence the aggregative ability of each microorganism and the maximum oxygen uptake rate, Q O 2max, of filamentous microorganism. The proportions of both microorganisms in model system were inverted reversibly by the DO level or the dilution rate changes.

Mixed microbial culture technology.

Conference Article| December 01 1984 Mixed microbial culture technology ALAN T. BULL ALAN T. BULL 1Biological Laboratory, University of Kent, Canterbury, Kent CT2 7NJ, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1984) 12 (6): 1137–1138. https://doi.org/10.1042/bst0121137 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation ALAN T. BULL; Mixed microbial culture technology. Biochem Soc Trans 1 December 1984; 12 (6): 1137–1138. doi: https://doi.org/10.1042/bst0121137 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1984 Biochemical Society1984 Article PDF first page preview Close Modal You do not currently have access to this content.

Immunosuppressive Effect of Uterine Secretory Protein from Angus and Brahman Cows upon Lymphocytes in Vitro3

Uterine luminal protein collected on d 17 (estrus = d 0) from Angus (n = 20) and Brahman (n = 19) cows of varying reproductive status was evaluated for immunosuppressive activity in vitro. Reproductive status consisted of the following categories: nonpregnant (uterine flushing was devoid of embryonic material); remnant (uterine flushing contained obvious degenerative fragments of embryonic tissue) and pregnant (uterine flushing contained an intact conceptus). Uterine protein was tested for suppressor activity in both phytohemagglutinin (PHA) and mixed lymphocyte culture (MLC) systems. Incorporation of [3H]-thymidine into 1 X 10(6) Angus or Brahman lymphocytes for PHA cultures and 5 X 10(5) lymphocytes from each breed for MLC experiments served as the index for lymphocyte blastogenesis. For all experiments, uterine luminal protein from nonpregnant, remnant and pregnant Angus and Brahman cows suppressed (P less than .01) lymphocyte blastogenesis for Angus and Brahman lymphocytes, respectively. In two lymphocyte-uterine protein specificity experiments containing PHA, uterine protein from Angus cows suppressed (P less than .01) blastogenesis of Brahman lymphocytes and uterine protein from Brahman cows suppressed (P less than .01) blastogenesis of Angus lymphocytes. Within and between breed comparisons of suppressor activity were evaluated when expressing uterine protein culture data as percentages of control (no test protein) cultures. At 200, 400 and 800 micrograms/ml of uterine protein, suppressor activity was consistently greater in secretions from pregnant than from nonpregnant cows for each breed. For between breed comparisons, there were nonsignificant trends toward greater suppressor activity for nonpregnant Angus than for nonpregnant Brahman cows at 200, 400 and 800 micrograms/ml of protein. Suppressor activity was greater (P less than .10) for pregnant Angus than for pregnant Brahman cows at 400 micrograms/ml of protein and tended to be greater for pregnant Angus than for Brahman cows at 800 micrograms/ml of protein. These data indicate that uterine secretory protein collected on d 17 from Angus and Brahman cows exerted immunosuppressive activity in vitro. Further, suppressor activity in each breed was greater in pregnant than in nonpregnant cows and suppressor activity tended to be greater for Angus than for Brahman cows.

Dynamics and control of an activated sludge process as a mixed culture system

AbstractOne of the difficulties encountered in the operation of an activated sludge process is the phenomenon of bulking sludge.In an activated sludge process which is composed of a completely mixed aeration tank and a sedimentation vessel, the dynamic behavior of the system can be analyzed using a mathematical model. The model developed here is based on the kinetics and settleability of the combination of floc‐forming sludge and bulking sludge. The operating conditions that cause the bulking phenomenon are clarified on the phase plane. It is also shown that a type of nonlinear state feedback regulator makes the system stable.

