Search

For Pichia pastoris fermentation process with multi-operating conditions, it is difficult to predict the cell concentration under the new operating conditions by the soft sensor model established under the specific operating conditions. Inspired by the idea of transfer learning, a method based on an improved balanced distribution adaptive regularization extreme learning machine (IBDA-RELM) was proposed to solve the problem. The domain adaptation (DA) method in transfer learning is developed to reduce distribution distance by transforming data. However, the joint distribution adaptation (JDA) and the balanced distribution adaptation (BDA) in DA cannot be directly applied to regression problems. The fuzzy sets (FSs) method was proposed to solve this issue. Finally, a soft sensor model of Pichia pastoris cell concentration was realized by inputting the converted data to the RELM model. Simulation verification was carried out with three operating conditions at the scene of fermentation. The transfer effects of three DA methods, including transfer component analysis (TCA), improved joint distribution adaptation (IJDA) as well as IBDA, were compared. The predicted results show that IBDA-RELM had a better performance in the soft sensor of Pichia pastoris cell concentration under multi-operating conditions.

Simulation modeling of microbial proliferation had increased in recent years using Monod and advanced kinetic models. Accurate data is limited to advance studies in cell utilization for various applications due to complexity of the process. In this research, behaviour of the Monod parameters at different substrate and biomass levels will be examined using predicted data obtained originally from empirical observations. Method involves deliberate variation of some variables to examine its effects on others starting from the basic Malthus equation. Results shows that, predicted data are more convenient and clearly presents the supposed dynamics of the process compared to ideal experimental results. By implications, improved procedures are necessary to allow for precise estimates of basic cell numbers and substrate concentration values

Conventional sample preparation techniques require bulky and expensive instruments and are not compatible with next-generation point-of-care diagnostic testing. Here, we report a manually operated syringe-tip inertial microfluidic centrifuge (named i-centrifuge) for high-flow-rate (up to 16 mL/min) cell concentration and experimentally demonstrate its working mechanism and performance. Low-cost polymer films and double-sided tape were used through a rapid nonclean-room process of laser cutting and lamination bonding to construct the key components of the i-centrifuge, which consists of a syringe-tip flow stabilizer and a four-channel paralleled inertial microfluidic concentrator. The unstable liquid flow generated by the manual syringe was regulated and stabilized with the flow stabilizer to power inertial focusing in a four-channel paralleled concentrator. Finally, we successfully used our i-centrifuge for manually operated cell concentration. This i-centrifuge offers the advantages of low device cost, simple hand-powered operation, high-flow-rate processing, and portable device volume. Therefore, it holds potential as a low-cost, portable sample preparation tool for point-of-care diagnostic testing.

The seeding of cells into an organ is an important step in cell therapy because the final functional properties of the organ are related to the initial cell distribution throughout the organ. However, vessel occlusion is a serious problem that prevents uniform distribution of the cells in the entire organ. Understanding the mechanism of vessel occlusion can help optimize the seeding process. In this study, the vessel occlusion phenomenon under perfusion conditions during cell seeding was investigated. First, we applied a microfluidic system that enabled the observation of the occlusion events during injection. Second, we applied a multiphase numerical model that can describe the cell–cell interactions and cell–fluid interactions to investigate the vessel occlusion phenomenon during the seeding process. In particular, the effects of cell concentration and flow rate were investigated. The results indicate the importance of cell–cell interactions and cell–vessel interactions for the occurrence of vessel occlusion. In addition, it is found that the probability of occurrence of vessel occlusion increases with the increase in cell concentration and decrease in flow rate. The simulation model can help determine the optimum parameters to enhance cell seeding efficiency.

Bacterial concrete is one of the methods of rectifying the micro-cracks developed in the structural elements made of concrete. The gram-positive type bacteria Bacillus subtilis when acquainted with concrete produces calcite precipitation which heals the micro cracks in the concrete. Bacillus subtilis was used with a cell concentration of 106. The optimised percentage replacement of fine aggregates with sugarcane fibres of grain size less than 4.75 mm was 0.1 %. The effect of sugarcane fibres on the durability of bacterial concrete is presented in this paper.To study the Stress -Strain behaviour of Sugarcane based Bacterial concrete (SBC), appropriate analytic SS model is developed that resembles the experimental behaviour of the various samples such as Conventional Concrete (CC), Bacterial Concrete (BC) and SBC. This work mainly targets on utilizing the earlier models and offers a new SS model that can well represent the actual SS behaviour of SBC samples. After finding the SS behaviour of CC, BC and SBC specimens experimentally, equations are developed to characterise axial SS behaviour of CC, BC and SBC samples. From these mathematical equations, theoretical stress for CC, BC and SBC are calculated and compared with test values. The proposed equations have exposed good connection with test values authorizing the mathematical model developed.

Compliance with the existing purity and safety requirements for immunobiologicals can be effectively achieved by the use of serum-free nutrient media and specialised supplements of non-animal origin. The paper shows the possibility of using Sheff-Vax ACF® supplements (Kerry, Inc., Ireland) for ВНК-21/SUSP/ARRIAH cell cultivation and FMDV reproduction. By passage 7, cell concentration and growth rate with Sheff-Vax Plus PF ACF were found to be 40–60% higher than with Sheff- Vax PF ACF and Sheff-Vax Plus ACF. No differences were observed as regards changes in pH. During FMDV reproduction in the cells, it was found that the number of 146+75S components in the test samples containing 1 million cells was 2.3–2.4 higher compared to the controls. Cells cultured with the use of Sheff-Vax Plus PF ACF supplement had normal morphology and multiple dynamic protrusions. In the presence of this supplement, growth rate and suspension concentration in the test and control samples became equal by passage 7. The number of immunogenic components of FMDV reproduced in the cells grown using Sheff-Vax Plus PF ACF was 20–30% higher than in the cells grown using other supplements. ВНК-21/SUSP/ARRIAH cell concentration and growth rate in the presence of specialised supplements were found to be lower than those in the control samples with serum and blood protein hydrolysate added to the nutrient medium. The virus yield from 1 million cells was higher in the culture grown using Sheff-Vax ACF supplements. Sheff-Vax Plus PF ACF was found to be the most suitable for ВНК-21/SUSP/ARRIAH cell cultivation and FMDV reproduction in the said cells out of the three tested supplements.

Aquatic microbial communities contribute fundamentally to biogeochemical transformations in natural ecosystems, and disruption of these communities can lead to ecological disasters such as harmful algal blooms. Microbial communities are highly dynamic, and their composition and function are tightly controlled by the biophysical (e.g., light, fluid flow, and temperature) and biochemical (e.g., chemical gradients and cell concentration) parameters of the surrounding environment. Due to the large number of environmental factors involved, a systematic understanding of the microbial community-environment interactions is lacking. In this article, we show that microfluidic platforms present a unique opportunity to recreate well-defined environmental factors in a laboratory setting in a high throughput way, enabling quantitative studies of microbial communities that are amenable to theoretical modeling. The focus of this article is on aquatic microbial communities, but the microfluidic and mathematical models discussed here can be readily applied to investigate other microbiomes.

