Biomass valorization of agriculture wastewater grown freshwater diatom Nitzschia sp. for metabolites, antibacterial activity, and biofertilizer

In-vitro assessment and characterization of anticancer, antibacterial, and antioxidant activity of diatom-derived metabolites

Microalgae are known to produce a spectrum of highly valuable metabolites with substantial nutritional content and pharmacogenetic properties. To explore the antioxidant, antibacterial, as well as anticancer activity of five such microalgal strains isolated from the Indian subcontinent, solvent-based extracts were prepared using methanol:chloroform (S1, v/v) and ethyl acetate (S2). The DPPH and ABTS radical scavenging assays revealed maximum inhibition (65.42% and 69.73%) by S1 extract of Cylindrotheca sp. (D3) and 72.08% and 77.43% by S2 extracts of Chaetoceros sp. (D1), respectively. Both S1 and S2 extract of Cylindrotheca sp. showed maximum zone of inhibition (24 ± 0.4 mm) against Aeromonas sp. and Streptococcus pneumoniae. Further, in-vitro anticancer assessment was also done against renal adenocarcinoma (ACHN), lung carcinoma (A549), and ovarian carcinoma (SK-OV3) cell lines. Highest cytotoxicity was observed when SK-OV3 (63.3%) and A549 (53.6% ) cells were treated with 250 µg mL-1 of S1D1 extract. Major bioactive constituents identified by GC-MS estimation included palmitic, heptadecaenoic, octadecanoic, linoleic, eicosapentaenoic acid, 2,4-Di tertbutyl phenol, and Desulphosinigrin amongst others. Thus, this study provides an insightful and holistic overview on microalgal bioactivities and their potential as natural therapeutic resources targeting different human pathogenic disorders and diseases.

Overexpression of PtNRPS1 enhances diatom-mediated bioremediation of salicylate pollution

The accumulation of the emerging pollutant salicylic acid (SA) in the environment has gained much attention. In this study, overexpression of the non-ribosomal peptide synthase (NRPS) gene, PtNRPS1 in the marine diatom Phaeodactylum tricornutum (PtNRPS1-OE) increased resistance to SA pollutants. It was assumed that the enhanced tolerance was due to the high binding affinity between recombinant PtNRPS1 (rNRPS1) and SA pollutants. Moreover, tandem mass spectrometry analysis determined the amino acids that participated in the covalently binding of SA. The removal efficiency of SA pollutants by PtNRPS1-OE cells was found to be markedly elevated. The mechanism underlying the removal of SA and 5-substituted SA (5-sSA) was proposed, following the co-localization analysis of rNRPS1 and SA. The purpose of this study was not about using PtNRPS1 as an enzyme to catalyze the synthesis of metabolite. Rather, it explored the possibility of using PtNRPS1 to remove pollutants, which further improves practical feasibility of microalgae-mediated bioremediation.

Review of recent advances in utilising aquaculture wastewater for algae cultivation and microalgae-based bioproduct recovery

Aquaculture operations produce large amounts of wastewater contaminated with organic matter, nitrogenous compounds, and other emerging contaminants; when discharged into natural water bodies, it could result in ecological problems and severely threaten aquatic habitats and human health. However, using aquaculture wastewater in biorefinery systems is becoming increasingly crucial as advancements in valuable bioproduct production continue to improve economic feasibility. Research on utilising microalgae as an alternative to producing biomass and removing nutrients from aquaculture wastewater has been extensively studied over the past decades. Microalgae have the potential to use carbon dioxide (CO2) effectively and significantly reduce carbon footprint, and the harvested biomass can also be used as aquafeed. Furthermore, aquaculture wastewater enriched with phosphorus (P) is a potential resource for P recovery for the production of biofertiliser. This will reduce the P supply shortage and eliminate the environmental consequences of eutrophication. In this context, the present review aims to provide a comprehensive overview of the current state of the art in a generation, as well as the characteristics and environmental impact of aquaculture wastewater reported by the most recent research. Furthermore, the review synthesized recent developments in algal biomass cultivation using aquaculture wastewater and its utilisation as biorefinery feedstocks for producing value-added products, such as aquafeeds, bioethanol, biodiesel, biomethane, and bioenergy. This integrated process provides a sustainable method for recovering biomass and water, fully supporting the framework of a circular economy in aquaculture wastewater treatment via resource recovery.

