Asian Journal of Microbiology and Biotechnology

Biodegradation of Nitroaromatic Compounds by Alkaliphilic Bacteria: Mechanisms, Applications and Future Perspectives

Rani J. Rathod — Sat, 06 Jun 2026 00:00:00 +0000

Nitroaromatic compounds are extensively utilized in various industries; however, their toxic and persistent nature creates serious environmental and health concerns. Conventional treatment methods are frequently costly and may not provide complete pollutant removal. The paper summarizes the classification and characteristics of alkaliphilic bacteria, describes the enzymatic mechanisms involved in nitroaromatic reduction, and highlights recent research findings from laboratory and field studies. Key applications in environmental bioremediation are highlighted. Current challenges, such as slow degradation rates and limited genetic understanding, are also discussed. The review concludes that alkaliphilic bacteria offer a promising, eco-friendly solution for treating nitroaromatic-contaminated sites adapted to alkaline environments in which many ordinary microorganisms fail to survive. Although microbial biodegradation has been widely investigated, comparatively limited attention has been given to alkaliphilic bacteria and their degradation potential under alkaline conditions. Furthermore, information regarding their enzymatic mechanisms, degradation efficiency, and environmental applications remains scattered across the available literature.

Endophytic Microbes: Natural Entities for Sustainable Agriculture and Human Health

Tue, 09 Jun 2026 00:00:00 +0000

Sustainable agriculture and human health can be significantly impacted by endophytic microbes. These microbes are the important component of the plant holobiont. By facilitating nutrient acquisition, producing phytohormones, and secreting stress relieving enzymes, these endophytic microbes support the plant growth and increase crop resistance against both biotic and abiotic stresses. Their ability to form symbiotic relationships without harming the host allows them to function as natural bio-stimulants and biocontrol agents, promoting environmental sustainability. Additionally, endophytes are known for the efficient production of different types of bioactive secondary metabolites, such as terpenoids, peptides, alkaloids, and polyketides, which possess strong antimicrobial, antioxidant, anticancer, and immunomodulatory properties. These compounds offer promising opportunities for new drug discovery to combat the increasing global challenge of drug resistance, which can provide aid and relief in all aspects of human life. Recent advancements in multi-omics techniques have enhanced our knowledge about the diversity of endophytic microorganisms, colonization strategies, and their functional capabilities across various plant species and environments. Therefore, the exploration of endophytic microbes can effectively address the dual challenges of enhancing agricultural productivity to meet increasing food demands and managing the pharmaceutical with naturally derived therapeutics. In this review, we discuss current insights regarding endophytic microbial diversity, colonization strategies, their roles in promoting plant growth, and their applications in the fields of sustainable agriculture and human health.

Microbial Biomass, Organic Carbon and Basal Soil Respiration: Indicators for Initialization of Microbial Community in Manganese Mine Spoil of Koira, Sundergarh, Odisha, India

Samapika Dash, Monty Kujur — Fri, 29 May 2026 00:00:00 +0000

The quantification of microbial biomass is instrumental in evaluating soil degradation and restoration, as it significantly influences nutrient cycling and organic matter turnover, as well as soil structural and functional stability in response to perturbations and management practices. This study aimed to assess the potential effects of microbial biomass, organic carbon, moisture content and basal soil respiration on the establishment of microbial colonies in relation to the fertility of various age series of mine spoil. The chronosequence manganese overburden mine spoils taken in the study are: fresh manganese overburden mine spoil, i.e., 0 yr (MBO0), 2 yr manganese overburden mine spoil (MBO2), 4yrs manganese overburden mine spoil (MBO4), 6 yrs manganese overburden mine spoil (MBO6), 8 yrs manganese overburden mine spoil (MBO8), 10 yrs manganese overburden mine spoil (MBO10). The analysis revealed an increase in microbial biomass carbon, nitrogen and phosphorus (MB-C, MB-N, MB-P), from MBO0 to MBO10. The percentage of organic carbon and moisture content exhibited an increasing trend across overburden spoil, supporting the progressive establishment of microbes. Microbial respiration increased from MBO0 to MBO10; this rise was probably caused by the organic carbon content gradually increasing. From MBO0 to MBO10, the number of colony-forming units of Azotobacter (AZB), Arthrobacter (ARB), Rhizobium (RHZ), Heterotrophic Aerobes (HAB), Yeast (YST), Actinomycetes (ACT), and Fungus (FUN) increased. The largest population was found in forest soil that helped initiate succession in mine-disturbed areas, while sulfur-reducing bacteria (SRB) showed the opposite trend. Multivariate analysis of variance (MANOVA) shown, HAB pertains highest (99.3%) contribution towards variations among all microbial colonies.

