Cell Mass Concentration Research Articles

KINETIC MODELLING OF CONTINUOUS-MIX ANAEROBIC REACTORS OPERATING UNDER DIURNALLY CYCLIC TEMPERATURE ENVIRONMENT

A two-culture dynamic model which incorporated the effects of diurnally cyclic temperature was developed and used to predict the dynamic response of anaerobic reactors operated on dairy manure under two diurnally cyclic temperature ranges of 20 -40°C and 15-25°C which represent the summer and winter in Nigeria. The digesters were operated at various hydraulic retention times and solid concentrations and some useful kinetic parameters w ere determined. The model predicted biogas production, volatile solid reduction, methane yield and treatment efficiency with reasonable accuracy (R 2 = 0.70 to 0.90). The model, however, under-predict ed the cell mass concentration in the reactor probably because the Volatile Suspended Solid (VSS), which was used as the estimator of the actual cell mass concentration in the reactor, was not a g ood indicator of the active cell mass concentration in anaerobic reactors operating on dairy manure.

Biotransformation of 3-cyanopyridine to nicotinic acid by free and immobilized cells of recombinant Escherichia coli

An efficient biocatalytic process for the production of nicotinic acid (niacin) from 3-cyanopyridine was developed using cells of recombinant Escherichia coli JM109 harboring the nitrilase gene from Alcaligenes faecalis MTCC 126. The freely suspended cells of the biocatalyst were found to withstand higher concentrations of the substrate and the product without any signs of substrate inhibition. Immobilization of the cells further enhanced their substrate tolerance, stability and reusability in repetitive cycles of nicotinic acid production. Under optimized conditions (37°C, 100mM Tris buffer, pH 7.5) for the immobilized cells, the recombinant biocatalyst achieved a 100% conversion of 1M 3-cyanopyridine to nicotinic acid within 5h at a cell mass concentration (fresh weight) of 500mg/mL. The high substrate/product tolerance and stability of the immobilized whole cell biocatalyst confers its potential industrial use.

On-line implementation of decoupled input-output linearizing controller in Baker's yeast fermentation

Baker's yeast fermentation is influenced by the relative concentration of glucose and dissolved oxygen (DO) in the reactor. The process is sensitive to the oxidative capacity of the cells and exhibits a range of metabolic regimes depending on available glucose and oxygen. The time profiles of cell mass, glucose, ethanol and DO concentrations possess strong nonlinear characteristics. A decoupled input-output linearizing controller (DIOLC), which exhibited satisfactory performance in simulation experiments, was implemented online for validation. Our results showed that the DIOLC was capable of negating the interaction between glucose and dissolved oxygen, and executed satisfactory control action in experiments carried out in a 5 liter bioreactor. The performance of DIOLC was better compared to that of a PID controller implemented under identical test conditions.

Influence of switchgrass generated producer gas pre-adaptation on growth and product distribution of Clostridium ragsdalei

Gasification-fermentation is a thermo chemical-biological process for the production of fuels and chemicals. Producer gas cleanup is a major issue that must be addressed for integration of these platforms. Pre-adaptation of producer gas fermenting microbes to gas impurities has improved tolerances to impurities and production of alcohols in certain bacteria. In this research, the effect of switchgrass generated producer gas was studied with adapted and unadapted cultures of C. ragsdalei and compared to fermentations with a control of clean custom producer gas. Results indicated no inhibition to microbial growth with unadapted cells and final cell mass concentrations were 22% higher when cells were exposed to switchgrass-based producer gas compared to control. The ethanol productivity with adapted cells was 1.9 and 2.8 times higher than unadapted and control treatments, respectively. Similarly, the ethanol yield (YETOH/X) of C. ragsdalei adapted to producer gas was 119% more than the control and 35% greater than the unadapted cells used in this study. The presence of switchgrass-based producer gas also induced metabolic shifts resulting in reduction of acetic acid to ethanol that increased ethanol to acetate ratios from 0.7 g/g in control to 4.9 g/g with unadapted cells and 13.7 g/g with adapted cells. Isopropanol was also observed as a product when switchgrass generated producer gas was used. We conclude that cultural adaptation of C. ragsdalei to biomass generated producer gas during preculture stages could be used as an important strategy to enhance ethanol yields for integrating gasification and fermentation platforms using C. ragsdalei.