Aim. To estimate in vitro the effect of DNA isolated from the probiotic strain Bifidobacterium bifidum 791 on the cell concentration and adhesive properties of fecal isolates of bifidobacteria and opportunistic microorganisms of different species.Materials and methods. DNA was isolated from the probiotic strain Bifidobacterium bifidum 791. Biomass containing bifidobacteria was washed from the nutrient medium. The suspension of bacteria in the buffer solution was subjected to ultrasonic disintegration with a frequency of 40 kHz three times for 30 minutes, followed by centrifugation. The supernatants were combined and purified chromatographically on CL-4B Sepharose. B. breve, B. bifidum, B. infantis, Staphylococcus aureus, Escherichia coli lac-, Enterococcus faecalis, and Candida albicans were used as test cultures, isolated from the intestines of conditionally healthy adults. Results. The nucleic acid solution with a concentration of 3.54 |jg/ml did not affect the cell number of bifidobacteria (p = 0.61). The DNA content in the solution of 14.15-21.23 jg/ml increased the titers of B. bifidum and B. breve by 2 lg CFU/ml compared to the control (p = 0.01), but did not affect the titers of S. aureus, E. coli lac-, E. faecalis, C. albicans (p = 0.73). The DNA solution stimulated the self-aggregation of bifidobacteria in 1.5-2.0 times. The ability to autoaggregate under the influence of bifidobacterial DNA in S. aureus, E. faecalis, C. albicans did not change, in E. coli lacincreased 2.3 times (p = 0.05).Conclusion. A DNA solution of the probiotic strain B. bifidum 791 with a content 14.15-21.23 jg/ml stimulates the reproduction and autoaggregation of fecal B. breve, B. bifidum.

The biovanillin production was influenced by varying the culture pH via single control strategy conducted by separate experiments during the fermentation processes. Highest biovanillin production (124 mg/L) with 32% molar yield at culture pH 6.0 from the one-stage control method was observed. Specific growth rates (μ) of the Phanerochaete chrysosporium and biovanillin production decreased by decreasing the culture pH from 6.0 to 3.5, which indicated that lower culture pH was not adequately apposite for biovanillin production using Phanerochaete chrysosporium in a 2-L stirred tank bioreactor. The development of two-stage control strategies had improved the biovanillin production (131 mg/L) and cell concentration (13.0 g/L) by about 6 and 5%, respectively. Therefore, the most influential control strategy for higher biovanillin production was discovered not to control the culture pH of the fermentation during active growth phase of the Phanerochaete chrysosporium, while the production phase should be controlled at pH 6.0.

Preconcentrating particulate and cellular matter for their isolation or detection is often a necessary and critical sample preparation or purification step in many lab-on-a-chip diagnostic devices. While surface acoustic wave (SAW) microcentrifugation has been demonstrated as a powerful means to drive efficient particle concentration, this has primarily been limited to micron dimension particles. When the particle size is around 1 μm or below, studies on SAW microcentrifugation to date have shown that particle ring-like aggregates can only be obtained in contrast to the localized concentrated clusters that are obtained with larger particles. Considering the importance of submicron particles and bioparticles that are common in many real-world samples, we elucidate why previous studies have not been able to achieve the concentration of these smaller particles to completion, and we present a practical solution involving a novel closed chamber configuration that minimizes sample heating and eliminates evaporation to show that it is indeed possible to drive submicron particle and cell concentration down to 200 nm diameters with SAW microcentrifugation over longer durations.

espanolEl objetivo del estudio fue determinar la concentracion celular y la biomasa seca en tres species de microalgas marinas: Chlorella vulgaris, Nannochloropsis oculata y Tetraselmis striata. Las cepas se suministraron por el Laboratorio Costero de Ilo perteneciente al Instituto del Mar del Peru (IMARPE) y luego, se acondicionaron las microalgas para ser cultivadas en medio semicontrolado. Las fases del cultivo de microalgas consistieron en el cepario, inicial, intermedia y masiva. El orden de maxima concentracion celular (cel/mL) para las microalgas fue: Nannochloropsis oculata > Chlorella vulgaris > Tetraselmis striata donde N. oculata represento 7,63 veces superior a T. striata. En el caso de la biomasa, el orden correspondio a: C. vulgaris > T. striata > N. oculata existiendo 1,32 g de diferencia. Se concluyo que, la especie de microalga Chlorella vulgaris indico la mayor ventaja para usarse en la acuicultura comparativamente con las otras dos especies. EnglishThe aim of study was to determine cell concentration and dry biomass in three species of marine microalgae: Chlorella vulgaris, Nannochloropsis oculata and Tetraselmis striata. The strains were supplied by the Ilo Coastal Laboratory belonging to the Peruvian Institute of the Sea (IMARPE) and then, the microalgae were conditioned to be cultivated in a semi-controlled medium. The phases of the microalgae culture consisted of the cepario, initial, intermediate and massive. The order of maximum cellular concentration (cel/mL) for the microalgae was Nannochloropsis oculata > Chlorella vulgaris > Tetraselmis striata where N. oculata represented 7.63 times higher than T. striata. In the case of biomass, the order corresponded to: C. vulgaris > T. striata > N. oculata, with a 1.32 g difference. It was concluded that the microalgae species Chlorella vulgaris indicated the greatest advantage to be used in aquaculture compared to the other two species.

Microalgae cell concentration is one of the most commonly used and important parameter in microalgae culture and ecological monitoring. The traditional detection process is cumbersome, laborious, a...

We reporte a three-stage spiral channel device for achieving high-fold and high-throughput passive volume reduction through coupling inertial microfluidics with cross-flow filtration. To understand the device physics and optimize the structure, the effects of critical channel design on particle dynamics and volume reduction performance were explored. Then the principle of volume reduction was used for concentrating cells from large-volume fluids, and the concentration performance of differently sized particles/cells in the determined device was quantitatively characterized over wide flow rates. The results indicated that our device could achieve high-efficiency cell concentration at a high throughput of over 4 mL/min. Finally, we successfully applied our device for the enrichment of rare tumor cells after being separated from the blood or peritoneal fluid and the extremely high fold concentration of white blood cells from the large-volume fluid. Using a serial concentration, an ultrahigh concentration fold of approximately 1100 could be achieved. Our device offers numerous advantages, such as high-processing throughput, high concentration fold, simple channel design, and low-cost fabrication. Thus, it holds the potential to be used as a sample concentration tool for disposable use in low-resource settings.

