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Open raceways are one of the principal commercial-scale systems for cultivating algae to produce biofuels and bioproducts. A critical process parameter in such a system is algae cell concentration in the aqueous culture, commonly measured in terms of optical density (OD). A prototype OD sensor exclusively for real-time measurement of algae cell concentration in open ponds was designed, constructed, and tested in a laboratory scale raceway and an open-pond raceway. In the lab test, the sensor OD measurements were highly correlated with spectrometer OD measurements. The OD curve recorded by the sensor clearly showed the diurnal pattern of algae growth associated with the on-off cycle of the lighting system in the lab facility. The test data also clearly highlighted unique cultivation activities such as growth media addition and harvesting. In the open pond raceway test, sensor OD data were also highly correlated with spectrometer-measured OD even though the range of OD variation was significantly less during this test. The OD curve clearly indicated a higher biomass accumulation rate in the pond from late morning to late afternoon than during the rest of the day. These tests of the OD sensor demonstrated its potential to provide accurate real-time algae concentration data in an open pond cultivation system, the type of data that would be necessary for timely management decision-making. This sensor would also eliminate the cost associated with frequently collecting and analyzing samples, making commercial-scale algae production more economically practical. Keywords: microalgae, optical density (OD), open pond raceway, sensor, pond monitoring, circuit design, optoelectronics DOI: 10.25165/j.ijabe.20181101.2839 Citation: Yao Y, Ge Y F, Thomasson J A, Sui R X. Algae optical density sensor for pond monitoring and production process control. Int J Agric & Biol Eng, 2018; 11(1): 212–217.

Microscopic investigations of any abnormality associated with erythrocyte/red blood cell morphology constitute an important segment of the age-old peripheral smear test. Though the test is conducted on a glass slide, the effect of glass and similar other solid substrates on erythrocyte morphology remained majorly unexplored. In the first of its kind investigation, we have outlined the effect of varying the substrate surface potential on erythrocyte morphology. Such a substrate induced phenomenon has been quantified for two distinctly different drying configurations (droplets and film) upon systematically varying the cell concentration. Experimental results and supporting theoretical analysis unambiguously show the surface potential of the solid substrate to be the most influential parameter in the process of morphological alteration. The findings of the present investigation may be utilized to formulate an error-free protocol for the baseline peripheral smear test of hematological diagnosis.

A previous molecular-genetic analysis of clonal cultures and single cells of Ostreopsis spp. that were isolated from Peter the Great Bay (the Sea of Japan) revealed three different genotypes according to the nucleotide sequences of ribosomal DNA (rDNA). Of these, Ostreopsis sp. 1 was earlier found only off the coast of Japan and described as being the most common and highly toxic. We have obtained further molecular evidence and have studied the morphological features of cells from one of the Ostreopsis strains with this genotype and some aspects of its growth at salinities of 24, 28, and 32‰. The results showed that in cells from the Russian coast of the Sea of Japan, the third apical (3') and the third precingular (3") plates do not adjoin one another, being separated by the elongated second apical (2') plate. Cells of Ostreopsis sp. 1 from the Russian coast are significantly larger than Ostreopsis sp. 1 cells with the same genotype from the coast of Japan. Salinity did not have a substantial effect on the growth of Ostreopsis sp. 1. The growth rate varied from 0.24 to 0.35 divisions per day, with maximum values at a salinity of 24‰. When salinity decreased to 24‰, the exponential growth phase was significantly extended and the maximum cell concentration doubled.

We present a microfluidic platform for automatic multi-size spheroid formation within constant volume hanging droplets (HDs) from a single inlet loading of a constant cell concentration. The platform introduces three technological improvements over the existing spheroid formation platforms: 1) cell seeding control is achieved by enrichment of a cell solution rather than dilution; 2) cell seeding in each HD is fully independent and pre-programmable at the design stage; 3) the fabricated chip operates well using a hydrophobic PDMS surface, ensuring long-term storage possibility for device usage. Pre-programmed cell seeding densities at each HD are achieved using a "microfluidic funnel" layer, which has an array of cone-shaped wells with increasing apex angles acting as a metering unit. The integrated platform is designed to form, treat, stain, and image multi-size spheroids on-chip. Spheroids can be analyzed on-chip or easily transferred to conventional well plates for further processing. Empirically, enrichment factors up to 37× have been demonstrated, resulting in viable spheroids of diameters ranging from 230-420 μm and 280-530 μm for OV90 and TOV112D cell lines, respectively. We envision that microfluidic funnels and single inlet multi-size spheroid (SIMSS) chips will find broad application in 3D biological assays where size-dependent responses are expected, including chemoresponse assays, photodynamic therapy assays, and other assays involving drug transport characterization in drug discovery.

