Potential of microbial inoculants for organic waste decomposition and decontamination
01 Jan 2021-pp 103-132
TL;DR: An overview of the current researches on microbial inoculation as a way forward to achieve sustainability in managing overwhelming quantity of organic wastes and to achieve clean environments heavily affected by pollution is presented in this article.
Abstract: Although industrialization has been a boon to our economy and self-sufficiency, yet it accompanies a major drawback of generation of a huge amount of wastes as well as pollutants that accumulate in soil and aquatic systems, eventually contaminating and degrading the ecosystem. Moreover, the ever-increasing human population is making the situation worse. It is therefore a great challenge to manage the rapidly generating enormous amount of organic wastes and the accompanying pollutants. In this respect, biodegradation and decontamination of organic waste by employing microbial inoculants is an eco-friendly and cost-effective sustainable solution. Although the concept of biodegradation and decontamination by microbes is not new, however, it is yet to reach its full application potential. In spite of the promising response of microbial inoculants under laboratory/controlled conditions, a large field-scale application has shown limited efficacy, possibly due to the complex nature and nonsegregation of wastes. Both the waste decomposition through composting and waste decontamination through bioremediation rely on active microbial participation where they perform complex multistep pathways to achieve the final product. Henceforth, improving our perception of the microbial mechanisms and their interactions with organic waste material is the key requirement for harnessing the full potential of microbial technology in maintaining sustainability of the environment. This chapter presents an overview of the current researches on microbial inoculation as a way forward to achieve sustainability in managing overwhelming quantity of organic wastes and to achieve clean environments heavily affected by pollution. Furthermore, the potential of vital processes employed by the microorganisms for sustainable development and environmental management are also discussed, followed by their future prospects.
Citations
More filters
Journal Article•
TL;DR: In this paper, Allgaier et al. used a green-waste inoculum to switchgrass (Panicum virgatum) and simulated thermophilic composting in a bioreactor to select for a switchgrass-adapted community and to facilitate targeted discovery of glycoside hydrolases.
Abstract: Targeted Discovery of Glycoside Hydrolases from a Switchgrass-Adapted Compost Community Martin Allgaier 1,3 , Amitha Reddy 1,2 , Joshua I. Park 1,6 , Natalia Ivanova 3 , Patrik D’haeseleer 1,4 , Steve Lowry 3 , Rajat Sapra 1,6 , Terry C. Hazen 1,5 , Blake A. Simmons 1,6 , Jean S. VanderGheynst 1,2 , and Philip Hugenholtz 1,3 * Deconstruction Division, Joint BioEnergy Institute, Emeryville, California, USA; Department of Biological and Agricultural Engineering, University of California Davis, Davis, California, USA; Department of Energy (DOE) Joint Genome Institute, Walnut Creek, California, USA; Microbial Systems Biology Group, Lawrence Livermore National Laboratory, Livermore, California, USA; Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA; Biomass Science and Conversion Technology Dept., Sandia National Laboratory, Livermore, California, USA Abstract Development of cellulosic biofuels from non-food crops is currently an area of intense research interest. Tailoring depolymerizing enzymes to particular feedstocks and pretreatment conditions is one promising avenue of research in this area. Here we added a green-waste compost inoculum to switchgrass (Panicum virgatum) and simulated thermophilic composting in a bioreactor to select for a switchgrass-adapted community and to facilitate targeted discovery of glycoside hydrolases. Small-subunit (SSU) rRNA-based community profiles revealed that the microbial community changed dramatically between the initial and switchgrass-adapted compost (SAC) with some bacterial populations being enriched over 20-fold. We obtained 225 Mbp of 454-titanium pyrosequence data from the SAC community and conservatively identified 800 genes encoding glycoside hydrolase domains that were biased toward depolymerizing grass cell wall components. Of these, ~10% were putative cellulases mostly belonging to families GH5 and GH9. We synthesized two SAC GH9 genes with codon optimization for heterologous expression in Escherichia coli and observed activity for one on carboxymethyl cellulose. The active GH9 enzyme has a temperature optimum of 50°C and pH range of 5.5 to 8 consistent with the composting conditions applied. We demonstrate that microbial communities adapt to switchgrass decomposition using simulated composting condition and that full-length genes can be identified from complex metagenomic sequence data, synthesized and expressed resulting in active enzyme. Funding: This work was part of the DOE Joint BioEnergy Institute (http://www.jbei.org) supported by the U. S. Department of Energy, Office of Science, Office of Biological and Environmental Research, through Contract No. DE- AC02-05CH11231 between Lawrence Berkeley National Laboratory and the U. S. Department of Energy. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Introduction Enzymatic hydrolysis is one of the most expensive steps in biofuel production from lignocellulosic biomass primarily due to the need for high enzyme loading caused by low catalytic efficiencies [1,2]. Microorganisms including bacteria and fungi are well- known plant biomass decomposers in nature, making them attractive targets for enzyme discovery. Since a variety of biomass sources are envisioned for future biofuel production (e.g. switchgrass, miscanthus, poplar), a broad spectrum of lignocellulolytic enzymes (cellulases, hemicellulases, ligninases) is required to meet future demands. These enzymes are highly modular and usually classified by their domain structure [3]. Glycoside hydrolases (GHs) are a prominent group of enzymes that hydrolyze the glycosidic bond between carbohydrate molecules. The GH families 5, 7 and 9 are the most diverse of the 115 currently recognized GH families, and are of great interest for industrial applications due to their plant cell wall depolymerizing activities [4]. Despite extensive efforts to engineer existing glycoside hydrolases to improve activity and stability, there is still a great need to expand the current enzyme repertoire as well as improve our understanding of how these enzymes function in complex environments [5]. In the present study, we incubated compost- inoculated switchgrass under high-solids and thermophilic conditions to facilitate the enrichment of switchgrass-adapted organisms and associated lignocellulolytic enzymes using a sequencing-based metagenomic approach. Composting is a very dynamic high-solids decomposition process in which microorganisms break down organic matter into carbon dioxide, water, and stable humus-like materials throughout mesophilic and thermophilic phases Therefore, compost microbial communities can tolerate large changes in temperature, redox conditions, and water activity, recovering quickly from major environmental perturbations. This adaptation to extremes in operating conditions suggests the potential for discovering robust lignocellulolytic enzymes that will also tolerate harsh pretreatment approaches under industry-relevant production standards (e.g. dilute acid, ionic liquid, ammonia fiber expansion).