A careful selection of culture mediums and feeds has become necessary to maximize yields of recombinant proteins during bioprocesses of mammalian cells. Supplements contain a variety of concentrate nutrients, and their beneficial effects vary according to recombinant cell lines. In this study, the effects of PowerFeed A on growth kinetics, productivity and cellular metabolism were evaluated for two Chinese hamster ovary cell lines producing a monoclonal antibody in a batch culture. Supplemented cultures increased integral viable cell density of CRL-12444 and CRL-12445 cells by 2.4 and 1.6 times through extension of culture time at which viability was above 90% in 72 and 36 h, respectively, and increment of maximal cell concentration in 3.25 × 106 cells/ml (69%) for CRL-12445 cells. Product titer augmented 1.9 and 2.5 times for CRL-12444 and CRL-12445 cells, respectively, without changes in growth rate and specific productivity. Feed supplementation also stimulated full consumption of glucose and free glutamine and reduced 10 times lactate accumulation, while ammonium, sodium and potassium remained at similar concentrations at the end of the culture. About 44% of calcium, mainly provided by feed, was consumed by both cell lines. Maximization of cellular growth, viability and protein titer through feeding encourages extending its use to other cell lines and exploring novel combinations with other basal mediums or feeds. A thorough investigation of its impact on protein quality and the molecular mechanisms behind these effects will allow designing effective feeds and strategies to rationally optimize protein production in the biomanufacturing industry., Graphical Abstract

Developing an effective and high-quality vaccine is an important issue in rabies prevention. This article presents the results of the studies aimed at selecting the optimum parameters for the cultivation of the VN-21 finite cell line and the CVS-11 strain of the rabies virus. Such parameters as inoculated cell concentration, the optimal dose of infection with the virus, the time and methods of cultivation, and the choice of the inactivant and the adjuvant were chosen.

Background: Rural/remote blood collection can cause delays in processing, reducing PBMC number, viability, cell composition and function. To mitigate these impacts, blood was stored at 4 °C prior to processing. Viable cell number, viability, immune phenotype, and Interferon-γ (IFN-γ) release were measured. Furthermore, the lowest protective volume of cryopreservation media and cell concentration was investigated. Methods: Blood from 10 individuals was stored for up to 10 days. Flow cytometry and IFN-γ ELISPOT were used to measure immune phenotype and function on thawed PBMC. Additionally, PBMC were cryopreserved in volumes ranging from 500 µL to 25 µL and concentration from 10 × 106 cells/mL to 1.67 × 106 cells/mL. Results: PBMC viability and viable cell number significantly reduced over time compared with samples processed immediately, except when stored for 24 h at RT. Monocytes and NK cells significantly reduced over time regardless of storage temperature. Samples with &gt, 24 h of RT storage had an increased proportion in Low-Density Neutrophils and T cells compared with samples stored at 4 °C. IFN-γ release was reduced after 24 h of storage, however not in samples stored at 4 °C for &gt, 24 h. The lowest protective volume identified was 150 µL with the lowest density of 6.67 × 106 cells/mL. Conclusion: A sample delay of 24 h at RT does not impact the viability and total viable cell numbers. When long-term delays exist (&gt, 4 d) total viable cell number and cell viability losses are reduced in samples stored at 4 °C. Immune phenotype and function are slightly altered after 24 h of storage, further impacts of storage are reduced in samples stored at 4 °C.

Bio-oxidation of refractory sulfidic gold minerals has been applied at the commercial scale as a pre-treatment to improve gold yields and reduce chemical consumption during gold cyanidation. In this study, the effect of initial cell concentration on the oxidation of pyritic gold ore was evaluated with four aerated bioreactors at 30 °C with 10% pulp density and pH maintained at 1.4 with NaOH. Results of NaOH consumption and changes in soluble Fe and S concentrations indicated that increasing the initial cell concentration from 2.3 × 107 to 2.3 × 1010 cells mL−1 enhanced pyrite oxidation during the first week. However, by day 18 the reactor with the lowest initial cell concentration showed profound performance enhancement based on soluble Fe and S concentrations, sulfide-S and pyrite contents in the residues, and subsequent gold leaching of the bio-oxidation residues by cyanidation. Overall, the results showed that the cell concentration was clearly beneficial during the initial stages of oxidation (first 7–8 days).

Monitoring of microalgae cell concentration during their growing phase is imperative to ensure efficiency in biomass production and to study the cell division kinetics since it impacts the ...

Process intensification for Peste des Petites Ruminants Virus (PPRV) vaccine production in anchorage dependent Vero cells is challenging, involving substantial amount of bioprocess development. In this study, we describe the implementation of a new, scalable bioprocess for PPRV vaccine production in Vero cells using serum-free medium (SFM), microcarrier technology in stirred-tank bioreactors (STB), in-situ cell detachment from microcarriers and perfusion. Vero cells were successfully adapted to ProVero™-1 SFM, reaching growth rates similar to serum-containing cultures (0.030 1/h vs 0.026 1/h, respectively). An in-situ cell detachment method was successfully implemented, with efficiencies above 85%. Up to 2.5-fold increase in maximum cell concentration was obtained using perfusion when compared to batch culture. Combining perfusion with the in-situ cell detachment method enabled the scale-up to 20 L STB directly from a 2 L STB, surpassing the need for a mid-scale platform (i.e. 5 L STB) and thus reducing seed train duration. Head-to-head comparison of cell growth and PPRV production in the 2 L and 20 L STB was performed, and no significant differences could be observed. Estimated infectious PPRV titers in Tissue Culture Infection Dose (TCID50) (TCID50/mL = 5 × 106 and TCID50/cell = 5) are within the log-range reported in literature for PPRV production in STB and SFM by Silva et al. (2008), thus confirming the feasibility and scalability of the seed train designed [1] . The novel and scalable vaccine production process herein proposed has the potential to assist the upcoming Peste des Petites Ruminants (PPR) Global Eradication Program (targeted by FAAO for 2030) by providing African local and/or regional manufacturers with a platform capable of generating over 25,000 doses of Nigeria 75/1 strain in just 19 days using a 20 L STB.