Two different process configurations SSP (simultaneous saccharification photo-fermentation) and SHP (separate hydrolysis photo-fermentation) for photo-fermentative hydrogen production using corn stover by mixed consortium of photosynthetic bacteria were compared. The effects of substrate concentration, initial pH and fermentative temperature on SSP and SHP were investigated. Cell growths and hydrogen production characteristics during the processes of SSP and SHP were also compared. The results showed that the optimal condition of SSP was substrate concentration of 30 g/L, initial pH of 5.5 and fermentative temperature of 40 °C, the corresponding hydrogen production was 83.87 mLH2/g corn stover, which was 27.8% higher than that of SHP. The cell growth time in SSP was longer than that in SHP, especially for extended exponential and stationary stages, which was helpful for hydrogen production. The highest cell concentration in SSP was 3.34 g/L, which was 36.3% higher than that of SHP. The peak hydrogen production rate in SSP increased linearly until 16.33 mL H2/h during 36–120 h, while the peak hydrogen production rate in SHP increased during 12–48 h and then decreased during 48–84 h, with a mean rate of 11.28 mL H2/h.

Long-term storage of cell stocks insures that cells are available for use whenever needed. Cryopreservation of cells is the method of choice for preservation of important or rare cell stocks. There are several factors to consider when establishing a protocol for freezing, thawing, and recovery of cells after storage. These parameters may include cell concentration, cryoprotectant choice and concentration, and thawing rate among others. Further, the assessment of cell viability and/or function prior to and following cryopreservation is imperative in order to accurately determine downstream utility as well for optimizing the cryopreservation process. This chapter is designed to provide guidance and insight into developing robust and successful protocols for preserving cells that will preserve cell stocks and provide optimal cell yield and viability.

Wine fermentations using rice media containing either Monascus koji or rice nuruk were performed and fermentative characteristics based on the koji type were investigated. Cultivations were performed in a 20 °C room in a 20 L bottle with the rice media that included Monascus rice koji at both 20 and 30%, or rice nuruk at 20%. After 22 days of cultivation, the ethanol yield reached 14.2–14.6% (v/v) for M. koji and 16.5% (v/v) for rice nuruk. This lower yield with use of M. koji was thought to be due to rapid cell concentration decreases in the later stage. Total amounts of organic acids and volatile compounds in fermentations using M. koji were 166–172 and 1779–1874 mg/L, respectively, being 8.7–12.9% and 46.3–54.1% higher than with use of rice nuruk. With M. koji, a high quality rice wine was produced with high levels of volatile compounds and monacolin K.

Since the infection strategy in the baculovirus-insect cell system mostly affects production of the vector itself or the target product, and given that individual infection parameters interact with each other, the optimal combination must be established for each such specific system. In this work an artificial neural network was used to model infection strategy, including the cell concentration at infection, the multiplicity of infection, the medium recycle, and agitation intensity, and to evaluate the relative importance of each factor in the baculovirus production obtained. The results demonstrate that this model can be used to select an optimal infection strategy. For the baculovirus-insect cell system used in this study, this includes low multiplicity of infection and agitation intensity, along with high cell concentration at infection and medium recycle. Our model is superior to regression methods and predicts baculovirus production more precisely, thus meaning that it could be useful for the development of feasible processes, thereby improving process performance and economy.

