Effects of artificial sweeteners on metal bioconcentration and toxicity on a green algae Scenedesmus obliquus

Differences in bioaccumulation of Ni and Zn by microalgae in the presence of fulvic acid

In the presence of dissolved organic matter, the mechanism of algal bioaccumulation of different metals is complex, and its significance goes far beyond the alga-metal binary system. In the presence of 10 and 20 mg L^-1 fulvic acid (FA), the maximum tolerance concentrations of Chlorella pyrenoidosa to Ni were 0.25 and 0.26 mmol L^-1, and to Zn were 0.62 and 0.68 mmol L^-1, respectively. Within the maximum tolerance concentration ranges, the bioaccumulation behaviors of Ni and Zn were systematically compared in the presence of FA. The presence of FA shortened the adsorption equilibrium time and decreased the maximum bioaccumulation capacity of Ni and Zn. The bioaccumulation mechanism of Ni by C. pyrenoidosa was more inclined to monolayer adsorption, while the bioaccumulation mechanism of Zn was more inclined to multilayer adsorption. More details were revealed after the bioaccumulated metals were separated into adsorption and internalization states by 0.01 M EDTA elution. The presence of FA decreased more adsorbed Zn than the adsorbed Ni, due to the different competitive roles of FA in the ternary system of Ni and Zn, but the presence of FA increased the internalized Ni might due to the stronger complexation of Ni-FA. This research indicated that algae had unique bioaccumulation mechanisms for different metals in the presence of FA, which is of great significance to accurately evaluate the ecological risk posed by heavy metals.

Removal of low-calorie sweeteners at five Brazilian wastewater treatment plants and their occurrence in surface water

The consumption of low-calorie sweeteners (LCSs) such as acesulfame (ACE), sucralose (SUC), saccharin (SAC), cyclamate (CYC), aspartame (ASP), neotame (NEO), and stevioside (STV) is increasing worldwide to meet the demand for reduced-calorie foods and beverages. However, there are no consumption data available in Brazil, as well as their concentration in sewage and removal on wastewater treatment plants (WWTPs). In the present study, ACE, SUC, SAC, CYC, ASP, NEO, and STV were assessed at five WWTPs located in the metropolitan region of Campinas (São Paulo State, Brazil), in operation with different treatment processes. Surface water was also analyzed. Analyses were carried out by on-line solid-phase extraction ultra-high performance liquid chromatography-tandem mass spectrometry. The major points are the following: LCS concentrations in the influents ranged from 0.25 to 189 μg L^-1 and followed the order CYC > ACE > SAC > SUC. NEO, ASP, and STV were not detected at any sampling site. Sweetener concentrations in the WWTP outputs differed mainly due to the different treatment setups employed. CYC and SAC were completely removed by biodegradation-based processes, while ACE removal was favored by the anaerobic-anoxic-aerobic process. SUC presented the highest concentration in the treated sewage, even at the WWTP operating with ultrafiltration membranes and therefore could be a marker compound for evaluation of the efficiency of removal of contaminants in WWTPs. Risk quotient estimation, using the PNEC and MEC values, indicated that the levels of the LCS reported here were harmless to the biota. The consumption of ACE, CYC, SAC, and SUC was estimated to be 2634 t year^-1.

Influence of zinc and manganese enrichments on growth, biosorption and photosynthetic efficiency of Chlorella sp

