Current Scenario and Future Prospects of Endophytic Microbes: Promising Candidates for Abiotic and Biotic Stress Management for Agricultural and Environmental Sustainability.

Globally, substantial research into endophytic microbes is being conducted to increase agricultural and environmental sustainability. Endophytic microbes such as bacteria, actinomycetes, and fungi inhabit ubiquitously within the tissues of all plant species without causing any harm or disease. Endophytes form symbiotic relationships with diverse plant species and can regulate numerous host functions, including resistance to abiotic and biotic stresses, growth and development, and stimulating immune systems. Moreover, plant endophytes play a dominant role in nutrient cycling, biodegradation, and bioremediation, and are widely used in many industries. Endophytes have a stronger predisposition for enhancing mineral and metal solubility by cells through the secretion of organic acids with low molecular weight and metal-specific ligands (such as siderophores) that alter soil pH and boost binding activity. Finally, endophytes synthesize various bioactive compounds with high competence that are promising candidates for new drugs, antibiotics, and medicines. Bioprospecting of endophytic novel secondary metabolites has given momentum to sustainable agriculture for combating environmental stresses. Biotechnological interventions with the aid of endophytes played a pivotal role in crop improvement to mitigate biotic and abiotic stress conditions like drought, salinity, xenobiotic compounds, and heavy metals. Identification of putative genes from endophytes conferring resistance and tolerance to crop diseases, apart from those involved in the accumulation and degradation of contaminants, could open new avenues in agricultural research and development. Furthermore, a detailed molecular and biochemical understanding of endophyte entry and colonization strategy in the host would better help in manipulating crop productivity under changing climatic conditions. Therefore, the present review highlights current research trends based on the SCOPUS database, potential biotechnological interventions of endophytic microorganisms in combating environmental stresses influencing crop productivity, future opportunities of endophytes in improving plant stress tolerance, and their contribution to sustainable remediation of hazardous environmental contaminants.

Exploitation of Potential Extremophiles for Bioremediation of Xenobiotics Compounds: A Biotechnological Approach.

Microorganisms that are capable of live and adapt in hostile habitats of different environmental factors such as extremes temperature, salinity, nutrient availability and pressure are known as extremophiles. Exposure to xenobiotic compounds is global concern influencing the world population as a health hazard. Hence their removal is warranted using biological means that is very sustainable, potentially cost-effective and eco-friendly. Due to adaptation in extreme environments and unique defense mechanisms, they are receiving more attention for the bioremediation of the xenobiotic compounds. They possess robust enzymatic and biocatalytic systems that make them suitable for the effective removal of pollutants from the contaminated environment. Additionally, the extremophiles act as microfactories having specific genetic and biotechnological potential for the production of biomolecules. This mini review will provide an overview of microbial degradation metabolic pathways for bioremediation along with the molecular and physiological properties of diverse extremophiles from variety of habitats. Furthermore, the factors affecting the bioremediation process is also summarized.

Utilization of microbial community potential for removal of chlorpyrifos: a review.

Chlorpyrifos (CP) is the most commonly used pesticide in agricultural fields worldwide. Exposure to CP and its metabolites creates severe neuron-disorders in human beings. Improper handling and uncontrolled application of CP by farmers have lead to the contamination of surface and ground water bodies. Biodegradation offers an efficient and cost effective method for the removal of CP and other toxic organophosphorus pesticides from the contaminated environment. The degradation of CP by various microorganisms has been investigated by several researchers over the past few years. This review presents a critical summary of the recent published results on the biodegradation of CP. A diverse range of bacterial species such as Agrobacterium sp., Alcaligenes faecalis, Enterobacter sp. Arthrobacter sp. Bacillus pumilus, Pseudomonas sp. etc., fungal species like Trichoderma viridae, Aspergillus niger, Verticillium sp., Acremonium sp. Cladosporium cladosporiodes, etc. and certain algal species viz. Chlorella vulgaris, Spirulina platensis, Synechocystis sp., etc., have been shown to degrade CP. The efficacy of these communities for CP degradation in batch and continuous modes has also been discussed but more studies are required on continuous reactors. Also, the available published information on kinetics of biodegradation of CP along with the available results on molecular biological approaches are discussed in this work.

