Cost-effective tannery wastewater treatment using cyanobacteria: insights on the growth pattern and seedling vigor improvement with spent biomass.

Nowadays to cope-up with the emerging global clean-water crisis, wastewater needs to be remediated properly to be used as an alternative source. Here a cost-effective approach has been taken to treat heavily-polluted (BOD-1234.33 mg L-1, COD-1706.64 mg L-1, TDS-6984 mg L-1, and sulfide-140.8 mg L-1 ammonium-134.5 mg L-1) Tannery Waste Water (TWW). Three cyanobacteria were (Arthrospira platensis, Leptolyngbyavalderiana, and Anabaenasphaerica) used as bio-reagents in pilot-scale treatment. Wastewater remediation-potential and biomass-generation capacity were evaluated in various TWW concentrations. The maximum biomass growth and the highest pollution removal percentage was observed when exposed to 50% TWW; although among the tested strain, Arthrospira and Leptolyngbya performed better than Anabaena by showing greater pollution removal potential (BOD 93%, COD 94%, sulfide 99%, ammonium 93%) in one hand and higher biomass production rate (100 mg L-1 Day-1) on the other. DO was increased noticeably by 10-15-fold. Morphological characterizations of tannery wastewater exposed Anabaena revealed unusual thick sheath formation, along with heterocyst and akinete formation in their trichome. Biochemical characterizations of remediating cyanobacteria showed presence of wastewater-accumulated nutrients (N, P, K). Nutrient-loaded biomass improved growth of rice and chickpea seedlings when used as a growth promoter. These facts have been illustrated by factor analysis and discriminant analysis. Cyanobacteria-mediated pilot-scale tannery wastewater treatment would create ecologically and economically-sustainable technology for clean-water production. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03712-x.

A state of the art review on the co-cultivation of microalgae-fungi in wastewater for biofuel production.

The microalgae have a great potential as the fourth generation biofuel feedstock to deal with energy crisis, but the cost of production and biomass harvest are the major hurdles in terms of large scale production and applications. Using filamentous fungi to culture targeted alga for biomass accumulation and eventually harvesting is a sustainable way to mitigate environmental impacts. Microalgal co-culture method could be an alternative to overcome limitations and increase biomass yield and lipid accumulation. It was found to be the high feasibility for the production of biofuels from fungi and microalgae using wastewater. This article aimed to state the synergistic approaches, their culture protocols, harvesting procedure and their potential biotechnological applications. Additionally, algal-fungal consortia could digest cellulosic biomass, potentially reducing operating costs as part of industrial need. As a result of co-cultivation, biofuel production could be economically feasible owing to its excellent ability to treat wastewater and be eco-friendly. The implications of the innovative co-cultivation technology have demonstrated the potential for further development based on the policies that have been supported and implemented.

Rice grain arsenic and nutritional content during post harvesting to cooking: A review on arsenic bioavailability and bioaccessibility in humans.

Rice (Oryza sativa L.) is considered as the staple food for 50% of the world's population. Humans are exposed to arsenic (As) through rice consumption, which is a global health issue that requires attention. The present review reflects the scenario of rice grown in As endemic regions of Asia that has a significant portion of inorganic As (iAs) compared to other rice grown areas around the world. Post-harvesting, pre-cooking, and cooking procedures in South and South-East Asian countries employ As-contaminated groundwater. Polishing of brown rice and parboiling, washing and cooking with As-safe water can reduce As concentration and nutrient level in cooked rice. However, in rural parts of South-east Asia, rice is usually cooked using As-contaminated groundwater and consumption of this As enriched rice and water may cause a significant health exposure in humans. Bioaccessibility and bioavailability of As can be determined using in-vitro and in-vivo techniques that can be utilized as a tool to assess As exposure in humans. Arsenic in cooked rice may be reduced by using newly developed cooking procedures such as Kateh cooking, steam percolating, and the parboiled and absorbed (PBA) method. For individuals living in rural regions, using rainwater or treated surface water for drinking and cooking is also an alternative. Although this study examined the processes involved in the post-harvesting, pre-cooking, and cooking stages, there are still significant research gaps in this area that must be addressed in near future.