Membrane markers, karyotypic abnormalities, ultrastructure and functional properties of lymphocytes in a case of ‘D-cell’ chronic lymphatic leukemia

D cells are lymphocytes bearing both receptors for the third complement component and the ability to form spontaneous rosettes with SRBC. We report the case of a patient with a D-cell chronic lymphatic leukemia who presented a long evolution without treatment and whose leukemic cell characteristics have been extensively studied. Cytogenetic analysis showed numerous karyotypic abnormalities among leukemic cells; all metaphases were hypodiploid and arranged in four different clones; seven marker chromosomes were present. The cells were found to bear human T-cell specific antigen, the T helper/inducer phenotype, HLA-A and HLA-B determinants, but no HLA-DR antigens. They displayed a high proliferative response to PHA and Con A, no response to PWM stimulation, and possibly the capacity of allogeneic stimulation in the mixed lymphocyte culture system. Assays for cell-mediated cytotoxicity in the CML system, and for K and NK activities were negative.

Macrocyst development in Dictyostelium discoideum. II. Mating-type-specific cell fusion and acquisition of fusion-competence.

The early events of macrocyst development in Dictyostelium discoideum have been investigated using a new culturing system. When cells of opposite mating-types, HM1 and NC4, are cultured together at the appropriate temperature in the dark, giant cells appear, ingest the surrounding amoebae, and develop into macrocysts. Although these giant cells have been assumed to be the products of the fusion of opposite mating-type cells, no experimental evidence to prove this assumption has been obtained using such mixed-culture systems. In order to avoid the complexities involved in mixed-culturing, we have developed a new system involving the separate culture, and later mixing, of opposite mating-type cells. This has enabled us to obtain direct evidence that giant cells are produced by fusion between opposite mating-type cells. Cell fusion occurs immediately after mixing and is completed within 30 min. As a number of cells fuse simultaneously, giant cells produced by this method are very large multinucleated cells, and not binucleated zygotes. Using this system we also discovered the following facts related to giant cell formation: (1) cells can acquire their fusion competence without the presence of cells of the opposite mating-type; (2) only HM1 cells require darkness to acquire their fusion competence; (3) the restrictive temperature, 25 degrees C, inhibits the induction of fusion competence in HM1 cells, but not in NC4 cells.

T cell progenitors in the mouse fetal liver.

Fourteen-day mouse fetal liver was found to contain cells capable of giving rise to T as well as B cell functions. The experimental system consisted of congenic C3H/DiSn and (C3H/DiSn X C3H.SW)F1 lethally irradiated (900 R) mice reconstituted with C3H/DiSn fetal liver or bone marrow cells. Assays included thyroid allograft rejection as well as in vitro measurement of reactivity to phytohemagglutinin (PHA) and concanavalin A (Con A) and in a mixed lymphocyte culture (MLC) system in spleen, lymph node, and thymus cells. The fetal liver chimeras were found to become as capable as the bone marrow chimeras in responding in these various assays. The T cell responses lagged behind the responses to the B cell mitogens dextran sulfate (DXS) and lipopolysaccharide (LPS) (30 days after reconstitution, as compared with 14 days for DXS and 21 for LPS). The reacting cells were of the donor genotype, as revealed after treatment with C3H/DiSn (H-2k) anti-C3H.SW (H-2b) congenic sera. T cell responses were not manifest in thymectomized (TX) chimeras. Hence, the liver seems to contain cells capable of developing into T cell lineages in a thymus-dependent process.

In vitro stimulation of Bacteroides fragilis growth by Escherichia coli.

The interaction between Bacteroides fragilis and Escherichia coli was investigated by following their growth kinetics in an in vitro mixed culture system. In Bacto-peptone or in a semisynthetic medium (SSM-M) Bacteroides fragilis could initiate growth only when a small number of viable Escherichia coli initially coexisted for a short period of time. Both Bacto-peptone and SSM-M previously spent by Escherichia coli also allowed Bacteroides fragilis growth to occur but the supplementation of heat killed Escherichia coli cells or viable cell homogenates to fresh media failed to stimulate Bacteroides fragilis growth. The in vitro stimulation of Bacteroides fragilis growth by Escherichia coli observed in this study may be best explained by the combination of (a) removal of oxygen and other toxic substances and (b) de novo production of Bacteroides fragilis growth stimulating factor(s) by coexistent Escherichia coli.