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Role of Indigenous Microbial Community in Bioremediation
Published in Vineet Kumar, Vinod Kumar Garg, Sunil Kumar, Jayanta Kumar Biswas, Omics for Environmental Engineering and Microbiology Systems, 2023
Bhupendra Pushkar, Pooja Sevak
The organic pollutant-degrading and metal-resistant gene groups are very important. The genes involved in aromatic and chlorinated compound degradation are increased in the presence of respective pollutants. The benzoyl-CoA reductase gene from Rhodopseudomonas palustris is abundant in organic polluted sites. The predicted microbial functional analysis indicated a shift and interrelationships between the genes involved in anaerobic and aerobic degradation of PAHs and the dissimilatory nitrate-reducing pathways (denitrification and dissimilatory nitrate reduction to ammonium – DNRA) (Ribeiro et al., 2018). The upregulation of functional genes such as dioxygenase and dehydrogenase is associated with the degradation of PAHs. Amino acid metabolism also plays an important role in the microbial detoxification process. The expression of PAH degradation genes improves upon modulation of carbohydrate and amino acid metabolisms (Li et al., 2020). The high abundance of nitrogen-containing organic pollutants-degrading functional genes is majorly contributed by microbial communities such as Dokdonella, Comamonas, Pseudoxanthomonas, Achromobacter, and Thermomonas, which also confirms the role of these taxa in the removal of nitrogen-containing organic pollutants (Zhang et al., 2021).
Bioprocessing of Agrofood Industrial Wastes for the Production of Bacterial Exopolysaccharide
Published in V. Sivasubramanian, Bioprocess Engineering for a Green Environment, 2018
J. Kanimozhi, V. Sivasubramanian, Anant Achary, M. Vasanthi, Steffy P. Vinson, R. Sivashankar
Glycerol, also known as glycerine or propane-1,2,3-triol, is a by-product of many industrial processes, mainly from biodiesel plants and soap manufacturing. Biodiesel is considered to be a green fuel and an alternative to fossil fuels. But large amounts of glycerol come from biodiesel plants and are disposed of without any conversion, which creates environmental pollution. Turning crude glycerol into an economically valuable product resolves waste management problems and also diminishes the cost of biodiesel. 1,3-propanediol is a simple organic chemical and has a variety of applications in the production of polymers, cosmetics, foods, lubricants, and medicines. Dipankar et al. (2012) have suggested the production of hydrogen from crude glycerol using a strain of Rhodopseudomonas palustris via photofermentation. The n-butanol acts as an ideal solvent for antibiotics, vitamins, and hormones in pharmaceuticals and as a feedstock for production of various polymers. Clostridium pasteurianum is immobilized on Amberlite to convert crude glycerol into n-butanol by anaerobic fermentation and yielded maximum n-butanol at 25 g/L of initial glycerol concentration (Swati et al. 2013). Glycerol acts as a carbon source in the fermentation process for the production of extracellular polysaccharide (EPS). As far as it concern the idea of conversion of glycerol into useful products is demanded while considering the market values.
Bioenergy Production from Waste Substrates
Published in Farshad Darvishi Harzevili, Serge Hiligsmann, Microbial Fuels, 2017
Amit Kumar, Anish Ghimire, Bo H. Svensson, Piet N.L. Lens
The extraordinary metabolic diversity found in nature is still far from being fully exploited. Several microbes, including Clostridium and Bacteroides, excrete cellulosomes (complexes of cellulolytic enzymes bound together by cohesion scaffoldings) that assist in the digestion or degradation of plant cell wall materials, most notably cellulose. Therefore, these organisms can be utilized for biofuel production by enhancing saccharification of complex substances such as plant biomass. As such, Rhodopseudomonas palustris, a purple photosynthetic bacterium widely distributed in nature, is among the most metabolically versatile bacteria known. It degrades plant biomass and chlorinated pollutants and also generates hydrogen as a product of nitrogen fixation. R. palustris uses light, inorganic compounds, or organic compounds for energy and grows both aerobically and anaerobically. It is thus a model organism to probe how the web of metabolic reactions that operates within the confines of a single cell adjusts and reweaves in response to changes in light, carbon, nitrogen, and electron sources (Larimer et al. 2004).