Spatiotemporal variations in the composition of algal mats in wastewater treatment ponds of tannery industry.

Wastewater Treatment Pond (WTP) is an effective remediation technology for economically developing nations. Although it's excessive organic and nutrient loads with higher water logging time triggers mixed and unprofitable microalgal mats. This may serve as a seeding source for Cyanobacterial bloom in receiving waterbodies. Since, to maintain the growth of desirable algal species in WTPs, understanding towards environmental regulation and algal mat composition is important, especially for tropical countries, like India. In this study, biological treatment pond (BTP) and outlet pond (OP), of a tannery effluent treatment plant in eastern coast of India, were chosen for surveying the algal community composition concerning ecological parameters. Nearly, both the ponds were polluted, but the diversity was lower in BTP due to its elevated nutrient content (Ammonia 173 mg L-1) and higher persistent organic matters (COD 301.7 mg L-1) than OP. Using canonical correspondence analysis, seasonal variations showed higher species abundance during early summer compared to other seasons. A total of 37 taxa forming thick algal mats were recorded. The matrix of mats was mainly composed of Cyanobacterial members such as Phormidium, Leptolyngbya, Spirulina, and Pseudanabaena, followed by diatoms, especially Amphora and Nitzschia. Diatoms commonly occurred as embedded component in the entangled matrix of blue-green algal filaments. Hierarchical cluster analysis was employed to group all these taxa based on their seasonal appearance and abundance. This year-long intensive study revealing seasonal algal mat composition patterns in these WTPs will ultimately safeguard the livelihood and security of adjoining localities through proper site-specific pollution control.

Co-Cultivation of Leptolyngbya tenuis (Cyanobacteria) and Chlorella ellipsoidea (Green alga) for Biodiesel Production, Carbon Sequestration, and Cadmium Accumulation.

The co-cultivation approach using cyanobacteria-Leptolyngbya tenuis and green alga-Chlorella ellipsoidea demonstrated in the present study showed additive and synergistic effects on biomass yield, biomass productivity, lipid yield, lipid productivity, CO2 fixation, and cadmium bioremediation efficiency. The results of co-culture in batch mode revealed about 2-3 times increase in biomass and two times increase in total lipid, when compared to the pure culture batches. The results revealed that co-cultures exhibited significantly high CO2 fixation rate of 2.63  ±  0.09 g/L/d, which is 1.5-2 times better than monocultures (P < 0.05). To explore the bioaccumulation of cadmium by co-cultures and pure cultures, different concentrations of cadmium nitrate was used in flask trials. Cadmium accumulation was observed in the order: co-culture (74%, 0.37 mg/L) > Chlorella (58%, 0.29 mg/L) > Leptolyngbya (50%, 0.25 mg/L) (P < 0.05). In addition, fatty acid composition, CHNS analysis, biodiesel characterization, and biochemical compositions were also determined using co-culture method. The maximum biomass yield, productivity, lipid content, and CO2 fixation rate in cadmium induced co-culture were 3.95  ±  0.13 g/L, 258.88  ±  15.75 mg/L/d, 41.43  ±  0.71%, and 3.21  ±  0.20 g/L/d, respectively which is 1.2, 1.3, 2.3, and 1.2 times higher than the control (P < 0.05). Cadmium induced changes in growth and lipid yield using co-culture suggests cost-effective and eco-friendly production of biodiesel and carbon mitigation.

In-situ green synthesis of fluorescent silica-silver conjugate nanodendrites using nanoporous frustules of diatoms: an unprecedented approach.