Potentiometry is one of method on measuring metals based on cell potential. Measurements using potentiometry are divided into comparative cells and concentration cells. Concentration cells are measurements of a cell's potential by using two solutions with different concentrations. The aim of this study was to develop a concentration cell potentiometric method equipped with applications so measurements are easier and faster. The added application able to calculate the results of experiments so that the calculation process becomes faster and easier. Validation results give the results of the R the value of 0.9990; LoD 7.6484x10-7, LoQ 6.2103x10-7, RSD 0.64%, and recovery 98.05%. This optimum measurement was carried out at 30 oC and pH 5. The results of Cu measurements in well water obtained the result of 0.9633 ppm. Measurements using the development of this method, get good validation results and can be used on measurements similar to those in the aquatic environment. Keywords: Potentiometry, cell concentration, Copper (Cu), validation, aquatic environment

Objective . To analyze publications devoted to the possibility of using bacterial nanocellulose as a plastic material for defects in the dura mater associated with spine and spinal cord pathology. Material and Methods . The PubMed database was searched with keywords “bacterial cellulose properties” and “bacterial cellulose”. The search was limited to articles published in English- and Russian-language journals in 2009–2019. The limitation was caused by the need for up-to-date evaluation of the properties of bacterial nanocellulose. The search with keywords “bacterial cellulose properties” returned a list of 963 articles and with key words “bacterial cellulose” – a list of 3908 articles. The Google search engine was also used, in which articles were found actually reflecting properties of bacterial nanocellulose without which complete understanding of its nature is impossible. After assessing the found data, 76 articles were selected that reflect this issue to the fullest extent. More than fifty percent of the reviewed articles were published within the last 10 years. Evidence level: IV; recommendation grade: C, though randomized trials with evidence level Ib and recommendation level A are used. Results . Implants made of bacterial nanocellulose are able to perform the function of the extracellular matrix by providing a barrier function, creating conditions for the circulation of metabolites and oxygen, and preventing the achievement of excess cell concentration. Conclusion . The use of bacterial nanocellulose as an implant for closure of the dura mater defects associated with the spinal cord pathology is a promising direction in neurosurgery, since nanocellulose does not cause adhesions to the nervous tissue and performs a barrier function.

The objective of this study was to develop kinetic models to predict the growth of Vibrio parahaemolyticus in raw Pacific white shrimp as affected by storage temperature. Shrimp samples inoculated with a 2-strain cocktail of V. parahaemolyticus were stored between 8 and 35 °C to observe the growth during storage. The growth curves were analyzed with two primary models (Huang model and No-lag phase model) in combination with a suboptimal Huang square-root model using a one-step kinetic analysis method and the USDA-IPMP Global Fit software to estimate the kinetic parameters that minimized the global error. No growth of V. parahaemolyticus in samples was observed at storage temperatures below 10 °C. The minimum growth temperatures were 10.8 and 10.5 °C as estimated by the Huang and No-lag phase models, respectively. The maximum V. parahaemolyticus population in shrimp samples reached approximately 8.0 log CFU/g during storage. The estimated kinetic parameters, including the minimum growth temperature and maximum cell concentration, matched well with the experimental observations. The kinetic models were validated with two dynamic temperature profiles. The validation showed that both models were equally suitable for predicting the growth of V. parahaemolyticus in Pacific white shrimp. The standard error of prediction is about 1.0 log CFU/g. The models obtained from this study can be used to predict the dynamic growth of V. parahaemolyticus in Pacific white shrimp during post-harvest refrigerated storage and temperature abuse conditions.

Peripheral blood mononuclear cells (PBMCs) are used in a wide variety of preclinical assays. Preanalytical variations can have a devastating impact on the results. In this review, we list critical preanalytical factors for PBMC-based assays to develop awareness and orientation to the types of sample preparation and storage that one may consider employing. Critical factors during blood collection are the blood collection tube and anticoagulant, possible stabilizer used, and the pre-isolation blood storage temperature and time. During PBMC isolation, critical factors are the isolation method, density gradient or magnetic sorting, use of barrier, possible RBC lysis, and centrifuge type. During cryopreservation, attention is needed for the cryomedium type and temperature, freezing device and program, cell concentration, and the long-term storage temperature. During the thawing process, the thawing procedure/device used and wash medium temperature are critical. To avoid biased results in PBMC assays, these critical preanalytical factors must be standardized and/or documented. Additionally, participation in external quality assurance programs is strongly recommended.

A fed-batch strategy is proposed to produce microalgae biomass under non-axenic heterotrophic conditions. The strategy induces the alternation of N-deplete (Glucose-replete) and N-replete (Glucose-deplete) cultivation phases by the periodic and uncoupled supply of glucose and NO3− to the culture. Cultivation of the microalga T. obliquus with this strategy reduced the ratio of the bacteria to microalgae cell concentration from 1.6, attained by conventional photoautotrophic cultivation, to 0.03. During the N-deplete phase, microalgae duplication stopped and biomass concentration increased 1.9 times, while during the N-replete phase, microalgae duplicated halving their average size and losing about 25% of their weight. The process proved to be effective under several consecutive cycles. Biomass productivity until 6.1 g/Ld and biomass concentration until 26 g/L were achieved. The results demonstrate that the proposed strategy can effectively prevent bacterial contamination, paving the way to the large scale production of microalgae biomass under non-axenic heterotrophic conditions.

Effect of various nitrate replete concentrations have been investigated in terms of biomass yield, cell and nitrate concentrations. Media used in this study is Bold’s basal medium which contains nitrate that act as nutrient. Its concentrations have been varied for obtaining the high biomass yield. The nitrate concentrations used were 30 mg nitrate/L, 35 mg nitrate/L, 40 mg nitrate/L, 45 mg nitrate/L and 50 mg nitrate/L) with 30 mg nitrate/L as a control. Microalgae Chlorella sp. is cultured and aerated in a Schott bottle with presents of light. Results showed that the best concentration to obtain highest biomass yield was 45 mg nitrate/L. It also gave the highest optical density reading at day 9 with 2.100 ± 0.070 and showed the highest cell concentration with 703 ± 29 x 106 cells/mL. Dry algae produced by this concentration after the end of the cycle was 291 ± 9 mg which was the highest compared to other concentration. It is suggested that as the biomass yield is increased by using 45 mg nitrate/L concentration, other methods to increase lipid content can be paired with nitrate replete method and can be further studied in the future.

Cryopreservation is a common methodology for long-term microalgae storage. Current cryopreservation methods are based on using diverse cryoprotectants and two-step cooling protocols, followed by sample storage at the temperature of liquid nitrogen (− 196 °C). However, the use of this methodology requires a continuous liquid N2 supply as well as facilities with dedicated equipment, which is not affordable for every laboratory. In our work, we report on the successful development of a simple and cost-effective method for the long-term cryogenic storage of Tetradesmus obliquus at temperatures (− 80 °C) used in commonly available deep freezers that are more readily accessible to laboratories. Two procedures were evaluated that were originally devised for other microalgae; this was followed by the optimization of critical parameters such as the sample’s microalgal concentration and the cryoprotectant reagent’s incubation time. Cell viability was monitored using the survival rates obtained by direct agar plating and the growth recovery times in liquid cultures. Viability-related variables were recorded following different storage times of up to 3 years. The main operational factors involved in the process (cell concentration, incubation time, and storage time) were statistically analyzed with regard to their influence on the survival rate. The statistical analysis showed interdependence (a two-factor interaction) between the cellular concentration and the cryoprotectant’s incubation time, on the one hand, and between the incubation time and the storage time on the other. Survival rates above 70% were obtained under optimized conditions after 3 months of storage, along with 20–35% viabilities after 3 years. These results open up the possibility of extending this method to other Scenedesmaceae, or even other microalgal species, and for its use in resource-limited laboratories.

