Initial Cell Concentration Research Articles

Characterization of Chlorococcum pamirum as a potential biodiesel feedstock.

To evaluate the potential of Chlorococcum pamirum for producing biodiesel, the effects of nitrogen, phosphate, initial cell concentrations and NaCl on lipid accumulation and growth were studied. The highest specific growth rate (μ(max)), biomass productivity and lipid content achieved was 1.888 d(-1), 350.1 mg L(-1) day(-1), and 64.9%, respectively. Under nitrogen-deficient condition, the cells accumulated lipids faster at low initial cell concentration. Additional NaCl to nitrogen-deficient media accelerated the lipid accumulation. When adding 10 g L(-1) NaCl to nitrogen-deficient media, the lipid content and productivity of cells cultured outdoors with high initial cell concentration increased from 38.2% and 153 mg L(-1) day(-1) to 54.3% and 192 mg L(-1) day(-1) respectively. Moreover, NaCl enhanced the saturated fatty acids content from 56.40% to 73.41% of total fatty acids. The results show that C. pamirum is a promising organism for biofuel production.

Co-digestion of oil palm trunk hydrolysate with slaughterhouse wastewater for thermophilic bio-hydrogen production by Thermoanaerobacterium thermosaccharolyticm KKU19

The key factors influencing a co-digestion of the oil palm trunk (OPT) hydrolysate with a slaughterhouse wastewater (SHW) to produce hydrogen by Thermoanaerobacterium thermosaccharolyticum KKU19 were investigated. The OPT hydrolysate was obtained by the hydrolysis of OPT by microwave-H2SO4 method using 1.56% (w/v) H2SO4 and 7.50 min reaction time at 450 W. The Plackett–Burman method was used to screen the key factors that influenced the hydrogen production potential (Ps). Results indicated that initial cell concentration, tCOD/TN (total COD/total nitrogen) ratio and CuSO4 concentration influenced the Ps. These factors were further optimized using response surface methodology (RSM) with central composite design (CCD). A maximum Ps of 2604 ± 86 mL H2/L substrate was achieved at an initial cell concentration of 224 mg dry cell/L, tCOD/TN ratio of 49.87 and CuSO4 concentration of 13.33 mg/L. The main soluble metabolite products were butyric and acetic acids. The Ps obtained when the hydrolysate was supplemented with SHW (2604mL ± 86 mL H2/L substrate) was comparable to the Ps obtained when it was supplemented with yeast extract at the same tCOD/TN (2802 ± 87 mL H2/L substrate). This result suggests that SHW can be used to replace the costly nitrogen source.

Hydrogen and ethanol fermentation of various carbon sources by immobilized Escherichia coli (XL1-Blue)

In this study, hydrogen and ethanol production by a facultative anaerobic bacterium Escherichia coli XL1-Blue immobilized in calcium-alginate beads have been investigated. Batch fermentations were carried out at mesophilic temperature (35 °C) and an initial cultivation pH of 6.5. Firstly, the influence of biomass concentration in terms of dry cell weight (expressed in g DCW/L, range 0.2–1.0) was investigated using fructose (5 g/L) as a carbon source. The peak hydrogen yield (HY) of 1.17 mol-H2/mol-fructoseutilized was obtained at an initial cell concentration of 0.4 g DCW/L. The hydrogen production potential of other simple carbon sources (glucose and xylose) was evaluated at this optimized cell concentration and peak HY values were attained as 0.96 mol-H2/mol-glucoseutilized and 0.69 mol-H2/mol-xyloseutilized, respectively. In addition, utilization of the beverage wastewater (BWW) showed the peak cumulative hydrogen production and ethanol concentration of 120 mL and 5.65 g/L, attained at the substrate concentration of 20 g(glucose equivalent)/L. However, peak HY (1.65 mol-H2/mol-glucose eqivalent utilized) was observed at low substrate concentration of 5 g(glucose equivalent)/L. The percentage of sugar utilization of BWW was ranged between 80 and 96.

