Specific Cell Growth Rate Research Articles

Optimization of iron, phosphate, and salinity in nutrient medium using response surface methodology for enhancing biochemical composition in Chlorella sp. culture

Microalga Chlorella sp. is a highly scientifically and commercially attractive unicellular microorganism and has developed a stable industry as a nutritional supplement for people and animals. Various nutrient media have been used to grow Chlorella sp. cultures to enhance their growth, pigmentation, and lipid content. However, the optimal biochemical composition and density of Chlorella sp. cultures require an understanding of optimizing the nutrient medium to study their production. The present study aims to investigate the effects of iron, phosphate, and salinity concentrations by working synergically in a nutrient medium on the growth responses, pigments, and lipid accumulation of Chlorella sp. culture using a response surface methodology (RSM) approach. Using the result from the RSM software, a total of 18 experimental groups (E1 – E18) were evaluated, and one confirmation (C) study was conducted. The results revealed that the E7 experiment in Chlorella sp. culture provided the highest cell density and specific growth rate (SGR) with 176.00 × 106 cells mL−1 and 0.35 day−1, respectively. Similarly, the E5 and E1 experiments produced the highest cell density of 166.10 × 106 cells. mL−1 and 152.13 × 106 cells mL−1, respectively. The SGR was also increased at 0.33 day−1 in the E5 experiment and 0.33 day−1 in the E1 experiment. Consequently, the culture of Chlorella sp. containing high iron and phosphate concentrations and lower salinity in a nutrient medium had the highest number of cells, SGR, and pigment accumulation (chlorophyll a and total carotenoid). In addition, the presence of high salinity concentrations reduces Chlorella sp. growth. However, the increase in the growth of Chlorella sp. culture did not indicate an increase in other biochemical compositions. In some cases, biochemical compositions are high due to nutritional limitations or stress factors. For example, in pigment accumulation, chlorophyll a pigment accumulation was increased in experiment E7 (51.57 μg mL−1), while total carotenoid accumulation was increased in experiment E8 (20.68 μg mL−1). In addition, increasing salinity concentration increased chlorophyll a and total carotenoid contents per cell, but decreased Chlorella sp. growth as shown in the E4 experiment, which achieved chlorophyll a levels of 1.38 pg cell−1 and total carotenoid levels of 0.52 pg cell−1. Furthermore, Chlorella sp. culture produces a higher lipid accumulation of 37.38 % in the E3 experiment. Hence, the results of this study contribute to understanding the optimal biochemical composition and cell growth of Chlorella sp. cultures.

Genetic Strategies and Mechanisms for Improving Ribonucleic Acid Levels of Saccharomyces pastorianus.

Developing microorganisms with a high ribonucleic acid (RNA) content is crucial for the RNA industry. Numerous studies have been conducted to enhance RNA production in yeast cells through genetic engineering, yet precise mechanisms remain elusive. Previously, upregulation of TAL1 or PGM2 and deleting PRS5 or DBP8 individually could increase the RNA content in Saccharomyces pastorianus. In this study, within these genetically modified strains, the intracellular nucleotide levels notably increased following cell fragmentation. Deletion of PRS5 and DBP8 within the strain prompted the upregulation of genes sharing similar functions, consequently augmenting the flow of the gene pathway. Furthermore, the upregulation of genes encoding cell-cycle-dependent protein kinases (CDK) was observed in the G03-△PRS5 strain. The influence of TAL1 and PGM2 on RNA content was attributed to the pentose phosphate pathway (PPP). The RNA content of polygenic recombinant strains, G03-△PRS5+△DBP8 and G03-△PRS5+△DBP8+PGM2, displayed the most significant improvement, increasing by 71.8 and 80.1% when compared to the parental strain. Additionally, the maximum specific growth rate of cells increased in these strains. This study contributes valuable insights into the genetic mechanisms underlying high nucleic acid synthesis in S. pastorianus.