Characterization by MALDI TOF Mass Spectrometry of Yeast and Lactic Acid Bacteria Isolated from ogi and Their Antibacterial Activity

Adesokan Isaac Ayanniran, Wolfram Manuel Bruck — Fri, 05 Jun 2026 00:00:00 +0000

Ogi is a Nigerian traditional fermented food commonly produced from maize, millet and/or sorghum. It serves as cheap breakfast meal for low income earners and complimentary meal for infants and convenient for the sick, convalescent and the elderly. It is produced by submerged fermentation and lactic acid bacteria and yeasts have been isolated as responsible for its fermentation. Consumption of ogi has many advantages which include enhanced nutritional value, digestibility, therapeutic benefits and safety against pathogens. Determining the protein profiles of microorganisms using MALDI-TOF (Matrix-assisted laser desorption-ionization time of flight) mass spectrometry are compatible with the results of identification obtained by molecular methods. MALDI-TOF MS are robust, reliable as well as fast and inexpensive to identify Gram-positive bacteria such as LAB and yeast isolates. In this study LAB and yeast isolates were identified using MALDI TOF MS and their antibacterial activity was determined using the agar disc diffusion assay. The 91 LAB isolates identified by the above named method belong to 12 different species. The LAB strain with the highest percentage of occurrence of 59% is Lactiplantibacillus plantarum and it is followed by Limosilactobacillus fermentum which had a percentage of occurrence of 15%. The lowest percentage of occurrence obtained was 1.1% which was recorded for Companilactobacillus pabuli, Enterococcus faecalis, Lactococuss allomyrinae and so on. A total of 43 yeasts were identified and they belong to 5 different species and these are Issatchenkia orientalis (34.9%), Geotrichum candidum (27.9), Pichia occidentalis (32.6), Candida rugosa (1%) and C. tropicalis (1%). The result of antibacterial activity shows that only 26 LAB isolates inhibited at least one of the spoilage and pathogenic organisms employed as indicator. The highest diameter of zone of inhibition (10.8 mm) recorded for L. plantarum OG58 against Escherichia coli while none of the LAB isolates was able to inhibit Bacillus subtilis. The method employed for identification of LAB and yeast isolates from ogi revealed the presence of certain strains which have not been reported before. Also, the LAB strains were able to inhibit the indicator organism tested to varying degree with exception of B. subtilis.

Isolation, Identification and Antimicrobial Sensitivity Pattern of Bacteria Causing Egg Peritonitis in Layer Birds

Mon, 15 Jun 2026 00:00:00 +0000

Egg peritonitis is an important reproductive disorder of commercial layer chickens and is commonly associated with bacterial infection of the peritoneal cavity. The present study was conducted to isolate and identify bacterial agents associated with egg peritonitis in commercial layer birds and to determine their in vitro antimicrobial sensitivity pattern. Peritoneal swabs were collected from 50 commercial layer birds showing gross lesions suggestive of egg peritonitis during necropsy examination at the Poultry Disease Diagnosis and Surveillance Laboratory, Namakkal, Tamil Nadu, India, from May 2019 to March 2020. The affected birds belonged to different age groups ranging from 21 to 72 weeks and included Lohman, Bovans, Babcock and Hyline strains. Samples were processed using standard bacteriological methods. Isolates were identified based on cultural characteristics, staining reaction, morphology and biochemical tests. Antimicrobial susceptibility testing was performed by the disc diffusion method using selected antibacterial agents. Among the 50 samples examined, Escherichia coli was the most frequently isolated bacterium, accounting for 35 isolates (70%). Other bacteria isolated were Salmonella species in 4 samples (8%), Proteus species in 4 samples (8%), Klebsiella species in 3 samples (6%), Pseudomonas species in 3 samples (6%) and Gallibacterium species in 1 sample (2%). The highest overall sensitivity was observed to levofloxacin, with 32 isolates (64%) showing sensitivity, followed by ciprofloxacin with 30 isolates (60%). Sensitivity to co-trimoxazole, gentamicin, ampicillin, chlortetracycline and amoxicillin was 32%, 22%, 18%, 4% and 2%, respectively. No sensitivity was observed to neomycin, tylosin, lincomycin, bacitracin, colistin and erythromycin. The findings indicate that E. coli was the predominant bacterial agent associated with egg peritonitis in the examined layer birds, and fluoroquinolones showed comparatively higher in vitro activity against the isolates.