Effect of optical panel distance in a photobioreactor for nutrient removal and cultivation of microalgae

The aim of present investigation is to assess the effect of illumination area and distance of an optical panel (OP) on the growth of microalgae with simultaneous removal of nutrients. Four different distances of OPs were used i.e. 225 mm OP (Run 1), 150 mm OP (Run 2), 112.5 mm OP (Run 3) and 90 mm distance OP (Run 4) in the photobioreactor (PBR) operations. The PBR was equipped with an OP and operated with a total volume of 37-l. A batch culture was prepared using an initial cell concentration of 1.12 ± 0.05 g l(-1). The experiments were conducted at neutral pH (7.2 ± 0.3) under dark and light cycles of 8 and 16 h, respectively. The diffuse light intensity was recorded as 91, 93, 95 and 98% for Run 1, Run 2, Run 3 and Run 4, respectively, at a 300 mm depth level in the PBR. The chlorophyll content per cell was found to be an average of 701, 721, 785 and 808 fg for Run 1, Run 2, Run 3 and Run 4, respectively. High chlorophyll content per cell and diffuse light intensity was observed for Run 4 compared to other fractions. However, Run 3 sample possessed approximately 10.51% higher biomass growth along with 15.22% chemical oxygen demand, 18.15% total nitrogen 2.37% NH4-N, 15.1% total phosphorus and 15.05% PO4-P more removal than the Run 1. These findings suggest that in terms of economic consideration and efficiency of nutrients removal, Run 3 is found to be more effective than other samples. Moreover, an enhanced growth of Chlorella vulgaris could further be utilized as a potential biodiesel source.

Two-step production of d-lactate from mixed sugars by growing and resting cells of metabolically engineered Lactobacillus plantarum

To develop cost-effective systems for D-lactate production, here, the effect of high-cell density cultivation of metabolically engineered Lactobacillus plantarum on D-lactate production was evaluated. A xylose-assimilating strain of L. plantarum was anaerobically cultured with mixed sugars (glucose and xylose) as substrates. Compared to undiluted nutrient-rich de Man, Rogosa, and Sharpe (MRS) medium, D-lactate production by cultivating in 10-fold diluted MRS (0.1 MRS) medium or normal saline solution was 89.7 and 81.3%, respectively. Notably, the xylose consumption rate was comparable in the three cultures, whereas the glucose consumption rate decreased by 18.3 and 26.1% in 0.1 MRS medium and normal saline solution, respectively, resulting in a reduction of the D-lactate production rate. The D-lactate productivity in high-cell density cultivation was proportional to the initial cell concentrations. The use of a two-step cultivation process involving growing and resting cells in a single bioreactor revealed that the ratio of the glucose and xylose consumption rates (based on grams consumed) in resting cell conditions was 1.88, whereas that in growing conditions was 2.58. Cultivation of L. plantarum in growing conditions for 24h produced 73.2g/l D-lactate with the yield of 0.90g/g, whereas cells cultivation under resting cell conditions in a saline solution for 24h produced 68.7g/l D-lactate with the yield of 0.93g/g. In total, 141.9g/l D-lactate was produced after 48h cultivation, a value that represents the highest reported concentration of D-lactate produced from mixed sugars to date. Our findings contribute to the cost-effective, large-scale production of D-lactate.

Effective removal of Microcystis aeruginosa and microcystin-LR using nanosilicate platelets

Drinking water safety has been threatened by increasing harmful algal blooms (HABs) in water sources. HABs are closely associated with eutrophication in freshwater lakes, e.g. Lake Tai in China, and marine environments as well, e.g. Baltic Sea in Europe. Among all HABs, Microcystis aeruginosa attracted much attention due to its easy proliferation and potent toxins, microcystins. Most of the current control technologies can result in immediate release of microcystins which are hard to remove by drinking water treatment processes. Here we propose to simultaneously remove M. aeruginosa and its toxin, microcystin-LR (MC-LR), using nanosilicate platelet (NSP) derived from natural clay mineral. In this study, NSP showed strong selective growth inhibition and good settling enhancing effects on M. aeruginosa and highly efficient removal of MC-LR. NSP can inhibit the growth of M. aeruginosa (initial cell concentration at 3.00×106cellmL−1) with a LC50 at 0.28ppm after 12h exposure. At the dosage of 100ppm, NSP can enhance settling of suspended M. aeruginosa. Bacterial growth inhibition tests showed NSP had very mild growth inhibition effects on Escherichia coli at high dosage but promoted the growth of Pseudomonas aeruginosa and Bacillus halodurans. For MC-LR removal, at an initial concentration of 100μgL−1, NSP achieved higher than 99% removal. Thus, the results suggest that NSP could be an excellent candidate for controlling M. aeruginosa-related HABs in water bodies.