Utilization of Cow's Rumen Bokashi Enriched with Chicken Manure on Chlorella sp. Cell Density

One of the organic fertilizers that has the potential to cultivate Chlorella sp. is the cow's rumen. To increase the nutrient content in the cow's rumen, the cow's rumen must be made into bokashi and enriched with chicken manure. This study aimed to determine the use of cow's rumen bokashi enriched with chicken manure at different doses on Chlorella sp cell density. The research design used was a Completely Randomized Design (CRD) with 5 treatments and 3 replications, namely P0 (2 g/L cow's rumen bokashi), P1 = 2 g/L cow's rumen bokashi enriched with 2.5 g/L chicken manure, P2 = 2 g/L cow's rumen bokashi enriched with 3.0 g/L chicken manure, P3 = 2 g/L cow's rumen bokashi enriched with 3.5 g/L chicken manure, and P4 = 2 g/L cow's rumen bokashi enriched with 4.0 g/L chicken manure. The results showed that the highest cell density of Chlorella sp. occurred in treatment P3 (i.e. 456.1 ± 15.1 í— 104 cells/mL) and the highest specific growth rate occurred in treatment P0 (i.e. 0.20 ± 0.0/day). Nutrient levels in the culture medium are optimal for Chlorella sp., with nitrate ranging from 0.1375 to 0.2833 mg/L and phosphate ranging from 2.4889 to 2.8650 mg/L. From the results of this study, it can be concluded that the use of cow's rumen bokashi enriched with chicken manure had a very significant effect on cell density and specific growth rate of Chlorella sp. (P<0.01).

Karenia brevis and Pyrodinium bahamense Utilization of Dissolved Organic Matter in Urban Stormwater Runoff and Rainfall Entering Tampa Bay, Florida

This study investigated how nitrogen and dissolved organic matter (DOM) from stormwater runoff and rainfall support the growth of Karenia brevis and Pyrodinium bahamense. Excitation–emission matrix spectroscopy coupled with parallel factor analysis tracked changes in the optical properties of DOM in each bioassay, revealing greater reactivity of terrestrial humic-like DOM. Significant increases in cell yield and specific growth rates were observed upon additions of runoff for both species, with significant increases in specific growth rates upon the addition of a 2 in simulated rain event for P. bahamense only. By hour 48, 100% of the dissolved organic nitrogen (DON) in each treatment was utilized by P. bahamense, and by hour 72, over 50% of the DON was utilized by K. brevis. The percentage of bioavailable dissolved organic carbon (DOC) was greater for P. bahamense compared to K. brevis, suggesting a greater affinity for DOC compounds by P. bahamense. However, the bioavailability of DOM for each species could be owed to distinct chemical characteristics of labile DOM conveyed from each site. This study demonstrates that stormwater runoff and rainfall are both sources of labile DOM and DON for K. brevis and P. bahamense, which has implications for blooms of these species in Tampa Bay waters.

Interaction of Fe2O3 nanoparticles with marine microalga Chlorella sorokiniana: Analysis of growth, morphological changes and biochemical composition

The wide utilization of iron-based nanoparticles (NPs) based on their preferential properties has led to the discharge and accumulation of these materials into the aquatic environment. In this regard, a comparative study of different concentrations of α-Fe2O3 NPs and their micro form was conducted using microalga Chlorella sorokiniana up to the stationary growth phase. This study revealed that high concentrations of NPs (100 and 200 mg L−1) imposed a stressful condition on algal cells documented by a reduction in microalga growth, including cell number and specific growth rate. The physical contact between the algal cells and NPs resulted in a shading effect as well as morphological changes validated by scanning electron microscope results. The biochemical composition of C. sorokiniana exposed to high levels of Fe2O3 NPs was also evaluated. The increase in total carbohydrate content of algal cells along with a significant reduction in unsaturated fatty acids was found. Moreover, Fe2O3 NPs exposure induced oxidative stress evidenced by an increase in lipid peroxidation. To cope with oxidative stress, superoxide dismutase activity and antioxidant potential of microalga as defensive mechanisms increased in the culture with high concentrations of NPs. Besides, due to the interactions, microalga tended to form a protective layer from further cell-NP interactions through the secretion of extracellular polymeric substances. Nonetheless, the nano form of Fe2O3 was more toxic than its micro form due to its small size. Overall, this trial may provide additional insight into the toxicological mechanism and safety assessments of Fe2O3 NPs in the aquatic environment.

