Atif Aziz Chowdhury, PhD

Synthetic dyes find their applications in industries including textile, medicine, cosmetics, and food for increasing the visual appeal. However, the deleterious environmental and biological impacts of the effluent of these industries are of growing concern. Researchers have come up with innovative and greener solutions to skip the alarming effects of using plant and microbial resources. Microbial pigments spanning a spectrum of colors, such as red, yellow, orange, pink, black, blue, and green, are produced by a specific group of microbes. However, there are still major hurdles to cross in terms of industrial mass production. Pigments, such as melanin—black-colored pigment from Burkholderia sp., ankaflavin and riboflavin—yellow-colored pigment from Monascus sp. and Ashbya gossipii , carotenoids—yellow-colored pigment from Streptomyces sp. showed multidimensional applications in diverse fields ranging from pharmaceuticals to the remediation of toxic substances. Flavins are pteridine-based organic yellow compounds derived from the isoalloxazine ring. Moreover, this is a precursor of riboflavin, better known as vitamin B2, must be taken by humans from external sources. Flavins specifically riboflavin used as antimicrobial agents, in the medicine and food processing industries. This chapter is an attempt to explore the microbial biosynthesis mechanism of the yellow pigment-flavin, alongside enlisting the microbial candidates and optimized conditions for industrial production. This chapter further delves into the pigment’s potential applications in diverse fields.

The growing demand for efficient biosurfactants in various industrial sectors has driven the search for sustainable alternatives, enhanced production methods, and low-cost substrates. This study aimed to optimize the production, characterize, and assess the bioactivities of biosurfactants produced by an oligotrophic PET plastic-associated Bacillus sp. EIKU23. The bacterium yielded the highest amount of biosurfactant after 6 days of incubation in Luria broth medium (pH 7.0) at 30 °C without any additives. FTIR and NMR analyses confirmed the lipopeptide nature of the biosurfactant, which exhibited a negative charge. The biosurfactant remained stable at 4 °C–80 °C and pH 7.0–8.0 for at least 7 days. It exhibited antioxidant properties comparable to the ascorbic acid standard, with efficacy ranging from 23.61% to 89.96% in different antioxidant assays. It showed antibacterial activity against both Gram-positive and Gram-negative potential pathogens. The biosurfactant induced substantial DNA leakage at a concentration of 10 mg/mL and eradicated approximately 48.4% of pre-formed Staphylococcus aureus biofilm and showed anti-attachment behaviour to a polystyrene surface. Additionally, the biosurfactant precipitated up to 98.7% uranium from an aqueous solution, demonstrating its potential for bioremediation. These findings suggest that the biosurfactant produced by Bacillus sp. EIKU23 is multifunctional with promising applications in bioremediation, antibacterial activity, antibiofilm formation, and antioxidant defense, offering a novel solution for sustainable industrial practices and plastic waste management.

Worsening water shortages due to climate change have underscored the need for sustainable agricultural practices, including mulching, to restore soil moisture and health. Environmental concerns associated with plastic mulching materials in agriculture have prompted the adoption of biodegradable alternatives. Topsoil cover (TSC), developed through the valorisation of wood industry by-products and xanthan gum, offers a sustainable solution. Indigenous microbiomes, predominantly Proteobacteria (e.g., Pseudomonas spp.), Firmicutes (e.g., Staphylococcus spp.), and Aspergillus spp., can biodegrade TSC under controlled condition. Germination tests confirm its effectiveness in weed control. A greenhouse experiment using tomato (Solanum lycopersicum) demonstrated that TSC enhances shoot and root length by 50 and 100%–160% and overall biomass by 30%–50%, without altering rhizosphere soil physicochemical properties or microbial community structure. Additionally, the reversible effect of TSC can enhance the early soil nitrogen pool by 20% through microbial interactions. It also increases soil microbial metabolic diversity, highlighting its potential for agricultural use. Our findings establish TSC as an innovative product that closes the loop on timber industry waste while enhancing soil fertility, promoting plant health, and enabling medium-term carbon storage in wood.