090 The influence of cryopreservation on marine microalgal cells

The development of cryopreservation methods for microalgae opens great prospects for marine biotechnology and aims to establish a bank of cryopreserved cultures. Nine of eleven marine microalgal species used in this study (the diatoms, green, red, and golden algae), including five previously untested species, were successfully recovered after freezing to ultra-low temperatures (−196 °C) using penetrating (Me 2 SO, glycerol, and ethylene glycol) and non-penetrating (trehalose and polyvinylpyrrolidone) cryoprotectants. The chief factor for the successful preservation of microalgal cells during freeze-thawing was shown to be the cooling rate. The survival rate for many algal species did not exceed 15%, but recovery of the initial cell concentration usually took 6–12 days after thawing. The pigment composition and content were evaluated as additional indicators of the algal functional activity. The pigment content tended to decrease after thawing as compared with unfrozen cells and increase during cell recovery. Three diatom species ( Attheya arenicola , A. longicornis , and A. ussurensis ) were successfully cryopreserved for the first time. For these weakly silicified marine diatoms, step freezing created the possibility of gradual cryoprotectant penetration inside the cells and a stepwise release of water out of the cells. None of the tested protocols gave a positive result for the diatoms of the Pseudo-nitzschia genus. The failure in cryopreservation of the Pseudo-nitzschia species may be explained by peculiarities in the cell wall composition: the Pseudo-nitzschia cell wall is composed of more silica and fewer organic components than those of the other tested diatoms, which makes the wall much more rigid and, probably, not permeable enough for penetrating protectants, even if the step freezing method is used. In our experiments with the Pseudo-nitzschia species, we observed that most of the thawed cells were dead but had almost undamaged cell walls. In contrast, the high tolerance to a wide range of cryopreservation conditions of the tiny green algae may be explained by its low water content, small cell size and thin cell wall. Cryosensitivity of marine algal cells was shown to depend on the differences in natural intrinsic characteristics rather than their taxonomic position. The mechanisms by which some algae withstand freezing better than others are not yet clear, but we suggest that the biochemical and physical properties of algal cell walls determine the water flow inside and outside the cell and enable the high flexibility needed for adaptation to different environments. Our results are a step in the development of a cryopreservation technology for some marine microalgae and the search for the nature of their cryoresistance. Source of funding: Grant 1 12-I-P6-07 of the Far Eastern Branch of Russian Academy of Sciences, grant 1 12-04-31974 of the Russian Foundation for Basic Research, grant 1 12-04-13006-12 of the Russian Foundation for Basic Research-Far Eastern Federal University, and grant 1 11 G34.31.0010 of Program at the Far Eastern Federal University. Conflict of interest: None declared. borodandy@gmail.com

Evaluation of Macroporous and Microporous Carriers for CHO-K1 Cell Growth and Monoclonal Antibody Production

The emergence of microcarrier technology has brought a renewed interest in anchorage-dependent cell culture for high-yield processes. Well-known in vaccine production, microcarrier culture also has potential for application in other fields. In this work, two types of microcarriers were evaluated for small-scale monoclonal antibody (mAb) production by CHOK1 cells. Cultures (5 ml) of microporous Cytodex 3 and macroporous CultiSpher-S carriers were performed in vented conical tubes and subsequently scaled-up (20 ml) to shake-flasks, testing combinations of different culture conditions (cell concentration, microcarrier concentration, rocking methodology, rocking speed, and initial culture volume). Culture performance was evaluated by considering the mAb production and cell growth at the phases of initial adhesion and proliferation. The best culture performances were obtained with Cytodex 3, regarding cell proliferation (average 1.85 ± 0.11 × 10(6) cells/ml against 0.60 ± 0.08 × 10(6) cells/ ml for CultiSpher-S), mAb production (2.04 ± 0.41 μg/ml against 0.99 ± 0.35 μg/ml for CultiSpher-S), and culture longevity (30 days against 10-15 days for CultiSpher-S), probably due to the collagen-coated dextran matrix that potentiates adhesion and prevents detachment. The culture conditions of greater influence were rocking mechanism (Cytodex 3, pulse followed by continuous) and initial cell concentration (CultiSpher-S, 4 × 10(5) cells/ml). Microcarriers proved to be a viable and favorable alternative to standard adherent and suspended cultures for mAb production by CHO-K1 cells, with simple operation, easy scale-up, and significantly higher levels of mAb production. However, variations of microcarrier culture performance in different vessels reiterate the need for optimization at each step of the scale-up process.