Artificial neural network and genetic algorithm coupled fermentation kinetics to regulate L-lysine fermentation

Fermentation plays a pivotal role in the industrialization of bioproducts, yet there is a substantial lag in the fermentation process regulation. Here, an artificial neural network (ANN) and genetic algorithm (GA) coupled with fermentation kinetics were employed to establish an innovative lysine fermentation control. Firstly, the strategy of coupling GA with ANN was established. Secondly, specific lysine formation rate (qp), specific substrate consumption rate (qs), and specific cell growth rate (μ) were predicted and optimized by ANN-GA. The optimal ANN model adopts a three-layer feed-forward back-propagation structure (4:10:1). The optimal fermentation control parameters are obtained through GA. Finally, when the carbon to nitrogen ratio, residual sugar concentration, ammonia nitrogen concentration, and dissolved oxygen were [2.5, 4.5], [6.5, 9.5] g·L−1, [1.0, 2.0] g·L−1 and [20, 30] %, respectively, the lysine concentration reaches its peak at 213.0 ± 5.10 g·L−1. The novel control strategy holds significant potential for optimizing the fermentation of other bioproducts.

Ecological and Physiological Characteristics and Biotechnological Potential of Diatom Algae Nitzschia amabilis H. Suzuki

The study is focused on the ecological and physiological properties, production, and biochemical characteristics of the diatom Nitzschia amabilis. The optimum salinity (35‒36‰), illumination (2.95 klx), and photoperiod (14 h) at which the highest specific cell growth rate is achieved was determined. The coefficient of light saturation (Ik) was calculated and turned out to be lower than one, which indicates the high energy efficiency of photosynthesis. The results of experiments on salinity showed the ability of the alga to grow in the range of 4–68‰, indicating its relatively broad euryhalinity. The biochemical composition of N. amabilis during acumulative cultivation was studied. In general, polyunsaturated fatty acids predominated in the studied strain; eicosapentaenoic, arachidonic, and docosahexaenoic acids were dominant. The main share of saturated fatty acids consisted of palmitic acid. The productivity indicators of N. amabilis in relation to lipids, fucoxanthin, and PUFAs, which were 2.5–3 times higher in the flow cultivation mode than in the cumulative mode, have been established.

Growth kinetics of lead resistant Bacillus infantis isolated from battery industry waste

The current investigation presents an innovative approach to address the challenge of removing heavy metal lead from industrial waste through advanced biological remediation techniques. By amalgamating theoretical insights with empirically acquired data, this research endeavours to develop efficient bioreactor strategies suitable for large-scale applications. Initially, bacteria naturally endowed with lead resistance has been isolated from a native source. Extensive microbiological assessments, including a 16S rDNA study, verified the identity of the lead-resistant bacterial cells as Bacillus infantis 4352-1T. In order to evaluate the efficacy of Bacillus infantis 4352-1T for lead removal an attempt has been made to study the growth dynamics of Bacillus infantis 4352-1T cells in batch mode, using lead amended selective media. It has been observed that Monod's equation effectively defined the cell growth behaviour within the lead concentration range of 0.05–0.25 kg lead/m3. Notably, the experiment was also facilitated the derivation of essential intrinsic kinetic parameters, such as the maximum specific cell growth rate (0.0237 h−1) and substrate saturation constant (0.018 kg/m3). Beyond lead concentrations of 0.25 kg lead/m3, up to 0.43 kg lead/m3, it has also been observed the pronounced influence of substrate inhibition which is quantitatively elucidated by the Haldane equation.

Decreased calcification to photosynthesis ratio in coccolithophores under reduced O2 and elevated CO2 environment

We examined the physiological performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi and Gephyrocapsa oceanica, which were treated with 8.3 (ambient O2 (AO)), 4.6 (medium O2 (MO)), and 2.5 (low O2 (LO)) mg L–1 O2 under 400 ppm (ambient CO2 (AC)) and 1000 (high CO2 (HC)) ppm CO2 conditions. Elevated CO2 decreased the specific growth rate of cells cultured under AO and LO conditions in both species, but it increased the rate in the MO-grown E. huxleyi. Regardless of the CO2 levels, diminished O2 concentration inhibited the growth rate in E. huxleyi while accelerating the rate in G. oceanica. LO reduced the particulate organic carbon (POC) production rate compared to the AO treatment in both species. Additionally, the decrease was higher in the HC cultures than in the AC ones. LO also inhibited the production rate of particulate inorganic carbon (PIC) compared to the AO/AC treatment. Due to a higher reduction in the production rate of PIC than POC, the PIC/POC ratio was decreased in the LO treatment compared to the AO/AC treatment. The current study reveals that low O2 can, individually or in combination with high CO2, considerably affect the physiology of marine photoautotrophic organisms.

