Freshwater Medium Research Articles

Growth of Vannamei Shrimp (Litopeneaus vannamei) in Rearing Media with Different Salinities

The addition of calcium, phosphorus and magnesium minerals has been carried out separately in vannamei shrimp cultivation activities using fresh water media. Furthermore, the combination of the three types of potassium is expected to mutually fulfill the mineral needs of vannamei shrimp so that their growth becomes more optimal. This research aims to analyze the growth of vannamei shrimp reared in various media with different mineral levels. The treatments in this study were P1 (30 ppt), P2 (20 ppt), P3 (10 ppt), P4 (0 ppt without the addition of minerals), and P5 (0 ppt with the addition of various types of mineral sources). The research results show that the best SGR weight is found in P1 at 12.42%/day. The highest SR value was also obtained at P1, namely 65%. The SR and SGR values at P5 are higher than at P4, but still lower than at P1, P2, and P3. Based on these results, it is known that the growth of vannamei shrimp reared in fresh water media with added minerals has increased compared to vannamei shrimp reared in fresh water media without added minerals, but is still lower compared to the growth of vannamei shrimp reared in water media. sea. Furthermore, research is needed on adding other types of minerals to low salinity vannamei shrimp cultivation media.

The impact of nTiO2 and GO (graphene oxide), and their combinations, on freshwater Chlorella sp.: a comparative study in lake water and BG-11 media.

Titanium dioxide nanoparticles (nTiO2) and graphene oxide (GO) are extensively used nanomaterials in various products and applications. Freshwater ecosystems are a crucial sink for these pollutants, posing severe threats to aquatic organisms. Although multiple studies have investigated the pristine toxicity of nTiO2 and GO in freshwater organisms, the combined toxicity of these materials remains unexplored. Interaction media is a crucial factor in evaluating toxicity nanomaterial toxicity towards algae. In this study, we have investigated the comparative effect of sterilized and filtered freshwater and BG-11 medium on the pristine and combined toxicity of nTiO2 and GO on freshwater algae Chlorella sp. Results indicated that the combination of nTiO2 and GO showed more toxicity when compared to their respective pristine forms. This could be due to the additive effect exhibited by nTiO2 and GO on Chlorella sp. The enhanced growth inhibition for the combined toxicity was in the order of 1 mg L-1 nTiO2 + 1 mg L-1 GO > 1 mg L-1 nTiO2 + 0.1 mg L-1 GO > 0.1 mg L-1 nTiO2 + 1 mg L-1 GO > 0.1 mg L-1 nTiO2 + 0.1 mg L-1 GO. All test groups that interacted in BG-11 media exhibited less toxicity when compared to corresponding groups in the lake water medium. This could be attributed to the cushioning effect of BG-11 medium, providing supplementary nutrition to the algal cells. This signifies that the environmentally relevant conditions could be more detrimental than the laboratory conditions. This study elucidates valuable insights into the potential detrimental effects associated with the combination of nTiO2 and GO on freshwater algae. Furthermore, we have evaluated the growth inhibition, oxidative stress, and photosynthetic activity of Chlorella sp. in both environmentally relevant interaction medium and well-defined culture medium.

Photosynthesis in a green alga (zoochlorella), Chlorella cf. vulgaris in the soft coral Sarcophyton sp.