Generally, nanodendrite synthesis is chemical mediated and expensive. The biogenesis of such hierarchical structures is still in its nascent stage. The present study aimed at exploiting the nanoporous frustules of Halamphora subturgida, as a source of biosilica for the biosynthesis and stabilization of conjugate nanodendrites of silica and silver. These minute diatom frustules when exposed to 9 mM of silver nitrate solution, a highly crystalline nanohybride dendrites were synthesized. The nanohybrid dendrite synthesis was initially confirmed by the formation of greyish-brown frustules after 72 h of exposure. The composite dendrites were thoroughly characterized by standard techniques. Electron microscopic images illustrated that the process began with the formation of isotropic hybrid nanospheres with an internal diameter of 20 nm and continued to develop anisotropic nanocrystals with time. The nanodendrites externally formed on the siliceous frustules, acting as a template for the former. They were characterized by distinct 100 nm wide and 1-2 µm long trunks and 70-100 nm wide and 220-220 nm long branches on either side of the trunk. The optical measurement revealed the fluorescence property of the nanostructures owing to the photoluminescent efficiency of the frustules. Both the externally derived hybrid nanodendrites and internally synthesized nanospheres possessed superior stability in the suspension with a zeta potential value of - 35.7 mV and - 24.8 mV, respectively. Thus, this method is eco-friendly and provides a new dimension for nanodendrite synthesis with minimal cost and maximal yield compared to its non-biologically synthesized counterparts that involve several other drawbacks like chemical hazards and high energy consumption.

Carbon sequestration in macroalgal mats of brackish-water habitats in Indian Sunderbans: Potential as renewable organic resource.

Large influx of excess nutrients into sub-tropical brackish-water habitats is expected to radically affect the algal populations in the heavily populated Sunderbans brackish-water ecozone. Twelve selected brackish-water sites in the Indian Sunderbans were surveyed to investigate the growth performance of mat-forming dominant algal/cyanobacterial macrophytes and their potential for carbon (C) sequestration into hydrologic and pedologic pools. The mats were dominated by particular taxa at different seasons related to physico-chemical properties of the wetland habitats. Different environmental variables and biomass productivity parameters were measured on fortnightly basis to assess the carbon cycle related to dominant algal blooms of the study area. The dominating species at the twelve sites included seven genera (Spirogyra, Rhizoclonium, Ulva, Cladophora, Pithophora, Chaetomorpha) belonging to Chlorophyta, three genera (Polysiphonia, Gracilaria, Catenella) belonging to Rhodophyta and Lyngbya majuscula from cyanobacteria. Multivariate statistical methods indicated that nutrient availability, particularly dissolved P concentration and N:P ratio in the water column, along with salinity in the water column mainly affected biomass yield and C sequestration of mat-forming macrophytes and OC input into water column. However, OC contents of underlying muck proved to be very stable, though small influxes of OC occurred at each bloom. High biomass yields (34-3107 g/m2) of the dominant mat components accumulated enormous stocks of OC, very little of which reaches the pedologic pool. This transient biomass might be utilized as dietary supplements or biofuel feedstocks. Availability of important dietary fatty acids in Spirogyra punctulata, Gracilaria sp., Polysiphonia mollis, Rhizoclonium riparium, R. tortuosum, Pithophora oedogonia and Ulva lactuca was considered as suitability of these species as nutraceuticals. Fatty acid compositions of L. majuscula, Catenella repens, R. tortuosum and Cladophora crystallina were estimated to be applicable for producing biodiesel for usage in sub-tropical climates.

Phytoplankton nutrient dynamics and flow cytometry based population study of a eutrophic wetland habitat in eastern India, a Ramsar site.