Mitigation of potentially toxic elements (PTEs) such as uranium (U) and arsenic (As), and fulfilment of global food demand requires a sustainable approach. Therefore, a multiple PTE-tolerant Methylobacterium sp. EIKU22 was explored for its bioremediation and biofertilization potential. This multi-metal tolerant isolate removed 29.88% U (initial dose: 100 mg L−1, pH 4.0, biosorption 3.74 mg g−1) after 14 days, following pseudo-second-order (PSO) kinetics. The isolate also showed 54% As(III) [pseudo-first-order kinetic; 3.72 mg g−1]; and ~ 37% As(V) (PSO; 2.4 mg g−1) removal within 60 min with the same initial dosing of either As(III) or As(V). Moreover, the strain precipitated > 96.5% and ~ 97% of U using released phosphate from inorganic and organic sources, respectively. Further analysis with inorganic phosphate showed > 31%, > 41% and > 98% of U precipitation from initial doses of 1000, 500 and 100 mg L−1 within 5 min. Methylobacterium sp. EIKU22 expresses the potential to solubilize ~ 178% phosphate, 169.8% potassium, 156–213% zinc within 6 days, and was able to withstand a pH range of 4.0–8.0, temperature range of 20–35 °C, and exhibited resilience to up to 10% NaCl exposure despite being affected by UV exposure. Further, the isolate showed to grow in nitrogen-free media and produce IAA, ammonia, siderophore, ACC deaminase, cellulase and catalase, suggesting potential application in plant growth promotion. The isolate harbours amoA, and nifH genes and imparts better survivability and vegetative growth in the rice seedling. These findings showcase the strain’s dual applicability. However, further investigation is needed to generalize the findings.

Plastic pollution has emerged as a persistent environmental issue, leading to the accumulation of plastics in various ecosystems, especially aquatic ones. A significant consequence of this pollution is the development of biofilms on plastic surfaces, housing diverse microbial communities. Understanding the dynamics and interactions within these biofilms is essential for evaluating the ecological impact of plastic pollution. Microbial gene transfer within these biofilms plays a crucial role in shaping microbial communities and influencing biofilm dynamics. These biofilms host complex microbial communities that engage in intricate interactions, shaping both their structure and function. Within these biofilms, microbial species cooperate and compete through various molecular mechanisms, which are pivotal for biofilm formation and stability. Communication pathways, such as quorum sensing, enable coordinated behaviour and biofilm maturation, while metabolic interactions facilitate nutrient and metabolite exchange, promoting biofilm growth and resilience. Furthermore, horizontal gene transfer (HGT) facilitates the sharing of genetic material among biofilm inhabitants, thereby influencing adaptability and antibiotic resistance. The dense population structure within these biofilms enhances plasmid dispersal by conjugation, further promoting genetic exchange and biofilm development. Additionally, biofilm-associated extracellular polymeric substances (EPSs) serve as a matrix for DNA adsorption, facilitating transformation and transduction processes. This chapter aims to explore the intricate community interactions and gene transfer mechanisms within plastic-associated biofilms comprehensively.

In light of the significant impact of climate change, it is imperative to identify effective solutions to promote afforestation and reforestation operations, which are often constrained by a low survival rate. To mitigate the impact of weed competition and enhance water availability, biodegradable groundcovers comprising xanthan gum and gelatine were developed and evaluated over the course of the growing season in a nursery setting on narrow-leaved ash (Fraxinus angustifolia) and alder (Alnus glutinosa) in 3.5 L pots. The results demonstrated a beneficial impact of all groundcovers, particularly the gelatine-based ones, on both the aboveground and belowground growth rates. The efficacy of weed competition was controlled using gelatine-based groundcovers in the case of ash trees. Furthermore, the gelatine-based groundcover altered the soil physiochemical characteristics and affected the bacterial community while maintaining its role in increasing the soil nitrogen pool. In contrast, the xanthan gum-based groundcover was demonstrated to enhance microbial richness and diversity, with an augmented contribution to the soil nitrogen pool. However, further trials with diverse tree species and soil conditions are necessary to gain a more comprehensive understanding of these effects.

The textile manufacturing industry generates significant environmental concerns due to the discharge of toxic dyes, heavy metals, detergents, and highly alkaline or acidic wastewater during fabric production. These pollutants harm living organisms and the environment, directly or indirectly impacting human well-being. Although widely used, traditional remediation methods often produce secondary toxic by-products that worsen the problem. Recognizing these challenges, sustainable and eco-friendly solutions are becoming critical. Approaches such as microbial remediation and agro-waste use have shown promising results in effectively treating textile effluents. These methods aim to mitigate the environmental impact while avoiding the generation of additional harmful by-products. This chapter provides an overview of the environmental issues caused by textile effluents and examines strategies for their mitigation. It emphasizes sustainable remediation practices and the need to adopt environmentally conscious approaches. The aim is to consolidate existing knowledge and inspire future research to develop effective solutions for managing toxic effluents in the textile industry.