Autogenous bone grafting is the gold standard for replacing large bone defects. Due to limitations in the quantity and quality of harvested bone from the iliac crest, and the potential associated morbidity, the technique of cell grafting has been developed. Autogenous bone marrow aspirate is concentrated (so called BMAC) and delivered locally to the intended site with minimally invasive techniques. However, there are only about 1 in 30,000 Colony Forming Unit-Fibroblast (CFU-F) progenitor cells in unconcentrated iliac crest aspirate. Current techniques for cell concentration only increase these numbers by about 5-fold. Thus, BMAC is not equivalent to “stem cell therapy”.

Summary High cell viability and recovered cell concentration are typical quality control requirements for single-cell processing and quality data. This protocol describes procedures for sampling, live-cell biobanking, preprocessing for single-cell RNA sequencing, and analysis of fine-needle aspiration (FNA) samples of the skin. The minimally invasive nature of FNA collection is more accepted by patients and allows for frequent longitudinal sampling, resulting in high-quality single-cell sequencing data that capture cellular heterogeneity in clinical samples., Graphical abstract, Highlights • Protocol for fine-needle aspirate collection from human skin lesions • Details for pre-processing of samples for single-cell RNA sequencing • RNA-seq data analysis with immune repertoire analysis and quality control, High cell viability and recovered cell concentration are typical quality control requirements for single-cell processing and quality data. This protocol describes procedures for sampling, live-cell biobanking, preprocessing for single-cell RNA sequencing, and analysis of fine-needle aspiration (FNA) samples of the skin. The minimally invasive nature of FNA collection is more accepted by patients and allows for frequent longitudinal sampling, resulting in high-quality single-cell sequencing data that capture cellular heterogeneity in clinical samples.

Microbial communities often respond to environmental cues by adopting collective behaviors—like biofilms or swarming—that benefit the population. Bioconvection is a distinct and robust collective behavior wherein microbes locally gather into dense groups and subsequently plume downward through fluid environments, driving flow and mixing on scales thousands of times larger than an individual cell. Though bioconvection was observed more than 100 years ago, effects of differing physical and chemical inputs, as well as its potential selective advantages to different species of microbes, remain largely unexplored. In the canonical microbial bioconvectorBacillus subtilis, density inversions that drive this flow are setup by vertically oriented oxygen gradients that originate from an air-liquid interface. In this work, we developEscherichia colias a complementary model organism for the study of bioconvection. We show that forE. coliandB. subtilis, bioconvection confers a context-dependent growth benefit with clear genetic correlates to motility and chemotaxis. We found that fluid depth, cell concentration, and carbon availability have complimentary effects on the emergence and timing of bioconvective patterns, and whereas oxygen gradients are required forB. subtilisbioconvection, we found thatE. colideficient in aerotaxis (Δaer) or energy-taxis (Δtsr) still bioconvect, as do cultures that lack an air-liquid interface. Thus, in two distantly related microbes, bioconvection confers context-dependent growth benefits, andE. colibioconvection is robustly elicited by multiple types of chemotaxis. These results greatly expand the set of physical and metabolic conditions in which this striking collective behavior can be expected and demonstrate its potential to be a generic force for behavioral selection across ecological contexts.

Connective tissue progenitors (CTPs) resident in native tissues serve as biological building blocks in tissue repair and remodeling processes. Methods for analysis and reporting on CTP quantity and quality are essential for defining optimal cell sources and donor characteristics and the impact of cell processing methods for cell therapy applications. The present study examines the influence of donor characteristics and cell concentration (nucleated cells/mL) on CTP prevalence (CTPs/million nucleated cells) and CTP concentration (CTPs/mL) in bone marrow aspirates (BMAs).Iliac crest bone marrow was aspirated from 436 patients during elective total knee or hip arthroplasty. Bone marrow-derived nucleated cells were plated at a density of 1.19 × 105 cells/cm2. Colony-forming unit analysis was performed on day 6.Large variation was seen between donors. Age (p0.05) and cell concentration (p0.001) significantly influenced CTP prevalence and CTP concentration. For every 1-year increase in age, the odds of having at least an average CTP prevalence and CTP concentration decreased by 1.5% and 1.6%, respectively. For every 1 million cells/mL increase in cell concentration, the odds of having at least an average CTP prevalence and CTP concentration increased by 2.2% and 7.9%, respectively. Sex, race, body mass index (BMI), and the presence of osteoporosis did not influence CTP prevalence or CTP concentration.BMA-derived CTPs were obtained from all patient groups. CTP prevalence and CTP concentration decreased with age. Cell concentration decreased with age and positively correlated with total CTP prevalence and CTP concentration. The mean CTP concentration in patients60 years of age was a third of the CTP concentration in patients30 years of age.Proper BMA techniques are necessary to obtain a high-quality yield and composition of cells and CTPs. The reduced CTP concentration and CTP prevalence in the elderly may be mitigated by the use of cell processing methods that increase CTP concentration and CTP prevalence (e.g., by removing red blood cells, serum, and non-CTPs or by increasing aspirate volumes). Cell concentration in the BMA can be measured at the point of care and is an appropriate initial assessment of the quality of BMA.

Cell counting has become an essential method for monitoring the viability and proliferation of cells. A hemacytometer is the standard device used to measure cell numbers in most laboratories which are typically automated to increase throughput. The principle of both manual and automated hemacytometers is to calculate cell numbers with a fixed volume within a set measurement range (105 ~ 106 cells/ml). If the cell concentration of the unknown sample is outside the range of the hemacytometer, the sample must be prepared again by increasing or decreasing the cell concentration. We have developed a new hemacytometer that has a multi-volume chamber with 4 different depths containing different volumes (0.1, 0.2, 0.4, 0.8 µl respectively). A multi-volume hemacytometer can measure cell concentration with a maximum of 106 cells/ml to a minimum of 5 × 103 cells/ml. Compared to a typical hemacytometer with a fixed volume of 0.1 µl, the minimum measurable cell concentration of 5 × 103 cells/ml on the multi-volume hemacytometer is twenty times lower. Additionally, the Multi-Volume Cell Counting model (cell concentration calculation with the slope value of cell number in multi-chambers) showed a wide measurement range (5 × 103 ~ 1 × 106 cells/ml) while reducing total cell counting numbers by 62.5% compared to a large volume (0.8 µl-chamber) hemacytometer.