Cost-Effective Cultivation of Native PGPB Sinorhizobium Strains in a Homemade Bioreactor for Enhanced Plant Growth.

The implementation of bioreactor systems for the production of bacterial inoculants as biofertilizers has become very important in recent decades. However, it is essential to know the bacterial growth optimal conditions to optimize the production and efficiency of bioinoculants. The aim of this work was to identify the best nutriment and mixing conditions to improve the specific cell growth rates (µ) of two PGPB (plant growth-promoting bacteria) rhizobial strains at the bioreactor level. For this purpose, the strains Sinorhizobium mexicanum ITTG-R7T and Sinorhizobium chiapanecum ITTG-S70T were previously reactivated in a PY-Ca2+ (peptone casein, yeast extract, and calcium) culture medium. Afterward, a master cell bank (MCB) was made in order to maintain the viability and quality of the strains. The kinetic characterization of each bacterial strain was carried out in s shaken flask. Then, the effect of the carbon and nitrogen sources and mechanical agitation was evaluated through a factorial design and response surface methodology (RSM) for cell growth optimization, where µ was considered a response variable. The efficiency of biomass production was determined in a homemade bioreactor, taking into account the optimal conditions obtained during the experiment conducted at the shaken flask stage. In order to evaluate the biological quality of the product obtained in the bioreactor, the bacterial strains were inoculated in common bean (Phaseolus vulgaris var. Jamapa) plants under bioclimatic chamber conditions. The maximum cell growth rate in both PGPB strains was obtained using a Y-Ca2+ (yeast extract and calcium) medium and stirred at 200 and 300 rpm. Under these growth conditions, the Sinorhizobium strains exhibited a high nitrogen-fixing capacity, which had a significant (p < 0.05) impact on the growth of the test plants. The bioreactor system was found to be an efficient alternative for the large-scale production of PGPB rhizobial bacteria, which are intended for use as biofertilizers in agriculture.

Production and Growth Performance of Nannochloropsis oculata (Droop) Hibberd in the Helical Photobioreactor

Phytoplankton species preferred in marine fish farming are the primary food source in the larval and young stages of bivalve mollusks, along with some fish and shellfish larvae. For this reason, selecting the appropriate phytoplankton and production technique for feeding marine fish larvae is crucial. Nannochloripsis oculata microalgae species, widely used in rearing sea bream and sea bass larvae and feeding rotifers, has an essential place in our country. N. oculata microalgae species, which is used in rearing sea bream and sea bass larvae and feeding rotifers, was produced in a helical photobioreactor by applying a continuous production technique at 30 ‰ salinity, and its growth performance was aimed to be investigated. In the study, N. oculata was grown in a helical photobioreactor at 30‰ salinity by applying the continuous production technique for two weeks, and the daily cell number and specific growth rate were determined. The study was repeated three times. The supply of live feed for marine fish fry and hatcheries established for this purpose is one of the most critical problems. The latest technology in the production of microalgae, which is the primary link of the live feed chain in this sector, is continuous algae production in helical tubular reactors. The helical tubular reactor used in the study consists of a transparent hose system consisting of a completely tubular helical reactor designed for microalgae production. The helical tubular continuous production system offers more efficient and economically more convenient alternatives than existing production systems. One of the most essential advantages of this system is that the system can be designed without requiring significant capital. The continuous culture technique allows the application of long-term and safe algae cultures. With this system, besides providing continuity in production, the negativities in batch production can be eliminated with adequate light. Since the algae production with the continuous method in the spiral photobioreactor remains in the maximum growth phase for a longer time than the batch production, it is a system with high production efficiency and quality, and production capacity is guaranteed. In addition, the algae product harvesting in the continuous system ensures the daily harvesting of algae as much as half of the system volume. A helical reactor enables automation in algae production and high-quality production over long periods. In the study, the sowing density of N. oculata was determined as 1.068x106 ±0.006 cells/mL. Algin cell growth increased logarithmically during the first five days. From the 5th day to the 15th day, the increase in the number of cells was determined as 12.35x106±0.165 cells/mL at the highest and 8.76x106±0.709 cells/mL at the lowest. However, on the 13th day, it was determined that the increase in algin cells was 12.35x106±0.165 cells/mL, and the specific growth rate decreased by 0.189±0.016 divisions/day. As a result of the study, the number of cells of N. oculata algae 5-15 increased. It was determined that it increased 10 times between days. In this context, it was possible to harvest half of the reactor volume of algae daily at maximum cell density for long periods in the helical reactor

