Initial Cell Concentration Research Articles

Some remarks on the evaluation of m-cresol and pyridine biodegradation kinetics

Wastewater produced from petroleum and coal processing industries can be contaminated with m-cresol and pyridine, which are two hazardous compounds with significant environmental and health effects. A bacterium known as Lysinibacillus cresolivorans has been demonstrated to effectively biodegrade m-cresol and this bacterium has been utilised by researchers to study the interaction effects of m-cresol and pyridine. Some variations in the literature were observed in the experimental data of the biodegradation of pyridine, which may be attributed to inaccurate estimation of initial cell mass concentration. In this work, simulations were run in combination with an algorithm to optimise initial biomass cell concentrations to describe the biodegradation kinetics of an inhibitory system in relation to experimental data. Simulated data on predicted cell concentrations and the results of this study may facilitate full-scale bioreactor design for m-cresol and pyridine removal from wastewater resulting from petroleum and coal processing.

Tuyển chọn chất mang để tồn trữ vi khuẩn Bacillus aerophilus đối kháng với vi khuẩn Xanthomonas oryzae pv. oryzae gây bệnh cháy bìa lá lúa

This study is aimed at evaluating effects of carrier materials on survival and biological activities of Bacillus aerophilus against Xanthomonasoryzae pv. oryzae (Xoo) causing rice bacterial leaf blight. Five carrier materials, i.e., talc, rice bran, rice kernel powder, rice grain powder and rice husk powder were used to prepare different B. aerophilus formulations at an initial cell concentration of 2×108 CFU/mL. Talc, rice bran and rice husk formulations maintained the number of viable B. aerophilus cells higher than 106 CFU per gram formulation as well as its antagonistic effects against Xoo after six months of storage. Under greenhouse conditions where rice plants were inoculated at 45 days after sowing, seed soaked with these three formulations after six months of storage effectively reduced lesion lengths until 15 days after inoculation compared to the untreated control. Thus, talc, rice bran and rice husk powder show their potentials for production of bio-products to control bacterial leaf blight in rice fields.

Microbial Production of Xylitol from Oil Palm Empty Fruit Bunch Hydrolysate: Effects of Inoculum and pH

Considering its high content of hemicellulose, oil palm empty fruit bunch (EFB) lignocellulosic biomass waste from palm oil processing has the potential to be utilized as the raw material for the production of xylitol, a low calorie, low GI, and anti cariogenic alternative sugar with similar sweetness to sucrose. This research explored the possibility of converting EFB to xylitol via green microbial fermentation, in particular the effects of inoculum and initial pH on the fermentation performance. It was observed that the cell concentration in the inoculum and the initial pH affect cell growth and xylitol production. pH 5 was observed to give the best fermentation performance. Further, the fermentation tended to yield more xylitol at higher initial cell concentration. It was also observed that no growth or fermentation inhibitory compounds were found in the EFB hydrolysate obtained from enzymatic hydrolysis of EFB. Thus it can be used directly as substrate for xylitol fermentation.

Control of the red tide dinoflagellate Cochlodinium polykrikoides by ozone in seawater

The inactivation of C. polykrikoides, a red tide dinoflagellate, by ozonation was investigated in seawater by monitoring numbers of viable and total cells. Parameters affecting the inactivation efficacy of C. polykrikoides such as the ozone dose, initial cell concentration, pH, and temperature were examined. The viable cell number rapidly decreased in the initial stage of the reaction (mostly in 1–2 min), whereas the decrease in total cell number was relatively slow and steady. Increasing ozone dose and decreasing initial cell concentration increased the inactivation efficacy of C. polykrikoides, while increasing pH and temperature decreased the cell inactivation efficacy. The addition of humic acid (a promoter for the ozone decomposition) inhibited the inactivation of C. polykrikoides, whereas bicarbonate ion (an inhibitor for the ozone decomposition) accelerated the C. polykrikoides inactivation. Observations regarding the effects of pH, temperature, humic acid, and bicarbonate ion collectively indicate that the inactivation of C. polykrikoides by ozonation is mainly attributed to oxidative cell damages by molecular ozone, rather than by hydroxyl radical, produced during the ozone decomposition. At high ozone dose (e.g., 5 mg/L), hypobromous acid formed by the reaction of bromide with ozone may partially contribute to cell inactivation. The use of ozone of less than 1 mg/L produced 0.75–2.03 μg/L bromate.