The hydrophobicity of coal limits the adsorption of microorganisms and the efficiency of biological desulfurization was influenced, while the surfactant can enhance the interaction of the four phases, air, water, bacteria, and coal grain. In this experiment, three types of surfactant, anionic (SDS), cationic (DTAB), and nonionic (Tween 20), were investigated at 30 °C, and the cell concentration, pH value, leaching time, and coal biodesulfurization rate of the coal desulfurization system were detected. It is shown that the total desulfurization rate approached 29.7% in 16 days when 1100 mg/L Tween 20 was added in the shaking test, which represented the optimum efficiency. Further column leaching desulfurizating experiments showed that the desulfurization rate of the experimental group with Tween 20 (12.75%) was notably higher than that of the control group (8.32%). Along with the processing of desulfurization, the cell concentration decreased at first, and then rapidly increased, and finally stayed constan...

To harvest for T cell therapy, a 1.6-fold higher number of CD3+ T cells was collected with MNC mode (N = 10) compared with Auto PBSC mode (N = 5) in COBE Spectra cell separator, but the blood product volume was increased by 3.5-fold. For therapeutic angiogenesis therapy, apheresis was initially performed using Auto PBSC mode (N = 4) to fine tune the blood product volume to omit cell concentration, but the collected number of mononuclear cells was lower than expected. However, an increase of the harvest cycle number from 3.8 ± 0.5 to 7.4 ± 2.0 cycles (N = 19) resulted in a 2.1-fold higher number of collected mononuclear cells (8.7 ± 4.1 × 109 vs. 4.1 ± 1.0 × 109 cells, P

Tagatose is a novel low-calorie sweetener which addition changes food product properties, e.g., aw, and formula, that may influence food-microbial growth dynamics in both liquid and solid products. The aim of this work was to study growth dynamics of Salmonella Typhimurium and Listeria monocytogenes in liquid and solid media enriched with tagatose (1.5, 4.5 and 7.5% (w/v)), at 4, 8 and 20 °C. More specifically, liquid media were chemically defined minimal medium, general medium and UHT skimmed milk; gelatine and a gelatine-dextran mixture were the gelling agents used, leading respectively a homogeneous and heterogeneous solid system. At regular intervals, cell concentration was determined and the Baranyi and Roberts (1994) model was fitted for growth parameter estimation. Results show a reduced and even no growth of S. Typhimurium with increasing tagatose concentrations, especially at low temperatures and when increasing media complexity. The behaviour of L. monocytogenes is not affected by tagatose, except in liquid at 4 °C, where tagatose facilitates the growth in general culture media. Varying responses of the studied bacteria to changes in media formulation should be considered for future product design.

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.

Background Blood vessels are constantly exposed to flow-induced stresses, and endothelial cells (ECs) respond to these stresses in various ways. Objective In order to facilitate endothelialization after endovascular implantation, cell behaviors around a metallic wire using a flow circulation system are observed. Methods A parallel flow chamber was designed to reproduce constant shear stresses (SSs) on cell surfaces and to examine the effects of a straight bare metal wire on cell monolayers. Cells were then exposed to flow for 24 h under SS conditions of 1, 2, and 3 Pa. Subsequently, cell distributions were observed on the plate of the flow chamber and on the surface of the bare metal wire. Flow fields inside the flow chamber were analyzed using computational fluid dynamics under each SS condition. Results After 24 h, ECs on the bottom plate were concentrated toward the area of flow reattachment. The matching of higher cell density and CFD result suggests that flow-induced stimuli have an influence on EC distributions. Conclusion Typical cell concentration occurs on dish plate along the vortexes, which produces large changes in SSs on cell layer.

In this work, the growth of a green microalgae strain in a referenced torus photobioreactor equipped with a data acquisition system was studied. The monitoring of the microalgal growth was carried out by the measurement of optical density, cell concentration and pH measurement. The culture was carried out under fixed operating conditions, as temperature, gaz flowrate and light intensity. The obtained specific growth rate during exponential phase of cultivation was 0.167 d-1. After a continuous photoperiod of two weeks, the biomass was valorized through its lipids content (an average value of 20%). The obtained results reveal the presence of a wide variety of fatty acids that are essential for conversion into biodiesel. Also, a better understanding of the behavior of the studied microalgae during its culture in torus photobioreactor was provided.