Marine diatom algae cultivation in simulated dairy wastewater and biomass valorization

Liquid byproducts and organic wastes generated from dairy processing units contribute as the largest source of industrial food wastewater. Though bacteria-mediated treatment strategies are largely implemented, a more effective and innovative management system is needed of the hour. Thus, the current study involves the cultivation of centric diatoms, Chaetoceros gracilis, and Thalassiosira weissflogii in simulated dairy wastewater (SDWW) formulated using varying amounts of milk powder with artificial seawater f/2 media (ASW). The results revealed that cell density and biomass productivity were highest in the 2.5% SDWW treatment cultures of both the strains, the maximum being in C. gracilis (7.5 × 106 cells mL - 1; 21.1 mg L-1 day-1). Conversely, the total carotenoid, chrysolaminarin, and phenol content were negatively impacted by SDWW. However, a considerable enhancement in the total lipid content was reported in the 2.5% SDWW culture of both species. Furthermore, the fatty acid profiling revealed that though the total polyunsaturated fatty acid (PUFA) content was highest in the control setups, the total mono polyunsaturated fatty acid (MUFA) content was higher in the 5% SDWW setups (30.66% in C. gracilis and 33.21% in T. weissflogii). In addition to it, in the cultures utilizing energy from external carbon sources provided by SDWW, the biodiesel produced was also enhanced owing to the heightened cetane number. Thus, the current study evidently highlights the organic carbon acquisition potential of marine diatoms with the scope of providing sustainable biorefinery.

Ultrasonic-assisted green extraction and incorporation of Spirulina platensis bioactive components into turmeric essential oil-in-water nanoemulsion for enhanced antioxidant and antimicrobial activities

The utilization of essential oils as natural antioxidants and preservatives is limited by high volatility, poor water solubility, and long-term instability. To address this, a novel ultrasonic-assisted method was used to prepare and stabilize a nanoemulsion of turmeric essential oil-in-water, incorporating bioactive components extracted from Spirulina platensis. Ultrasonic treatment enhanced the extraction efficacy and nanoemulsion stability. Algal biomass subjected to ultrasonic treatment (30 min at 80% amplitude) yielded a dry extract of 73.66 ± 3.05%, with the highest protein, phenolic, phycocyanin, and allophycocyanin content, as well as maximum emulsifying activity. The resulting nanoemulsion (5% oil, 0.3% extract, 10 min ultrasonic treatment) showed reduced particle size (173.31 ± 2.24 nm), zeta potential (-36.33 ± 1.10 mV), low polydispersity index, and enhanced antioxidant and antibacterial properties. Rheology analysis indicated shear-thinning behavior, while microscopy and spectroscopy confirmed structural changes induced by ultrasonic treatment and extract concentration. This initiative developed a novel ultrasonic-assisted algal-based nanoemulsion with antioxidant and antibacterial properties.

Biomimetic Diatom Biosilica and Its Potential for Biomedical Applications and Prospects: A Review

Diatom biosilica is an important natural source of porous silica, with three-dimensional ordered and nanopatterned structures referred to as frustules. The unique features of diatom frustules, such as their high specific surface area, thermal stability, biocompatibility, and adaptable surface chemistry, render diatoms valuable materials for high value-added applications. These attributes make diatoms an exceptional cost-effective raw material for industrial use. The functionalization of diatom biosilica surface improves its biophysical properties and increases the potential applications. This review focuses on the potential uses of diatom biosilica including traditional approaches and recent progress in biomedical applications. Not only well-studied drug delivery systems but also promising uses on bone regeneration and wound healing are covered. Furthermore, considerable aspects and possible future directions for the use of diatom biosilica materials are proposed to develop biomedical applications and merit further exploration.

Towards sustainable diatom biorefinery: Recent trends in cultivation and applications

Diatoms, with their complex cellular architecture, have been recognized as a source of limitless potential. These microbes are common in freshwater and marine habitats and are essential for primary production and carbon sequestration. They are excellent at utilizing nutrients, providing a sustainable method of treating wastewater while also producing biomass rich in beneficial substances like vitamins, carotenoids, polysaccharides, lipids, omega-3 fatty acids, pigments, and novel bioactive molecules. Additionally, they are highly efficient organisms that can be employed to monitor the environment by acting as trustworthy indicators of water quality. This comprehensive review explores the multifaceted applications of diatoms in a variety of fields, such as bioremediation, aquaculture, value-added products, and other applications. The review set out on a path towards greener, more sustainable methods amicable to both industry and the environment by utilizing theenormous diverse biotechnological potentials of diatoms.