Effects of the Light Irradiance on the Growth and Lipids Content of Amphidinium Carterae (Dinophyceae) for Biofuels Production

The irradiance level used to the microalgae cultures can modify the growth and proximate composition, however, this response is specie specific. The dinoflagellate group had the potential to be used as a source to biofuel production. In this study was evaluated the effect of five irradiance levels (50, 100, 150, 200, and 250 µmol photon m-2 s­-1) on the growth rate, proximal composition, pigment content, and photosynthesis of Amphidinium carterae. The highest cell concentration was for the cultures at 150 µmol photon m-2 s-1 (130 × 103 cells mL-1), and the lowest values for 50 µmol photon m-2 s-1 (49 × 103 cells mL-1). The cultures maintained under the low irradiance (50 µmol photon m-2 s-1) had the highest values of total dry weight (TDW) (13418 pg cell-1), organic dry weight (ODW) (3836 pg cell-1), and inorganic dry weight (IDW) (9582 pg cell-1). The protein content as the general trend increases significantly concerning the irradiance level, with the higher values (87.47 pg cell-1) at high irradiance (250 µmol photon m-2 s-1). Carbohydrate content was different by the effect of irradiance, with the higher values (32.85 pg cell-1) at the low irradiance used (50 µmol photon m-2 s-1). Lipid content was modified by the effect of irradiance, with the highest values (534.74 pg cell-1) at the low irradiance used (50 µmol photon m-2 s-1). As a general trend, the high irradiances increased the photosynthesis curves. These findings demonstrate that the strain of A. carterae used in this work can grow in high irradiances (100 to 250 µmol photon m-2 s-1) and increase significantly the lipid content on low irradiance used (50 µmol photon m-2 s-1).

Antibacterial activity in three Chaetoceros microalgae species cultures by using antibiotics

Diatoms, such as Chaetoceros, grow in a mutualistic relationship with bacteria. However, in some cases, it is necessary to grow them in bacteria-free cultures. To reduce bacterial load, antibiotics are used, and on certain occasions it is necessary to use a mixture with more than one antibiotic. This work aimed to obtain a quick and effective protocol to reduce the bacterial load and evaluate the response of three Chaetoceros species with aquacultural importance. Single and mix antibiotics were used. Microalgal and bacterial growth was measured. The growth parameters for diatoms showed that the significantly highest cell concentration was for C. muelleri (3.15 x106 cells mL-1) and the lowest values to C. calcitrans (2.98 x106 cells mL-1). The significantly highest growth rate was for C. calcitrans (0.77 divisions per day), and the lowest values for Chaetoceros sp. (0.60 divisions per day). The growth parameters for heterotrophic bacteria showed that the significantly highest bacterial load was for Chaetoceros sp. (19.16 x106 CFU (Colony-Forming Units) mL-1) and the lowest values were for C. calcitrans (12.23 x106 CFU mL-1). The growth rate of the heterotrophic bacteria present in Chaetoceros cultures was similar among the three studied species. Streptomycin® and sulfate G41® produced a partial reduction of bacterial load. The most effective treatment for all three species was the use of an antibiotic mix composed of ampicillin® (250 μg mL-1), kanamycin® (200 μg mL-1), neomycin® (50 μg mL-1), and streptomycin® (100 μg mL-1) for three days. The mix prepared with the highest antibiotic concentration produced a reduction of bacteria (100%) for three days; however, it also induced a significant reduction of the growth of the three Chaetoceros species.

Hand-Powered Inertial Microfluidic Syringe-Tip Centrifuge

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.