9 citations
TL;DR: In this paper , a review of various types of Potassium solubilizing microorganisms in soil, their mechanism of action, and their importance in sustainable crop production is discussed.
Abstract: Abstract Background An increase in population has led to a higher demand for food. Meeting up this demand has necessitated the use of chemical fertilizers. However, utilization of these fertilizers has a considerable deleterious effect on the soil, plant, human, environmental sustainability, and only increase the cost and reduced profitability. With these identified problems, there is a need for efficient and sustainable methods regarding managing natural resources to enhance food production. Naturally, potassium (K) is an abundant element present in the soil but in an inaccessible form. There is therefore a need to seek an alternative method to improve the K availability to plants noting that K is an essential plant nutrient that plays a major role in plant physiological and metabolic processes. Subsequently, employing microbial potassium solubilizers is an efficient method to enhance the potassium availability in the soil, which in turn improves productivity. Therefore, this review discusses the various types of potassium solubilizing microorganisms in soil, their mechanism of action, and their importance in sustainable crop production. Main body Potassium solubilizing microorganisms (KSM) such as bacteria and fungi can solubilize K from an insoluble form to a soluble form to enhance uptake by plants. These microorganisms solubilize K through the production of organic acids such as tartaric acid, citric acid, and oxalic acid to release K from its minerals. Apart from making potassium available, these microbes can improve soil health and crop yield and act as bio-control agents by producing antibiotics. Potassium solubilizing microbes also produce hormones that help plants withstand both biotic and abiotic stresses. Hence, the application of KSM to agricultural soils will reduce the use of chemical fertilizers and enhance the sustainability of food production. Conclusion One of the most efficient ways of improving plant utilization of potassium in the soil is to use potassium solubilizing microbes, which can make potassium ions available from minerals of both igneous and sedimentary origins. The use of potassium solubilizing microbes as biofertilizers may be the awaited solution to increasing crop productivity, concerns linked to chemical fertilizer application, and earth resource diminution.
2 citations
References
More filters
TL;DR: This review focuses on the known, the putative, and the speculative modes-of-action of PGPR, which include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses.
Abstract: Numerous species of soil bacteria which flourish in the rhizosphere of plants, but which may grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria). The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to exploit them commercially as biofertilizers. After an initial clarification of the term biofertilizers and the nature of associations between PGPR and plants (i.e., endophytic versus rhizospheric), this review focuses on the known, the putative, and the speculative modes-of-action of PGPR. These modes of action include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses. The combination of these modes of actions in PGPR is also addressed, as well as the challenges facing the more widespread utilization of PGPR as biofertilizers.
2,982 citations
01 Mar 2012
TL;DR: In this paper, the authors estimate that the amount of municipal solid waste (MSW) generated by urban populations is growing even faster than the rate of urbanization and that by 2025 this will likely increase to 4.3 billion urban residents.
Abstract: Solid waste management is the one thing just about every city government provides for its residents. While service levels, environmental impacts and costs vary dramatically, solid waste management is arguably the most important municipal service and serves as a prerequisite for other municipal action. As the world hurtles toward its urban future, the amount of municipal solid waste (MSW), one of the most important by-products of an urban lifestyle, is growing even faster than the rate of urbanization. Ten years ago there were 2.9 billion urban residents who generated about 0.64 kg of MSW per person per day (0.68 billion tonnes per year). This report estimates that today these amounts have increased to about 3 billion residents generating 1.2 kg per person per day (1.3 billion tonnes per year). By 2025 this will likely increase to 4.3 billion urban residents generating about 1.42 kg/capita/day of municipal solid waste (2.2 billion tonnes per year).
2,233 citations
TL;DR: Rhizobacteria-mediated induced systemic resistance (ISR) is effective under field conditions and offers a natural mechanism for biological control of plant disease.
Abstract: Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.
2,146 citations
11 Oct 2012
TL;DR: It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies.
Abstract: The worldwide increases in both environmental damage and human population pressure have the unfortunate consequence that global food production may soon become insufficient to feed all of the world's people. It is therefore essential that agricultural productivity be significantly increased within the next few decades. To this end, agricultural practice is moving toward a more sustainable and environmentally friendly approach. This includes both the increasing use of transgenic plants and plant growth-promoting bacteria as a part of mainstream agricultural practice. Here, a number of the mechanisms utilized by plant growth-promoting bacteria are discussed and considered. It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies. While there may not be one simple strategy that can effectively promote the growth of all plants under all conditions, some of the strategies that are discussed already show great promise.
2,094 citations
TL;DR: The basic concepts of the composting process and how manure characteristics can influence its performance are explained and a summary of those factors such as nitrogen losses, organic matter humification and compost maturity which affect the quality of composts produced by manure composting is presented.
1,795 citations