Anaerobic digestion of sugarcane bagasse for biogas production and digestate valorization.

Sugarcane bagasse is an abundantly available agricultural waste having high potential that is still underutilized and mostly burnt as fuel. There are various processes available for bagasse utilization in improved ways and one such process is anaerobic digestion (AD) of bagasse for biogas production. The complex structure of biomass is recalcitrant to degradation and is a major hindrance for the anaerobic digestion, so different pretreatment methods are applied to deconstruct the bagasse for microbial digestion. In this review, different processes developed for the pretreatment of bagasse and their effect on biogas production have been extensively covered. Moreover, combination of pretreatment methods, co-digestion of bagasse with other waste (nitrogen rich or easily digestible) for enhanced biogas production and biomethane generation along with other value-added products has also been reviewed. The digestate contains a significant amount of organics with partial recovery of energy and products and is generated in huge amount that further creates disposal problem. Therefore, integration of digestate valorization with AD through gasification, pyrolysis, hydrothermal carbonization and use of microalgae for maximum recovery of energy and value-added products have also been evaluated. Thus, this review highlights major emerging area of research for improvement in bagasse based processes for enhanced biogas production along with digestate valorization to make the overall process economical and sustainable.

The role of conductive nanoparticles in anaerobic digestion: Mechanism, current status and future perspectives.

In the current scenario, alternative energy sources are the need of the hour. Organic wastes having a larger fraction of biodegradable constituents present a sustainable bioenergy source. It has been reported that the calorific value of biogas generated by anaerobic digestion (AD) is 21-25 MJ/m3 with the treatment which makes it an excellent replacement of natural gas and fossil fuels and can reduce more than 80% greenhouse gas emission to the surroundings. However, there are some limitations associated with the AD process for instance ammonia build-up at the first stage reduces the rate of hydrolysis of biomass, whereas, in the last stage it interferes with methane formation. Owing to special physicochemical properties such as high activity, high reactive surface area, and high specificity, tailor-made conductive nanoparticles can improve the performance of the AD process. In the AD process, H2 is used as an electron carrier, referred as mediated interspecies electron transfer (MIET). Due to the diffusion limitation of these electron carriers, the MIET efficiency is relatively low that limits the methanogenesis. Direct interspecies electron transfer (DIET), which enables direct cell-to-cell electron transport between bacteria and methanogen, has been considered an alternative efficient approach to MIET that creates metabolically favorable conditions and results in faster conversion of organic acids and alcohols into methane. This paper discusses in detail the application of conductive nanoparticles to enhance the AD process efficiency. Interaction between microbes in anaerobic conditions for electron transfer with the help of CNPs is discussed. Application of a variety of conductive nanomaterials as an additive is discussed with their potential biogas production and treatment enhancement in the anaerobic digestion process.

Towards sustainable agriculture with carbon sequestration, and greenhouse gas mitigation using algal biochar.

With the increase in the world's population, demand for food and other products is continuously rising. This has put a lot of pressure on the agricultural sector. To fulfill these demands, the utilization of chemical fertilizers and pesticides has also increased. Consequently, to overcome the adverse effects of agrochemicals on our environment and health, there has been a shift towards organic fertilizers or other substitutes, which are ecofriendly and help to maintain a sustainable environment. Microalgae have a very high potential of carbon dioxide (CO2) capturing and thus, help in mitigating the greenhouse effect. It is the most productive biological system for generating biomass. The high growth rate and higher photosynthetic efficiency of the algal species compared to the terrestrial plants make them a wonderful alternative towards a sustainable environment. Moreover, they could be cultivated in photobioreactors or open ponds, which in turn reduce the demand for arable land. Biochar derived from algae is high in nutrients and exhibits the property of ion exchange. Therefore, it can be utilized for sustainable agriculture by partial substituting the chemical fertilizers that degrade the fertility of the soil in the long run. This review provides a detailed insight on the properties of algal biochar as a potential fertilizer for sustainable agriculture. Application of algal biochar in bio-refinery and its economic aspects, challenges faced and future perspective are also discusses in this study.

Remediation strategies for mitigation of phthalate pollution: Challenges and future perspectives.

Phthalates are a group of emerging xenobiotic compounds commonly used as plasticizers. In recent times, there has been an increasing concern over the risk of phthalate exposure leading to adverse effects to human health and the environment. Therefore, it is necessary to not only understand the current status of phthalate pollution, their sources, exposure routes and health impacts, but also identify remediation technologies for mitigating phthalate pollution. Present review article aims to inform its readers about the ever increasing data on health burdens posed by phthalates and simultaneously highlights the recent advancements in research to alleviate phthalate contamination from environment. The article enumerates the major phthalates in use today, traces their environmental fate, addresses their growing health hazard concerns and largely focus on to provide an in-depth understanding of the different physical, chemical and biological treatment methods currently being used or under research for alleviating the risk of phthalate pollution, their challenges and the future research perspectives.

Green technology for sustainable biohydrogen production (waste to energy): A review.