Xylella fastidiosa subsp. pauca is the causal agent of “olive quick decline syndrome” in Salento (Apulia, Italy). On April 2015, we started interdisciplinary studies to provide a sustainable control strategy for this pathogen that threatens the multi-millennial olive agroecosystem of Salento. Confocal laser scanning microscopy and fluorescence quantification showed that a zinc-copper-citric acid biocomplex—Dentamet®—reached the olive xylem tissue either after the spraying of the canopy or injection into the trunk, demonstrating its effective systemicity. The biocomplex showed in vitro bactericidal activity towards all X. fastidiosa subspecies. A mid-term evaluation of the control strategy performed in some olive groves of Salento indicated that this biocomplex significantly reduced both the symptoms and X. f. subsp. pauca cell concentration within the leaves of the local cultivars Ogliarola salentina and Cellina di Nardò. The treated trees started again to yield. A 1H-NMR metabolomic approach revealed, upon the treatments, a consistent increase in malic acid and γ-aminobutyrate for Ogliarola salentina and Cellina di Nardò trees, respectively. A novel endotherapy technique allowed injection of Dentamet® at low pressure directly into the vascular system of the tree and is currently under study for the promotion of resprouting in severely attacked trees. There are currently more than 700 ha of olive groves in Salento where this strategy is being applied to control X. f. subsp. pauca. These results collectively demonstrate an efficient, simple, low-cost, and environmentally sustainable strategy to control this pathogen in Salento.

The effect of light on biomass and fucoxanthin (Fx) productivities was studied in two microalgae, Tisochrysis lutea and Phaeodactylum tricornutum. High and low biomass concentrations (1.1 and 0.4 g L−1) were tested in outdoor pilot‐scale flat‐panel photobioreactors at semi‐continuous cultivation mode. Fluorescence spectroscopy coupled with chemometric modeling was used to develop prediction models for Fx content and for biomass concentration to be applied for both microalgae species. Prediction models showed high R 2 for cell concentration (.93) and Fx content (.77). Biomass productivity was lower for high biomass concentration than low biomass concentration, for both microalgae (1.1 g L−1: 75.66 and 98.14 mg L−1 d−1, for T. lutea and P. tricornutum, respectively; 0.4 g L−1: 129.9 and 158.47 mg L−1 d−1, T. lutea and P. tricornutum). The same trend was observed in Fx productivity (1.1 g L−1: 1.14 and 1.41 mg L−1 d−1, T. lutea and P. tricornutum; 0.4 g L−1: 2.09 and 1.73 mg L−1 d−1, T. lutea and P. tricornutum). These results show that biomass and Fx productivities can be set by controlling biomass concentration under outdoor conditions and can be predicted using fluorescence spectroscopy. This monitoring tool opens new possibilities for online process control and optimization., Graphical abstract Biomass and fucoxanthin outdoor production and monitoring with brown microalgae

Cell mass and viability are tightly linked to the productivity of fermentation processes. In 2nd generation lignocellulose-based media quantitative measurement of cell concentration is challenging because of particles, auto-fluorescence, and intrinsic colour and turbidity of the media. We systematically evaluated several methods for quantifying total and viable yeast cell concentrations to validate their use in lignocellulosic media. Several automated cell counting systems and stain-based viability tests had very limited applicability in such samples. In contrast, manual cell enumeration in a hemocytometer, plating and enumeration of colony forming units, qPCR, and in situ dielectric spectroscopy were further investigated. Parameter optimization to measurements in synthetic lignocellulosic media, which mimicked typical lignocellulosic fermentation conditions, resulted in statistically significant calibration models with good predictive capacity for these four methods. Manual enumeration of cells in a hemocytometer and of CFU were further validated for quantitative assessment of cell numbers in simultaneous saccharification and fermentation experiments on steam-exploded wheat straw. Furthermore, quantitative correlations could be established between these variables and in situ permittivity. In contrast, qPCR quantification suffered from inconsistent DNA extraction from the lignocellulosic slurries. Development of reliable and validated cell quantification methods and understanding their strengths and limitations in lignocellulosic contexts, will enable further development, optimization, and control of lignocellulose-based fermentation processes.

Recently, even though 3D bioprinting has made it possible to fabricate 3D artificial tissues/organs, it still faces several significant challenges such as cell sedimentation and aggregation. As the essential element of 3D bioprinting, bioink is usually composed of biological materials and living cells. Guided by the initially dominant gravitational force, cells sediment, resulting in the non-uniformity of the bioink and the decrease in the printing reliability. This study primarily focuses on the quantification of cell sedimentation-induced cell concentration change and cell aggregation within the bioink reservoir during inkjet-based bioprinting. The major conclusions are summarized as follows: (1) with 0.5% (w/v) sodium alginate, after around 40-min printing time, almost all the cells have sedimented from the top region. The cell concentration at the bottom is measured to be more than doubled after 60-min printing time. On the contrary, due to the slow cell sedimentation velocity with 1.5% and 3% (w/v) sodium alginate, the uniformity of the bioink is still highly maintained after 60-min printing; and (2) more cell aggregates are observed at the bottom with the printing time, and severe cell aggregation phenomenon has been observed at the bottom using 0.5% (w/v) sodium alginate starting from 40-min printing time. With the highest cell concentration 2 × 106 cells/mL, 60.9% of the cells have formed cell aggregates at 40-min printing time. However, cell aggregation is dramatically suppressed by increasing the polymer concentration.

As the secondary primary producer in aquatic ecosystem, zooplankton play key roles in energy flow and biogeochemical cycles through food chain. For herbivorous zooplankton, many measurement methods can be used for the determination of feeding rate, such as the dilution technique, fluorescence analysis of zooplankton gut contents, radiotracer technique, fluorescence-labeled technique, and cell concentration subtractive method. We will brief introduce these methods in this chapter.