Treating biosolids from industrial, urban, and agricultural plants produces high amounts of water. After organic pollutants and non-essential heavy metals have been removed, these wastewaters are still rich in trace elements such as zinc (Zn), copper, or manganese (Mn) and have high conductivity and extremely variable pH. In this study, an isolated Chlorella sp. strain was grown for 21 days in nutrient solutions enriched with known amounts of Zn or Mn to obtain concentrations three (4.0 mg L^-1)- and six (1.0 mg L^-1)-fold higher than the basal medium levels, respectively, and over the limits permitted in aquatic environments. The green alga exhibited high tolerance to Zn and Mn, with the maximum abatement of Zn (28-30%) and Mn (60-63.5%) after 14 and 7 days of culture, respectively. Mn stimulated the growth rate and biomass production of Chlorella, which showed the highest carbon levels just in the first week. In both treatments, the nitrogen and protein contents remarkably increased. The photosynthetic pigments increased until the 14th day, with a higher extent in the Zn-enriched solution. An increasing photochemical efficiency was observed after 7 days of treatment, when the microalgae grown in Zn- and Mn-enriched solutions showed a slightly higher maximum photochemical efficiency than control. The autotrophic and controlled growth system adopted was designed to monitor the dynamic balance of Zn and Mn contents in the solutions and in the algal biomass. This system has proved to be useful in identifying the optimal nutritional conditions of the microalgae, along with the optimal temporal patterns of both metal biosorption capacity for water remediation and element bioaccumulation in the algal biomass.

Effects of heavy metals released from sediment accelerated by artificial sweeteners and humic acid on a green algae Scenedesmus obliquus

Artificial sweeteners (ASs) are emerging polar organic contaminants, which can chelate with heavy metals in the environment. Recently, the ASs have been widely detected in the aquatic environment. However, little is known about the influence of ASs on the mobility and toxicity of heavy metals associated in sediment. In the present study, the release of heavy metals from a lake sediment and the toxicity to a green algae Scenedesmus obliquus were examined in the presence of two most frequently detected ASs, acesulfame and sucralose, and humic acid (HA), respectively. The existence of 1.00-100 mg/L of acesulfame, sucralose, and HA enhanced the release rates (R_release) of Cd, Cu, and Pb from the virgin lake sediment significantly by up to 46.7%, 86.0%, and 79.9%, respectively. Further, the results from microcosm experiments revealed that the existence of 1.00-10.0 mg/L of acesulfame, sucralose, and HA in the water phase prompted the release and toxicity of heavy metals associated with Cd- and Cu-spiked sediment, and the promotion capacity followed the order of HA > acesulfame > sucralose. The inhibitions on cell-specific growth rate (μ) of the algae were found increasing significantly with the elevated levels of acesulfame and HA (p < 0.05). Additionally, photosynthesis of the algae was affected by the co-existence of ASs or HA and heavy metals released from sediments, as indicated by the changes in fluorescence parameters. The present study provides valuable insight into the likelihood of the combined effect of ASs and heavy metals on aquatic organisms.

Artificial Sweeteners in Pig Feed: A Worldwide Survey and Case Study in Pig Farms in Tianjin, China

Some artificial sweeteners (ASs) are used in pig feeds, although little is known on this regard. An investigation was conducted by determining seven common ASs in pig feed, manure, wastewater, compost, and soil from 16 pig farms in Tianjin, China. Saccharin (SAC) was predominant in feed (1.41-326 mg/kg) and manure samples (1.06-401 mg/kg). The annual mass loads of ASs in pig feeds were estimated at 5.69-119, 4.92-149, and 1.29-35 kg per 10³ piglets, hogs, and sows, respectively. The annual emission of ASs via biowaste (i.e., manure) was estimated at 3.58-85.2, 0.04-26.2, and 0.08-9.97 kg per 10³ capita for the three dominant ASs, i.e., SAC, neotame (NEO), and cyclamate (CYC). On a global scale, SAC was also widely detected at concentrations of 0.01-326 mg/kg in pig feed from China, Switzerland, Japan, Chile, and the United States, suggesting the worldwide use of ASs in pig feed. NEO and CYC were found in 41% and 30% of the feed samples, respectively, at concentrations of 0.05-70 mg/kg, whereas other ASs were barely found with rather lower concentrations. The annual mass loads of ASs consumed via pig feed consumption were estimated at 2400 tons worldwide. Thus, pig farming is an important source of ASs to the environment.