Phytoplankton diversity, their abundance based on flow cytometric (FCM) analysis and seasonal nutrient dynamics were investigated from a waste water fed wetland of Eastern India (88° 24.641'E and 22° 33.115'N). The primary objective of the study was to correlate the seasonal fluctuations in phytoplankton abundance to the environmental variables. Total chlorophyll content and FCM based cell counts were used to characterize and quantify the phytoplankton population. Multivariate statistical methods were employed in predicting the possible relationships between biotic and abiotic variables. Distinct seasonal variations characterized by high abundance during the pre-summer period compared to other seasons were detected. The results indicated that environmental factors like water temperature and nutrients, such as various forms of nitrogen and phosphate, influenced the seasonal phytoplankton accumulation. Cluster analysis and non-metric multidimensional scaling helped analyze the seasonal distribution of phytoplankton based on their composition. The dominant genera among the entire phytoplankton community were Scenedesmus spp. of Chlorophyta, followed by Merismopedia spp. of Cyanoprokaryota. Around 3.7 × 105 phytoplankton mL-1 were recorded during the study period. Due to the very high count of individual species in the community, FCM based counting was applied for determination of Species Diversity Index. The entire population was divided into 13 subpopulations based on the cell sorting method and the seasonal abundance in each sub-population was illustrated.

Nitric oxide sensing by chlorophyll a.

Nitric oxide (NO) acts as a signalling molecule that has direct and indirect regulatory roles in various functional processes in biology, though in plant kingdom its role is relatively unexplored. One reason for this is the fact that sensing of NO is always challenging. There are very few probes that can classify the different NO species. The present paper proposes a simple but straightforward way for sensing different NO species using chlorophyll, the source of inspiration being hemoglobin that serves as NO sink in mammalian systems. The proposed method is able to classify NO from DETA-NONOate or (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino] diazen-1-ium-1,2-diolate, nitrite, nitrate and S-nitrosothiol or SNO. This discrimination is carried out by chlorophyll a (chl a) at nano molar (nM) order of sensitivity and at 293 K-310 K. Molecular docking reveals the differential binding effects of NO and SNO with chlorophyll, the predicted binding affinity matching with the experimental observation. Additional experiments with a diverse range of cyanobacteria reveal that apart from the spectroscopic approach the proposed sensing module can be used in microscopic inspection of NO species. Binding of NO is sensitive to temperature and static magnetic field. This provides additional support for the involvement of the porphyrin ring structures to the NO sensing process. This also, broadens the scope of the sensing methods as hinted in the text.

Hydrolysate of lipid extracted microalgal biomass residue: An algal growth promoter and enhancer.

The present study demonstrates the utilization of the algal hydrolysate (AH) prepared from lipid extracted residual harmful bloom-forming cyanobacteria Lyngbya majuscula biomass, as a growth supplement for the cultivation of green microalgae Chlorella vulgaris. BG-11 replacements with AH in different proportions significantly affects the cell count, dry cell weight (DCW), biomass productivity (BP) and pigments concentration. Among all, 25% AH substitution in BG11 media was found to be optimum which enhanced DCW, BP and pigments content by 39.13%, 40.81% and 129.47%, respectively, compared to control. The lipid content (31.95%) was also significantly higher in the 25% AH replacement. The volumetric productivity of neutral lipids (ideal for biodiesel) and total protein content of the cells significantly increased in all AH substitutions. Thus, lipid extracted microalgal biomass residue (LMBR) hydrolysate can be a potential growth stimulating supplement for oleaginous microalgae C. vulgaris.

Rapid Accumulation of Total Lipid in Rhizoclonium africanum Kutzing as Biodiesel Feedstock under Nutrient Limitations and the Associated Changes at Cellular Level.

Increase of total lipid and the proportion of the favorable fatty acids in marine green filamentous macroalga Rhizoclonium africanum (Chlorophyceae) was studied under nitrate and phosphate limitations. These stresses were given by both eliminating and doubling the required amounts of nitrate and phosphate salts in the growth media. A significant twofold increase in total lipid (193.03 mg/g) was achieved in cells in absence of nitrate in the culture medium, followed by phosphate limitation (142.65 mg/g). The intracellular accumulation of neutral lipids was observed by fluorescence microscopy. The scanning electron microscopic study showed the major structural changes under nutrient starvation. Fourier transform infrared spectroscopy (FTIR) revealed the presence of ester (C-O-C stretching), ketone (C-C stretching), carboxylic acid (O-H bending), phosphine (P-H stretching), aromatic (C-H stretching and bending), and alcohol (O-H stretching and bending) groups in the treated cells indicating the high accumulation of lipid hydrocarbons in the treated cells. Elevated levels of fatty acids favorable for biodiesel production, that is, C16:0, C16:1, C18:1, and C20:1, were identified under nitrate- and phosphate-deficient conditions. This study shows that the manipulation of cultural conditions could affect the biosynthetic pathways leading to increased lipid production while increasing the proportion of fatty acids suitable for biodiesel production.