Survival and Growth of Vibrio cholerae, Escherichia coli, and Salmonella Spp. in Well Water Used for Drinking Purposes in Garoua (North Cameroon).

The ability of strains of faecal bacteria (Vibrio cholerae, Escherichia coli ATCC 25922, and four strains of Salmonella isolated, resp., from well water, pig, poultry, and human urine in Garoua) to survive or grow in well water microcosms was compared. Water samples were obtained from two wells in Garoua (north Cameroun). Autoclaving at 121°C for 15 min and filtration through 0.2 µm filter were used to make microcosms. Microcosms were constituted of unfiltered-autoclaved, filtered-nonautoclaved, and filtered-autoclaved well waters. Bacterial strains were inoculated at initial cell concentration of 3 Log10CFU/mL. All strains were able to survive/grow in used microcosms, and a maximal concentration of 5.61 Log10CFU/mL was observed. Survival abilities were strain and microcosm dependent. The declines were more pronounced in filtered-nonautoclaved water than in the other microcosms. E. coli and Salmonella sp. (poultry strain) lowered to undetectable levels (<1 Log10CFU/mL) after two days of water storage. V. cholera decreased over time, but surviving cells persisted for longer period in filtered-nonautoclaved water from well W1 (1.91 Log10CFU/mL) and well W2 (2.09 Log10CFU/mL). Competition for nutrients and/or thermolabile antimicrobial substances synthesized by “ultramicrocells” or by the autochthonous bacteria retained by the filter might affect the bacterial survival.

Continuous conversion of rice starch hydrolysate to 2-keto-D-gluconic acid by Arthrobacter globiformis C224

A continuous conversion process of rice starch hydrolysate to 2-keto-D-gluconic acid (2KGA) by Arthrobacter globiformis C224 was developed. Its feasibility for industrial application was also evaluated. Results showed that the initial cell concentration exceeding 1.25 g/L met the continuous 2KGA production at a stable dilution rate and media composition, while the dilution rate and feeding glucose concentration had a significant effect on 2KGA production performance. The optimal operating parameters were obtained as: 0.090/h of dilution rate and 171.0 g/L of feeding glucose concentration. Under these conditions, the steady state had a produced 2KGA concentration of 124.74 g/L, average volumetric productivity of 11.23 g/L/h, and yield of 0.97 g/g. In conclusion, continuous 2KGA production by the A. globiformis C224 strain would be a superior industrial process for the production of 2KGA in terms of its high 2KGA productivity and yield.

Effect of selected aldehydes found in the corncob hemicellulose hydrolysate on the growth and xylitol fermentation of Candida tropicalis

The effects of four aldehydes (furfural, 5-hydroxymethylfurfural, vanillin and syringaldehyde), which were found in the corncob hemicellulose hydrolysate, on the growth and xylitol fermentation of Candida tropicalis were investigated. The results showed that vanillin was the most toxic aldehyde for the xylitol fermentation, followed by syringaldehyde, furfural and 5-hydroxymethylfurfural. Moreover, the binary combination tests revealed that furfural amplified the toxicity of other aldehydes and the toxicities of other binary combinations without furfural were simply additive. Based on the fermentation experiments, it was demonstrated that the inhibition of aldehydes could be alleviated by prolonging the fermentation incubation, increasing the initial cell concentration, enhancing the initial pH value and minimizing the furfural levels in the hydrolysate evaporation process. The strategies that we proposed to suppress the inhibitory effects of the aldehydes successfully avoided the complicated and costly detoxifications. Our findings could be potentially adopted for the industrial xylitol fermentation from hydrolysates.