α-Ketoglutarate stimulates cell growth through the improvement of glucose and glutamine metabolism in C2C12 cell culture.

Cellular adaptation to physical training and energy metabolism play an important role during physical exercise. This study sought to investigate the effects of α-KG on cell growth and energy metabolism in C2C12 cell culture. C2C12 cells were cultured in media pretreated without (control) or with α-KG at different concentrations, and cells and media were harvested every 24 h for 8 days. From cell counts, specific cell growth rate (SGR) and doubling time were calculated. The content of glucose, glutamine, lactate, and ammonia in media was determined, and the specific consumption rate (SCR) or production rate (SPR) was calculated. Additionally, cell colony-forming efficiency (CFE) was determined. The control cells showed a CFE at 50%, a typical cell growth curve in the first 5 days with a mean SGR at 0.86/day, and a mean cell count doubling time at 19.4 h. In the group with α-KG at 100 mM, the cells underwent rapid cell death, and thus no further analysis was made. The treatment with α-KG at lower concentrations (0.1 mM and 1.0 mM) led to a higher CFE at 68 and 55%, respectively, whereas those in groups with higher α-KG concentration decreased (10 and 6% for 20 mM and 30 mM α-KG, respectively). The mean SGR was 0.95/day, 0.94/day, 0.77/day, 0.71/day, and 0.65/day for groups treated with α-KG at 0.1, 1.0, 10.0, 20.0, and 30.0 mM, respectively, and the corresponding cell count doubling time was 17.6, 17.8, 20.9, 24.6, and 24.7 h, respectively. In comparison with that of the control group, the mean glucose SCR decreased in all the groups treated with α-KG, while the mean glutamine SCR remained unchanged; the mean lactate SPR increased in the groups treated with α-KG ≥ 20.0 mM. Finally, the mean SPR of ammonia was lower in all α-KG groups than that in the control. The treatment with α-KG at lower concentrations increased cell growth whereas at higher concentrations decreased cell growth, and α-KG reduced glucose consumption and ammonia production. Therefore, α-KG stimulates cell growth in a dose-dependent manner, which is likely through the improvement of glucose and glutamine metabolism in a C2C12 culture setting.

The Potential of an Inexpensive Plant-Based Medium for Halal and Vegetarian Starter Culture Preparation

The restrictions for halal and vegetarian fermented products apply not only to the food ingredients, but also to the inoculum media. The utilization of a medium for lactic acid bacteria (LAB) leads to some issues from animal-derived proteins sources that may be doubtful for halal and/or vegetarian use. This study aimed to develop a plant-based medium for culturing and maintaining LAB. The result demonstrated that 10 g/L soybean powder in sweet potato extract was suitable for cultivating Lactiplantibacillus plantarum TISTR 2075 with no significant difference (p &lt; 0.05) from MRS (de Man, Rogosa and Sharpe) in the cell number (9.12 log CFU/mL) and specific growth rate (0.04). The feasibility of a plant-based medium to grow and maintain the LAB strains from different origins was evaluated. Compared to MRS, Lpb. plantarum TISTR 2075, Lpb. plantarum MW3, and Lacticaseibacillus casei TISTR 1463 could grow almost as well in a plant-based medium. This medium was also suitable for maintaining the viability of LAB during storage, especially when subjected to slant agar stock culture. It is practical and costs at least 10 times less than MRS. Thus, this study created a low-cost plant-based medium that could be used in laboratories, especially for applications in halal and vegetarian food products.