Simultaneous saccharification and fermentation by engineered Saccharomyces cerevisiae without supplementing extracellular β-glucosidase

Simultaneous saccharification and fermentation (SSF) has been considered a promising and economical process for cellulosic ethanol production. Further cost savings could be gained by reducing enzyme loading and engineering host strain for ethanol production. In this study, we demonstrate efficient ethanol production by SSF without supplementation of β-glucosidase using an engineered Saccharomyces cerevisiae strain expressing a cellodextrin transporter and an intracellular β-glucosidase from Neurospora crassa. Ethanol production profiles by the engineered yeast without supplementation of β-glucosidase and by a parental strain with supplementation of β-glucosidase were examined under various fermentation conditions. When initial cell mass concentrations were low, the traditional SSF with supplementation of β-glucosidase showed better ethanol production than SSF with the engineered strain without supplementing β-glucosidase. However, the engineered strain without supplementation of β-glucosidase showed almost the same or even better ethanol productivity than the parental strain with supplementation of β-glucosidase when initial cell mass concentrations were elevated. Our results suggest that efficient ethanol production by SSF could be achieved by engineered yeast capable of fermenting cellobiose without addition of extracellular β-glucosidase, leading to economic production of cellulosic ethanol.

Biosynthesis of Selenium Nanoparticle by Whole Cells of Saccharomyces boulardii and its Evaluation as Anticancer Agent

Selenium is known to have cytoprotective role, which is important especially in reducing mortality due to cancer, a leading cause of death worldwide. The present work addresses synthesis and evaluation of selenium nanoparticles (SeNPs) as therapeutic alternative to conventional chemotherapeutic agents. Selenium nanoparticles were synthesized by an eco friendly method using whole cells of Saccharomyces boulardii. Parameters like culture age (stationary phase growth), cell mass concentration (100 mg/ml), temperature (35°C) and reaction time (72 h) were optimized to produce nanoparticle with controlled properties. Nanoparticles were recovered by alkali hydrolysis and subjected to UV-Vis spectroscopy, EDX (energy dispersive X-rays) analysis, electron microscopy, elemental analysis and size determination. Dynamic light scattering analysis reveals negative zeta potential value of 14.8 mV and PDI of 0.25. Experiments to prove possible involvement of sulfite reductase in nanoparticle formation has been carried out. Moreover, cytoprotective role of selenium nanoparticle has been shown by cell viability in MTT assay. Keywords: Cytoprotective, MTT assay, Saccharomyces boulardii, Selenium nanoparticle, Sulfite reductase.

One-pot synthesis of (R)-1-(1-naphthyl)ethanol by stereoinversion using Candida parapsilosis

R)-1-(1-Naphthyl)ethanol is an essential chiral substrate for the synthesis of nonactin and dihydro-(1H)- quinoline-2-one derivatives. Stereoinversion of (S)-1-(1-naphthyl)ethanol to (R)-1-(1-naphthyl)ethanol by whole cell biocatalysis, using Candida parapsilosis, is reported here. Candida parapsilosis possesses a requisite redox system for the stereoinversion of secondary alcohol. The reaction conditions (tempera- ture, time, pH, organic solvent, etc.) significantly influenced the stereoinversion process. Optimum con- ditions were found to be the reaction temperature of 30 C, a cellmass concentration of 200 mg/mL, pH 7 (phosphate buffer, 50 mM), a shaking speed of 200 rpm, and a 12 h reaction time. Under these optimum conditions, (R)-1-(1-naphthyl)ethanol was obtained in 100% eeR and 88% yield.