ABSTRACT An undescribed variety of the green alga Chlorella cf. vulgaris was found living in the octocoral (soft coral) Sarcophyton sp., which also has dinoflagellate zooxanthellae. The green alga is present in very small numbers and is capable of photoheterotrophy based on growth in the presence of an inhibitor of photosynthesis, DCMU, with glycerol provided as a carbon source. The presence of zoochlorellae (Chl a + b), in soft corals appears to have been unsuspected. The easily cultured green alga was unicellular, unflagellated and very small, c. 2 to 6 µm in diameter and had a relatively high Chl b content (Chl b/a = 0.379 ± 0.063). Rapid light curves using PAM fluorometry on the cultured cells showed that Yield vs. irradiance had a low maximum yield (Ymax, 0.388 ± 0.0132; Irradiance ½ point, E½Ymax = 139 ± 11.1 µmol photon m–2 s–1). The overall optimum irradiance (Eopt) for the alga was 314 ± 18.8 µmol photon m–2 s–1. The alga can photosynthesize at 50% or more of the optimum rate from 70 to 900 µmol photon m–2 s–1 but would be severely inhibited under full sunlight. Most naturally occurring low irradiance habitats may have a low median irradiance but are exposed intermittently to very high irradiances and so a relatively high Eopt is advantageous in minimizing photochemical damage. Like the green algal symbiont Elliptochloris marina of sea anemones, Chlorella cf. vulgaris is not exclusively marine: it grows better in freshwater medium where it has different photosynthetic characteristics (higher Ymax, Eopt and ETRmax). Chlorella cf. vulgaris appears to be capable of photoheterotrophy and it is not clear if it is a symbiont, a commensal or a parasite.

A Comparison Study on the δD Value of Polycyclic Aromatic Hydrocarbons in Hydrous Pyrolysate of Herbaceous Peat with Different Water Medium

AbstractTo investigate the influence of diagenetic water media on the hydrogen isotopes of individual sedimentary aromatic compounds, a series of hydrous pyrolyses were conducted on herbaceous peat. Polycyclic aromatic hydrocarbons (PAHs) in hydrous pyrolysed samples and their hydrogen isotopic composition characteristics were studied. The aqueous medium demonstrated a significant influence on the hydrogen isotopic composition of the individual PAHs generated during pyrolysis. The results showed that the PAHs formed after pyrolysis in the presence of a saltwater medium with high δD value from a salt lake had a heavy hydrogen isotopic composition. The PAHs formed after pyrolysis in the presence of a fresh water medium with low δD value from a swamp had a light hydrogen isotopic composition. The difference in the average PAH δD value between the two hydrous experiments varied from –174‰ to –109‰, suggesting that the hydrogen isotopic composition of individual sedimentary PAHs can reflect the source of the diagenetic water medium. In addition, a comparative study found that the hydrogen isotopes of PAHs were superior to those of n‐alkanes in the same sample for diagenetic water indications. The results indicated that the exchange of water‐derived inorganic hydrogen and organic hydrogen was more intensive in freshwater experiments than in saltwater experiments. With an increase in the simulation temperature, the average δD value of PAHs generated in the hydrous simulation experiments showed an increasing trend, reflecting that the δD value of sedimentary PAHs formed with the participation of diagenetic water media was still closely related to the thermal maturity of organic matter. Comparative studies showed that the δD values of different types of organic compounds produced by hydrous pyrolysis of peat were in the order, PAHs > n‐alkanes > methane.

Removal of weed algal contamination in cultures of Botryococcus braunii with enlarged colonies using rotifers

We proposed a biological contamination control technology that preyed on and removed only invading weed algae by introducing rotifers into the culture ponds of Botryococcus braunii that had enlarged colonies. Botryococcus braunii strains Showa and Sanshiro belonging to race B were used, and the colonies were grown on a high-salt medium containing 3 g L−1 NaCl. Brachionus calyciflorus, a freshwater rotifer with large prey size, was used as the predator, and Westella sp. was used as the model weed algae. In the mixed culture of B. braunii and B. calyciflorus, the growth rate of B. braunii cultured in Chu13, a freshwater medium, was reduced due to predation by B. calyciflorus. However, enlarged B. braunii cultured in a high-salt concentration medium escaped predation and maintained a growth rate equivalent to or higher than that of the control. In the three trials combining B. braunii, B. calyciflorus, and Westella sp., B. calyciflorus was initially applied such that the ratio of the number of rotifers to the algal density of Westella sp. was 2.0 × 10−6. Under these conditions, the initial growth of Westella sp. was suppressed when using the Showa strain, which showed significant growth. The larger colony size of the Sanshiro strain showed greater proliferation of Westella sp. because its optical density was lower than that of the Showa strain. The growth of the Sanshiro strain was suppressed until day 6, when predation reduced Westella sp. density, but the growth rate recovered thereafter. A model for the optimum number of rotifer inputs, considering the optical density and the number of rotifers remaining in the future, and technology for outdoor cultivation must be developed in the future. We demonstrated the potential of an eco-friendly weed-algae-removal technology that uses a predation ecosystem without using special culture environments or pesticides.