In Vitro Development and Characterization of a Tissue-Engineered Conduit Resembling Esophageal Wall Using Human and Pig Skeletal Myoblast, Oral Epithelial Cells, and Biologic Scaffolds

Tissue engineering represents a promising approach for esophageal replacement, considering the complexity and drawbacks of conventional techniques. To create the components necessary to reconstruct in vitro or in vivo an esophageal wall, we analyzed the feasibility and the optimal conditions of human and pig skeletal myoblast (HSM and PSM) and porcine oral epithelial cell (OEC) culture on biologic scaffolds. PSM and HSM were isolated from striated muscle and porcine OECs were extracted from oral mucosa biopsies. Myoblasts were seeded on an acellular scaffold issue from porcine small intestinal submucosa (SIS) and OEC on decellularized human amniotic membrane (HAM). Seeding conditions (cell concentrations [0.5×10(6) versus 10(6) cells/cm(2)] and culture periods [7, 14 and 21 days]), were analyzed using the methyl thiazoltetrazolium assay, quantitative PCR, flow cytometry, and immunohistochemistry. Phenotypic stability was observed after cellular expansion for PSM and HSM (85% and 97% CD56-positive cells, respectively), and OECs (90% AE1/AE3- positive cells). After PSM and HSM seeding, quantities of viable cells were similar whatever the initial cell concentration used and remained stable at all time points. During cell culture on SIS, a decrease of CD56-positive cells was observed (76% and 76% by D7, 56% and 70% by D14, 28% and 60% by D21, for PSM and HSM, respectively). Multilayered surface of α-actin smooth muscle and Desmine-positive cells organized in bundles was seen as soon as D7, with no evidence of cell within the SIS. Myoblasts fusion was observed at D21. Pax3 and Pax7 expression was downregulated and MyoD expression upregulated, at D14.OEC proliferation was observed on HAM with both cell concentrations from D7 to D21. The cell metabolism activity was more important on matrix seeded by 10(6) cells/cm(2). With 0.5×10(6) OEC/cm(2), a single layer of pancytokeratin-positive cells was seen at D7, which became pluristratified by D14, while when 10(6) OEC/cm(2) were used, a pluristratified epithelial structure was seen as soon as D7. Proliferative cells (Proliferating Cell Nuclear Antigen staining) were mainly located at the basal layer. In this model, the optimal conditions of cell seeding in terms of cell concentration and culture duration were 0.5×10(6) myoblasts/cm(2) and 10(6) OEC/cm(2), and 7 days.

Optimum conditions for cultivation of Chlorella sp. FC-21 using light emitting diodes

The purpose of this study was to determine the optimum conditions for the cultivation of Chlorella sp. FC-21 under light-emitting diodes (LEDs). Specific growth rates and Chlorella cell concentrations were measured when they were grown under different LED wavelengths (red, blue, white, and mixed). The red LEDs were the most effective light source as determined by increases in specific growth rates and cell concentrations. Cell concentrations increased as light intensity was increased; however, the specific growth rate decreased as the initial cell concentration rose due to the shading effect of cells in the reactor. To determine if aeration is beneficial during cell cultivation, micro-air bubbles were aerated at 0.70 vvm in the reactor under red LED illumination. Aeration led to two- and ten-times greater specific growth rates. Our findings show that red LEDs with aeration are optimal for cultivation of Chlorella sp. FC-21.

Batch‐to‐batch variability of two human designer cell lines – AGE1.HN and AGE1.HN.AAT – carried out by different laboratories under defined culture conditions using a mathematical model

Systems biology approaches involve collaboration of a larger number of research groups. Experiments are being performed in different laboratories dealing with different aspects of the topic of interest. Therefore, comparability of data collected for further analysis and modeling needs critical assessment. Here, growth and product formation of two human designer cell lines (AGE1.HN and its α1‐antitrypsin producing clone AGE1.HN.AAT) were investigated by four research laboratories. Cell lines were cultivated in shake flasks and stirred tank bioreactors operated at standardized conditions using a chemically defined medium, and a simple mathematical model was used to estimate characteristic process parameters. Results obtained for 35 batches showed that neither the initial viable cell concentration nor the initial concentration of glucose and glutamine showed significant differences between laboratories. For these measurements with low variations, specific growth rate and yields varied between 8.5 and 26% (relative standard error), indicating comparability of cultivations between laboratories for exponential growth. Higher variations of fitted parameters related to measurements with high initial variation. Comparing the nonproducing with the producing cell line, no significant differences were found regarding growth dynamics and metabolism. Overall, it seems justified to draw conclusions based on the entire experimental dataset of this systems biology project.