Recent advances in arsenic mitigation in rice through biotechnological approaches
Published in International Journal of Phytoremediation, 2023
Shraddha Singh, Sudhakar Srivastava
Methylation of As is considered an important strategy for detoxification in bacteria, fungi, algae, animals, and humans; however, it is not well known in plants (Qin et al. 2006). ArsM is the gene responsible for As methylation and its expression in rice may catalyze methylation and volatilization of As and provides an efficient alternative to decrease As levels in rice grains. Meng et al. (2011) transformed the ArsM gene of soil bacterium Rhodopseudomonas palustris into rice and reported that transgenic rice generated methylated As species, which led to higher levels of volatile arsenicals (10 times more) than the WT and As accumulation decreased in transgenic rice grains. Recently, transgenic rice with WaarsM gene from Westerdykella aurantiaca showed the methylation of inorganic As to organic species showing lower As accumulation in grain as well as straw (Verma et al. 2018). However, it is very crucial to optimize heterologous gene expression and its regulation in rice before introducing As methylation and it is also important to study the toxicity of the intermediate organic As species generated during the methylation process in transgenic rice plants. A list of studies carried out for transgenic rice development for As accumulation regulation is presented as Table 1.
Co-metabolic biodegradation of 4-chlorophenol by photosynthetic bacteria
Published in Environmental Technology, 2021
Binchao Lu, Liang Wang, Xin Zheng, Zhongce Hu, Zhiyan Pan
PSB have been used in a wide range of fields to treat wastewater under both aerobic and anaerobic conditions because they can simultaneously biodegrade organic pollutants in wastewater and recycle biomass [11–13]. PSB are very flexible and can thrive under different light levels and oxygen concentrations [14]. They are able to change their metabolism as light and oxygen conditions change [15]. Under dark aerobic conditions, PSB lack chromophores and mainly use organic matter as a respiratory matrix for aerobic growth. This process is carried out via the tricarboxylic acid cycle, and the final electron acceptor is oxygen. PSB can more rapidly form chromophores under light anaerobic conditions, mainly via fermentation and photosynthesis. This process metabolizes the energy created via photophosphorylation, and the final electron acceptor is an intermediate fermentation product [16]. For example, Rhodopseudomonas palustris DCP3 and Rhodobacter sphaeroides Z08 can use organic compounds as carbon and energy sources under dark aerobic and light anaerobic conditions [16,17], and PSB can degrade starchy wastewater and recycle biological resources [18]. The biodegradation of 2,6-dichlorophenol and 2,4,6-trichlorophenol by PSB under dark aerobic conditions has previously been studied [19]. The process proceeds through the Krebs cycle, and the final electron acceptor is oxygen. Compared with light anaerobic conditions, it is easier to achieve dark aerobic conditions in practical engineering applications. Therefore, it is important to explore the ability of PSB to degrade chlorophenols in wastewater under such conditions.
Comparative study between compost and granular sludge inoculums as promising microbial consortia sources for biohydrogen production from food industry wastewater
Published in Biofuels, 2022
Alfredo Cruz-Méndez, Santiago Iván Suárez-Vázquez, Lirio María Reyna-Gómez, Arquímedes Cruz-López
In recent decades, considerable and collective efforts among all sectors of society have been directed towards improving the relationship between humans and the environment, emphasizing the study and development of renewable energy sources. The purpose of these efforts is to efficiently meet global energy demands while reducing the generation of greenhouse gases [1]. This indicates that research into the biological production of biohydrogen is strategically important because this process can bioremediate industrial wastewater via dark fermentation (DF), thereby improving the economy of and reducing the accumulation of waste in several important industrial regions worldwide. DF also has several advantages over other biotechnological processes, including the fact that the process is markedly less complex; DF is performed at temperature and pressure conditions that closely resemble atmospheric conditions, reducing the need for the provision of additional heat or pressure to the system. Additionally, illumination is not a necessary requirement for conducting DF, that can be performed using substrates derived from finite sources [2–4]. Nevertheless, there are several drawbacks at producing biohydrogen from biological waste products, most of them relate to the substrate type, as this may affect the bioreactor’s performance, the microbial communities within the system, and microbial metabolic activities [5]. Various studies indicate that substrates rich in carbohydrates, such as glucose, sucrose, and starch mixtures, are easily assimilated during DF by pure cultures (Clostridia, Citrobacter spp., Rhodopseudomonas palustris, Klebsiella oxytoca HP1, and so on), thereby achieving good biohydrogen production rates ranging from 0.21 to 2.49 L L−1 h−1 [6]; however, large scale use of these substrates is not possible, necessitating identification of complex carbon sources, primarily from wastewater [2,7,8].