Synthesis of Gold Nanoparticles Using Whole Cells of Geotrichum candidum

The synthesis of nanoparticles with desired size and shape is an important area of research in nanotechnology. Use of biological system is an alternative approach to chemical and physical procedures for the synthesis of metal nanoparticles. An efficient environment-friendly approach for the biosynthesis of rapid and stable Gold nanoparticles (AuNPs) using whole cells of Geotrichum candidum is discussed in this paper. The enzymes/proteins present in the microorganism might be responsible for the reduction of metal salts to nanoparticles. Various reaction parameters such as culture age, temperature, pH, metal salt, and cell mass concentrations were optimized. The AuNPs were characterized by UV-visible spectroscopy, dynamic light scattering (DLS), energy dispersive spectroscopy (EDS), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Nanoparticles were isolated by sonicating the whole cells after treatment with Tween 80. The whole cell mediated process showed the simplistic, feasible, easy to scale up, and low-cost approach for the synthesis of AuNPs.

Isolation of a BTEX-degrading bacterium, Janibacter sp. SB2, from a sea-tidal flat and optimization of biodegradation conditions

An enrichment culture was established using seawater containing BTEX (benzene, toluene, ethylbenzene and xylene) compounds to isolate a BTEX-degrading bacterium from contaminated sea-tidal flat. The enriched microbial communities were characterized by 16S rRNA-based DGGE profiling, which indicated that a Janibacter species was dominant during the enrichment. Strain SB2, corresponding to the major band and able to degrade all BTEX compounds, was isolated and characterized. NH4Cl, NaH2PO4, cell mass and BTEX concentrations were used as independent variables to optimize the degradation of BTEX by strain SB2 in a tidal flat and a statistically significant (R(2)=0.8933, p<0.0001) quadratic polynomial mathematical model was suggested. For the initial concentration of 240 mg/L BTEX in a slurry system containing 3.0×10(7) cells/L, 45.5% BTEX removal was observed under the optimum condition of NH4Cl and NaH2PO4, while 32.2% BTEX removal was observed under the untreated condition of NH4Cl and NaH2PO4.

Green and Rapid Synthesis of Anticancerous Silver Nanoparticles bySaccharomyces boulardiiand Insight into Mechanism of Nanoparticle Synthesis

Rapidly developing field of nanobiotechnology dealing with metallic nanoparticle (MNP) synthesis is primarily lacking control over size, shape, dispersity, yield, and reaction time. Present work describes an ecofriendly method for the synthesis of silver nanoparticles (AgNPs) by cell free extract (CFE) of Saccharomyces boulardii. Parameters such as culture age (stationary phase growth), cell mass concentration (400 mg/mL), temperature (35°C), and reaction time (4 h), have been optimized to exercise a control over the yield of nanoparticles and their properties. Nanoparticle (NP) formation was confirmed by UV-Vis spectroscopy, elemental composition by EDX (energy dispersive X-rays) analysis, and size and shape by transmission electron microscopy. Synthesized nanoparticles had the size range of 3–10 nm with high negative zeta potential (−31 mV) indicating excellent stability. Role of proteins/peptides in NP formation and their stability were also elucidated. Finally, anticancer activity of silver nanoparticles as compared to silver ions was determined on breast cancer cell lines.

Microbial Decolorization and Degradation of Orange 16 Dye by a Newly Isolated Aeromonas Spp. Etl-1949

A bacterial strain ETL-1949, identified as Aeromonas spp. was isolated from sediment from a textile wastewater treatment plant in Ankleshwar, Gujarat, India. The strain could decolorize an azo dye, Orange 16 under the static condition after the shaking culture. In order to increase cell concentration by the shaking culture, the optimum culture condition was investigated for following the decolorization incubation. The dye was decolorized completely up to concentration of 750 mg/l for 50 hr under static condition by using 12 hr-cultured cells at optimal shaking culture condition. Effect of initial cell mass showed that higher cell mass concentration can accelerate decolorization process with maximum of 92% decolorization observed at 2.5 g/l cell mass within 6.5 h. Effect of various metal ions showed Mn & Mg has positive inducing effect whereas Zn strongly inhibited the decolorization process at 5 mM concentration. Analysis of biodegradation products carried out with UV–vis spectroscopy, HPTLC and FTIR confirmed the decolorization and degradation of Orange 16.