Influence of Anions on the Corrosion Behavior of 9Cr-1Mo Ferritic Steel in Aqueous Media

Modified 9Cr-1Mo steel is used as steam generator material in prototype fast breeder reactors, owing to its good corrosion resistance, creep, and thermal conductivity characteristics. In the present study, the corrosion behavior of modified 9Cr-1Mo steel in aqueous environments containing various corrosive ions at potentiodynamic polarization conditions is reported. In chloride-exposed samples, randomly distributed dense shallow pits were seen, whereas mixed anions (, Cl−, and ) in fresh water resulted in deeper pits uniformly distributed on the entire surface. Laser Raman spectroscopy studies revealed the formation of Fe-oxides/hydroxides and Cr(VI) species, except in alkaline solution. A very thin film of only Fe-oxides (Fe3O4, γ-Fe2O3, and α-Fe2O3) was identified in an OH– ion-dominated solution. X-ray photoelectron spectroscopy results confirm the corroded surfaces comprised of Fe, Cr, and Mo-oxides of varying composition and enrichment of Mo-oxides in alkaline solution. Chloride ions present in the corroded layer influenced the pitting corrosion in neutral chloride and fresh water solutions. Field emission scanning electron microscopy images revealed abundant crystalline lepidocrocite with laminar morphology and doughnut-type magnetite together with pits on the samples exposed in neutral chloride and fresh water media.

Isolation and cultivation of freshwater diatom <italic>Nitzschia palea</italic> HY1 for increasing biomass and fucoxanthin production

Diatoms, a type of microalgae distributed worldwide, have been identified as potential sources of biomass, lipids, and high-value compounds. While marine diatoms have been extensively studied, the potential of freshwater diatoms still needs to be explored. In this study, a novel strain of freshwater diatom was isolated from the Jungnangcheon stream located in Seoul, Republic of Korea (37°33'08.0" N, 127°02'40.0" E). This newly isolated strain was classified through phylogenetic analysis, and its morphology was investigated using light and electron microscopy; it was named Nitzschia palea HY1. N. palea HY1 grown in freshwater media (FDM) produced higher biomass (0.68 g L<sup>-1</sup>) and fucoxanthin production (9.19 mg L<sup>-1</sup>) than in conventional diatom media. Furthermore, increasing the bicarbonate concentration from 2 to 10 mM enhanced the maximum biomass and fucoxanthin production in FDM by 2.7 fold and 1.5 fold, respectively. Remarkably, the introduction of aeration to the modified FDM (MFDM) led to a substantial increase in the maximum biomass and fucoxanthin production of N. palea HY1, exhibiting 3.8-fold and 4.1-fold enhancement, respectively, compared to FDM alone. These findings suggest that optimizing the cultivation of N. palea HY1 using MFDM could provide an alternative to marine sources for fucoxanthin production.

Impact of disposable mask microplastics pollution on the aquatic environment and microalgae growth.

