Nishant Dafale

Kinetic study approach of remazol black-B use for the development of two-stage anoxic–oxic reactor for decolorization/biodegradation of azo dyes by activated bacterial consortium

The laboratory-isolated strains Pseudomonas aeruginosa, Rhodobacter sphaeroides, Proteus mirabilis, Bacillus circulance, NAD 1 and NAD 6 were observed to be predominant in the bacterial consortium responsible for effective decolorization of the azo dyes. The kinetic characteristics of azo dye decolorization by bacterial consortium were determined quantitatively using reactive vinyl sulfonated diazo dye, remazol black-B (RB-B) as a model substrate. Effects of substrate (RB-B) concentration as well as different substrates (azo dyes), environmental parameters (temperature and pH), glucose and other electron donor/co-substrate on the rate of decolorization were investigated to reveal the key factor that determines the performance of dye decolorization. The activation energy (E(a)) and frequency factor (K(0)) based on the Arrhenius equation was calculated as 11.67 kcal mol(-1) and 1.57 x 10(7)mg lg MLSS(-1)h(-1), respectively. The Double-reciprocal or Lineweaver-Burk plot was used to evaluate V(max), 15.97 h(-1) and K(m), 85.66 mg l(-1). The two-stage anoxic-oxic reactor system has proved to be successful in achieving significant decolorization and degradation of azo dyes by specific developed bacterial consortium with a removal of 84% color and 80% COD for real textile effluents vis-à-vis >or=90% color and COD removal for synthetic dye solution.

Selection of indicator bacteria based on screening of 16S rDNA metagenomic library from a two-stage anoxic-oxic bioreactor system degrading azo dyes.

Dye degradation has gained attention of late due to indiscriminate disposal from user industries. Enhancing efficiency of biological treatment provides a cheaper alternative vis-à-vis other advanced technologies. Dye molecules are metabolized biologically via anoxic and oxic treatments. In this study, bacterial community surviving on dye effluent working in anoxic-oxic bioreactor was analyzed using 16S rDNA approach. Azo-dye decolorizing and degrading bacterial community was enriched in lab-scale two-stage anoxic-oxic bioreactor. 16S rDNA metagenomic libraries of enriched population were constructed, screened and phylogenetically analyzed separately. Removal of approximately 35% COD with complete decolorization was observed in anoxic bioreactor. Process was carried out by uncultured gamma proteobacterium constituting 48% of the total population and 12% clones having homology to Klebsiella. Aromatic amines generated during partial treatment under anoxic bioreactor were treated by aerobic population having 72% unculturable unidentified bacterium and rest of the population consisting of Thauera sp., Pseudoxanthomonas sp., Desulfomicrobium sp., Ottowia sp., Acidovorax sp., and Bacteriodetes bacterium sp.

Control of Multidrug-Resistant Gene Flow in the Environment Through Bacteriophage Intervention

The spread of multidrug-resistant (MDR) bacteria is an emerging threat to the environment and public wellness. Inappropriate use and indiscriminate release of antibiotics in the environment through un-metabolized form create a scenario for the emergence of virulent pathogens and MDR bugs in the surroundings. Mechanisms underlying the spread of resistance include horizontal and vertical gene transfers causing the transmittance of MDR genes packed in different host, which pass across different food webs. Several controlling agents have been used for combating pathogens; however, the use of lytic bacteriophages proves to be one of the most eco-friendly due to their specificity, killing only target bacteria without damaging the indigenous beneficial flora of the habitat. Phages are part of the natural microflora present in different environmental niches and are remarkably stable in the environment. Diverse range of phage products, such as phage enzymes, phage peptides having antimicrobial properties, and phage cocktails also have been used to eradicate pathogens along with whole phages. Recently, the ability of phages to control pathogens has extended from the different areas of medicine, agriculture, aquaculture, food industry, and into the environment. To avoid the arrival of pre-antibiotic epoch, phage intervention proves to be a potential option to eradicate harmful pathogens generated by the MDR gene flow which are uneasy to cure by conventional treatments.

Insights in Waste Management Bioprocesses Using Genomic Tools.

Microbial capacities drive waste stabilization and resource recovery in environmental friendly processes. Depending on the composition of waste, a stress-mediated selection process ensures a scenario that generates a specific enrichment of microbial community. These communities dynamically change over a period of time while keeping the performance through the required utilization capacities. Depending on the environmental conditions, these communities select the appropriate partners so as to maintain the desired functional capacities. However, the complexities of these organizations are difficult to study. Individual member ratios and sharing of genetic intelligence collectively decide the enrichment and survival of these communities. The next-generation sequencing options with the depth of structure and function analysis have emerged as a tool that could provide the finer details of the underlying bioprocesses associated and shared in environmental niches. These tools can help in identification of the key biochemical events and monitoring of expression of associated phenotypes that will support the operation and maintenance of waste management systems. In this chapter, we link genomic tools with process optimization and/or management, which could be applied for decision making and/or upscaling. This review describes both, the aerobic and anaerobic, options of waste utilization process with the microbial community functioning as flocs, granules, or biofilms. There are a number of challenges involved in harnessing the microbial community intelligence with associated functional plasticity for efficient extension of microbial capacities for resource recycling and waste management. Mismanaged wastes could lead to undesired genotypes such as antibiotic/multidrug-resistant microbes.