Effect of short-term GH and testosterone administration on body composition and glucose homoeostasis in men receiving chronic glucocorticoid therapy

Long-term pharmacological glucocorticoid (GC) therapy leads to skeletal muscle atrophy and weakness. The objective of this study was to investigate whether short-term treatment with GH and testosterone (T) can increase lean mass without major impairment of glucose homoeostasis in patients on GC therapy. This was a prospective, open-label, randomised, crossover study. Twelve men (age 74±6 years) on chronic GC treatment participated. The effects of 2 weeks' treatment with GH, testosterone and the combination of both on lean body mass (LBM), appendicular skeletal muscle mass (ASMM), extracellular water (ECW), body cell mass (BCM) and plasma glucose concentrations were investigated. LBM increased significantly after GH (Δ1.7±1.4 kg; P=0.007) and GH+testosterone (Δ2.4±1.1 kg; P=0.003), but not testosterone alone. ASMM increased after all three treatment periods; by 1.0±0.8 kg after GH (P=0.005), 1.7±0.4 kg after GH+testosterone (P=0.002) and 0.8±1.0 kg after testosterone (P=0.018). The increase in ASMM was larger with combined treatment than either GH or testosterone alone (P<0.05). ECW increased significantly after GH+testosterone by 1.5±2.6 l (P=0.038) but not after GH or testosterone alone. BCM increased slightly after single and combined treatments, but the changes were not significant. Fasting glucose increased significantly after GH (Δ0.4±0.4 mmol/l, P=0.006) while both fasting (Δ0.2±0.3 mmol/l, P=0.045) and post glucose-load (Δ1.8±2.3 mmol/l, P=0.023) plasma glucose concentrations increased after GH+testosterone. GH and testosterone induce favourable and additive body compositional changes in men on chronic, low-dose GC treatment. In the doses used, combination therapy increases fasting and postprandial glucose concentration.

Effect of carbon dioxide on the rheological behavior of submerged cultures of Chlorella minutissima in stirred tank reactors

The objective of this study was to quantify the effect of algal biomass concentration on the rheology of the algal culture broth. Batch cultivations of Chlorella minutissima were carried out with air and carbon dioxide in a stirred tank bioreactor with a working volume of 1.8 L. The apparent viscosity of the culture broth was significantly affected by the cell mass concentrations in the bioreactor. Culture broth containing 50 g/L cell mass from air fed was found to exhibit an apparent viscosity of 1.52 mPa.s. The apparent viscosity of the carbon‐dioxide‐fed cultivations was found to increase by 20% at a shear rate of 100 s−1. The flow behavior of the system was adequately described by the Herschel–Bulkley model with a small yield stress.

Kinetics of growth and ethanol formation from a mix of glucose/xylose substrate by Kluyveromyces marxianus UFV-3

The fermentation of both glucose and xylose is important to maximize ethanol yield from renewable biomass feedstocks. In this article, we analyze growth, sugar consumption, and ethanol formation by the yeast Kluyveromyces marxianus UFV-3 using various glucose and xylose concentrations and also under conditions of reduced respiratory activity. In almost all the conditions analyzed, glucose repressed xylose assimilation and xylose consumption began after glucose had been exhausted. A remarkable difference was observed when mixtures of 5gL(-1) glucose/20gL(-1) xylose and 20gL(-1) glucose/20gL(-1) xylose were used. In the former, the xylose consumption began immediately after the glucose depletion. Indeed, there was no striking diauxic phase, as observed in the latter condition, in which there was an interval of 30h between glucose depletion and the beginning of xylose consumption. Ethanol production was always higher in a mixture of glucose and xylose than in glucose alone. The highest ethanol concentration (8.65gL(-1)) and cell mass concentration (4.42gL(-1)) were achieved after 8 and 74h, respectively, in a mixture of 20gL(-1) glucose/20gL(-1) xylose. When inhibitors of respiration were added to the medium, glucose repression of xylose consumption was alleviated completely and K. marxianus was able to consume xylose and glucose simultaneously.