The Diversity and Dynamics of Indigenous Yeast Communities in Grape Must from Vineyards Employing Different Agronomic Practices and their Influence on Wine Fermentation

The current study evaluated the diversity of yeast species in Cabernet Sauvignon grape must derived from three neighbouring vineyards from a similar terroir but on which significantly different management practices are employed. The fermentation kinetics and yeast population dynamics were monitored from the beginning to the end of spontaneous fermentation. The grape musts were characterised by distinct yeast populations comprising oxidative, weakly fermentative and strongly fermentative yeasts. Different combinations of dominant non-Saccharomyces yeasts were observed in each must, with significantly different assortments of dominant species, including Starmerella bacillaris (synonym Candida zemplinina), Lachancea thermotolerans, Hanseniaspora uvarum, Candida parapsilosis and Wickerhamomyces anomalus. None of these yeast consortia appeared to affect the growth of Saccharomyces cerevisiae or inhibit the overall progress of fermentation. However, the percentage of fermentative yeasts was positively correlated with the fermentation rate. Glucose and fructose consumption rates suggested active participation of both glucophilic and fructophilic yeasts from the onset of fermentation. The data highlight two parameters, viz. initial cell concentration and yeast community composition, as important fermentation drivers and open the possibility to predict fermentation behaviour based on the initial composition of the yeast community.

Effect of culture age and initial inoculum size on lipid accumulation and productivity in a hybrid cultivation system of Chlorella vulgaris

Chlorella vulgaris was cultivated in a hybrid (two-stage) system. The effect of the transferring time from nutrient-replete phase with a low light intensity (photobioreactor) to the nutrient deprivation phase (open pond) with a higher light intensity, as well as the effect of initial cell concentration in the deprivation phase, on the growth rate and lipid content of the microalgae was investigated. The microalgae were transferred to the nutrient deprived medium at different intervals with various initial cell concentrations. Transferring the cultivated medium of the 4th day with the initial cell concentration of 66mgL−1 into the deprivation phase resulted in a highest lipid productivity of 9.21±0.64mgL−1d−1 and lipid content of 53.97±4.30%. In a single-stage cultivation where a medium with nitrogen deficiency was used, despite a low lipid content (maximum 30%), a lipid productivity of 9.95±0.46mgL−1d−1 was observed that was slightly higher than that for the hybrid system.

Mitigation of carbon dioxide by oleaginous microalgae for lipids and pigments production: Effect of light illumination and carbon dioxide feeding strategies

Oleaginous microalgae Nannochloropsis sp. was selected as potential strain for CO2 mitigation into lipids and pigments. The synergistic effects of light intensity and photoperiod were evaluated to provide the adequate light energy for this strain. The saturation light intensity was 60μmol·photon·m−2s−1. With full illumination, the biomass obtained was 0.850±0.16g·L−1 with a lipid content of 44.7±1.2%. The pigments content increased with increasing light energy supply. Three main operating factors including initial cell concentration, CO2 content and gas flow rate were optimized through Response Surface Methodology. The feedings with low CO2 content at high gas flow rate gave the maximum biomass but with low lipid content. After optimization, the biomass and lipid production were increased up to 1.30±0.103g·L−1 and 0.515±0.010g·L−1, respectively. The CO2 fixation rate was as high as 0.729±0.04g·L−1d−1. The fatty acids of Nannochloropsis sp. lipids were mainly C16-C18 indicating its potential use as biodiesel feedstocks.

Biosynthesis of two quercetin O-diglycosides in Escherichia coli.

