Microalgal consortia differentially modulate progressive adsorption of hexavalent chromium

Assessing the Impact of Hexavalent Chromium (Cr VI) at Varied Concentrations on Spirulina platensis for Growth, Metal Sorption, and Photosynthetic Responses

Spirulina platensis, a photosynthetic cyanobacterium, has garnered attention for its potential role in environmental remediation due to its ability to absorb and metabolize toxic heavy metals. Understanding its response toward toxicity of one of the most common contaminants, Cr(VI) is crucial for assessing its efficacy in bioremediation efforts. This study aims to investigate the physiological and biochemical responses of Spirulina platensis to varying concentrations of Cr(VI) from 0.5 to 5 ppm, shedding light on its potential as a bioindicator for environmental contamination and its suitability for bioremediation purposes. The impact of Cr(VI) on cell density, biosorption, pigment levels, nutrient content, fluorescence response, and photosynthetic efficiency was examined. The study revealed a gradual reduction in cell density, biomass production, and biosorption efficiency with increasing Cr(VI) concentrations. Pigment levels, carbohydrate, protein, and lipid content showed significant decreases, indicating physiological stress. Fluorescence response and photosynthetic efficiency were also adversely affected, suggesting alterations in electron transfer dynamics. A threshold for chromium toxicity was observed at 0.5 ppm, beyond which significant physiological disturbances occurred. This investigation highlights the sensitivity of Spirulina platensis to Cr(VI) toxicity and its potential as a bioindicator for heavy metal contamination. Metal sorption was highest in 0.5 ppm Cr(VI) with 56.56% removal. Notably, at lower concentrations, Cr(VI) acted as an intermediate electron acceptor, enhancing the electron transport chain and potentially increasing biomass under controlled conditions. The findings underscore the importance of understanding the mechanisms underlying heavy metal stress in microalgae for effective environmental remediation strategies. The research highlights the dual role of chromium(VI) in influencing S. platensis, depending on the concentration, and underscores the importance of understanding metal ion interactions with photosynthetic organisms for potential applications in bioremediation.

Microalgal-induced remediation of wastewaters loaded with organic and inorganic pollutants: An overview

The recent surge in industrialization has intensified the accumulation of various types of organic and inorganic pollutants due to the illegal dumping of partially and/or untreated wastewater effluents in the environment. The pollutants emitted by several industries pose serious risk to the environment, animals and human beings. Management and diminution of these hazardous organic pollutants have become an incipient research interest. Traditional physiochemical methods are energy intensive and produce secondary pollutants. So, bioremediation via microalgae has appeared to be an eco-friendly and sustainable technique to curb the adverse effects of organic and inorganic contaminants because microalgae can degrade complex organic compounds and convert them into simpler and non-toxic substances without the release of secondary pollutants. Even some of the organic pollutants can be exploited by microalgae as a source of carbon in mixotrophic cultivation. Literature survey has revealed that use of the latest modification techniques for microalgae such as immobilization (on alginate, carrageena and agar), pigment-extraction, and pretreatment (with acids) have enhaced their bioremedial potential. Moreover, microalgal components i.e., biopolymers and extracellular polymeric substances (EPS) can potentially be exploited in the biosorption of pollutants. Though bioremediation of wastewaters by microalgae is quite well-studied realm but some aspects like structural and functional responses of microalgae toward pollutant derivatives/by-products (formed during biodegradation), use of genetic engineering to improve the tolerance of microalgae against higher concentrations of polluatans, and harvesting cost reduction, and monitoring of parameters at large-scale still need more focus. This review discusses the accumulation of different types of pollutants into the environment through various sources and the mechanisms used by microalgae to degrade commonly occurring organic and inorganic pollutants.

Chlorella sp. Protective Effect on Acetaminophen-Induced Liver Toxicity in ICR Mice

Background:

A Chlorella sp. (CLC) has a health supplement in health effects including an ability to treat cancer. The Chlorella sp. Ability to reduce acetaminophen-induced liver injury is still unknown. The hepatoprotective function of CLC was determined in an APAP-induced liver injury mouse model.

Methods:

Male ICR mice were randomly divided into normal control, APAP, APAP + Sm (silymarin) and APAP + CLC (0.2%, 0.5% and 1%) groups. The glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), Albumin, and BUN plasma activities were detected using blood biochemistry assay. The hepatic tissue GOT, GPT, superoxide dismutase (SOD) and catalase (CAT) activity were also detected. Lipid peroxidation, MDA, protein expression levels were examined.