The COVID-19 pandemic has mandated people to use medical masks to protect the public. However the improper management of disposable mask waste has led to the increase of marine pollution, in terms of water quality, and the decline in aquatic microorganisms. The aim of this research was to investigate the impact of disposable mask waste on fresh water and microalgae biomass quality. Disposable masks (untreated or treated with Enterococcus faecalis) were placed in 10-L glass reactors containing fresh water or water containing algal Chlorella sp. and its growth supplements (Chlorella medium) (four 10-L reactors in total) and kept in controlled conditions for 3months. Water and biomass yield quality were evaluated using water quality analysis, spectroscopy, scanning electron microscopy (SEM), and proximate lipid and protein analysis. Disposable masks, incubated in either fresh water or Chlorella medium, affected several water quality parameters such as chemical oxygen demand (COD), biological oxygen demand (BOD), dissolved oxygen (DO), and pH. Microplastic identification revealed that some fibers were present in the water following a 100-day treatment process. Fourier transform-infrared spectroscopy (FTIR) analysis was used to determine the change in important, organic functional groups and highlighted the disappearance of a peak at 1530cm-1 corresponding to the primary protein (C-N) and the appearance of new peaks at 1651cm-1 and 1270cm-1 corresponding to methyl alcohol (CH2OH) and ketone (C = O), respectively. This indicated the detrimental effect of disposable mask fragmentation on the biomass quality. The SEM investigation has shown a damage to the surface membrane of Chlorella sp. cells. Altogether, disposable masks decreased the water quality and damaged microalgae by inhibiting their growth. Therefore, the disposable mask contaminated by various microbes, after being used by a human, may be one of the most dangerous hazards to the environment.

Supplemented desalinated seawater using sulfuric acid activated zeolit as hydroponic medium for mustard (Brassica juncea L.)

Sufficient agricultural water for irrigation is an important factor in food production, yet available fresh water only occupies 1% of the water on the earth. Seawater, through desalination, becomes rational solution to provide agricultural water due to abundant quantities and beneficial nutrients for crops. Hydroponic using desalinated seawater as medium is an approach to accomplish food security, especially in the arid and coastal areas. This study aimed to examine the growth of mustard (Brassica juncea L.) on a blend of fresh water and desalinated seawater using sulfuric acid activated zeolite as hydroponic medium. The experiment consisted of one control (100% fresh water+AB mix) and treatments namely a blend of 70% fresh water and 30% desalinated seawater using sulfuric acid activated zeolite with various sulfuric acid concentrations i.e 0.5, 1, 1.5, 2, 2.5, 3, and 3.5 N. The growth of mustard in blend of 70% fresh water and 30% desalinated seawater was lower than fresh water. A blend of 70% fresh water and 30% desalinated seawater using 1.5 N sulfuric acid activated zeolite showed no significant different mustard growth compared with fresh water medium and the fresh weight reduction was about 24%. Insignificant different growth between optimum treatment and control indicated a simple desalination method in this study can be utilized to desalinating seawater for hydroponic medium purpose. This finding emphasized that the simple seawater desalination method in this study for hydroponic medium was promising and interesting to be further developed for sustainable water management and agriculture.

Effect of calcium hydroxide (Ca(OH)2) and magnesium sulfate (MgSO4) on vaname shrimp (Litopenaeus vannamei) cultivation in freshwater media

The purpose of this study was to determine the effect of giving the ratio of Calcium Hydroxide (Ca(OH)2) and Magnesium Sulfate (MgSO4) with different doses on the growth of white shrimp (Litopenaeus vannamei) production in freshwater media. This research was conducted by experimental method using Completely Randomized Design (CRD). The parameter studied was how the effect of the addition of Ca(OH)2 and Magnesium Sulfat (MgSO4) lime with different doses in the maintenance container with 5 treatments and 3 replications, so that 15 experiments were obtained. The treatments applied were: Treatment 1 (P1) Seawater without the addition of calcium and magnesium, P2 Freshwater + 80 ppm Ca(OH)2, P3 Freshwater + 80 ppm Ca(OH)2 and 40 ppm MgSO4, P4 Freshwater + 80 ppm Ca(OH)2 and 80 ppm MgSO4, and P5 Freshwater + 80 ppm Ca(OH)2 and 120 ppm MgSO4. The results showed that the highest survival rate using fresh water was at P4 which was 82%, the specific weight growth rate was 3.9%, and the specific length growth rate was 2.6%. the value of the feed conversion ratio is 0.8. For water quality parameters, the temperature ranges from 30.4-30.60C, water pH 7.2-8.2, DO 6.4-6.6 mg/L, Alkalinity 68-72 ppm, and Ammonia 0.1 mg /L.Keywords: Ca(OH)2; Freshwater; MgSO4; Vannamei Shrimp