Bacteriophage Diversity in Different Habitats and Their Role in Pathogen Control

Bacteriophages are selective to their host bacteria and do not have any direct interaction with other members of the indigenous flora of the community. In any niche, the diversity of phage is directly proportional to the associated discriminating bacterial population as a host. Pathogens including MDR bacteria in wastewater are responsible for big outbreaks in many developing nations and the biggest emerging threat to public health. Every effort leading to reduction of pathogens in the environment has to be promoted and implemented for establishing a healthy and sustainable environment. The inefficient functioning of STPs is the significant reservoir of diverse bacterial population, including MDR. A biocontrol capability through phage has been demonstrated in the control of pathogens in food industry, medicine, aquaculture and agriculture and could be implemented to environment. In order to apply phage formulation in the environment, it must be a wild type and should be well characterised; that includes genome annotation, validation of genes of obligate lytic cycle and without the virulence factors. The implementation will demand long-term trials with microbial community. This can be ensured through advances in metagenomics, which will monitor shifts in the community structure after phage interventions. Phages would emerge as eco-friendly biocontrol agents and could be considered as an obvious alternative to chemical disinfectant and preservatives.

An Insight into Phage Diversity at Environmental Habitats using Comparative Metagenomics Approach

Bacteriophages play significant role in driving microbial diversity; however, little is known about the diversity of phages in different ecosystems. A dynamic predator–prey mechanism called “kill the winner” suggests the elimination of most active bacterial populations through phages. Thus, interaction between phage and host has an effect on the composition of microbial communities in ecosystems. In this study, secondary phage metagenome data from aquatic habitats: wastewater treatment plant (WWTP), fresh, marine, and hot water spring habitat were analyzed using MG-RAST and STAMP tools to explore the diversity of the viruses. Differential relative abundance of phage families—Siphoviridae (34%) and Myoviridae (26%) in WWTP, Myoviridae (30%) and Podoviridae (23%) in fresh water, and Myoviridae (41%) and Podoviridae (8%) in marine—was found to be a discriminating factor among four habitats while Rudiviridae (9%), Globuloviridae (8%), and Lipothrixviridae (1%) were exclusively observed in hot water spring. Subsequently, at genera level, Bpp-1-like virus, Chlorovirus, and T4-like virus were found abundant in WWTP, fresh, and marine habitat, respectively. PCA analysis revealed completely disparate composition of phage in hot water spring from other three ecosystems. Similar analysis of relative abundance of functional features corroborated observations from taxa analysis. Functional features corresponding to phage packaging machinery, replication, integration and excision, and gene transfer discriminated among four habitats. The comparative metagenomics approach exhibited genetically distinct phage communities among four habitats. Results revealed that selective distribution of phage communities would help in understanding the role of phages in food chains, nutrient cycling, and microbial ecology. Study of specific phages would also help in controlling environmental pathogens including MDR bacterial populations using phage therapy approach by selective mining and isolation of phages against specific pathogens persisting in a given environment.

Microbial CO 2 Fixation Bioprocesses and Desert as Future Carbon Sink

Increasing levels of carbon dioxide (CO2) in the atmosphere are causing serious effect on climatic changes. Thereby the most concerned environmental issue is global warming these days. The same culprit carbon dioxide is also involved in the most important process called autotrophy, which supports life on earth. Autotrophy could be one of the probable answers for the management of atmospheric CO2 in an eco-friendly manner. Plants contribute a major part in CO2 fixation but often ignored microbes are also involved in CO2 fixation by different CO2 fixation pathways. Since desert represents sparse green cover, we cannot ignore the microbes present in such soil, which would be contributing for carbon fixation. Oligotrophic soil like desert harbours microbes that are capable of surviving in low-carbon conditions, thus opening an area of research for the study of CO2 fixation by oligotrophs. Since microbes require carbon for their growth, and hence under carbon starvation, they might have the mechanism for autotrophy. By exploring CO2 fixation through oligotrophs of desert, we could probably enrich the desert soil by carbon in near future. Such microbe-based CO2 fixation studies could help us to channelize CO2 for the synthesis of some important bioproducts.

Transformation of azo dyes during moist heat sterilisation: a potential source of error in microbial decolourisation

This paper presents the role of moist heat sterilisation in decolourisation of azo dyes during autoclaving itself, thereby leading to over estimation of actual decolourisation through subsequent microbial process. This surprise phenomenon was probed in detail by studying the effects of temperature, pressure and role of electron donor/carbon sources on decolourisation. In the presence of 10 g/litre glucose, 75% decolourisation of Reactive Black 5 (RB-5) dye was observed after autoclaving of medium at 121°C for 15 min at 15 psi. Studies repeated with other azo dyes revealed that Reactive Orange 16 (RO-16) was affected by autoclaving whereas Reactive Red 11 (RR-11) and Reactive Red 141 (RR-141) did not show significant decolourisation. The reduction of dye was dependent on concentration of electron donor/carbon source and autoclave conditions. The results indicate that investigators must screen the dyes for decolourisation during autoclaving and choose the appropriate means of sterilisation to remove the artifice or incorporate correction factor for dye concentration at the start of experiment.