Results:

The results showed that the 1% CLC supplementation group and Silymarin (Sm) could significantly alleviate increased serum GOT, GPT and BUN, and the decreased serum Albumin. At the same time, the increased hepatic tissue GOT and GPT activities were alleviated as well as MDA. Enhanced SOD and CAT protein expression levels were increased in APAP-induced liver injury. Lipofuscin and hepatic veins cups disappeared in the Sm and 1% CLC supplementation groups shown with H&E staining.

Conclusions:

Therefore, CLC probably could develop hepatoprotective products against chemical-induced liver damage.

Bioremediation of heavy metals using microalgae: Recent advances and mechanisms

Five heavy metals namely, arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb) and mercury (Hg) are carcinogenic and show toxicity even at trace amounts, posing threats to environmental ecology and human health. There is an emerging trend of employing microalgae in phycoremediation of heavy metals, due to several benefits including abundant availability, inexpensive, excellent metal removal efficiency and eco-friendly nature. This review presents the recent advances and mechanisms involved in bioremediation and biosorption of these toxic heavy metals utilizing microalgae. Tolerance and response of different microalgae strains to heavy metals and their bioaccumulation capability with value-added by-products formation as well as utilization of non-living biomass as biosorbents are discussed. Furthermore, challenges and future prospects in bioremediation of heavy metals by microalgae are also explored. This review aims to provide useful insights to help future development of efficient and commercially viable technology for microalgae-based heavy metal bioremediation.

Evaluation of carbon capture in competent microalgal consortium for enhanced biomass, lipid, and carbohydrate production

Enrichment of carbon dioxide (CO₂) in environment is a major factor for enhancement of global warming on Earth surface. Microalgal consortia play an important role in inhibiting the alarming fluxes of CO₂ through sustainable mechanism of bioconversion of CO₂ into biomass. In the present investigation, eight heterogeneous consortia of cyanobacteria and green algae such as MC1, MC2, MC3, MC4, MC5, MC6, MC7, and MC8 for the sustainable utilization of effective CO₂ sequestration and biomass production were studied. Two factorial central composite designs (% CO₂ and pH) were used for optimization of cellular morphology, growth, and development of consortia. The photosynthetic quantum yield of consortium MC8 was found to be maximum (0.61) in comparison with other consortia. The morphological and physiological behavior of the above consortium was analyzed under C, 5, 10, and 15% concentrations of CO₂ resource capture in 250 mL BG-11⁺ medium. We have identified that 10% CO₂ concentrated medium maximally promoted the cellular growth in terms of cell dimension, dried biomass, carbohydrate, and lipid contents in this consortium. As such, the elemental composition of carbon and carbon capturing capability was high at 10% CO₂ concentration. However, further CO₂ enrichment (15%) led to decline in growth and morphology of cell size as compared to control. The results indicate that the optimum CO₂ enrichment in consortia exhibits potent commercial utilization for rapid biomass production and plays a distinguished role in global carbon sequestration and mitigation agent.

Noninvasive determination of toxic stress biomarkers by high-throughput screening of photoautotrophic cell suspension cultures with multicolor fluorescence imaging

BACKGROUND

With increasing pollution, herbicide application and interest in plant phenotyping, sensors capturing early responses to toxic stress are demanded for screening susceptible or resistant plant varieties. Standard toxicity tests on plants are laborious, demanding in terms of space and material, and the measurement of growth-inhibition based endpoints takes relatively long time. The aim of this work was to explore the potential of photoautotrophic cell suspension cultures for high-throughput early toxicity screening based on imaging techniques. The investigation of the universal potential of fluorescence imaging methods involved testing of three toxicants with different modes of action (DCMU, glyphosate and chromium).

RESULTS

The increased pace of testing was achieved by using non-destructive imaging methods-multicolor fluorescence (MCF) and chlorophyll fluorescence (ChlF). These methods detected the negative effects of the toxicants earlier than it was reflected in plant growth inhibition (decrease in leaf area and final dry weight). Moreover, more subtle and transient effects not resulting in growth inhibition could be detected by fluorescence. The pace and sensitivity of stress detection was further enhanced by using photoautotrophic cell suspension cultures. These reacted sooner, more pronouncedly and to lower concentrations of the tested toxicants than the plants. Toxicant-specific stress signatures were observed as a combination of MCF and ChlF parameters and timing of the response. Principal component analysis was found to be useful for reduction of the collected multidimensional data sets to a few informative parameters allowing comparison of the toxicant signatures.

CONCLUSIONS

Photoautotrophic cell suspension cultures have proved to be useful for rapid high-throughput screening of toxic stress and display a potential for employment as an alternative to tests on whole plants. The MCF and ChlF methods are capable of distinguishing early stress signatures of at least three different modes of action.