Replacing expensive synthetic media with banana stem compost extract medium for production of Chlorella vulgaris

ABSTRACT Microalgal cultivation by small scale aquaculture farmers is limited by the high cost of synthetic culture media. The current study was conducted to investigate use of banana stem compost extract (BSCE) as an alternative medium for cultivation of the microalga Chlorella vulgaris. C. vulgaris was batch cultured for 24 days in the laboratory using synthetic Bold Basal Medium (BBM) as a control and BSCE at concentrations of 2%, 5% and 10% (by volume) as the treatments. Algal growth was evaluated by measuring dry cell weight and specific growth rate (SGR) during the experimental period. Chemical composition was analysed following standard analytical methods. Variations in growth trends among culture media were attributed to variations in nutrient concentration and lack of acclimatization period. Some macro- and micronutrients in BSCE-cultivated C. vulgaris were higher than or similar to those observed in BBM-cultivated algae. The macronutrients differed among BSCE treatments. It was concluded that BSCE can be used as the culture medium, providing similar nutritional value and supporting similar growth performance to synthetic media. However, selection of BSCE concentration should be based on macronutrients and take into account the intended use of cultivated microalgae.

Long term culturing of CHO cells: phenotypic drift and quality attributes of the expressed monoclonal antibody

Establishing cell lines with enhanced protein production requires a deep understanding of the cellular dynamics and cell line stability. The aim of the study is to investigate the impact of long term culturing (LTC) on cell morphology and altered cellular functions possibly leading to phenotypic drift, impacting product yield and quality. Study highlights the orthogonal cellular and analytical assay toolbox to define cell line stability for optimal culture performance and product quality. We investigated recombinant monoclonal antibody (mAb) expressing CHO cells for 60 passages or 180 generations and assessed the cell growth characteristics and morphology by confocal and scanning electron microscopy. Quality attributes of expressed mAb is accessed by performing charge variants, glycan, and host cell protein analysis. We observed a 1.65-fold increase in viable cell population and 1.3-fold increase in cell specific growth rate. A 2.5-fold decrease in antibody titer and abatement of actin filament indicate cellular phenotypic drift. Mitochondrial membrane potential (∆ΨM) signified cell health and metabolic activity during LTC. Host cell protein production is reduced by 1.8-fold. Charge heterogeneity was perturbed with 12.5% and 43% reduction in abundance of acidic and basic charge variants respectively. Glycan profile indicated a decline in fucosylation with 17% increase in galactosylated species as compared with early passaged cells. LTC impinges on cellular phenotype as well as the quality of the expressed antibody, suggesting a defined subculturing limit to retain stable protein expression and cell morphology to achieve consistent product quality. Study signifies the changes in cellular and metabolic markers, suggesting cellular and analytical toolbox which could play a significant role in defining cell characteristics and ensured product quality.

EVALUATION OF THE TOLERANCE THRESHOLD OF THE MARINE BENTHIC DIATOM PLEUROSIGMA AESTUARII (BRéB. IN KüTZ.) W. SMITH, 1853 (BACILLARIOPHYTA) UNDER THE IMPACT OF COPPER (II) IONS

Copper compounds accumulate in marine bottom sediments as the result of human activity and, being highly toxic, affect microphytobenthos. Evaluation of the tolerance ranges of benthic diatoms to copper pollution is important for biotesting and assessment of coastal marine environment. This work is aimed to reveal the dynamics of growth and cell death of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 under the impact of a wide range of copper (II) ions concentrations over the course of a 10-day experiment in clonal culture, as well as to identify a tolerance threshold for this species, critical for its survival when exposed to the toxicant. The study has focused on assessment of the changes in the proportion (%) of alive cells, absolute cell number and specific growth rate of the culture at different exposure durations and concentrations of Cu2+ ions (32-1024 μg/L) and was meant to evaluate the applicability of this species as a new test object for ecotoxicology. In the control culture and in the cultures exposed to Cu2+ in the range of concentrations 32-256 μg/L, the proportion of alive cells did not change over the course of the experiment (95-99 %). At Cu2+ concentration 320 μg/L, the proportion of alive cells decreased to 23 % on the 3rd day and to 10 % on the 5th day, which provided a basis to consider this value as a threshold one for P. aestuarii survival. At Cu2+ concentrations 384 μg/L and higher, up to the maximum one (1024 μg/L), drastic inhibition of the culture was recorded as early as on the 1st day, and on the days 3-5, all the cells died. The increase in the absolute cell number in the concentration range 32- 256 μg/L were consistent with the dose-response sigmoid model. Over the timespan of days 1-7, the cell number increased by 3-5 times, reaching its maximum, and then it decreased by 10-12 % by the 10th day. At Cu2+ concentrations 320 μg/L and higher, the increase in the cell number was strongly suppressed since the 1st day. Within the 32-256 μg/L range, the test culture is characterized by positive specific cell growth rate for the period up to 7 days; at the threshold concentration 320 µg/L and higher, this test parameter becomes negative. Thus, P. aestuarii should be recommended as a new appropriate test object both for toxicological experiments and for monitoring of coastal marine environment affected by technogenic pollution.