The current study employed a rice root plaque-associated bacterium, Burkholderia sp. EIKU24, with the competency to synthesize spherical and crystalline biogenic selenium nanoparticles (BioSeNPs) that have size variability between 230-330 nm, as confirmed by SEM and TEM analysis. FT-IR and electron microscopy further revealed a biomolecular coating around the NPs that might have contributed significantly to their antibacterial activity against potential pathogenic Gram-positive and Gram-negative bacteria. The BioSeNPs suspension (10 mg mL−1) inhibited 78% and 67% of Staphylococcus aureus and Pseudomonas aeruginosa biofilms, respectively. Furthermore, BioSeNPs showed very high antioxidant capability, reflected by 90% relative DPPH scavenging activity and photocatalytic capability by the degradation of 86% methylene blue (10 mg L−1) solution within a contact time of 30 min. Compared to hydro or Na2SeO3 priming, rice seeds from BioSeNPs-priming outperformed in all tested seed germination parameters. Hydroponic cultivation showed better health and growth of the rice plants by an increase in root and shoot lengths, wet and dry biomass, and chlorophyll content, both in arsenic (As)-exposed and unexposed seedlings emerging from BioSeNPs-primed seeds. Notably, in such seedlings, exposure to As did not alter the growth much, indicating increased resilience to As through BioSeNPs priming. Besides, the priming of BioSeNPs decreased the translocation of As to shoot and root by about 50% compared with hydro priming. The bioactivities, dye degradation, and growth promotion coupled with As resilience in rice seedlings consolidate the sustainable agricultural potential of BioSeNPs. However, their impact on soil ecology and interaction with other contaminants requires further study.

Industrialization and urbanization have resulted in ecosystems being contaminated with persistent toxic elements and chemical dyes, posing significant threats to both environmental health and human well-being. To tackle this issue, bioremediation has emerged as a promising method. However, conventional bioremediation techniques have their limitations in terms of efficiency and practicality. Nanotechnology, particularly the development of BioNPs, has opened up new possibilities for addressing these challenges. Various biological entities such as bacteria, fungi, yeast, and algae have been explored for synthesizing metal NPs through intracellular or extracellular processes. These NPs find applications in healthcare, agriculture, and environmental management. Nano-bioremediation offers a potential solution to the current limitations of bioremediation. BioNPs exhibit unique properties and interactions with PTE&Cs, making them a promising option for environmental applications. In this chapter, we dig into the application of BioNPs for targeting PTE&Cs in bioremediation to ensure sustainability. We explore the types of NPs utilized and their mechanisms of action. Additionally, we address the advantages, challenges, and drawbacks associated with this approach while also discussing future prospects and research directions. By presenting cutting-edge research insights so far, we enlighten to the advancement of eco-friendly solutions for remediating persistent toxic elements and chemical dye contaminated environments, paving the way for a healthier and more sustainable future.

With the increasing demand for various pharmaceuticals and personal care products (PPCPs) among the population, the concern about their impact on the environment is also raising as they have emerged as serious contaminants. Antibiotics, antidepressants, hormones, sunscreen agents, fragrances, and preservatives are common PPCPs that are released into nature mainly in water bodies and soil systems through industrial and domestic wastewater. At their low concentrations, they are sufficient to cause alteration of water quality and affect aquatic and human life. Inefficient traditional techniques make people discover sustainable green technology including bacterial bioremediation. Through aerobic and anaerobic oxidative degradation and biosorption, bacteria transform these PPCPs into nontoxic substances. As they can act from different dimensions, bacterial consortia are favored over single species. Moreover, as the majority of them are uncultivable in in-vitro conditions, in a real-life setting, it is tough to grasp the complete picture. Elucidation of these indigenous bacterial consortia is possible through various omics technology such as genomics, proteomics, transcriptomics, metabolomics, and phenomics using molecular and in-silico tools. Indigenous bacterial consortia are important for efficient bioremediation and gained knowledge through multiomics studies about these consortia can speed up the remediation process and make it more feasible and productive. Here, we have discussed how omics technology can contribute to a better understanding of bacterial bioremediation in PPCPs removal from the environment.