Effect of calcium hydroxide (Ca(OH)2) and magnesium sulfate (MgSO4) on vaname shrimp (Litopenaeus vannamei) cultivation in freshwater media

The purpose of this study was to determine the effect of giving the ratio of Calcium Hydroxide (Ca(OH)2) and Magnesium Sulfate (MgSO4) with different doses on the growth of white shrimp (Litopenaeus vannamei) production in freshwater media. This research was conducted by experimental method using Completely Randomized Design (CRD). The parameter studied was how the effect of the addition of Ca(OH)2 and Magnesium Sulfat (MgSO4) lime with different doses in the maintenance container with 5 treatments and 3 replications, so that 15 experiments were obtained. The treatments applied were: Treatment 1 (P1) Seawater without the addition of calcium and magnesium, P2 Freshwater + 80 ppm Ca(OH)2, P3 Freshwater + 80 ppm Ca(OH)2 and 40 ppm MgSO4, P4 Freshwater + 80 ppm Ca(OH)2 and 80 ppm MgSO4, and P5 Freshwater + 80 ppm Ca(OH)2 and 120 ppm MgSO4. The results showed that the highest survival rate using fresh water was at P4 which was 82%, the specific weight growth rate was 3.9%, and the specific length growth rate was 2.6%. the value of the feed conversion ratio is 0.8. For water quality parameters, the temperature ranges from 30.4-30.60C, water pH 7.2-8.2, DO 6.4-6.6 mg/L, Alkalinity 68-72 ppm, and Ammonia 0.1 mg /L.Keywords: Ca(OH)2; Freshwater; MgSO4; Vannamei Shrimp

Enhanced phycocyanin production from Spirulina subsalsa via freshwater and marine cultivation with optimized light source and temperature

To find out optimum and cost-efficient strategy for phycocyanin production, the effect of light source and temperature on Spirulina subsalsa growth were studied in chemically defined freshwater medium and seawater supplied with wastewater from glutamic acid fermentation tank. Maximum growth rate and the highest phycocyanin content were obtained by 35 °C and green light, respectively. A two-stage cultivation strategy was proposed and applied, which combines biomass accumulation at 35 °C and phycocyanin synthesis simulated under green light. As a result, phycocyanin production reached 70 mg/L/d and 11 mg/L/d from freshwater and seawater medium, respectively. With all tested conditions, a strong correlation between biomass and phycocyanin/chlorophyll ratio, rather than phycocyanin, revealed the dependence of Spirulina subsalsa growth on coordinating regulation of photosynthetic pigments. The relationship between growth and phycocyanin production under various light and temperature can be a good basis for improving phycocyanin production from Spirulina subsalsa with or without freshwater consumption.

Friction and wear behavior of cemented carbide self-matching pairs under different water lubrication conditions

The friction and wear behavior of WC based cemented carbides ring-ring samples in different water environments were systematically tested. The average grain size of WC is 1.2 μm and the mass fraction of binder Co is 8%. The water environments include distilled fresh water, artificial seawater with NaCl mass content of 4%, and sediment water with SiO2 mass content of 0.6% and average particle size of 88 μm. The friction torque was measured for each friction pairs at different speeds and specific pressure loads. The surface morphology of the friction pairs before and after the test were observed by a scanning electron microscope, and the weight losses were also measured by a balance. The test results suggest that the friction coefficient of all the sample pairs decreases exponentially with the increase of load at proper revolution speed. In the range of 4–10 MPa specific pressure, the friction coefficient of the bearing during stable operation is between 0.01–0.02. The wear rate of the stationary ring is about 3 times that of the matching rotary ring, no matter in the environment of artificial seawater, distilled fresh water or sediment water lubrication medium. However, the wear rates of the samples in artificial seawater are higher than those of the two rings friction under the same speed and load conditions in the other two water environments. SiO2 particles in the sediment water has no effect on the bearings wear rate. The wear of cemented carbide self-matching pair bearings is mainly the peeling of WC particles caused by the alternating contact and friction force or plowing of WC abrasive particles. The corrosivity of artificial seawater can aggravate the peeling of WC particles. The results and conclusions of this study can provide a meaningful reference for the design of cemented carbide bearings utilized in water lubrication environment.