Acoustic manipulation is an emerging non-invasive method enabling precise spatial control of cells in their native environment. Applying this method for organizing neurons is invaluable for neural tissue engineering applications. Here, we used surface and bulk standing acoustic waves for large-scale patterning of Dorsal Root Ganglia neurons and PC12 cells forming neuronal cluster networks, organized biomimetically. We showed that by changing parameters such as voltage intensity or cell concentration we were able to affect cluster properties. We examined the effects of acoustic arrangement on cells atop 3D hydrogels for up to 6 days and showed that assembled cells spontaneously grew branches in a directed manner towards adjacent clusters, infiltrating the matrix. These findings have great relevance for tissue engineering applications as well as for mimicking architectures and properties of native tissues.

Colony formation provides excellent advantages for the dominance of Microcystis. However, studies on microenvironments during the process of colony formation are rare, especially regarding intra–colony light usage. This study analyzed the attenuation of light intensity in Microcystis colonies, where most objects followed Lambert-Beer law ( I = I 0 10 - 1.256 × 10 - 3 bc ). Intra–colony light limited the maximum thickness of the colony ( B Max = 4.3 × 10 5 c − 1 ) and thus affected colony size. Field data showed that the colony size for M. ichthyoblabe was small and limited to approximately 300 μm, while larger colonies were mainly formed by M. aeruginosa and M. wesenbergii respectively. These results imply that the strategies used by morphospecies to allow colonies to tolerate intra–colony light limitation might be different; M. aeruginosa benefited from a reticular growth pattern, and M. wesenbergii colonies were large (500 μm), obtaining a large thickness by lowering cell concentration. The results obtained in this work suggest that M. aeruginosa and M. wesenbergii had more advantages regarding intra–colony light usage, colony size level and bloom formation ability in summer and autumn.

Biceps femoris steaks were inoculated with each of four Lactobacillus sp. (atypical streptobacteria and beta bacteria) at a high or low level of cell concentration, vacuum-packaged and stored for up to 35 days at 1-3 C. Total lactobacillus counts of inoculated steaks were numerically higher than those of corresponding control (non-inoculated) steaks at nearly all of the storage intervals tested. Differences in lactobacillus counts between steaks inoculated with a high concentration of Lactobacillus cultures 5, 8 and 642, and those of control steaks usually were significant (P0.05) after storage for 0 to 28 days. Differences in lactobacillus counts between steaks inoculated with a low concentration of Lactobacillus cultures and those of control steaks were seldom significant (P0.05). After storage for 35 days at 1-3 C, differences in lactobacillus counts of inoculated (high or low levels of inoculum) and control steaks usually were not significant (P0.05). The lactobacilli encountered on the inoculated steaks consisted primarily of the type added by inoculation.

Controlling and suppressing bacterial accumulation at solid surfaces is essential for preventing biofilm formation and biofouling. Whereas various chemical surface treatments are known to reduce cell accumulation and attachment, the role of complex surface geometries remains less well understood. Here, we report experiments and simulations that explore the effects of locally varying boundary curvature on the scattering and accumulation dynamics of swimming Escherichia coli bacteria in quasi-two-dimensional microfluidic channels. Our experimental and numerical results show that a concave periodic boundary geometry can decrease the average cell concentration at the boundary by more than 50% relative to a flat surface., 10 pages, 5 figures