Various flavonoid glycosides are found in nature, and their biological activities are as variable as their number. In some cases, the sugar moiety attached to the flavonoid modulates its biological activities. Flavonoid glycones are not easily synthesized chemically. Therefore, in this study, we attempted to synthesize quercetin 3-O-glucosyl (1→2) xyloside and quercetin 3-O-glucosyl (1→6) rhamnoside (also called rutin) using two uridine diphosphate-dependent glycosyltransferases (UGTs) in Escherichia coli. To synthesize quercetin 3-O-glucosyl (1→2) xyloside, sequential glycosylation was carried out by regulating the expression time of the two UGTs. AtUGT78D2 was subcloned into a vector controlled by a Tac promoter without a lacI operator, while AtUGT79B1 was subcloned into a vector controlled by a T7 promoter. UDP-xyloside was supplied by concomitantly expressing UDP-glucose dehydrogenase (ugd) and UDP-xyloside synthase (UXS) in the E. coli. Using these strategies, 65.0mg/L of quercetin 3-O-glucosyl (1→2) xyloside was produced. For the synthesis of rutin, one UGT (BcGT1) was integrated into the E. coli chromosome and the other UGT (Fg2) was expressed in a plasmid along with RHM2 (rhamnose synthase gene 2). After optimization of the initial cell concentration and incubation temperature, 119.8mg/L of rutin was produced. The strategies used in this study thus show promise for the synthesis of flavonoid diglucosides in E. coli.

Hydrogen gas production from waste paper by dark fermentation: Effects of initial substrate and biomass concentrations

In this study, waste paper was used as the raw material for hydrogen gas production by dark fermentation at different initial substrate and cell concentrations. Glucose obtained from acid hydrolyzed waste paper was used at six different concentrations between 3.84 and 45.5 gL−1 to determine the effects of sugar concentration on bio-hydrogen production. The highest cumulative hydrogen gas was obtained at 18.9 gL−1 initial sugar concentration. Sugar concentrations above 18.9 gL−1 resulted in product inhibition. Similarly, the initial biomass concentration was varied between 0.25 and 2 gL−1 while sugar concentration was kept constant at 18.58 ± 2.45 gL−1 to determine the effects of initial biomass concentration. The highest cumulative hydrogen gas production was obtained with the initial biomass concentration of 0.5 gL−1. The highest hydrogen yield (140 ml H2 g−1 total sugar) was observed at 3.84 gL−1 total sugar concentration. Hydrogen yield decreased with increasing initial sugar concentration due to inhibition by volatile fatty acids (VFAs) produced by dark fermentation and furan derivatives produced from acid hydrolysis of waste paper.

Improved ethanol production in the presence of cadmium ions by a Saccharomyces cerevisiae transformed with a novel cadmium-resistance gene DvCRP1

ABSTRACTThe DvCRP1 gene obtained from Dunaliella viridis is a cadmium-resistance gene that induces cadmium accumulation in microbial and plant cells. In the present study, Saccharomyces cerevisiae was used as a model system to investigate the effect of DvCRP1 on both cadmium detoxification and ethanol production. Inhibitory effects of cadmium (50–300 µmol/L) on growth (29–92%), glucose consumption (23–89%), and ethanol production (17–92%) were observed at 24 h by S. cerevisiae. DvCRP1 alleviated the inhibitory effect of cadmium, with increase in the ethanol production. The established mathematical model showed that the initial inoculation concentration, cadmium concentration, and transformation of DvCRP1 were the most important factors for cell growth, glucose consumption, and ethanol production. Cadmium detoxification of yeast was also enhanced by increasing the initial concentration of yeast cells. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations (200 µmol/L). The present results evidenced the potential of the insertion of the DvCRP1 gene into yeast for use in bio-refineries during fermentation of heavy metals-contaminated substrates. In addition, this is a promising method for phytoremediation of agricultural soils highly contaminated by heavy metals.

Adaptation of CHO cells in serum-free conditions for erythropoietin production: Application of EVOP technique for process optimization.