Current trends in trichloroethylene biodegradation: a review.

Over the past few years biodegradation of trichloroethylene (TCE) using different microorganisms has been investigated by several researchers. In this review article, an attempt has been made to present a critical summary of the recent results related to two major processes--reductive dechlorination and aerobic co-metabolism used for TCE biodegradation. It has been shown that mainly Clostridium sp. DC-1, KYT-1, Dehalobacter, Dehalococcoides, Desulfuromonas, Desulfitobacterium, Propionibacterium sp. HK-1, and Sulfurospirillum bacterial communities are responsible for the reductive dechlorination of TCE. Efficacy of bacterial communities like Nitrosomonas, Pseudomonas, Rhodococcus, and Xanthobacter sp. etc. for TCE biodegradation under aerobic conditions has also been examined. Mixed cultures of diazotrophs and methanotrophs have been used for TCE degradation in batch and continuous cultures (biofilter) under aerobic conditions. In addition, some fungi (Trametes versicolor, Phanerochaete chrysosporium ME-446) and Actinomycetes have also been used for aerobic biodegradation of TCE. The available information on kinetics of biofiltration of TCE and its degradation end-products such as CO2 are discussed along with the available results on the diversity of bacterial community obtained using molecular biological approaches. It has emerged that there is a need to use metabolic engineering and molecular biological tools more intensively to improve the robustness of TCE degrading microbial species and assess their diversity.

A Comprehensive Review of Lab-Scale Studies on Removing Hexavalent Chromium from Aqueous Solutions by Using Unmodified and Modified Waste Biomass as Adsorbents.

Anthropogenic activities and increasing human population has led to one of the major global problems of heavy metal contamination in ecosystems and to the generation of a huge amount of waste material biomass. Hexavalent chromium [Cr(VI)] is the major contaminant introduced by various industrial effluents and activities into the ecosystem. Cr(VI) is a known mutagen and carcinogen with numerous detrimental effects on the health of humans, plants, and animals, jeopardizing the balance of ecosystems. Therefore, the remediation of such a hazardous toxic metal pollutant from the environment is necessary. Various physical and chemical methods are available for the sequestration of toxic metals. However, adsorption is recognized as a more efficient technology for Cr(VI) remediation. Adsorption by utilizing waste material biomass as adsorbents is a sustainable approach in remediating hazardous pollutants, thus serving the dual purpose of remediating Cr(VI) and exploiting waste material biomass in an eco- friendly manner. Agricultural biomass, industrial residues, forest residues, and food waste are the primary waste material biomass that could be employed, with different strategies, for the efficient sequestration of toxic Cr(VI). This review focuses on the use of diverse waste biomass, such as industrial and agricultural by-products, for the effective remediation of Cr(VI) from aqueous solutions. The review also focuses on the operational conditions that improve Cr(VI) remediation, describes the efficacy of various biomass materials and modifications, and assesses the general sustainability of these approaches to reducing Cr(VI) pollution.

Recent Strategies for the Remediation of Textile Dyes from Wastewater: A Systematic Review.

The presence of dye in wastewater causes substantial threats to the environment, and has negative impacts not only on human health but also on the health of other organisms that are part of the ecosystem. Because of the increase in textile manufacturing, the inhabitants of the area, along with other species, are subjected to the potentially hazardous consequences of wastewater discharge from textile and industrial manufacturing. Different types of dyes emanating from textile wastewater have adverse effects on the aquatic environment. Various methods including physical, chemical, and biological strategies are applied in order to reduce the amount of dye pollution in the environment. The development of economical, ecologically acceptable, and efficient strategies for treating dye-containing wastewater is necessary. It has been shown that microbial communities have significant potential for the remediation of hazardous dyes in an environmentally friendly manner. In order to improve the efficacy of dye remediation, numerous cutting-edge strategies, including those based on nanotechnology, microbial biosorbents, bioreactor technology, microbial fuel cells, and genetic engineering, have been utilized. This article addresses the latest developments in physical, chemical, eco-friendly biological and advanced strategies for the efficient mitigation of dye pollution in the environment, along with the related challenges.