A novel optical panel photobioreactor for cultivation of microalgae

In this study, a novel optical panel photobioreactor (OPPBR) equipped with a V-cut/or flat optical panel (OP) and a light source, i.e., light-emitting diodes (LEDs) was developed. The performance of this OPPBR was assessed using cultures of Chlorella vulgaris. Growth rates of biomass were compared in bioreactors operated separately using a V-cut OP, or a flat-plate OP both equipped with LEDs or a fluorescent light source without any OP. The experiments were conducted at neutral pH (7.2 ± 0.3) with an initial cell concentration of 0.15 ± 0.05 g L(-1), at 23 ± 1 °C under dark and light cycles of 8 and 16 h, respectively, using LEDs and fluorescent lamps for 11 days. The results demonstrated that the amount of biomass produced using the V-cut OP was three times higher than the flat-plate OP and five times higher than without the OP. Parametric studies demonstrated that a distance of 3 mm between the OP and the LEDs produced the highest illumination uniformity, i.e., 65.7% for the flat-plate OP and 87.6% for the V-cut OP. The OPPBR system can be scaled up and could be used to enhance biomass production using an LED and OP combination.

Assessment of key biological and engineering design parameters for production of Chlorella zofingiensis (Chlorophyceae) in outdoor photobioreactors

For the design of a large field of vertical flat plate photobioreactors (PBRs), the effect of four design parameters-initial biomass concentration, optical path length, spacing, and orientation of PBRs-on the biochemical composition and productivity of Chlorella zofingiensis was investigated. A two-stage batch process was assumed in which inoculum is generated under nitrogen-sufficient conditions, followed by accumulation of lipids and carbohydrates in nitrogen-deplete conditions. For nitrogen-deplete conditions, productivity was the most sensitive to initial biomass concentration, as it affects the light availability to individual cells in the culture. An initial areal cell concentration of 50 g m(-2) inoculated into 3.8-cm optical path PBR resulted in the maximum production of lipids (2.42 ± 0.02 g m(-2) day(-1)) and carbohydrates (3.23 ± 0.21 g m(-2) day(-1)). Productivity was less sensitive to optical path length. Optical path lengths of 4.8 and 8.4 cm resulted in similar areal productivities (biomass, carbohydrate, and lipid) that were 20 % higher than a 2.4-cm optical path length. Under nitrogen-sufficient conditions, biomass productivity was 48 % higher in PBRs facing north-south during the winter compared to east-west, but orientation had little influence on biomass productivity during the spring and summer despite large differences in insolation. An optimal spacing could not be determined based on growth alone because a tradeoff was observed in which volumetric and PBR productivity increased as space between PBRs increased, but land productivity decreased.

Mechanical cell disruption for lipid extraction from microalgal biomass

Cell disruption is an integral part of the downstream operation required to produce biodiesel from microalgae. This study investigated the use of ultrasonication and high-pressure homogenization (HPH) as cell disruption methods for two microalgal species, Tetraselmis suecica (TS) and Chlorococcum sp. (C sp.). The kinetics of cell disruption followed a first-order model (0.65<R(2)<1.00). Disruption rate constant for ultrasonication was directly proportional to power level and followed a parabolic relationship with initial cell concentration, while that for HPH was directly proportional to operating pressure and inversely proportional to initial cell concentration. Mean disruption rate constant for HPH was approximately seven times that for ultrasonication. Mean disruption rate constant for TS cells was roughly 20% higher than that for C sp. cells. Subjecting TS culture to cell disruption prior to lipid extraction resulted in 5-8-fold increase in lipid yield and 3-5-fold increase in triglyceride yield.