The role of algal EPS in reducing the combined toxicity of BPA and polystyrene nanoparticles to the freshwater algae Scenedesmus obliquus

Both Bisphenol A (BPA) and polystyrene nanoplastics (PSNPs) are routinely found in several consumer products such as packaging materials, flame retardants, and cosmetics. The environment is seriously endangered by nano- and microplastics. In addition to harming aquatic life, nanoplastics (NPs) also bind to other pollutants, facilitating their dispersion in the environment and possibly promoting toxicity induced by these pollutants. The toxic effects of polystyrene nanoplastics (PS-NPs) and BPA were examined in this study, as well as the combined toxic impacts of these substances on the freshwater microalgae Scenedesmus obliquus. In addition, the exopolymeric substances (EPS) secreted by algae will interact with the pollutants modifying their physicochemical behaviour and fate. This work aimed to investigate how algal EPS alters the combined effects of BPA and PSNPs on the microalgae Scenedesmus obliquus. The algae were exposed to binary mixtures of BPA (2.5, 5, and 10 mg/L) and PSNPs (1 mg/L of plain, aminated, and carboxylated PSNPs) with EPS added to the natural freshwater medium. Cell viability, hydroxyl and superoxide radical generation, cell membrane permeability, antioxidant enzyme activity (catalase and superoxide dismutase), and photosynthetic pigment content were among the parameters studied to determine the toxicity. It was observed that for all the binary mixtures, the carboxylated PSNPs were most toxic when compared to the toxicity induced by the other PSNP particles investigated. The maximum damage was observed for the mixture of 10 mg/L of BPA with carboxylated PSNPs with a cell viability of 49%. When compared to the pristine mixtures, the EPS-containing mixtures induced significantly reduced toxic effects. A considerable decrease in reactive oxygen species levels, activity of antioxidant enzymes (SOD and CAT), and cell membrane damage was noted in the EPS-containing mixtures. Reduced concentrations of the reactive oxygen species led to improved photosynthetic pigment content in the cells.

Addition of Calcium Carbonate (CaCO3) and Magnesium Sulfate (MgSO4) to Vannamei Shrimp (Litopenaeus vannamei) Rearing Media in Fresh Water

Vannamei shrimp cultivation in freshwater media is still not optimal. Scabra et al., 2022 stated that the growth of vannamei shrimp reared on media supplemented with CaCO3 was higher than that reared on media without the addition of CaCO. However, it is still lower than the vannamei shrimp reared in seawater media. The addition of other types of minerals is needed to complement CaCO3 in supporting growth. The purpose of this study was to determine the effect of rearing vaname shrimp on low-salinity media with the addition of CaCO3 and MgSO4 ratios with different doses. The treatment in the study was the addition of CaCO3 : MgSO4 with different ratios, namely 40:0 (P2), 40:20 (P3), 40:40 (P4), and 40:60 (P5). A treatment was also applied which was a positive control, namely the rearing of vannamei shrimp in seawater media (P1). The results showed that the best specific growth values were P1 (3.83%), P4 (3.64%), P5 (3.5%), P3 (3.46%), and P2 (3.42%) ). In fresh water rearing, P4 was the best treatment which resulted in a survival rate of 77%, a specific weight growth rate of 3.64%, and a specific length growth rate of 2.14%. Shrimp growth in fresh water media is still not as high as maintenance in seawater media. Therefore, it is still necessary to add other types of minerals that can support growth.