espanolContextualizacion: actualmente se ha incrementado el interes en la produccion de microalgas debido a los diferentes usos de la biomasa microalgal en algunos sectores industriales, ademas de la posibilidad de emplearse en la mitigacion de gases de efecto invernadero gracias a su alta capacidad para la captura de CO2. Vacio de conocimiento: como parte del Acuerdo de Paris en 2015, Colombia se comprometio en reducir un 20% sus emisiones de gases efecto invernadero, con el proposito de contribuir a la meta establecida para 2050; por esta razon, se deben desarrollar investigaciones y planes de accion enfocados a este objetivo. Proposito del estudio: el proposito de este estudio es evaluar del efecto de la induccion de CO2 en diferentes concentraciones sobre la cinetica de crecimiento de Chlorella Vulgaris CV_2714A y Scenedesmus Obliquus SOB_001 en un sistema de fotobiorreactores a escala laboratorio, en un volumen de 3,8 L de medio de cultivo (solucion NPK + micronutrientes). Metodologia: los ensayos se realizaron en fotoperiodos con 12 h de luz y 12 h de oscuridad durante 5 dias consecutivos. El diseno experimental aleatorizado cuyas fuentes de variacion fueron: especie microalgas y dosificacion de CO2 (0, 2, 6,5, y 12,8 L. dia-1) con iluminacion artificial por lampara fluorescente de 4400 lumenes. Se estimo la concentracion celular por medio de la aproximacion numerica en camara de “Neubauer” con la metodologia usada por Darki et al. (2017), ademas de tasa de crecimiento y tiempo de duplicacion celular en dias de acuerdo con Andersen, (2005). Los datos fueron sometidos al analisis de varianza y pruebas de medias de Tukey (p Resultados y conclusiones: los resultados en los diferentes ensayos mostraron mayor concentracion celular en C. vulgaris en comparacion con S. obliquus. En cuanto al suministro de CO2, las 2 especies obtuvieron respuesta significativamente mayor (p EnglishContextualization: Currently, interest in the production of microalgae has increased due to the different uses of microalgal biomass in some industrial sectors, in addition to being used in the mitigation of greenhouse gases thanks to its high capacity for CO2 capture. Knowledge gap: Being part of the Paris Agreement in 2015, Colombia is committed to reduce its greenhouse gases emissions by 20%, to contribute to the goal set for 2050, for this reason, it must adopt research and action plans focused on this objective. Purpose: the purpose of this study was to evaluate the effect of CO2 induction at different concentrations on the growth kinetics of Chlorella Vulgaris CV_2714A and Scenedesmus Obliquus SOB_001 in a laboratory scale photobioreactor system in a volume of 3.8 L of culture medium (NPK solution + micronutrients). Methodology: The tests were carried out in photoperiods with 12 hours of light and 12 hours of darkness for 5 consecutive days. The completely randomized experimental design whose sources of variation were microalgae species and CO2 dosage (0.2, 6.5 and 12.8 L. day-1) with artificial lighting by a 4400-lumen fluorescent lamp. The cellular concentration was estimated by means of the numerical approximation in the “Neubauer” chamber with the methodology used by Darki et al. (2017), in addition to growth rate and cell doubling time in days according to Andersen, (2005). The data were submitted to analysis of variance and Tukey's mean tests (p Results and conclusions: The results in the different tests showed a higher cell concentration in C. vulgaris compared to S. obliquus. Regarding CO2 supply, the 2 species obtained a significantly greater response (p

Automated flow cytometry (FCM) adapted to real-time quality surveillance provides high4 temporal-resolution data about the microbial communities in a water system. The cell concentration calculated from FCM measurements indicates sudden increases in the number of bacteria, but can fluctuate significantly due to man-made and natural dynamics; it can thus obscure the presence of microbial anomalies. Cytometric fingerprinting tools enable a detailed analysis of the aquatic microbial communities, and could distinguish between normal and abnormal community changes. However, the vast majority of current cytometric fingerprinting tools use offline statistical computations which cannot detect anomalies immediately. Here, we present a computational model, entitled Microbial Community Change Detection (MCCD), which transforms microbial community characteristics into an online process control signal (herein called outlier score) that remains close to zero if the microbial community remains stable and increases with fluctuations in the community. The model is based on fingerprints and distance-based outlier calculations. We tested it in silico and in vitro by simulating accute contaminations to real-world water systems with large inherent microbial fluctuations. We showed that the outlier score was robust against these dynamic variations, while reliably detecting intentional contaminations. This model can be used with automated FCM to quickly detect potential microbiological contamination, and this especially when the time between treatment and distribution is very short.

Light availability is an important driver of algal growth and for the formation of surface blooms. The formation of Microcystis surface scum decreases the transparency of the water column and influences the vertical distribution of light intensity. Only few studies analysed the interactions between the dynamics of surface blooms and the light distribution in the water column. Particularly the effect of light attenuation caused by Microcystis colonies (self-shading) on the formation of surface scum has not been explored. In the present study, we simulate the effect of variable cell concentration of Microcystis colonies on the vertical distribution of light in the water column based on experimental estimates of the extinction coefficient of Microcystis colonies. The laboratory observations indicated that higher cell concentration of Microcystis enhance the light attenuation in water column and promotes surface scum formation. We extended an existing model for the light-driven migration of Microcystis by introducing the effect of self-shading and simulated the dynamics of vertical migration for different cell concentrations and different colonial morphologies. The simulation results show that high cell concentrations of Microcystis promote surface scum formation, as well as its persistence throughout diel photoperiods. Large and tight Microcystis colonies facilitate scum formation, while small and loose colonies increase scum stability and persistence. This study reveals a positive feedback regulation of Microcystis surface scum formation and stability by self-shading and provides novel insights into the underlying mechanisms.

Activated sludge process is the most common method for biological treatment of industrial and municipal wastewater. One of the most important parameters in performance of activated sludge systems is quantitative monitoring of biomass to keep the cell concentration in an optimum range. In this study, a novel method for activated sludge quantification based on image processing and RGB analysis is proposed. According to the results, the intensity of blue color in the macroscopic image of activated sludge culture can be a very accurate index for cell concentration measurement and R2 coefficient, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) which are 0.990, 2.000, 0.323, and 13.848, respectively, prove this claim. Besides, in order to avoid the difficulties of working in the three-parameter space of RGB, converting to grayscale space has been applied which can estimate cell concentration with R 2 = 0.99. Ultimately, an exponential correlation between RGB values and cell concentrations in lower amounts of biomass has been proposed based on Beer-Lambert law which can estimate activated sludge biomass concentration with R 2 = 0.97 based on B index.

Anisotropic silver nanoparticles sensitized by various lectins were applied for detection of yeast (Saccharomyces cerevisiae) which was used as a model of fungal cells. It was shown that high concentrations of yeast cells have stabilized silver nanoparticles, preventing their aggregation in the presence of NaCl whereas at low concentrations of cells, the salt has induced aggregation of nanoparticles with drastic changes in optical spectra. These changes depend on cell concentration and permit the detection of cells in the range from 3.2 × 103 to 7 × 107 cell per ml. This approach was used for the determination of these cells in urine and its applicability was demonstrated.

In the present study we aimed firstly to assess the resistance of a set of yeasts, isolated from the black olive pomace, to various phenolic compounds; and to evaluate their growth capacities on an olive leaf extract rich of oleuropein. The results showed that only three yeasts were able to both resist to the different phenolic compounds tested and grow on the olive leaf extract at a concentration of 1%. The second step was devoted to studying the bioconversion of oleuropein of an olive leaf extract into hydroxytyrosol by the above selected three yeasts. The oleuropein degradation and hydroxytyrosol formation were monitored by HPLC-UV. Only one yeast isolate; identified using molecular tools; was chosen to optimize the bioconversion throughout the optimization of the most influencing parameters: temperature, substrate concentration, cell concentration, and pH of the extract using a method of experimental design. The results showed that the three yeasts; F6, F4, and F12 were capable of producing hydroxytyrosol from oleuropein with different concentrations 317 ± 14 mg/l, 210 ± 14 mg/l, and 149 ± 21 mg/l; respectively. The strong oleuropienolytic activity manifested by the F6 isolate was further optimized, and the results showed that the optimal conditions for producing the maximum of hydroxytyrosol are: a temperature of 31 °C, a cell concentration of 2%, a substrate concentration of 1%, and a non-adjusted pH of the extract. Based on the molecular approaches F6 was identified as Nakazawaea molendini-olei.

