Koushik Ghosh

The aquatic biome is exposed to a significant threat of persistent contamination by polyethylene (PE) in the ecosystem. A critical research gap exists in PE‐induced tissue‐specific bioaccumulation, associated immune and stress responses in fish, followed by potential bioremediation solutions. The present study investigated the bioaccumulation of PE particles and subsequent oxidative stress in Labeo rohita induced by two different doses (0.1 and 0.5 mg/L) over 2 weeks. Additionally, the biodegradation potential of gut‐associated microbial isolates was also evaluated. We found that PE accumulation was highest in the intestine (33.0 ± 2.5 particles/g), followed by gills (20.5 ± 1.9 particles/g) and liver (8.0 ± 1.4 particles/g), indicating a significant, dose‐ and time‐dependent increase. Substantially, it triggered a tissue‐wise oxidative stress response of antioxidant ( SOD , CAT , GPx ) and stress marker ( Hsp70 ) genes, showing significant upregulation in gill, liver, and intestine. Furthermore, this work identified a gut‐associated bacterium, Proteus vulgaris KG‐SD‐15807, demonstrating significant PE biodegradation capability. Quantitative analysis revealed achievement of 3.00% ± 0.16% weight loss over 30 days of incubation. Qualitative characterization through FT‐IR, FE‐SEM, and GC–MS analyses indicated polymer oxidation, surface erosion, and formation of distinct metabolic degradation intermediates. The present findings reveal the significant bioaccumulation and stress response due to PE in a commercially important fish, Labeo rohita . Moreover, the identified bacterium acted as a PE biodegradation agent. This research has significant implications for future explorations focused on the long‐term impacts of PE in aquatic animals and the optimization of biodegradation efficiency of Proteus vulgaris for applied bioremediation.

1. The expansion and intensification of aquaculture have heightened concerns regarding pathogenic diseases and stress in fish populations. While antibiotics are frequently employed to manage these ...

The microbial community on plastic surfaces, known as the plastisphere, plays a vital role in the bioremediation of complex environmental pollutants at urban waste disposal sites. Since non‐culturable strains that survive on polymer substrates are very common, only a small group of microbes has been identified to date. This study examined the predictive functional dynamics of beneficial microbial communities associated with the plastisphere at four plastic‐rich urban disposal sites near Kolkata, West Bengal, India. Collection of disposed polyethylene carry bags were followed by biofilm extraction, gDNA isolation, library preparation, and sequencing. Results showed that Betaproteobacteria (0.35%–37.02%), Gammaproteobacteria (3.10%–22.38%), Dehalococcoides sp. (0.05%–10.15%), Flavobacterium sp. (0.02%–8.31%), and Spirulina sp. (0.06%–1.21%) were the most prevalent genera with strong bioremediation potential. Functional profiling identified essential metabolic pathways, such as general function prediction (10.37%–20.45%), followed by amino acid transport and metabolism (13.64%–15.85%), cell wall/membrane/envelope biogenesis (5.49%–18.18%), and coenzyme transport and metabolism (2.27%–14.29%). Key enzymes like Lipase (0.04%–66.67%), Cytochrome p450 (1.90%–36.63%), OpdA (0.03%–33.33%), and Laccase Dehalogenase (2.46%–15.03%), that aid in environmental pollutant remediation were also predicted. The present study provides a comprehensive metagenomic profiling to identify key microbial taxa and their functional genes involved in pollutant degradation in the said locations. This work offers insights for developing a predictive framework for targeted bioremediation strategies in pollution mitigation.

The widespread use and environmental persistence of polyethylene (PE) have led to a global pollution crisis, which is intensified by its fragmentation into hazardous micro- and nanoplastics. Although bioremediation using polymer-degrading microbes presents a sustainable alternative, only a limited microbes have been identified, primarily due to the challenges of culturing potential degraders in the laboratory. We isolated two P. aeruginosa strains (SKD-SD-3171 and SS-SD-7780) from urban waste disposal areas and comparatively evaluated their PE degrading efficacy, over 120 days. Both strains utilized PE as a carbon source, as confirmed by weight loss (24.53±0.35% for P. aeruginosa SKD-SD-3171 and 22.50±0.35% for P. aeruginosa SS-SD-7780), polymer reduction rate (K=0.00235 day⁻¹±0.00004 for P. aeruginosa SKD-SD-3171 and 0.00212 day⁻¹±0.00004 for P. aeruginosa SS-SD-7780), and calculation of half-life (t1/2=295.55±4.77 for P. aeruginosa SKD-SD-3171 and 326.39±5.94 for P. aeruginosa SS-SD-7780) after the incubation in a carbon-free medium. Biodegradation was further validated using fourier transform infrared spectroscopy (FT-IR), which showed structural alterations, and field emission scanning electron microscopy (FE-SEM), which revealed surface erosion in PE, following microbial treatment. Additionally, gas chromatography-mass spectrometry (GC-MS) identified degradation intermediates whose kinetic profiling revealed effective polyethylene degradation through biodegradation efficiency metrics. Our findings demonstrate that P. aeruginosa SKD-SD-3171 exhibits comparatively faster and consistent polyethylene degradation kinetics than P. aeruginosa SS-SD-7780 under laboratory-based conditions and it also establishes effective methodological framework for isolation, selection and evaluation of specific polymer-degrading microorganisms using advanced analytical techniques. These findings provide insights into developing PE-waste management strategies like enzyme characterization, followed by field-scale validation to enhance degradation kinetics.