Model Transferability and Reduced Experimental Burden in Cell Culture Process Development Facilitated by Hybrid Modeling and Intensified Design of Experiments

Reliable process development is accompanied by intense experimental effort. The utilization of an intensified design of experiments (iDoE) (intra-experimental critical process parameter (CPP) shifts combined) with hybrid modeling potentially reduces process development burden. The iDoE can provide more process response information in less overall process time, whereas hybrid modeling serves as a commodity to describe this behavior the best way. Therefore, a combination of both approaches appears beneficial for faster design screening and is especially of interest at larger scales where the costs per experiment rise significantly. Ideally, profound process knowledge is gathered at a small scale and only complemented with few validation experiments on a larger scale, saving valuable resources. In this work, the transferability of hybrid modeling for Chinese hamster ovary cell bioprocess development along process scales was investigated. A two-dimensional DoE was fully characterized in shake flask duplicates (300 ml), containing three different levels for the cultivation temperature and the glucose concentration in the feed. Based on these data, a hybrid model was developed, and its performance was assessed by estimating the viable cell concentration and product titer in 15 L bioprocesses with the same DoE settings. To challenge the modeling approach, 15 L bioprocesses also comprised iDoE runs with intra-experimental CPP shifts, impacting specific cell rates such as growth, consumption, and formation. Subsequently, the applicability of the iDoE cultivations to estimate static cultivations was also investigated. The shaker-scale hybrid model proved suitable for application to a 15 L scale (1:50), estimating the viable cell concentration and the product titer with an NRMSE of 10.92% and 17.79%, respectively. Additionally, the iDoE hybrid model performed comparably, displaying NRMSE values of 13.75% and 21.13%. The low errors when transferring the models from shaker to reactor and between the DoE and the iDoE approach highlight the suitability of hybrid modeling for mammalian cell culture bioprocess development and the potential of iDoE to accelerate process characterization and to improve process understanding.

Growth, respiratory activity and chlorpyrifos biodegradation in cultures of Azotobacter vinelandii ATCC 12837

This study aimed to evaluate the growth, respiratory activity, and biodegradation of chlorpyrifos in cultures of Azotobacter vinelandii ATCC 12837. A strategy based on the modification of culture media and aeration conditions was carried out to increase the cell concentration of A. vinelandii , in order to favor and determine its tolerance to chlorpyrifos and its degradation ability. The culture in shaken flasks, using sucrose as a carbon source, significantly improved the growth compared to media with mannitol. When the strain was cultivated under oxygen-limited (5.5, 11.25 mmol L- 1 h- 1 ) and no-oxygen-limited conditions (22 mmol L -1 h -1 ), the growth parameters were not affected. In cultures in a liquid medium with chlorpyrifos, the bacteria tolerated a high pesticide concentration (500 ppm) and the growth parameters were improved even under conditions with a reduced carbon source (sucrose 2 g L -1 ). The strain degraded 99.6 % of chlorpyrifos at 60 h of cultivation, in co-metabolism with sucrose; notably, A. vinelandii ATCC 12837 reduced by 50% the initial pesticide concentration in only 6 h (DT 50 ).

Valorization of Oil Waste for Biodetergent Production Using Serratia Marcescens N2 and Gamma Irradiation Assisted Biorecovery

The aim of the present work is to valorize previously used frying oil and use it as biodetergent. Serratia marscens N2 valorized 20% used oil and 8% cell concentration, the biosurfactant produced was a negatively charged lipopeptide with surface tension of 26.8 mN/m. Gamma radiation was used to obtain the higher yield of the biosurfactant by exposing the cells after growth under optimal conditions to low dose gamma radiation. The results showed that the use of radiation led to an increase in the amount of biosurfactant, and the biorecovery took place in a shorter time than usual. The chemical or functional form of the substance did not change at doses of 500 and 1000 gray, while there was a change in production and chemical and functional form at the dose of 2000 gray. The produced biosurfactant was used before and after irradiation to wash oil soiled cloths, the results showed 87% removal at 60oC under stirring conditions. Skin irritation tests performed on experimental mice showed that the surfactant does not cause any inflammation or red spots. Optical images of cloth patches showed no effect on fabric threads post washing the oil soiled cloth patches with biosurfactant. This study proved that 1) previously used oil can be bioconverted into biosurfactant and 2) the use of low doses gamma radiation results in an increase in biosurfactant yield by creating holes in the bacterial cell wall, which helps to recover more quantities of the biosurfactant without change in its chemical or functional form.