The study present in this paper reveals the corrosion inhibiting efficiency of M25 grade concrete induced with Sporosarcina pasteurii bacteria. The accelerated corrosion induced crack method is applied on reinforced bacterial concrete which is the modified philosophy of constant voltage technique. In the current investigation, for different cover thicknesses considered, total time required for charge passed until full longitudinal crack occurs along the cover thickness due to corrosion of steel reinforcement in concrete specimens are measured using which Charge Deterioration Factors (ChDFs) are evaluated for bacterial reinforced concrete beams made with various cell concentrations of Sporosarcina pasteurii bacteria. It was established that beams made with cell concentration of 105cells/ml of mixing water offers superior corrosion inhibition ability as time taken to form full length longitudinal crack is more than in other beams made with 103cells/ml, 104cells/ml and 106cells/ml cell concentration of bacteria chosen for the study.

In accordance with the State Pharmacopoeia (SPh) requirements for live plague vaccine, a reference standard has to be used when testing the specific activity and thermal stability of plague vaccine commercial batches in order to assess the consistency and acceptability of the test results. Since there is no international reference standard for plague vaccine, the certification of a new batch of the industry reference standard (IRS) of live plague vaccine in terms of the above-mentioned quality parameters is an urgent challenge. Therefore, a certification programme for the industry reference standard was developed that establishes the design and scope of testing required to obtain statistically significant results. A candidate IRS was represented by a commercial batch of the product meeting the specification requirements for live plague vaccine. The certification parameters were: «Specific activity: microbial cell concentration», «Specific activity: live microbial cell percentage» and «Thermal stability». The article presents the results of the certification of a new batch of the live plague vaccine IRS, detailed evaluation of the candidate IRS in terms of: «Average weight and uniformity of weight», «Loss on drying», and statistical interpretation of the test results. It also summarises the results of the product testing in terms of «Specific activity: immunogenicity». The results of application of the previous batch of the live plague vaccine IRS (OSO 42-28-392-2013) and the results of monitoring the stability of its certification parameters demonstrated that the IRS shelf life could be extended by 6 months relative to the established period (from 2 to 2.5 years). All the certified and additional characteristics are reflected in the official documents for the scientific/technological product — live plague vaccine IRS, OSO 42-28-392-2017: passport, labelling and patient information leaflet.

A new biological approach was explored to harvest microalgae in situ with bacterial cellulose produced by Gluconacetobacter xylinus grown in microalgal culture by adding different proportions of glucose/yeast extract (GY) media. This study attempted to optimize this process in terms of GY media concentration, process time, microalgae cell concentration, and oscillation speed. Bacterial cellulose successfully harvested nearly 90% of Scenedesmus obliqnus and Chlamydomonas reinhardtii after only 8 h, and 92% of Chlorella vulgaris after 48 h, with supplementation of 30% (v/v) GY media to the microalgae culture. This method allows harvested media to be recycled instead of GY media, and can be used for a variety of cell densities. Scanning electron microscopy revealed that microalgae cells were harvested after being embedded in a network of bacterial cellulose. These results suggest this effective and simple operation has the potential for developing a cost-effective harvest method for microalgae production.

The objective of this study was to investigate the growth of Escherichia coli O157:H7 in raw ground beef under competition from background flora. The growth of E. coli O157:H7 was observed in sterile irradiated and non-irradiated raw ground beef under dynamically changing temperature conditions. A one-step dynamic analysis method was used to directly construct tertiary models for describing bacterial growth with and without competition and to estimate the kinetic parameters from dynamic growth curves to prove the hypothesis that the growth of E. coli O157:H7 was significantly affected by competition from background flora in raw ground beef. The one-step dynamic method successfully modelled the growth of E. coli O157:H7 and background flora in ground beef and the competition between the two. The estimated minimum growth temperature for E. coli O157:H7 was 7.7 °C, and the maximum cell concentration was 9.0 log CFU/g in irradiated ground beef. Under competition, the specific growth rate of E. coli O157:H7 was reduced by approximately 18% in raw ground beef. The resulting dynamic models and kinetic parameters were validated with separate dynamic growth data, showing that the Root Mean Square Error (RMSE) of prediction was The results of this study demonstrated that the one-step dynamic analysis is a useful and efficient method for investigating bacterial growth with and without competition under dynamic conditions and for developing growth kinetic models. Since the dynamic models have been validated, they can be used to predict the shelf-life of ground beef (background flora) and conduct risk assessment of E. coli O157:H7 and non-O157 STEC.

In this work the influence of acerola (Malpighiae marginata DC) pulp, at concentrations of 0, 10, 15, 25 and 30%, on mead production by Saccharomyces cerevisiae AWRI 796 was evaluated. A novel approach based on cell growth to obtain high accuracy fits for the data and to estimate optimization parameters such as Gibbs free energy was used. Fermentation was done using 107 cells/mL at pH 5.0 and 30 °C for up to 288 h. The addition of increasing concentrations of acerola pulp progressively enhanced the cell growth, with the highest cell concentration reached being ∼2.09 × 108 cells/mL. Under these conditions, the lowest Gibbs free energy of growth was −4.81 kJ/mol after fermentation for 288 h at a pulp concentration of ∼18%. The velocity of substrate consumption was −14 × 10−3 A.U./h whereas the velocity of ethanol formation was 17 × 10−3 A.U./h with ethanol production of 15.2% v/v or 120.1 g/L.

Microbial oxidation of ferrous to ferric iron allows efficient oxidative processing of sulfide minerals under ambient conditions. This study determined the effect of cell concentration of a mixed mesophilic microbial culture on iron oxidation rate, and evaluated if there was a cell concentration threshold that dictates a maximal volumetric iron oxidation rate. A bioreactor with feedback-loading of ferrous media was operated at 30 °C to maintain a redox potential of +480 mV vs. Ag/AgCl at pH of 1.3. A positive and linear correlation (R2 = 0.955) between the cell concentration (6.8 × 107–7.1 × 109 cells mL−1) and volumetric biological iron oxidation (up to 6.9 g L−1 h−1) was observed. The specific iron oxidation was not affected by cell concentration, and no biocatalytic threshold was observed. This indicated that a high cell concentration can be used to achieve a high volumetric iron oxidation rate, enabling the use of a compact reactor size.