This paper presents a facile and effective method for the large-scale production of carbon dots (CDs) from diverse coconut wastes (fronds, husk and shell). On comparing two different methods, namely (i) hydrothermal carbonization and (ii) novel sequential synthesis processes (pyrolysis followed by sonication), the latter procedure recorded a higher recovery of CDs (14.0%) over the hydrothermal method (2.33%). Doping agents such as urea, polyethyleneimine (PEI) and hexamethylenetetramine (HMTA) were chosen at varying concentrations to synthesize surface-modified CDs (SMCDs) for enhanced antibacterial properties. Among these SMCDs, urea-doped CDs _(1:1) @ 1000 ppm registered significantly higher cytotoxicity (20.6%) against Escherichia coli (E. coli). Subsequently, to assess the applicability of CDs as a disinfectant in water purification systems, two products, namely (i) CD-infused chitosan beads and (ii) pelletized CDs, were developed to ensure the immobilization of CDs. Studies with lab-scale prototypes have revealed that CDs infused chitosan beads reduced the colonies of E. coli from 5.41 × 10² CFU/mL (control group) to 2.16 × 10² CFU/mL, in comparison with pelletized CDs that decreased to 3.30 × 10² CFU/mL. The biosafety of CDs was assessed against Eisenia fetida for 21 days, and the observations revealed no mortality, even at 2000 ppm. Overall, this research demonstrated that a waste biomass can be effectively transformed into a novel water disinfectant. Furthermore, this scientific endeavor opens up research avenues to evolve advanced water purifiers using low-cost and eco-friendly nanomaterials.

The most effective agricultural practice to prevent iron deficiency in calcareous soils is fertilizing with synthetic chelates. These compounds are non-biodegradable, and persistent in the environment and hence there is a risk of leaching metals into the soil horizon. To tackle iron deficiency-induced chlorosis (IDC) in crops grown under calcareous soils, an environmentally friendly effective solutions are needed rather than chemical application as it affects the soil health further. Hence the present work aimed at isolating and screening calcareous soil-specific bacteria capable of producing the iron-chelating siderophores. Siderophore producing bacteria (SPB) was isolated from the rhizosphere of calcareous soil-grown groundnut (Arachis hypogea L.), of which seventeen bacterial isolates were positive for siderophore production assayed by Chrome Azurol Sulphonate. The performance of SPB isolates was compared for siderophore kinetics, level of siderophore production, type of siderophore produced (using Arnow and Csaky's tests), and iron-chelating capacity under 15mM KHCO₃. Four best performing bacterial isolates were screened, with average siderophores yield ranging ∼60–80% under pH 8, with sucrose as a carbon source and NH₂SO₄ as a nitrogen source at 37°C. The four efficient SPB were molecularly identified as Bacillus licheniformis, Bacillus subtilis, and Ochrobactrum grignonense based on 16S rDNA sequencing. The strains also showed a strong antagonistic effect against the phytopathogenic fungal strains viz., Sclerotium rolfsi and Macrophomina phaseolina in vitro. Our results indicate that the optimized conditions enhanced siderophores chelation and by suppressing the stem and root rot fungi which could help in cost effective and environmentally friendly manner.

Background: Naturally occurring iodide iodine exhibits complex soil behavior. Even though higher plants don’t consider iodine a vitamin, living things need it. Iodine is part of the thyroid hormone, which is vital to human health and metabolism. Potassium is the most effective cation for tomato plants and has a crucial role in improving several post-harvest quality characteristics in tomato fruits as well as in almost all vegetables. Methods: In the present work, we assessed the growth, yield and quality (Ascorbic acid, Titrable acidity and soluble solids) of tomatoesfrom different sources of chitosan and potassium iodate alone and combinations. The field experiment was carried out in the Thondamuthur block of Viraliyur village in the Coimbatore district of Tamil Nadu in 2022. The experiments were performed in randomized block design with three replications in palaviduthi soil series using hybrid tomato “Shivam”. Result: The chitosan iodate complex and foliar application combination enhanced the growth, yield and quality of tomato. Potassium iodate alone applied to soil and foliar, improved fruit quality but did not prevent acid loss during ripening. Chitosan reduces respiration and oxygen permeability to preserve losses. Thus, potassium iodate chitosan complex was favoured for boosting plant growth, fruit yield and quality.