Pre-diabetes is a long-lasting condition that precedes type 2 diabetes (T2D). T2D has been shown to suppress the immune response. However, it remains unclear if immune activation occurs before the onset of T2D during the progression of the pre-diabetic state. This study sought to characterize the changes in general immunity occurring during the progression from pre-diabetes to T2D. Male rats were fed a high-fat high-carbohydrate diet for 20 weeks (pre-diabetes induction period) and kept on the same diet being monitored for a further 12 weeks (experimental period). Blood was collected for haemocytometer analysis on week 0, 4, 8, and 12 of the experimental period after which the animals were sacrificed. Plasma was collected from centrifuged blood for ELISA (TNF-α, CRP, P-selectin, CD40 L, fibrinogen, and IL-6). Blood neutrophils percentage significantly decreased at week 12 possibly due to recruited neutrophils migrating to an inflamed area such as visceral adipose tissue as further observed. Due to hyperglycaemia, there was significant increase in blood lymphocytes percentage at week 12. Blood monocytes percentage significantly increased at week 12. Monocytes recruited and circulated in blood due to hyperglycaemia for glucose uptake to decrease it from circulation. Blood eosinophils percentage significantly decreased at week 12. Eosinophils migrated to inflamed areas such as visceral adipose tissue as further observed. Blood basophils percentage significantly increased due to their recruitment and activation. TNF-α, CRP, and IL-6 increased significantly after 12 weeks. There was also upregulation of fibrinogen, P-selectin, and CD40L. The results of this study show that there are changes in immune cells concentration and that immune cells such as neutrophils and eosinophils migrate to inflamed areas such as adipose tissue. There is also upregulation of various inflammatory cytokines. Based on these findings, immune activation begins during the pre-diabetic state as there is upregulation of inflammatory markers.

Grade A raw milk which had initial psychrotrophic counts of less than 103/ml was inoculated with an antibiotic-resistant Pseudomonas sp. to a final cell concentration of 102, 104, or 106/ml. The inoculated milk was held at 4 C for 14 h and then exposed to the following time-temperature treatments: 72 C for 15 sec, 79 C for 15 sec, 88 C for 10 sec, and 95 C for < 5 sec. An uninoculated raw milk control was handled and analyzed along with inoculated samples. Aliquots of milk were analyzed for marked Pseudomonas sp., total psychrotrophic counts, numbers of Pseudomonas, and for distribution of nitrogen before and after each heat treatment and after storage of non-heat-treated raw milk and heat-treated samples for 7 and 14 days at 7 C. Psychrotrophic counts were significantly affected by heat treatment, initial cell inoculum, days stored, and plating media. Non-casein N, non-casein protein, total albumin, β-lactoglobulin, proteose-peptone, and globulin N were significantly decreased by heat treatment. Non-case...

This study is about the potential for bacteria to fill the micro pores in the concrete the experimental investigation was to find the ability of the concrete with and without bacteria. The micro pores are filled by calcite precipitation created by the bacteria that will create autogenous healing to the concrete. The bacillus family bacteria was create the alkali-resistant spore this formation make as self-healing of the concrete. The active viable period of the bacteria was 4 months in water before adding to the concrete. The continuous decrease of the spore size diameter in concrete its helps to increase the compressive strength of the concrete. The life span and the concrete that is the durability of the concrete was increased we have a sustainable concrete. The present investigation is aimed to answer the following queries: Growth and culture of bacteria, effect of different cell concentration of bacteria embedded on the strength and durability characteristics of concrete.

Despite its simplicity, which makes it the most commonly used bioprinting method today, extrusion-based bioprinting suffers from its inability to reproduce the complex tissue architecture found in organs. Generally, this printing method allows for the dispensing of solutions of a predefined cell concentration through a rudimentary needle. Moreover, to avoid cell lysis in the dispensing needle, which is detrimental to the viability of the printed tissue, as well as cell loss in dead volumes of tubing, thereby increasing the cost of printing tissue, a common strategy has been to print with cell concentrations much lower in comparison to the concentrations found in living tissues. As a result, cell-to-cell distance is increased in the dispensed samples impairing communication through cytokines. Here, we present a microfluidic-based print head capable of modulating the printed cell concentration in real-time. This device allows bioprinting at high cell concentrations by concentrating and dispensing fibroblasts at concentrations up to 10 million cells∙mL−1. We also demonstrate that this device can be used to print bladder organoids. As the cell seeding concentration is of major importance for organogenesis in 3D culture, organoid printing allows the user to standardize the process of organoid formation and achieve more reliable and reproducible results.