Spray Dried Extract of Phormidium valderianum as a Promising Source of Natural Antioxidant.

Microencapsulation of antioxidant-rich fraction obtained by supercritical carbon dioxide extraction (at 50°C, 500 bar with extraction time of 90 min, and flow rate of CO2 at 2 L/min) of lyophilized biomass of Phormidium valderianum was carried out in a spray dryer using maltodextrin and gum arabic. Microencapsulation conditions that provided the best combination of phytochemical properties such as antioxidant activity, phenolic content, and reducing power with reasonable powder yield were an inlet temperature of 130°C and wall material composition as maltodextrin: gum arabic = 70 : 30. Toxicological study reported that the Anatoxin-a content of this encapsulated powder was below the limit of detection of HPLC. Storage study established that encapsulation of this antioxidant-rich algal extract resulted in eight times enhancement of half-life (T 1/2) values. The release profile of microencapsulated antioxidant-rich fraction from the encapsulated powder was found to follow first order anomalous transport kinetics. Therefore, this microencapsulated algal extract with minimum toxicity is a source of natural antioxidant and could have promising use as novel dietary supplement.

Accumulation of lead by free and immobilized cyanobacteria with special reference to accumulation factor and recovery.

Lead accumulation by free and immobilized cyanobacteria, Lyngbya majuscula and Spirulina subsalsa was studied. Exponentially growing biomass was exposed to 1-20mg L(-1) of Pb(II) solution at pH 6, 7 and 8 for time periods ranging from 10 min to 48 h. L. majuscula accumulated 10 times more Pb (13.5 mg g(-1)) than S. subsalsa (1.32 mg g(-1)) at pH 6 within 3h of exposure to 20mg L(-1) Pb(II) solution and 76% of the Pb could be recovered using 0.1M EDTA. This chelator (2 µM) did not influence Pb accumulation whereas 100 µM citrate increased that of S. subsalsa 6- to 8-fold. L. majuscula filaments enmeshed in a glass wool packed in a column removed 95.8% of the Pb from a 5mg L(-1) Pb solution compared to free and dead biomass which removed 64 and 33.6% Pb respectively. A 92.5% recovery of accumulated Pb from the immobilized biomass suggests that repeated absorption-desorption is possible.

Variations in seasonal phytoplankton assemblages as a response to environmental changes in the surface waters of a hypo saline coastal station along the Bhagirathi-Hooghly estuary.

Due to the close proximity of the Bay of Bengal and the freshwater inflow of Bhagirathi-Hooghly, Diamond Harbour appeared as an important coastal station of the Bhagirathi-Hooghly estuary. The spatial and temporal composition and abundance of microphytoplankton species was examined in relation to physical and chemical surface water variables (i.e., salinity, nutrient, and temperature).The primary objective of the study was to observe the variations in phytoplankton species assemblages as a response to environmental variables. Hierarchical cluster analysis and non-metric multidimensional scaling were used to find out distinct seasonal groups based on the composition of phytoplankton. The results indicate that several key environmental factors like temperature, DIN content, and molar ratio of nutrients like DIN-DIP and DIN-DSi influenced seasonal phytoplankton assemblages within the estuary. The distribution of phytoplankton population showed two main groups where the blue-green and green algal populations favored the warmer conditions of summer and monsoon months, whereas the diatom population primarily flourished in the cooler months of autumn and winter.