Humic acid-mediated reduction in toxicity of Co3O4 NPs towards freshwater and marine microalgae in surfactant mixed medium.

The ever-increasing applications of Co3O4 nanoparticles (NPs) have posed a serious concern about their discharge in the aquatic environment and ecotoxic implications. Being toxic towards aquatic species, the impact of other aquatic components such as dissolved organic matter (DOM), salinity, and surfactants are not studied sufficiently for their effect on the stability and ecotoxicity of Co3O4 NPs. The present study aims at the influence of humic acid (HA) on the toxicity of Co3O4 NPs in freshwater (C. minutissima) and marine (T. suecica) microalgae under surfactants mixed medium. The measure of % reduction in biomass and photosynthetic pigment were used as toxicity endpoints. Among various tested concentrations of HA, 25mg/L HA was found suitable to minimize the NP's toxicity with or without the presence of surfactants. Co3O4 NPs mediated reduction in biomass of C. minutissima was significantly minimized by the cumulative effect of HA with T80 (51.68 ± 4.55%) followed by CTAB (46.23 ± 5.62%) and SDS (42.60 ± 2.46%). Similarly, HA with T80 (26.93 ± 6.38%) followed by SDS (17.02 ± 6.64%) and CTAB (13.01 ± 3.81%) were found to minimize the growth inhibitory effect of Co3O4 NPs in T. suecica. The estimation of chlorophyll - a content also indicated that microalgae treated with HA could maintain their photosynthetic ability more than control even in the co-presence of surfactants. Also, the reduced toxicity of Co3O4 NPs were attributed to an increase in hydrodynamic sizes of HA-treated Co3O4 NPs in both marine media (f/2) and freshwater media (BG11) due to increased aggregation and faster sedimentation of Co3O4 NPs.

Fatty acid profile of Spirulina sp cultivated in Bangka Seawater

Microalgae can be used as a good biodiesel raw material because there are quite a lot of oil microalgae, one of which is Spirulina sp. Cultivation Process of Spirulina sp. using seawater media produces more optimal biomass than freshwater media. This study used Bangka Seawater as a growth medium for Spirulina sp., and identification fatty acid of Spirulina extract by GC-MS methode. cell growth of Spirulina sp. on media Bangka seawater using Walne fertilizer can experience an exponential phase until the 9th day due to the addition of Walne fertilizer. Culture with 1 ml of Walne fertilizer had the best growth. The use of Bangka sea water without fertilizer can also grow Spirulina sp with a peak on day 5. The total fatty acid in the hexane extract of Spirulina in this study was 69.60% with similarity indeks above 70%. As many as 33.78% are Saturated Fatty Acids (SFA) such as docosanoic acid, hexadecanoic acid, octadecanoic acid, and hexanedioic acid. While 35.82% are Unsaturated Fatty Acids (UFA). The profile of fatty acid from Bangka seawater media showed that the largest fatty acids contained in Spirulina sp. is palmitic acid (hexadecanoic acid) with presentage 25.21%.

Azithromycin resistance genes in Escherichia coli isolated from wastewater: Characterization and modeling-based evaluation of factors affecting the prevalence