This work has the objective of producing inoculum to enable tempeh production from aged common bean, by checking fermentation development according to the soybean/common bean ratio and defining the procedure for tempeh preparing in compliance with regulation on standards for acceptable microbiological contamination. Tempehs of common bean (BT), soybean (ST) and both (SBT) were produced by two methods (traditional and modified). The viable BT was used for hamburger preparation, which was evaluated for sensory acceptance in comparison to the traditional ST. The best inoculum Rhizopus oligosporus obtained was made with a medium with rice flour and presented a cell concentration of 106cells/mL. Tempehs made in a traditional method presented a bacterium grown beyond limit allowed by regulation. Instead, the modified method can be recommended to the industries to ensure the sanitary quality of tempeh. Finally, BT hamburger had a good acceptance (58%) regarding general appearance, but its flavor must be improved. Este trabajo tiene como objetivo producir inóculo que permita la producción de tempeh a partir de frijol común envejecido, mediante el control del desarrollo de la fermentación de acuerdo con la relación soja / frijol común y definiendo el procedimiento de preparación del tempeh de acuerdo con la normativa sobre estándares de contaminación microbiológica aceptable. Los tempehs de frijol común (BT), soja (ST) y ambos (SBT) fueron producidos por dos métodos (tradicional y modificado). El BT viable se utilizó para la preparación de hamburguesas, cuya aceptación sensorial se evaluó en comparación con el ST tradicional. El mejor inóculo de Rhizopus oligosporus obtenido fue elaborado con un medio con harina de arroz y presentó una concentración celular de 106 células/mL. Los tempeh elaborados con un método tradicional presentaban una bacteria que crecía más allá del límite permitido por la regulación. En cambio, el método modificado puede recomendarse a las industrias para garantizar la calidad sanitaria del tempeh. Finalmente, la hamburguesa BT tuvo una buena aceptación (58%) en cuanto al aspecto general, pero hay que mejorar su sabor. Este trabalho tem como objetivo produzir inóculo para viabilizar a produção de tempeh a partir do feijão envelhecido, verificando o desenvolvimento da fermentação segundo a relação soja / feijão comum e definindo o procedimento de preparo do tempeh de acordo com a regulamentação dos padrões de contaminação microbiológica aceitável. Tempehs de feijão (BT), soja (ST) e ambos (SBT) foram produzidos por dois métodos (tradicional e modificado). O BT viável foi utilizado para o preparo de hambúrguer, que foi avaliado quanto à aceitação sensorial em comparação ao ST tradicional. O melhor inóculo obtido de Rhizopus oligosporus foi feito com meio de farinha de arroz e apresentou concentração celular de 106 células/mL. Tempehs feitos em um método tradicional apresentaram contagem de bactérias além do limite permitido pela regulamentação. Logo, o método modificado pode ser recomendado às indústrias para garantir a qualidade sanitária do tempeh. Por fim, o hambúrguer BT teve uma boa aceitação (58%) quanto ao aspecto geral, mas seu sabor deve ser aprimorado.

We present a clinical device for simple, rapid, and viable isolation of circulating tumor cells (CTCs) from cancer patient bloods. In spite of the clinical importance of CTCs, the lack of easy and non-biased isolation methods is a big hurdle for implementing CTC into clinical use. The present device made of photosensitive polymer was designed to attach to conventional syringe to isolate the CTCs at minimal resources. Its unique tapered-slits on the filter are capable not only to isolate the cell based on their size and deformability, but also to increase sample flow rate, thus achieving label-free rapid viable CTC isolation. We verified our device performance using 9 different types of cancer cells at the cell concentration from 5 to 100cells/ml, showing that the device capture 77.7% of the CTCs while maintaining their viability of 80.6%. We extended our study using the 18 blood samples from lung, colorectal, pancreatic and renal cancer patients and captured 1-172 CTCs or clustered CTCs by immunofluorescent or immunohistochemical staining. The captured CTCs were also molecularly assayed by RT-PCR with three cancer-associated genes (CK19, EpCAM, and MUC1). Those comprehensive studies proved to use our device for cancer study, thereby inaugurating further in-depth CTC-based clinical researches.