Mammalian cell cultures are the preferred expression systems for the production of biopharmaceuticals requiring posttranslational processing. Usually, cell cultures are cultivated in medium supplemented with serum, which supports cell proliferation, viability, and productivity. However, due to scientific and regulatory concerns, serum-free conditions are required in recombinant protein production. Cell lines that are intended for commercial recombinant protein production have to adapt to serum- or protein-free conditions early in their development. This is a labor- and time-consuming process because of the specific cell requirements related to their adaptation in new microenvironment. In the present study, a Chinese hamster ovary (CHO) cell line producing glycosylated recombinant human erythropoietin (rhEPO) was adapted for growth and rhEPO production in serum- and protein-free conditions. The physiology, growth parameters, and morphology of the CHO cells and rhEPO biosynthesis and structure were closely monitored during the adaptation process to avoid unwanted selection of cell subpopulations. The results showed that the CHO cells were successfully adapted to suspension growth and rhEPO production in the protein-free conditions and that the structure of rhEPO remained nearly unchanged. In addition, during rhEPO production in the protein-free suspension conditions, the agitation rate seem to be significant for optimal process performance in contrast to the initial cell concentration, evaluated through evolutionary operation method.

Isolation and characterization of xylitol-assimilating mutants of recombinant Saccharomyces cerevisiae

To clarify the mechanisms of xylitol utilization, three xylitol-assimilating mutants were isolated from recombinant Saccharomyces cerevisiae strains showing highly efficient xylose-utilization. The nucleotide sequences of the mutant genomes were analyzed and compared with those of the wild-type strains and the mutation sites were identified. gal80 mutations were common to all the mutants, and recessive to the wild-type allele. Hence we constructed a gal80Δ mutant and confirmed that the gal80Δ mutant showed a xylitol-assimilation phenotype. When the constructed gal80Δ mutant was crossed with the three isolated mutants, all diploid hybrids showed xylitol assimilation, indicating that the mutations were all located in the GAL80. We analyzed the role of the galactose permease Gal2, controlled by the regulatory protein Gal80, in assimilating xylitol. A gal2Δ gal80Δ double mutant did not show xylitol assimilation, whereas expression of GAL2 under the control of the TDH3 promoter in the GAL80 strain did result in assimilation. These data indicate that Gal2 was needed for xylitol assimilation in the wild-type strain. When the gal80 mutant with an initial cell concentration of A660=20 was used for batch fermentation in a complex medium containing 20g/L xylose or 20g/L xylitol at pH 5.0 and 30°C under oxygen limitation, the gal80 mutant consumed 100% of the xylose within 12h, but <30% of the xylitol within 100h, indicating that xylose reductase is required for xylitol consumption in oxygen-limited conditions.

A strain of Meyerozyma guilliermondii isolated from sugarcane juice is able to grow and ferment pentoses in synthetic and bagasse hydrolysate media.

The search for new microbial strains that are able to withstand inhibitors released from hemicellulosic hydrolysis and are also still able to convert sugars in ethanol/xylitol is highly desirable. A yeast strain isolated from sugarcane juice and identified as Meyerozyma guilliermondii was evaluated for the ability to grow and ferment pentoses in synthetic media and in sugarcane bagasse hydrolysate. The yeast grew in xylose, arabinose and glucose at the same rate at an initial medium pH of 5.5. At pH 4.5, the yeast grew more slowly in arabinose. There was no sugar exhaustion within 60 h. At higher xylose concentrations with a higher initial cell concentration, sugar was exhausted within 96 h at pH 4.5. An increase of 350 % in biomass was obtained in detoxified hydrolysates, whereas supplementation with 3 g/L yeast extract increased biomass production by approximately 40 %. Ethanol and xylitol were produced more significantly in supplemented hydrolysates regardless of detoxification. Xylose consumption was enhanced in supplemented hydrolysates and arabinose was consumed only when xylose and glucose were no longer available. Supplementation had a greater impact on ethanol yield and productivity than detoxification; however, the product yields obtained in the present study are still much lower when compared to other yeast species in bagasse hydrolysate. By the other hand, the fermentation of both xylose and arabinose and capability of withstanding inhibitors are important characteristics of the strain assayed.