Rational design of Aspergillus flavus A5p1-immobilized cell system to enhance the decolorization of reactive blue 4 (RB4)

Anthraquinone dyes are a class of typical carcinogenic and hard-biodegradable organic pollutants. This study aimed to enhance the decolorization of anthraquinone dye by rationally designing an expected immobilized system. Reactive blue 4 (RB4) was used as a substrate model and a previous isolated dye-degrading strain Aspergillus flavus A5p1 was purposefully immobilized. Considering the effects of cell attachment and mass transfer, the polyurethane foam (PUF) with open pore structure was selected as the immobilization carrier. Results showed that the RB4 decolorization efficiency was significant enhanced after immobilization. Compared to the free mycelium system, the decolorization time of 200 mg·L −1 RB4 was shortened from 48 h to 28 h by the PUF-immobilized cell system. Moreover, the PUF-immobilized system could tolerate RB4 up to 2000 mg·L −1 . In the packed bed bioreactor (PBBR), an average decolorization efficiency of 93.3% could be maintained by the PUF-immobilized system for 26 days. The decolorization process of RB4 was well described by the logistic equation and the degradation pathway was discussed. It was found that the higher specific growth rate of the PUF-immobilized cells was one of reasons for the enhanced decolorization. The good performance of the PUF-immobilized cell system would make it have potential application value for RB4 bioremediation.

Chain or sphere? Perspectives on colony shapes and sizes in microalgae

Abstract Some microalgal species can increase their collective size by forming colonies; notable examples are chained colonies in diatoms and Scenedesmus sp., and spherical colonies in Phaeocystis globosa. For a given cell-specific growth rate, chain formation increases collective length quickly to fend off ciliates, but not against tube- and pallium-feeding heterotrophic dinoflagellates or metazoan grazers with ability to manipulate chains to aid ingestion. Sphere increases in volume relatively slowly but would be difficult to manipulate even for metazoan grazers. Diffusive nutrient supply to a chained colony would be a fixed proportion of that to solitary cells, regardless of chain length, whereas cells within a spherical colony would experience increasing nutrient limitation with increasing colony size. One hemisphere of a spherical colony would inevitably receive less irradiance, creating an auto-light limitation. Experimental data showed that light decreased substantially as it passed through a P. globosa colony, and the optical density of the colony increased linearly with colony diameter. However, neither in situ nutrient nor light limitation alone can explain an order-of-magnitude difference in colony size between the European and the Asian P. globosa populations. Instead, some evidence of different expression of gene(s) involved in colony formation and enlargement suggests genomic variations among the different populations.

Activation of galactose utilization by the addition of glucose for the fermentation of agar hydrolysate using Lactobacillus brevis ATCC 14869.

To investigate the application of carbon catabolite repression (CCR) relaxed Lactobacillus brevis ATCC 14869 in the utilization of agar hydrolysate to produce bioethanol and lactic acid through fermentation. As a single carbon source, galactose was not metabolized by L. brevis. However, L. brevis consumed galactose simultaneous to glucose and ceased cell growth after depletion of glucose. For complete use of galactose from agar hydrolysis, glucose need to beperiodically replenished into the growth medium. Overall, L. brevis successfully used agar hydrolysate and produced 17.2g/L of ethanoland 31.9g/Lof lactic acid. The maximum specific cell growth rate on galactose and glucose mixture was the same with the glucose-only medium at 0.12h-1. The molar product yields from glucose for lactic acid and ethanol were 1.02 and 0.95 respectively, equal to values obtained from the simultaneous utilization of glucose and galactose. In contribution to the ongoing efforts to utilize marine biomass, the relaxed CCR in Lactobacillus brevis ATCC 14869 was herein exploited to produce bioethanol and lactic acid from red seaweed hydrolysates.