Biodecolorization of Azo Dye Remazol Orange by Pseudomonas aeruginosa BCH and Toxicity (Oxidative Stress) Reduction in Allium cepa Root Cells

In this report a textile azo dye Remazol orange was degraded and detoxified by bacterium Pseudomonas aeruginosa BCH in plain distilled water. This bacterial decolorization performance was found to be pH and temperature dependent with maximum decolorization observed at pH8 and temperature 30°C. Bacterium tolerated higher dye concentrations up to 400mg l(-1). Effect of initial cell mass showed that higher cell mass concentration can accelerate decolorization process with maximum of 92% decolorization observed at 2.5g l(-1) cell mass within 6.5h. Effect of various metal ions showed Mn has inducing effect whereas Zn strongly inhibited the decolorization process at 5mM concentration. Analysis of biodegradation products carried out with UV-vis spectroscopy, HPTLC and FTIR confirmed the decolorization and degradation of Remazol orange. Possible route for the degradation of dye was proposed based on GC-MS analysis. During toxicological scrutiny in Allium cepa root cells, induction in the activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX) and inhibition of catalase (CAT) along with raised levels of lipid peroxidation and protein oxidation in dye treated samples were detected which conclusively indicated the generation of oxidative stress. Less toxic nature of the dye degraded products was observed after bacterial treatment.

Response surface methodology mediated optimization of Remazol Orange decolorization in plain distilled water by Pseudomonas aeruginosa BCH

The bacterium Pseudomonas aeruginosa BCH decolorized and degraded the sulphonated azo dye Remazol Orange in plain distilled water. The effects of different parameters, i.e. pH, temperature and cell mass concentration on the biodegradation of dye in aqueous phase was evaluated using response surface methodology. Optimization was carried out using three-level Box–Behnken design. Predicted values were found to be in good agreement with experimental values (R 2 0.9997 and pred R 2 0.9984), which indicated suitability of the employed model and the success of response surface methodology. Optimum dye decolorization was maximized and the favourable conditions were pH 7.43, temperature 29.39 °C and cell mass concentration 2.88 g l−1, which resulted in 96.01 % decolorization within 5 h. It was validated from the predicted response (97.37 %). According to the analysis of variance results, the proposed model can be used to navigate the design space. 3D plot analysis disclosed the significant interaction between all three tested factors on decolorization process. The combinations of the three variables predicted during response surface methodology were confirmed through confirmatory experiments. Observations indicated that higher cell mass accelerated the decolorization process. Degradation of the dye was verified through high performance liquid chromatography analysis. Phytotoxicity studies carried out with dye and dye metabolites using Phaseolus mungo, Triticum aestivum and Sorghum vulgare indicated the detoxification of dye.

Effects of photobioreactor configuration, nitrogen source and light intensity on the fed-batch cultivation of Arthrospira (Spirulina) platensis. Bioenergetic aspects

Bioenergetic analysis may be applied in order to predict microbial growth yields, based on the Gibbs energy dissipation and mass conservation principles of the overall growth reaction. The bioenergetics of the photoautotrophic growth of the cyanobacterium Arthrospira (Spirulina) platensis was investigated in different bioreactor configurations (tubular photobioreactor and open ponds) using different nitrogen sources (nitrate and urea) and under different light intensity conditions to determine the best growing conditions in terms of Gibbs energy dissipation, number of photons to sustain cell growth and phototrophic energy yields distribution in relation to the ATP and NADPH formation, and release of heat. Although an increase in the light intensity increased the Gibbs energy dissipated for cell growth and maintenance with both nitrogen sources, it did not exert any appreciable influence on the moles of photons absorbed by the system to produce one C-mol biomass. On the other hand, both bioenergetic parameters were higher in cultures with nitrate than with urea, likely because of the higher energy requirements needed to reduce the former nitrogen source to ammonia. They appreciably increased also when open ponds were substituted by the tubular photobioreactor, where a more efficient light distribution ensured a remarkably higher cell mass concentration. The estimated percentages of the energy absorbed by the cell showed that, compared with nitrate, the use of urea as nitrogen source allowed the system to address higher energy fractions to ATP production and light fixation by the photosynthetic apparatus, as well as a lower fraction released as heat. The best energy yields values on Gibbs energy necessary for cell growth and maintenance were achieved in up to 4–5 days of cultivation, indicating that it would be the optimum range to maintain cell growth. Thanks to this better bioenergetic situation, urea appears to be a quite promising low-cost, alternative nitrogen source for Arthrospira platensis cultures in photobioreactors.