Effect of culture density on sexual reproduction of Ardissonea crystallina (Bacillariophyta) inhabiting the Black Sea

One of the key factors that affect the sexual reproduction of diatoms is the cell concentration in the mating experiments. The concentration of pheromones, which probably initiate gametogenesis in the mixture of cells of opposite sexes, depends on the culture density. The influence of the cell concentration and inoculation pattern on the sexual reproduction has been studied in the experiments with the taxonomically important marine diatom Ardissonea crystallina (C. Agardh) Grunow. Several clones have been isolated from samples collected near Sevastopol (Black Sea). The cell concentration that is most favorable for the species reproduction has been estimated. A low initial density may also increase the time required to start heterothallic sexual reproduction. The optimum cell concentration that is most favorable for the species reproduction has been estimated. Larger volume of the medium allowed reproduction at higher cell concentration. If the initial concentration of cells was greater than the optimal density, reproduction often did not occur, probably due to the cell metabolism products accumulated in the culture.

The suitability of the ISO 11290-1 method for the detection of Listeria monocytogenes

Published data suggest that detection of Listeria monocytogenes is affected by presence of other Listeria species in matrix. In this study efficacy for traditional standard detection method (ISO 11290-1) of L. monocytogenes was investigated, focussing on the growth in Fraser broth (FB). The multiplication ability of different mixtures of L. monocytogenes strains and Listeria innocua strain was investigated in half FB (hFB) and FB. Growth parameters were determined by DMFit software using the Baranyi-model. When initial cell concentration of L. innocua was higher than that of L. monocytogenes inhibition of the latter was observed. Based on the results it was concluded that the strain of L. monocytogenes was overgrown by L. innocua in Fraser broth. When their growth was monitored during co-culturing in hFB the lag phase of L. monocytogenes was prolonged by 3.4 h. When L. monocytogenes grew in the presence of L. innocua in 1:1 ratio a three log cycle difference was observed at the end of Fraser culturing step. Testing the suitability of ALOA plates for detection of L. monocytogenes it was determined that halo formation has to be checked after 24, 34 and 48 h incubation. All these difficulties might lead to false negative results.

Propiedades de crecimiento de las líneas celulares DH82 y RF/6A bajo condiciones normales de laboratorio

La línea celular RF/6A ha sido utilizada en estudios de corto plazo evaluando fármacos o infecciones experimentales con Anaplasma marginale; en contraste, DH82 es utilizada para la multiplicación de Ehrlichia canis. No obstante, se desconocen condiciones específicas de su crecimiento, por lo que se diseñaron varios experimentos para resolver interrogantes de su propagación. Ambas líneas, se adquirieron de la American Type Culture Collection, mantenidas en Medio Mínimo Esencial suplementado con suero fetal bovino, piruvato de Na y NaHCO3 e incubadas en atmósfera de 5% de CO2 en aire, a 37 °C. Los primeros ensayos, en placas de 24 pozos, esclarecieron los valores de dosis mínima inicial, que fueron 62,500 y 8,836 células/pozo para DH82 y RF/6A; así como los de densidad de siembra; cultivos con concentraciones de 5, 10, 20 y 40 células por mm2, cosechados con solución Tripsina-EDTA al alcanzar &gt;95% de confluencia. Los índices estimados fueron: 3,319.32, 1,956.70, 870.73 y 422.14 para DH82 y 62.38, 63.51, 25.31 y 12.16 veces con RF/6A. La cinética del crecimiento, en cajas de Petri de 35 mm Ø, incluyó la siembra de 20 células/mm2, cambio del medio cada 63 h y cosecha cada 21 h para DH82; para RF/6A; la siembra fue 10 células/ mm2, cambio de medio cada 45 h y cosecha cada 15 h. El máximo crecimiento se observó hasta las 336 y 315 h con tiempos de duplicación de 42.9 y 36.9 h respectivamente para DH82 y RF/6A. Los datos permitieron proponer un modelo patrón de cultivo, para estudios futuros.