Combined effects of artificial sweetener acesulfame on the uptake of Cd in rice (Oryza sativa L.)

Organic pollutants are widely detected in surface water, groundwater and irrigation sewage in farmland soil, some of which can form complexes with heavy metal ions as ligands in the environment. Acesulfame (ACE), one of the most popular artificial sweeteners, has been found in wastewater sometimes at tens of microgram per liter. However, the combined effects of heavy metals and ACE are still unclear. In the present study, the effects of ACE on cadmium (Cd) absorption and translocation in rice seedlings (Oryza sativa L.) under different exposure conditions were investigated using hydroponic experiments. Under the combined exposure treatments of ACE and Cd, absorption of Cd and ACE in rice significantly decreased when compared with the single exposure treatments, while the alleviation of oxidative damage in rice was also found. Under the sequential exposure treatments of Cd and ACE, the post-exposed ACE activated the pre-absorbed Cd in plant, and accelerated the release of Cd to the environment as well as its translocation from the roots to shoots. In addition, compared with the single Cd exposure, the accumulated ACE can alleviate the oxidative damage in rice shoots induced by Cd, although the Cd concentrations in shoots changed little. In summary, the combined pollution of artificial sweetener ACE was beneficial to relieve the toxicological damage and ecological risk caused by Cd.

Influences of carbon and nitrogen sources and metal ions on the heterotrophic culture of Scenedesmus sp. LX1

In this study, the influences of organic carbon sources (OCS, including xylose, glucose, maltose, sucrose, and starch) and inorganic and organic nitrogen sources (INS, including ammonia chloride and sodium nitrate; ONS, including arginine, alanine, proline, and valine) and metal ions (including Na⁺, K⁺, Mn²⁺, Zn²⁺ and Cu²⁺) on the growth, lipid accumulation, and nitrogen and phosphorus (N&P) removal capabilities of oleaginous Scenedesmus sp. LX1 under heterotrophic conditions were investigated. The results showed that glucose was the only OCS for Scenedesmus sp. LX1 to grow well with specific growth rate of 0.935 days^-1, maximum biomass of 1.72 g L^-1, and largest removal rates of N&P and organic carbon reaching 72.228%, 93.034%, and 19.208%, respectively. After 11 days of cultivation, the maximal biomass reached in the group with starch or glucose while maximal lipid and triacylglycerol (TAG) yields reached in the groups with maltose and sucrose, respectively. Sodium nitrate was best nitrogen source as the largest algal density, maximal yields of lipids and TAGs, and highest N&P removal rates reached up to 1.105 × 10⁷ cells·mL^-1, 196.70 mg L^-1, 5.19 mg L^-1, 89.61% and 100%, respectively. Scenedesmus sp. LX1 was found to have great tolerance to Na⁺, K⁺, Mn²⁺, and Zn²⁺ while 0.5 mg L^-1 Cu²⁺ had a strong inhibition on growth and N&P removal rate of Scenedesmus sp. LX1. Concentration increasing of five metal ions all caused the yield increases of microalgal lipid and TAGs. Graphical abstract.

Fate of artificial sweeteners through wastewater treatment plants and water treatment processes

Five full-scale wastewater treatment plants (WWTPs) in China using typical biodegradation processes (SBR, oxidation ditch, A²/O) were selected to assess the removal of four popular artificial sweeteners (ASs). All four ASs (acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC)) were detected, ranging from 0.43 to 27.34μg/L in the influent. Higher concentrations of ASs were measured in winter. ACE could be partly removed by 7.11–50.76% through biodegradation and especially through the denitrifying process. The A²/O process was the most efficient at biodegrading ASs. Adsorption (by granular activated carbon (GAC) and magnetic resin) and ultraviolet radiation-based advanced oxidation processes (UV/AOPs) were evaluated to remove ASs in laboratory-scale tests. The amounts of resin adsorbed were 3.33–18.51 times more than those of GAC except for SUC. The adsorption ability of resin decreased in the order of SAC > ACE > CYC > SUC in accordance with the pKa. Degradation of ASs followed pseudo-first-order kinetics in UV/H₂O₂ and UV/PDS. When applied to the secondary effluent, ASs could be degraded from 30.87 to 99.93% using UV/PDS in 30 minutes and UV/PDS was more efficient and economic.