The present study was performed to investigate the basic chemical composition and nutritional value of 10 terrestrial plant leaves (viz. Mangifera indica, Litchi chinensis, Artocarpus heterophyllus, Ziziphus mauritiana, Albizia lebbeck, Tamarindus indica, Cicer arietinum, Bauhinia acuminata, Delonix regia and Peltophorum pterocarpum ) abundant in tropical and subtropical environments. The leaf meals were evaluated comprehensively, encompassing proximate composition (% dry matter), amino acids, fatty acids, antinutritional factors (ANFs), antioxidants and antibacterial potential using established methodologies. The crude protein (CP) content of the leaves ranged from 10.92% to 20.74% (w/w), with the highest content observed in A . lebbeck leaves. The crude lipid (CL) and crude fibre (CF) contents varied between 1.23%–5.38% and 13.73%–24.63%, respectively (w/w). The protein‐to‐energy ratio (P/E) ranged between 32.32 and 60.70 mg/kcal, with significantly higher ( p < 0.05) P/E in A. lebbeck compared to the other leaves. Dominant fatty acids in the evaluated plant leaves included palmitic acid (C16:0), oleic acid (C18:1n9c) and linolenic acid (C18:3n3). Considerable amounts of essential amino acids (EAAs) and nonessential amino acids (NEAAs) were recorded in the plant leaves, with maximum quantities detected in A. lebbeck and A. heterophyllus , respectively. Notably, substantial amounts of mineral elements were also detected in the plant leaves. Z. mauritiana was identified as a rich source of iron (Fe), copper (Cu) and manganese (Mn), while the highest calcium (Ca), phosphorus (P) and magnesium (Mg) levels were recorded in A. heterophyllus . Furthermore, the aqueous extracts of the leaves exhibited antioxidant and antibacterial potentials, with the maximum activities for both observed in T. indica . Analyses of ANFs indicated the presence of trypsin inhibitor (TI) (1.62–3.69 mg/g), tannin (21.25–61.25 mg/g), phytic acid (1.74–5.42 mg/g), cellulose (14.53%–21.37%) and hemicellulose (5.48%–10.56%) in the leaves. The study conclusively proposes the utilization of leguminous plants, particularly A. lebbeck , B. acuminata and P. pterocarpum , as potential nonconventional ingredients after eliminating or deactivating the major ANFs. This information on nutrients and ANFs of the less explored terrestrial plant leaves can be used to optimize low‐cost carp diet formulation to ensure the economic profitability of fish farmers in the region.

The present study evaluated the potential of Ashoka, Saraca asoca leaf meal (SLM), in carp diets following fermentative processing with a tannase-producing fish gut bacterium, Bacillus subtilis (KP765736). The processing of SLM led to a significant (P < 0.05) reduction in major anti-nutrients (tannin, trypsin inhibitor, and crude fiber), while crude protein content increased. Seven sets of isonitrogenous (35% crude protein) and isocaloric (18.82 kJg⁻¹) diets were prepared using raw (R1, R2, R3) and fermented SLM (F1, F2, F3) at 10%, 20%, and 30% levels by weight replacing fishmeal and de-oiled rice bran in the reference diet (RD). Diets were fed to rohu, Labeo rohita fingerlings (4.01 ± 0.08 g), for 70 days in triplicate. Fish fed diets containing 30% fermented SLM (F3) exhibited significantly (P < 0.05) better growth (241.25%), improved nutrient utilization, and enhanced activities of digestive enzymes compared to raw SLM-fed groups. Furthermore, tannin accumulation in the liver and muscle was significantly lower (P < 0.05) in fish fed fermented SLM diets compared to those fed raw SLM diets. Additionally, tannin contents in the diets were noticed to be positively correlated (P < 0.05) with tannin accumulation in fish tissues and negatively correlated (P < 0.05) with growth. Hepatic and muscle enzymes associated with carbohydrate metabolism in fish fed RD performed similarly to those reared on fermented SLM diets. Conversely, key enzymes involved in protein metabolism, hexose monophosphate shunt, and the tri-carboxylic-acid cycle showed increased activities in fish fed raw SLM diets, indicating dietary stress and a shift from carbohydrate metabolism to protein catabolism. Moreover, protein, glycogen, and amino acids in hepatopancreas and muscle showed a progressive increase with the gradual inclusion of fermented SLM in the diets. In conclusion, this study might suggest incorporating 30% (w/w) fermented SLM in the diets of rohu without interfering with growth, feed utilization, and metabolic function.

With the intensification of aquaculture to meet the rising demands of fish and shellfish, disease outbreaks during the larval and adult stages are a major challenge faced by aqua culturists. As the prophylactic use of vaccines and antibiotics has several limitations, research is now focused on sustainable alternatives to vaccines and antibiotics, e.g., medicinal plants, probiotics, postbiotics, prebiotics, and synbiotics, as promising candidates to strengthen the immune response of fish and shellfish and to control disease outbreaks. With respect to probiotics, numerous studies are available revealing their health-promoting and beneficial impacts in aquaculture. However, most studies focus on Bacillus and Lactobacillus species. Keeping in view the positive effects of probiotic lactic acid bacteria in aquaculture, researchers are now looking for other probiotic bacteria that can be used in aquaculture. Recently, many non-lactic acid bacteria (non-LAB), which are mainly host-associated, have been reported to reveal beneficial effects in fish and shellfish aquaculture. The main non-LAB probiotic genera are Bifidobacterium, Clostridium, Microbacterium, Micrococcus, Paenibacillus, Acinetobacter, Alcaligenes, Enterobacter, Phaeobacter Pseudoalteromonas, Pseudomonas, Pseudomonas, and Vibrio. Despite the promising effects of non-LAB probiotics, comparably, there is limited available information in this context. This review focuses only on probiotic strains that are non-LAB, mostly isolated from the host digestive tract or rearing water, and discusses their beneficial effects in fish and shellfish aquaculture. This review will provide detailed information on the use of various non-LAB bacteria and provide a roadmap to future studies on new probiotics for sustainable aquaculture.