A spectral radiation-transport model was integrated with a three dimensional computational fluid dynamics model to simulate the hydrodynamics and light transfer in open raceway ponds (ORPs). The predicted three-dimensional velocity and light intensity agreed well with measured values collected on a lab-scale ORP. However, there was a slight difference in the predicted velocity profiles using two different types of boundaries for the paddlewheel, i.e., the moving zone boundary and inlet velocity boundary, with R2 values between the predicted and measured velocities of 0.9947 and 0.9838, respectively. The R2 value between the predicted and measured light intensity was 0.9939. Simulations were further conducted on a large-scale ORP with 100 m2 surface area operated at total medium depths of 0.2 and 0.3 m, average cell concentration of 0.4 g/L, and inlet velocities of 0.1, 0.2 and 0.3 m/s from the paddlewheel. The increase of inlet flow velocity from 0.1 to 0.2 m/s resulted in a more uniform cell concentration profile. However, when the inlet velocity was further increased from 0.2 to 0.3 m/s, there was only a slight increase in the uniformity of the cell concentration. In addition, the simulation results showed that sedimentation of cells more likely occurred at the bottom of the ORP with a total medium depth of 0.2 m than at 0.3 m at the same inlet velocity. The increase of inlet velocity from the paddlewheel resulted in a uniformly distributed light intensity in the region near the medium surface (e.g., 0.05 m depth from the surface) owing to improved mixing. However, owing to a sudden drop in the light intensity after a few centimeters from the medium surface, the cell sedimentation that occurred at the bottom of the ORPs had negligible effects on the light penetration depth in the medium.

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

In situ Microscopy (ISM) is an optical non-invasive technique to monitor cells in bioprocesses in real-time. Pichia pastoris is one of the most promising protein expression systems. This yeast combines fast growth on simple media and important eukaryotic features such as glycosylation. In this work, the ISM technology was applied to Pichia pastoris cultivations for online monitoring of the cell concentration during cultivation. Different ISM settings were tested. The acquired images were analyzed with two image processing algorithms. In seven cultivations the cell concentration was monitored by the applied algorithms and offline samples were taken to determine optical density (OD) and dry cell mass (DCM). Cell concentrations up to 74 g/L dry cell mass could be analyzed via the ISM. Depending on the algorithm and the ISM settings, an accuracy between 0.3 % and 12 % was achieved. The overall results show that for a robust measurement a combination of the two described algorithms is required.

Cut surfaces of fresh produce, which directly expose plant cell walls to the environment, are particularly susceptible to contamination by pathogens, including Salmonella enterica . The effect of Salmonella cell concentration in liquids (such as rinses or washes) on their attachment to plant cell walls was investigated using bacterial cellulose-based plant cell wall models. Numbers of Salmonella cells attaching to the plant cell wall models increased linearly with cell concentration. A simple linear model (y = 0.916x) was constructed to predict the number of Salmonella cells that will attach to per unit surface area of plant cell wall (CFU/cm 2 ), assuming their initial inoculum concentration lies within the range of 3 log to 8 log CFU/mL. The linear regression model generated from the model surfaces was validated for a range of variables (different plant tissues, S. enterica subspecies and other foodborne bacteria). The validation supported the use of the linear regression model in predicting Salmonella attachment to plant cell walls regardless of the Salmonella subspecies. The use of the model can also be extended to other bacteria within the cell concentration range. This work may contribute to generating risk-assessment tools for control of Salmonella associated with the processing of fresh produce.

To ensure cell-based assays are performed properly, both cell concentration and viability have to be determined so that the data can be normalized to generate meaningful and comparable results. Cell-based assays performed in immuno-oncology, toxicology, or bioprocessing research often require measuring of multiple samples and conditions, thus the current automated cell counter that uses single disposable counting slides is not practical for high-throughput screening assays. In the recent years, a plate-based image cytometry system has been developed for high-throughput biomolecular screening assays. In this work, we demonstrate a high-throughput AO/PI-based cell concentration and viability method using the Celigo image cytometer. First, we validate the method by comparing directly to Cellometer automated cell counter. Next, cell concentration dynamic range, viability dynamic range, and consistency are determined. The high-throughput AO/PI method described here allows for 96-well to 384-well plate samples to be analyzed in less than 7 min, which greatly reduces the time required for the single sample-based automated cell counter. In addition, this method can improve the efficiency for high-throughput screening assays, where multiple cell counts and viability measurements are needed prior to performing assays such as flow cytometry, ELISA, or simply plating cells for cell culture.