Investigation of ozonation kinetics and transformation products of sucralose

Sucralose is one of widely used artificial sweeteners, which has been ubiquitously detected in various water sources, such as wastewater and randomly in reservoir water. It is also reported to be persistent to various water treatment techniques. Although there are some studies on removal of sucralose by advanced oxidation process, limited information, in terms of reaction kinetics, transformation products and degradation pathway etc., was reported in its ozonation process. In this study, the reaction kinetics, removal efficiency, influence of pH, humic acid and carbonate on sucralose degradation by ozone, have been studied systematically. The results demonstrated that ozonation of sucralose was initiated by the formation of OH radical. Sucralose could be completely removed with excess O₃ at neutral and basic conditions in ultrapure water. The rate of degradation decreased significantly in acidic condition and in the presence of carbonate and OH radical scavenger (e.g. tert-butanol). The acidity was the key factor affecting the degradation of sucralose. The rate constant was about 500 times higher at pH7 than that at pH4. Transformation products study indicated that the ozonation of sucralose were more complex than that in photolysis reaction. Although ozonation of sucralose was initiated by OH radical, both OH radical and O₃ might be involved in the formation of transformation products and total organic carbon (TOC) removal. Various transformation products, such as aldehydes, carboxylic acids and probable chloride containing products, were identified and characterized in details. An ozonation degradation pathway of sucralose was proposed as well.

Characterization, Preparation, and Purification of Marine Bioactive Peptides

Marine bioactive peptides, as a source of unique bioactive compounds, are the focus of current research. They exert various biological roles, some of the most crucial of which are antioxidant activity, antimicrobial activity, anticancer activity, antihypertensive activity, anti-inflammatory activity, and so forth, and specific characteristics of the bioactivities are described. This review also describes various manufacturing techniques for marine bioactive peptides using organic synthesis, microwave assisted extraction, chemical hydrolysis, and enzymes hydrolysis. Finally, purification of marine bioactive peptides is described, including gel or size exclusion chromatography, ion-exchange column chromatography, and reversed-phase high-performance liquid chromatography, which are aimed at finding a fast, simple, and effective method to obtain the target peptides.

Occupational and life-style factors-acquired mutagenicity in agric-workers of northeastern Brazil

Pesticides are a complex mixture of chemicals used to protect crops from a number of pests and diseases. They have been considered as potential mutagenic agents. This study aims at evaluation of the mutagenic effect of pesticide exposure to agricultural workers through chromosomal aberrations (CA) and micronucleus (MN) assay in peripheral blood lymphocytes and oral mucosal cells, respectively. The exposed group was consisted with 97 farmers, while the control (un-exposed) group consisted of 55. The results showed a significant (p < 0.05) increase in frequency of CA and MN in the exposed group. Both CA and MN profiles were linked to a significant (p < 0.05) co-relation with the confounding factors such as smoking habits, alcohol, vegetables, tea/coffee, vitamins, and sweetener consumptions. More cytogenetic events were denoted in smoking and alcohol consumption as well as non-personal protective equipment (non-PPE) and low/no vegetables user farmers. In conclusion, a deficiency of dietary and medicaments-derived antioxidants, while consumption of alcohol and tobacco, as well as effects of radiation, heavy metal poisoning (especially from sweeteners), and non-PPE using habits, may contribute cytogenetic damage to the workers.