Evaluation of Antifungal Activities of Silver Nanoparticles Impregnated Hydrogel for Advanced Biomedical Applications

Sakshi Chaudhary, Jayanand Manjhi, Bibhas Kumar Bhunia — Mon, 15 Jun 2026 00:00:00 +0000

Fungal contamination of wounds and biomedical surfaces remains a relevant challenge in infection management, and hydrogel-based antimicrobial materials may provide a useful platform for localized protection. In this study, a silver nanoparticle-loaded hydrogel was prepared using a κ-carrageenan, polyethylene glycol, and polyvinylpyrrolidone polymer matrix and evaluated for antifungal activity against Aspergillus niger. The hydrogel formulation was prepared by blending aqueous polymer solutions, followed by incorporation of silver nanoparticles at 10 ppm and potassium chloride-mediated stabilization. The resulting AgNP-loaded hydrogel formed a uniform sheet with a light brown appearance, while the nanoparticle-free hydrogel served as the control. Antifungal activity was assessed using two in vitro models representing contaminated and freshly exposed wound-like conditions. In the treatment model, A. niger was spread over agar plates, and hydrogel sheets were placed on the inoculated surface. The AgNP-loaded hydrogel produced visible inhibition of fungal growth at the hydrogel–agar interface, whereas the control hydrogel did not show comparable antifungal activity. In the preventive model, a biphasic nutrient-containing hydrogel system was prepared with one half containing AgNPs and the other half without nanoparticles. After inoculation with A. niger, fungal growth was observed on the control side, while the AgNP-containing region showed visible suppression of colonization. These findings indicate that incorporation of AgNPs into the κ-carrageenan/PEG/PVP hydrogel matrix retained antifungal activity under the tested in vitro conditions. Further physicochemical characterization, quantitative antifungal analysis, cytocompatibility testing, and in vivo evaluation are required before biomedical application can be established.

Assessment of Cotton Wilt Incidence and in Vitro Evaluation of Botanical Extracts and Biocontrol Agents against, Fusarium, Hanumangarh District, Rajasthan, India

Mohd Aftab Alam, Ramesh Singh — Mon, 29 Jun 2026 00:00:00 +0000

Cotton (Gossypium spp.) is an important fibre crop, but its production is constrained by Fusarium wilt. The present study assessed the influence of sowing date on wilt incidence and evaluated selected botanical extracts and biocontrol agents against the pathogen under in vitro conditions. Field experiments were conducted at the Agricultural Field Research Centre, Hanumangarh, Rajasthan, during Kharif 2023–24 and 2024–25 in a randomised block design with three replications. Cotton was sown on five dates from 1 June to 29 June, and disease incidence was recorded at 15 days after first symptom appearance, 30 days after symptom appearance, and maturity. Early sowing reduced wilt incidence in both years. The 1 June sowing recorded the lowest mean disease incidence of 8.75%, 14.90%, and 23.30% at the respective stages, whereas the 29 June sowing recorded the highest mean incidence of 34.55%, 53.15%, and 74.00%. The inhibitory effect of six botanical extracts was tested at 2.5%, 5.0%, and 7.5% concentrations using the poisoned food technique. Neem showed the highest inhibition of mycelial growth, with 68.51%, 73.70%, and 79.63% inhibition at the respective concentrations, followed by tulsi with 64.44%, 70.37%, and 76.30% inhibition. Among the biocontrol agents, Trichoderma harzianum produced the highest inhibition of 85.19% at 5% culture filtrate concentration, followed by Trichoderma viride with 82.96% inhibition. The results indicate that early sowing, neem extract, and effective Trichoderma spp. may contribute to integrated management of Fusarium wilt in cotton.

Isolation, Molecular Identification, and Lipid Productivity of Indigenous Chlorella sorokiniana under BG11, Algal Broth, and NPK Fertilizer Media: Implications for Low-Cost Biodiesel Feedstock Development in Northern Nigeria