Current advances and research prospects for agricultural and industrial uses of microbial strains available in world collections.

Microorganisms are an important component of the ecosystem and have an enormous impact on human lives. Moreover, microorganisms are considered to have desirable effects on other co-existing species in a variety of habitats, such as agriculture and industries. In this way, they also have enormous environmental applications. Hence, collections of microorganisms with specific traits are a crucial step in developing new technologies to harness the microbial potential. Microbial culture collections (MCCs) are a repository for the preservation of a large variety of microbial species distributed throughout the world. In this context, culture collections (CCs) and microbial biological resource centres (mBRCs) are vital for the safeguarding and circulation of biological resources, as well as for the progress of the life sciences. Ex situ conservation of microorganisms tagged with specific traits in the collections is the crucial step in developing new technologies to harness their potential. Type strains are mainly used in taxonomic study, whereas reference strains are used for agricultural, biotechnological, pharmaceutical research and commercial work. Despite the tremendous potential in microbiological research, little effort has been made in the true sense to harness the potential of conserved microorganisms. This review highlights (1) the importance of available global microbial collections for man and (2) the use of these resources in different research and applications in agriculture, biotechnology, and industry. In addition, an extensive literature survey was carried out on preserved microorganisms from different collection centres using the Web of Science (WoS) and SCOPUS. This review also emphasizes knowledge gaps and future perspectives. Finally, this study provides a critical analysis of the current and future roles of microorganisms available in culture collections for different sustainable agricultural and industrial applications. This work highlights target-specific potential microbial strains that have multiple important metabolic and genetic traits for future research and use.

Characterization of bacterial isolates from rubber dump site and their use in biodegradation of isoprene in batch and continuous bioreactors.

Bacterial isolates from contaminated soil of a waste rubber dumping site were isolated and characterized using biochemical and molecular approaches. Isoprene degradation kinetics in batch mode (isoprene concentration: 100-1000 ppm) revealed the degradation efficiency of isolates as: Pseudomonas sp. (83%)>Alcaligenes sp. (70%)>Klebsiella sp. (68.5%). The most efficient isolate Pseudomonas sp. was finally inoculated in a specifically designed bioreactor system comprising a bioscrubber and a biofilter packed with polyurethane foam connected in series. The bioscrubber and biofilter units when operated in a series showed more than 90% removal efficiency up to the inlet loading rate (IL) of 371.1g/m(3)/h. Maximum elimination capacity (EC) of biofilter was found to be an order of magnitude greater than that for bioscrubber. Oxidative cleavage of the double bond of isoprene has been revealed through IR spectra of the leachate.

Efficacy of Aspergillus sp. for degradation of chlorpyrifos in batch and continuous aerated packed bed bioreactors.

Aerobic biodegradation of chlorpyrifos (CP) by Aspergillus sp. was investigated in batch and continuous packed bed bioreactors. The optimal process parameters for achieving the maximum removal efficiency (RE), determined using a batch bioreactor packed with polyurethane foam pieces, were inoculum level: 2.5 mg (wet weight) mL(-1), pH 7.0, temperature 28 °C, DO 5.8 mg L(-1), and CP concentration 300 mg L(-1). The continuous packed bed bioreactor was operated at flow rates ranging from 10 to 40 mL h(-1) while keeping other parameters at their optimal level. Steady-state CP removal efficiencies greater than 85 % were obtained up to the inlet loading of 180 mg L(-1) d(-1). The continuous bioreactor behaved as a plug flow unit and was able to stabilize quickly after perturbation in the inlet loading.