Calcium Electroporation Reduces Viability and Proliferation Capacity of Four Uveal Melanoma Cell Lines in 2D and 3D Cultures.

Simple SummaryCalcium electroporation (CaEP) is an innovative anti-tumor treatment modality that induces cell death by introducing supraphysiological concentrations of calcium into cells with a limited effect on normal cells. The objective of the present study is to assess the effect of CaEP in uveal melanoma (UM) cell lines in comparison to electrochemotherapy (ECT) with bleomycin using 2D monolayer cell cultures as well as 3D tumor spheroid models in four different UM cell lines. The morphological changes of the spheroids, the cell viability, growth rate as well as the cytotoxic effect of electroporation (EP) with calcium chloride and bleomycin were evaluated with various drug concentrations. The results of CaEP and ECT both suggest a comparable dose-dependent reduction in cell viability and proliferation rate in all tested 2D cell lines and 3D tumor spheroids. These data point out that CaEP is an established anticancer treatment causing cell death by ATP depletion in in vitro and in vivo, representing an efficient alternative therapy with a lower cytotoxic potency for the local UM tumor control.Electrochemotherapy (ECT) is the combination of transient pore formation following electric pulse application with the administration of cytotoxic drugs, which enhances the cytotoxic effect of the applied agent due to membrane changes and permeabilization. Although EP represents an established therapeutic option for solid malignancies, recent advances shift to the investigation of non-cytotoxic agents, such as calcium, which can also induce cell death. The present study aims to evaluate the cytotoxic effect, the morphological changes in tumor spheroids, the effect on the cell viability, and the cell-specific growth rate following calcium electroporation (CaEP) in uveal melanoma (UM) 2D monolayer cell cultures as well as in 3D tumor spheroid models. The experiments were conducted in four cell lines, UM92.1, Mel270, and two primary UM cell lines, UPMD2 and UPMM3 (UPM). The 2D and 3D UM cell cultures were electroporated with eight rectangular pulses (100 µs pulse duration, 5 Hz repetition frequency) of a 1000 V/cm pulse strength alone or in combination with 0.11 mg/mL, 0.28 mg/mL, 0.55 mg/mL or 1.11 mg/mL calcium chloride or 1.0 µg/mL or 2.5 µg/mL bleomycin. The application of calcium chloride alone induced an ATP reduction only in the UM92.1 2D cell cultures. Calcium alone had no significant effect on ATP levels in all four UM spheroids. A significant decrease in the intracellular adenosine triphosphate (ATP) level was documented in all four 2D and 3D cell cultures for both CaEP as well as ECT with bleomycin. The results suggest a dose-dependent ATP depletion with a wide range of sensitivity among the tested UM cell lines, control groups, and the applied settings in both 2D monolayer cell cultures and 3D tumor spheroid models. The colony formation capacity of the cell lines after two weeks reduced significantly after CaEP only with 0.5 mg/mL and 1.1 mg/mL, whereas the same effect could be achieved with both applied bleomycin concentrations, 1.0 µg/mL and 2.5 µg/mL, for the ECT group. The specific growth rate on day 7 following CaEP was significantly reduced in UM92.1 cell lines with 0.5 and 1.1 mg/mL calcium chloride, while Mel270 showed a similar effect only after administration of 1.1 mg/mL. UM92.1 and Mel270 spheroids exhibited lower adhesion and density after CaEP on day three in comparison to UPM spheroids showing detachment after day 7 following treatment. CaEP and bleomycin electroporation significantly reduce cell viability at similar applied voltage settings. CaEP may be a feasible and inexpensive therapeutic option for the local tumor control with fewer side effects, in comparison to other chemotherapeutic agents, for the treatment of uveal melanoma. The limited effect on normal cells and the surrounding tissue has already been investigated, but further research is necessary to clarify the effect on the surrounding tissue and to facilitate its application in a clinical setting for the eye.