Modeling the intracellular pathogen-immune interaction with cure rate

Many common and emergent infectious diseases like Influenza, SARS, Hepatitis, Ebola etc. are caused by viral pathogens. These infections can be controlled or prevented by understanding the dynamics of pathogen-immune interaction in vivo. In this paper, interaction of pathogens with uninfected and infected cells in presence or absence of immune response are considered in four different cases. In the first case, the model considers the saturated nonlinear infection rate and linear cure rate without absorption of pathogens into uninfected cells and without immune response. The next model considers the effect of absorption of pathogens into uninfected cells while all other terms are same as in the first case. The third model incorporates innate immune response, humoral immune response and Cytotoxic T lymphocytes (CTL) mediated immune response with cure rate and without absorption of pathogens into uninfected cells. The last model is an extension of the third model in which the effect of absorption of pathogens into uninfected cells has been considered. Positivity and boundedness of solutions are established to ensure the well-posedness of the problem. It has been found that all the four models have two equilibria, namely, pathogen-free equilibrium point and pathogen-present equilibrium point. In each case, stability analysis of each equilibrium point is investigated. Pathogen-free equilibrium is globally asymptotically stable when basic reproduction number is less or equal to unity. This implies that control or prevention of infection is independent of initial concentration of uninfected cells, infected cells, pathogens and immune responses in the body. The proposed models show that introduction of immune response and cure rate strongly affects the stability behavior of the system. Further, on computing basic reproduction number, it has been found to be minimum for the fourth model vis-a-vis other models. The analytical findings of each model have been exemplified by numerical simulations.

A stochastic nominal control optimizing the adoptive immunotherapy for cancer using tumor-infiltrating lymphocytes

In this work, a stochastic nominal optimal control approach is proposed with a view to treating cancer using the adoptive T-cell immunotherapy based on the administration of tumor-infiltrating lymphocytes. Indeed, the stochastic analysis is relevant and appropriate for studying the possible tumor-immune cellular interactions in order to better understand both dynamics of immune system and cancer evolution process. However, in the presence of an additional initial concentration of tumor cells, the therapeutic enhancement of immune response is considered using an appropriate neighboring treatment as a supplement to the adopted nominal therapy. Moreover, the Pontryagin-type stochastic maximum principle and the Pontryagin’s procedure are used to provide the explicit formulations of optimal controls. Finally, an adapted iterative method is implemented to solve numerically the optimal systems.

Artificial neural network modeling for predicting the growth of the microalga Karlodinium veneficum

A feed-forward back-propagation neural network (FBN) was used as a tool for predicting the growth dynamics of the microalga Karlodinium veneficum in a culture medium with any specified concentrations of the key nutrients. A 3-layered FBN configuration of 27-25-1 nodes was used. This FBN satisfactorily represented the nonlinear interactions among all the nutrients of a culture medium containing up to 25 different components. The FBN model was trained using the growth dynamics data from more than 420 batch culture experiments involving different media compositions. The relative impact of individual nutrients, the initial cell concentration and the culture duration on growth profiles were determined through a systematic analysis of the partitioning of the FBN connection weights. Microelements and vitamins together had a higher relative impact on growth compared to the impact of the macronutrients. The trained FBN successfully predicted the cell concentration dynamics in cultures with previously untested initial conditions. The FBN proved to be an excellent tool for predicting the growth curves in the range of culture conditions that were relevant to this study.

INFLUENCE OF INITIAL CELL CONCENTRATIONS ON THE GROWTH RATE AND BIOMASS PRODUCTIVITY OF MICROALGAE IN DOMESTIC WASTEWATER

The aim of this study was to compare the specific growth rate and biomass productivity of microalgae in domestic wastewater according to the initial cell concentration. The initial microalgae cell concentrations tested started from 103 cell/mL, 104 cell/mL, 105 cell/mL, 106 cell/mL, and 107 cell/mL under outdoor condition. The result revealed that the highest biomass productivity occurred at 106 cell/mL concentration with a value of 1.24 × 104 cell/mL/day, 0.26 day-1 of specific growth rate, and a doubling time of 2.63 days. Meanwhile, the lowest biomass productivity occurred at 103 cell/mL concentration with the lowest specific growth rate of 0.1 day-1 and the longest doubling time, which reached up to 7.14 day. As a result, the initial cell concentration of microalgae did influence the algal biomass productivity and growth rate differently. Thus, the maximum growth rate and biomass productivity were obtained at 106 cell/mL concentration which is recommended to be used in biotechnology industries and any wastewater treatment.