Utilizing of Sugar Refinery Waste (Cane Molasses) for Production of Bio-Plastic Under Submerged Fermentation Process

In the present study, depending upon the availability and cheaper cost, different carbon source were tested for the production of PHAs (Polyhydroxyalkonoates) by soil bacterium Pseudomonasaeruginosa and it was found that sugar refinery waste (cane molasses) produced the maximum PHA (biodegradable polymer) which is precursor for bio-plastic development. Urea served as potent nitrogen source over other inorganic nitrogen sources in bio-plastic synthesis. Effect of different physical parameters viz; pH, temperature and agitation speed were also studied on PHA production. Batch cultivation kinetics under optimized cultural and physical condition showed maximum cell mass and PHA concentration of 7.32 ± 0.2 and 5.60 ± 0.3 g/L, respectively after 54.0 h of cultivation. Sugar refinery waste (Total sugar 4%) and urea (0.8%) improved the economics of the process which exhibited a yield (YP/X) of 0.70 with productivity of 0.11 g/L/h. PHA was further characterized as PHB by using Fourier Transform Infra-red Spectroscopy (FT-IR).

Immobilization ofErwiniasp. D12 Cells in Alginate-Gelatin Matrix and Conversion of Sucrose into Isomaltulose Using Response Surface Methodology

Isomaltulose is a noncariogenic reducing disaccharide and also a structural isomer of sucrose and is used by the food industry as a sucrose replacement. It is obtained through enzymatic conversion of microbial sucrose isomerase. An Erwinia sp. D12 strain is capable of converting sucrose into isomaltulose. The experimental design technique was used to study the influence of immobilization parameters on converting sucrose into isomaltulose in a batch process using shaken Erlenmeyer flasks. We assessed the effect of gelatin and transglutaminase addition on increasing the reticulation of granules of Erwinia sp. D12 cells immobilized in alginate. Independent parameters, sodium alginate concentration, cell mass concentration, CaCl2 concentration, gelatin concentration, and transglutaminase concentration had all a significant effect (P < 0.05) on isomaltulose production. Erwinia sp. D12 cells immobilized in 3.0% (w/v) sodium alginate, 47.0% (w/v) cell mass, 0.3 molL−1 CaCl2, 1.7% (w/v) gelatin and 0.15% (w/v) transglutaminase presented sucrose conversion into isomaltulose, of around 50–60% in seven consecutive batches.

A batch decolorization and kinetic study of Reactive Black 5 by a bacterial strain Enterobacter sp. GY-1

An Enterobacter strain (GY-1) with high activity of decolorization of Reactive Black 5 (RB 5) was isolated from textile wastewater treating sludge. The kinetic characteristics of dye decolorization by the strain GY-1 were determined quantitatively using the diazo dye, RB 5. Effects of different operation parameters (inoculum size, pH, temperature and salinity) and various electron donors on decolorization of the azo dye by GY-1 were systematically investigated to reveal the primary factors that determine the performance of the azo dye decolorization. The decolorization of RB 5 was attributed to extracellular enzymes. A kinetic model was established giving the dependence of decolorization rate on cell mass concentration (first order). Decolorization rate increased with increasing temperature from 20 to 35 °C, which can be predicted by Arrhenius equation with the activation energy ( E a) of 8.50 kcal mol −1 and the frequency factor ( A 0) of 6.28 × 10 7 mg l g MLSS −1 h −1. Michaelis–Menten kinetics and Eadie–Hofstee plot were used to determine V max, 1.05 mg l −1 h −1 and K m, 24.06 mg l −1.