BIOSORPTION OF TEXTILE DYE USING IMMOBILIZED BACTERIAL (&lt;i&gt;PSEUDOMONAS AERUGINOSA&lt;i/&gt;) AND FUNGAL (&lt;i&gt;PHANEROCHATE CHRYSOSPORIUM&lt;i/&gt;) CELLS

Wastewater containing dyes presents a serious problem due to its high toxicity which leads to creating enormous environmental pollution and ecological hazards. Therefore the removal of the high stable dyes from the textile effluents is of major importance. The purpose of this study is to remove the reactive dye Procion Blue 2G from textile dye solution by biosorption process using immobilized cells of Pseudomonas aeruginosa and Phanerochate chrysosporium. It was found that maximum dye uptake is 1.648 mg g-1 of bead for P. aeruginosa and it is 1.242 mg g-1 of bead for P. chrysosporium. Both the results are derived from higher initial dye concentration (100 mg L-1) and high cell concentration (in terms of volume of inoculum 20 mL) and at low mass of biosorbent (5 g of bead). Comparatively better results are produced by the beads having the cells of P. aeruginosa than P. chrysosporium. Further, due to the cell immobilization, both the cell beads can be utilized repeatedly in continuous reactors by selecting suitable eluent in industrial scale with the advantage of avoiding wash out of cells.

Dried Spent Yeast and Its Hydrolysate as Nitrogen Supplements for Single Batch and Repeated-Batch Ethanol Fermentation from Sweet Sorghum Juice

Dried spent yeast (DSY) and its hydrolysate (DSYH) were used as low-cost nitrogen supplements to improve ethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP01 under very high gravity (VHG) fermentation (280 g·L−1 of total sugar) conditions. The supplemented DSY and DSYH concentrations were 11, 16 and 21 g·L−1, corresponding to a yeast extract nitrogen content of 6, 9 and 12 g·L−1, respectively. The initial yeast cell concentration for ethanol fermentation was approximately 5 × 107 cells·mL−1. The fermentation was carried out in single batch mode at 30 °C in 1-L air-locked bottles with an agitation rate of 100 rpm. Ethanol production from the juice with and without yeast extract (9 g·L−1) was also performed as control treatments. The results showed that DSY at 21 g·L−1gave the highest ethanol concentration (PE, 107 g·L−1) and yield (Yp/s, 0.47 g·g−1). The use of DSYH at the same DSY concentration improved ethanol productivity (Qp), but not PE and Yp/s. The ethanol production efficiencies of the juice under DSY and DSYH supplementations were markedly higher than those without nutrient supplementation. However, the PE and Qp values of the juice containing 21 g·L−1 of DSY was approximately 7 g·L−1 and 0.62 g·L−1·h−1 lower than those under the presence of yeast extract (9 g·L−1), respectively. At the end of the single batch fermentation under the optimum DSY concentration, the sugar consumption was approximately 80%. Therefore in the repeated-batch fermentation, the initial total sugar was reduced to 240 g·L−1. The results showed that the system could be carried out at least 20 successive batches with the average PE, Yp/s and Qp of 95 g·L−1, 0.46 g·g−1 and 1.45 g·L−1·h−1, respectively.

Advances and Drawbacks of the Adaptation to Serum-Free Culture of CHO-K1 Cells for Monoclonal Antibody Production

Currently, mammalian cell technology has become the focus of biopharmaceutical production, with strict regulatory scrutiny of the techniques employed. Major concerns about the presence of animal-derived components in the culture media led to the development of serum-free (SF) culture processes. However, cell adaptation to SF conditions is still a major challenge and limiting step of process development. Thus, this study aims to assess the impact of SF adaptation on monoclonal antibody (mAb) production, identify the most critical steps of cell adaptation to the SF EX-CELL medium, and create basic process guidelines. The success of SF adaptation was dependent on critical steps that included accentuated cell sensitivity to common culture procedures (centrifugation, trypsinization), initial cell concentration, time given at each step of serum reduction, and, most importantly, medium supplements used to support adaptation. Indeed, only one of the five supplement combinations assessed (rhinsulin, ammonium metavanadate, nickel chloride, and stannous chloride) succeeded for the Chinese hamster ovary-K1 cell line used. This work also revealed that the chemically defined EX-CELL medium benefits mAb production in comparison with the general purpose Dulbecco's Modified Eagle's Medium, but the complete removal of serum attenuates these positive effects.