Desiccation survival in Salmonella enterica, Escherichia coli and Enterococcus faecium related to initial cell concentration and cellular components

Salmonella enterica is well-known for its ability to survive and persist in low-moisture environments. Previous studies have indicated a link between the initial cell concentration and the population of Salmonella that survive upon desiccation and subsequent storage; however, how the initial cell concentration affects survival is unknown. This study examined the basis of this phenomena and whether it occurred in other microorganisms, specifically Shiga toxigenic Escherichia coli (STEC), and Enterococcus faecium . Salmonella, STEC, and E. faecium were grown as lawns on TSAYE and harvested using buffered peptone water (BPW). To determine recovery at different initial cell levels, cultures were diluted to 9, 7, and 5 log CFU/mL and applied to filters. Filters were dried for 24 h, then stored for 28 d at 25°C/33% RH. During storage, cells were recovered from filters using BPW and cultivated on TSAYE. Both Salmonella and E. coli , but not E. faecium , showed non-proportional recovery. Less viability remained with lower initial starting population after 24 h desiccation such that ≥10 log CFU/mL were recovered when 11 log CFU/mL was desiccated, but <3 log CFU/mL were recovered when 5 log CFU/mL was desiccated. Once dried, persistence did not appear affected by initial cell concentration. When dead cells (heat-treated) were added to the diluent, recovery of Salmonella was proportional with respect to the initial cell concentration. To further examine the response on desiccation, Salmonella was diluted in BPW containing one of 11 different test cell components related to quorum sensing or known to affect desiccation resistance to assess recovery and persistence. Of the 11 additions only cell debris fractions, cell-free extract, and peptidoglycan improved recovery of Salmonella . Desiccation survival appears related to cell wall components, however, the exact mechanism affecting survival remains unknown.

Growth, respiratory activity and chlorpyrifos biodegradation in cultures of Azotobacter vinelandii ATCC 12837

This study aimed to evaluate the growth, respiratory activity, and biodegradation of chlorpyrifos in cultures of Azotobacter vinelandii ATCC 12837. A strategy based on the modification of culture media and aeration conditions was carried out to increase the cell concentration of A. vinelandii, in order to favor and determine its tolerance to chlorpyrifos and its degradation ability. The culture in shaken flasks, using sucrose as a carbon source, significantly improved the growth compared to media with mannitol. When the strain was cultivated under oxygen-limited (5.5, 11.25 mmol L−1 h−1) and no-oxygen-limited conditions (22 mmol L−1 h−1), the growth parameters were not affected. In cultures in a liquid medium with chlorpyrifos, the bacteria tolerated a high pesticide concentration (500 ppm) and the growth parameters were improved even under conditions with a reduced carbon source (sucrose 2 g L−1). The strain degraded 99.6% of chlorpyrifos at 60 h of cultivation, in co-metabolism with sucrose; notably, A. vinelandii ATCC 12837 reduced by 50% the initial pesticide concentration in only 6 h (DT50). Graphical Abstract

Effect of Various Calcite Precipitating Bacteria on Compressive Strength of Concrete: A Comparative Study

The presence of micro pores in concrete makes the concrete weak and less durable, in this study an ecofriendly attempt has been made to minimize these micro pores by calcite precipitating bacteria i.e. Escherichia Coli, bacillus subtilisand pseudomonas aeruginosa which produce calcium carbonate when they blend with calcium lactate in presence of water and air thus filling up the micro pores, thus comparing their effects on compressive strength of concrete.Various proportions of E. coli, B.subtilisand P. aeruginosa bacterial media were impregnated in concrete viz. 10%,20% and 30% replacing the proportion of mixing water, small proportion of fine aggregate was also replaced by calcium lactate and silica gel. It was observed that concrete with 10% replacement of P. aeruginosa culture media with mixing water showed maximum compressive strength with 79.6% increase in the compressive strength of concrete where as concrete with B.subtilisbacterial media showed 61.1% increase in the compressive strength of concrete and concrete with E.coli bacterial media showed 23.5% increase in the compressive strength of the concrete, keeping 10-6 cells/ml the cell concentration for all bacterial concretes.