Ecotoxicological assessments show sucralose and fluoxetine affect the aquatic plant, Lemna minor

Pharmaceuticals and personal care products (PPCP) are prevalent in aquatic systems, yet the fate and impacts on aquatic plants needs quantification for many compounds. We measured and detected sucralose (an artificial sweetener), fluoxetine (an antidepressant), and other PPCP in the Portneuf River in Idaho, USA, where Lemna minor (an aquatic plant in the environment and used in ecotoxicology studies) naturally occurs. Sucralose was hypothesized to negatively affect photosynthesis and growth of L. minor because sucralose is a chlorinated molecule that may be toxic or unusable for plant metabolism. A priori hypotheses were not created for fluoxetine due to lack of previous studies examining its impacts on plants. We conducted laboratory ecotoxicological assessments for a large range of concentrations of sucralose and fluoxetine on L. minor physiology and photosynthetic function. Frond green leaf area, root length, growth rate, photosynthetic capacity, and plant carbon isotopic composition (discrimination relative to a standard; δ¹³C) were measured among treatments ranging from 0 to 15000nmol/L-sucralose and 0-323nmol/L-fluoxetine. Contrary to our predictions, sucralose significantly increased green leaf area, photosynthetic capacity, and δ ¹³C of L. minor at environmentally relevant concentrations. The increase of δ ¹³C from sucralose amendments and an isotope-mixing model indicated substantial sucralose uptake and assimilation within the plant. Unlike humans who cannot break down and utilize sucralose, we documented that L. minor-a mixotrophic plant-can use sucralose as a sugar substitute to increase its green leaf area and photosynthetic capacity. Fluoxetine significantly decreased L. minor root growth, daily growth rate, and asexual reproduction at 323nmol/L-fluoxetine; however, ambiguity remains regarding the mechanisms responsible and the applicability of these extreme concentrations unprecedented in the natural environment. To our knowledge, this was the first study to show aquatic plants can uptake and metabolize sucralose as a carbon source. This study further supports the common notion that L. minor can be useful in bioremediation of PPCP from wastewaters.

Biological effects of TiO2 and CeO2 nanoparticles on the growth, photosynthetic activity, and cellular components of a marine diatom Phaeodactylum tricornutum

It is very important to have a good understanding of the biological effects of nanoparticles (NPs) on marine diatoms. In this study, the physiological and biochemical responses of a marine diatom Phaeodactylum tricornutum to titanium dioxide NPs (nano-TiO₂) and cerium oxide NPs (nano-CeO₂) were compared and evaluated using 96h growth tests in a batch-culture system. At 96h of exposure, the growth inhibition rate (IR, %) of P. tricornutum increased from 5.46 to 27.31% with increasing nano-TiO₂ concentrations from 2.5 to 40mgL^-1. The maximum IR of 49.59% occurred in 40mgL^-1 nano-TiO₂ treatments at 48h of exposure. Growth of the diatom was increased in low nano-CeO₂ treatments (≤5mgL^-1), but was inhibited in high nano-CeO₂ treatments (≥10mgL^-1). Large aggregates of NPs were attached to the cells of P. tricornutum in 20 and 40mgL^-1 nano-TiO₂ and nano-CeO₂ treatments. In addition, the effective quantum yields (Φ_PSII) of P. tricornutum in 40mgL^-1 nano-TiO₂ and nano-CeO₂ treatments were 83.33 and 71.13% of that in the controls at 96h of exposure, respectively. Compared with that of the controls at 96h of exposure, chlorophyll a content, soluble sugar content, malondialdehyde (MDA) content, SOD and POD activities of P. tricornutum in 40mgL^-1 nano-TiO₂ and nano-CeO₂ treatments increased by 57.56, 142.97, 373.25, 698.76, 204.85% and 21.43, 89.41, 194.97, 340.05, 502.86%, while soluble protein content decreased by 70.38 and 28.64%, respectively. These findings will be helpful to understand the effect mechanisms of NPs on marine organisms.