Azithromycin is becoming an effective alternative medicine against antibiotic resistant Escherichia coli (E. coli), and in parallel, is frequently detecting in wastewater and fresh water media. The current study aimed to evaluate the presence of azithromycin resistance genes (AzRGs) in E. coli isolated from urban wastewater for which there is a serious lack of information. For this, the samples were collected from four vital points of an urban wastewater treatment plant (WWTP), analyzed for physicochemicfial parameters, and identified for the azithromycin resistant isolates. The isolates were then subjected to 13 other extensively used antibiotics (from seven different classes), including amikacin, aztreonam, ceftazidime, ciprofloxacin, cefepime, ceftriaxone, cefotaxime, doxycycline, gentamicin, imipenem, norfloxacin, tetracycline, and trimethoprim/sulfamethoxazole; detected for AzRGs, phylogenic group, and molecular typing. The results clearly showed that: a) except for amikacin in all samples and gentamicin in effluent samples, E. coli isolates were resistant to all other the antibiotics studied in the mean respective values of 53.8%, 90.4%, 50%, 40.4%, 86.5%, 86.5%, 63.5%, 13.5%, 73.1%, 46.2%, 65.4%, 69.2%; b) for 75% of them (i.e. except for amikacin, gentamicin, and trimethoprim/sulfamethoxazole), the antibiotic resistance prevalence in effluent samples were significantly higher than that of sludge (p-value = 0.011), aeration (p-value = 0.023), and even influent (p-value = 0.038) samples, suggesting that WWTP facilities acquiring the resistance gene; c) The high values of multiple antibiotic resistance (MAR) index in almost all of the isolates (0.21–0.91) were categorized them in high-risk group, though the values were not found to be influenced by WWTP. Surprisingly, from 10 AzRGs, only two genes of mph(A) and erm(B) were detected in 100% and 67.3% of the isolates, respectively. The prevalence of erm(B) was significantly influenced by MAR index (p-value = 0.004), which MAR in turn, influenced by physicochemical parameters of wastewater in the relative effectiveness of COD (36%) > EC (29%) > TS (16%) > TDS (9%) > temperature (6%) > pH (4%), as modeled using artificial neural network (ANN) approach (R2 = 0.85 and MSE = 0.006302). The phylogenetic group A (59.6%) and clusters of III and V with 23 and 18 isolates, respectively, were dominant among the isolates which both showed a high correlation with MAR indices and therefore erm(B) prevalence. These results were interesting as highlight the effect of WWTP on acquiring antibiotic resistance and AzRGs prevalence in E. coli. Therefore, defining new strategies for relieving the challenge is of great importance.

Biodegradation of microplastic in freshwaters: A long-lasting process affected by the lake microbiome.

Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using 13 C-labelled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.45% ± 0.21% per year) than in the clear-lake waters (0.07% ± 0.06% per year) or the artificial freshwater medium (0.02% ± 0.02% per year). Complete biodegradation of PE-MP was calculated to last 100-200 years in humic-lake waters, 300-4000 years in clear-lake waters, and 2000-20,000 years in the artificial freshwater medium. The concentration of 18:1ω7, characteristic phospholipid fatty acid in Alpha- and Gammaproteobacteria, was a predictor of faster biodegradation of PE. Uncultured Acetobacteraceae and Comamonadaceae among Alpha- and Gammaproteobacteria, respectively, were major bacteria related to the biodegradation of PE-MP. Overall, it appears that microorganisms in humic lakes with naturally occurring refractory polymers are more adept at decomposing PE than those in other waters.

Nitrosomonas supralitoralis sp. nov., an ammonia-oxidizing bacterium from beach sand in a supralittoral zone.

A betaproteobacterial chemolithotrophic ammonia-oxidizing bacterium designated APG5T was isolated from supralittoral sand of the Edmonds City Beach, WA, USA. Growth was observed at 10-35°C (optimum, 30°C), pH 5-9 (optimum, pH 8) and ammonia concentrations as high as 100mM (optimum, 1-30mM NH4Cl). The strain grows optimally in a freshwater medium but tolerates up to 400mM NaCl. It is most closely related to 'Nitrosomonas ureae' (96.7% 16S rRNA and 92.4% amoA sequence identity). The 3.75-Mbp of AGP5T draft genome contained a single rRNA operon and all necessary tRNA genes and has the lowest G+C content (43.5%) when compared to the previously reported genomes of reference strains in cluster 6 Nitrosomonas. Based on an average nucleotide identity of 82% with its closest relative ('N. ureae' Nm10T) and the suggested species boundary of 95-96%, a new species Nitrosomonas supralitoralis sp. nov. is proposed. The type strain of Nitrosomonas supralitoralis is APG5T (= NCIMB 14870T = ATCC TSD-116T).