Tue, 07 Jul 2026 00:00:00 +0000

Microalgae are potential third-generation feedstocks for biodiesel production; however, region-specific information on indigenous strains and low-cost cultivation media remains limited in Northern Nigeria. This study isolated freshwater microalgae from aquatic environments within Abdullahi Fodio University of Science and Technology, Aliero, Kebbi State, Nigeria, and evaluated the growth and lipid productivity of selected Chlorella sorokiniana isolates cultivated in BG11, algal broth, and NPK fertiliser media. Eighteen water samples were collected from ponds, drainage water, runoff water, reservoir water, and botanical garden ponds. Microalgae were initially screened by microscopy, and selected Chlorella isolates were further characterised using ITS rRNA gene amplification, sequencing, BLAST comparison, and phylogenetic analysis. Cultures were maintained under controlled laboratory conditions at 25 ± 2°C with a 12:12 h light-dark cycle for 44 days. Biomass accumulation was monitored by dry cell weight, while lipids were extracted using the Bligh and Dyer method. Microscopic examination revealed Chlorella spp., Spirogyra spp., Chlamydomonas spp., Oedogonium spp., Microspora spp., Euglena spp., and Characium spp. Molecular analysis confirmed the selected isolates as Chlorella sorokiniana. BG11 supported the highest biomass production, with a final dry biomass of 35.48 g/L, a specific growth rate of 0.140 day⁻¹, and biomass productivity of 0.842 g/L/day. Algal broth produced intermediate growth performance, with final biomass of 19.61 g/L, a specific growth rate of 0.126 day⁻¹, and biomass productivity of 0.465 g/L/day. NPK medium produced the lowest values, with final biomass of 7.26 g/L, a specific growth rate of 0.102 day⁻¹, and biomass productivity of 0.170 g/L/day. The reported lipid contents were 27.07%, 23.13%, and 16.00% for BG11, algal broth, and NPK medium, respectively. The findings indicate that BG11 was the most effective medium under laboratory conditions, while algal broth may provide a practical alternative for further optimisation.

Diversity of Endophytic Fungi Associated with the Aerial Roots of Ficus benghalensis L. in the Sacred Groves of Ponnamaravathi, Pudukkottai District, Tamil Nadu, India

Wed, 08 Jul 2026 00:00:00 +0000

Endophytic fungi are asymptomatic microorganisms that colonise internal plant tissues and contribute to plant health, ecological interactions and secondary metabolite production. This study investigated the diversity of culturable endophytic fungi associated with the aerial roots of Ficus benghalensis L. collected from sacred groves at Ponnamaravathi, Pudukkottai District, Tamil Nadu, India. Healthy aerial root samples were collected during different seasonal periods and processed using surface-sterilisation and culture-dependent isolation methods. Sterilised root segments were inoculated on Potato Dextrose Agar (PDA) and incubated under laboratory conditions. Emerging fungal colonies were purified through repeated sub-culturing and identified using macroscopic and microscopic characters, including colony morphology, hyphal features, conidial arrangement and spore morphology. Nine culturable fungal taxa were recorded: Aspergillus flavus, Aspergillus niger, Aspergillus oryzae, Aspergillus fumigatus, Paecilomyces sp., Neotyphodium sp., Pseudosigmoidea sp., Rhizopus sp. and members of Mucormycotina. Seasonal variation was observed, with the highest recorded richness during summer. Aspergillus was the predominant genus among the isolates. The findings indicate that the aerial roots of F. benghalensis harbour a diverse assemblage of culturable endophytic fungi and may represent a useful source of fungal biodiversity. Because identification was based on morphology, molecular confirmation using ITS rDNA sequencing and further ecological, biochemical and functional studies are needed to confirm taxonomy and evaluate potential applications.

Foliar Application of HYPER Bio-stimulant Improves Growth, Yield and Soil Nutrient Status of Blackgram (Vigna mungo L.) under Vertisols

Y. D. Charjan, R. S. Wankhede, S. M. Nage, P. N. Magare — Fri, 10 Jul 2026 00:00:00 +0000

A field experiment was conducted at the Agriculture Research Station, Achalpur, District Amravati, under Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, during the kharif 2024-25 season to evaluate the efficacy of HYPER on the growth, yield and soil nutrient status of blackgram (Udid). A plant bio-stimulant is any substance applied to plants to enhance nutrient-use efficiency, abiotic stress tolerance and crop-quality traits, regardless of its nutrient content. The field topography was fairly uniform and levelled. The experiment was laid out in a Randomised Block Design with six treatments and four replications. The mean number of seeds per pod (5.45) was significantly higher under Urea Briquette and T5: RDF + HYPER at 2.5 ml/litre of water. Grain yield was significantly highest under T6: RDF + HYPER at 3 ml/litre of water (1196.23 kg ha-1), and it was at par with T4: RDF + HYPER at 2 ml/litre of water (1151.91 kg ha-1). RDF + HYPER at 3 ml/litre of water recorded the highest grain yield (1196.23 kg ha-1), followed by RDF + HYPER at 2.5 ml/litre of water (1165.03 kg ha-1). Growth parameters, including plant height, number of branches and pod characteristics, improved significantly with HYPER application. Post-harvest soil nutrient availability also increased in treated plots, with the highest available N (213.25 kg ha-1), P (18.14 kg ha-1) and K (652.85 kg ha-1) recorded under T6. The findings indicate that RDF + HYPER at 3 ml/litre of water significantly enhanced blackgram productivity and post-harvest soil fertility under Vertisol conditions.