Perceiving and detecting a sustainable source of energy is very critical issue for current modern society. Hydrogen on combustion releases energy and water as a byproduct and has been considered as an environmental pollution free energy carrier. From the last decade, most of the researchers have recommended hydrogen as one of the cleanest fuels and its demand is rising ever since. Hydrogen having the highest energy density is more advantageous than any other fuel. Hydrogen obtained from the fossil fuels produces carbon dioxide as a byproduct and creates environment negative effect. Therefore, biohydrogen production from green algae and cyanobacteria is an attractive option that generates a benign renewable energy carrier. Microalgal feedstocks show a high potential for the generation of fuel such as biohydrogen, bioethanol and biodiesel. This article has reviewed the different methods of biohydrogen production while also trying to find out the most economical and ecofriendly method for its production. A thorough review process has been carried out to study the methods, enzymes involved, factors affecting the rate of hydrogen production, dual nature of algae, challenges and commercialization potential of algal biohydrogen.

Cell density, Lipidomic profile, and fatty acid characterization as selection criteria in bioprospecting of microalgae and cyanobacterium for biodiesel production.

Selection of indigenous and potential algal strain with high lipid content is paramount challenge in the avenues of microalgal biodiesel production. Particularly, hyper lipid producing algae with maximal triacyglycerols (TAGs) content and preferable fatty acid composition is of interest for sustainable biodiesel. Hence, the present study on comparative assessment of Chlorella vulgaris, Scenedesmus sp. and Synechococcus sp. was done in terms of cell density, lipid, TAGs and fatty acid. Higher biomass yield was obtained in Chlorella vulgaris (0.54 gL-1) on 13th day while maximal lipid content of 36% was observed in Scenedesmus sp. followed by Chlorella vulgaris (33%). Lipidomic analysis revealed higher non-polar lipids inChlorella vulgaris (57%) and Scenedesmus sp. (54%), whereas in Synechococcus sp. 69% polar lipids were present. In fatty acid profile, C24:0 (22.11%) was predominant in Chlorella vulgaris, while C20:0 (31.72%) and C18:2 (22.26%) was prevalent in Scenedesmus sp. and Synechococcus sp. respectively.

Upgrading of microalgal consortia with CO2 from fermentation of wheat straw for the phycoremediation of domestic wastewater.

Algae have been considered as a best feedstock for combating CO2. In the present study, two mixed microalgal cultures i.e. MAC1 and MAC2 were evaluated in batch mode with an extraneous supply of CO2 from the fermentation of wheat straw. Both the mixed cultures displayed promising CO2 sequestration potentials of 287 and 263 mg L-1d-1, respectively. The removal efficiencies in terms of ammonium, phosphate, chemical oxygen demand, and nitrate were found to be 87%, 78%, 68% and 65%, respectively. Enriching the tolerance of the microalgal consortia to CO2 supply and wastewater as the nutrient source significantly enhanced the lipid production for both the microalgae consortia. Lipid contents of MAC1 and MAC2 were observed to be 12.29 & 11.37%, respectively while the biomass yield from both the consortia was 0.36 g L-1. Total chlorophyll and protein contents of MAC1 and MAC2 were 14.27 & 12.28 µgmL-1 and 0.13 & 0.15 mgmL-1, respectively. Both the consortia found to have significant potential for CO2 sequestration, wastewater remediation and biofuel production.

Alkalinity and salinity favor bioelectricity generation potential of Clostridium, Tetrathiobacter and Desulfovibrio consortium in Microbial Fuel Cells (MFC) treating sulfate-laden wastewater.

Clostridium, Tetrathiobacter and Desulfovibrio species are identified as suitable biocatalysts for treating organic-rich and sulfate-laden wastewater. Results from this study show that the power generation was much higher under alkaline conditions, i.e., pH of 8 when compared to neutral and acidic conditions. The effect of salinity was studied by varying the sodium chloride concentration at (1.5, 3, 4.5, 6, and 7.5 g/L NaCl) in anolyte. The highest power density of 1188 mW/m3 was produced at a sodium chloride concentration of 6 g/L in the anolyte. Results from cyclic voltammetry and linear scan voltammetry analysis suggested the direct electron transfer mechanism favored by cytb and cytc, Redox peaks observed for the biogenic synthesis of sulfite and sulfide support the complete one-step mineralization of sulfate. Bioelectrochemical behavior of the selectively enriched microbial consortium confirms its use for the treatment of wastewaters high in salinity and sulfate concentrations.

Valorization of agricultural waste for biogas based circular economy in India: A research outlook.

Environmental deterioration and the need for energy security are intrinsic problems linked with the linear economy based on fossil fuels. Recently, a transformation to a sustainable circular bio-economy is being experienced where biomass waste is being valorized for energy production as well as minimization of waste and greenhouse gas emissions. The agricultural waste, generated in vast quantities in India is a prospective feedstock for biogas production. Agri-waste to biogas based circular economy requires an integration of agri-waste management, biogas production and utilization and policy support. This paper comprehensively discusses the potential of biogas production from agricultural waste, its upgradation and utilization along with the government initiatives, policy regulations. In addition, barriers that impede the development of an efficient agri-waste to biogas based circular economy, and the future research opportunities to meet the growing needs for agri-waste management, energy production and climate change mitigation are discussed.

Industrial wastes: Fly ash, steel slag and phosphogypsum- potential candidates to mitigate greenhouse gas emissions from paddy fields.

Waste management and global warming are the two challenging issues of the present global scenario. Increased human population has set the platform for rapid industrialization and modern agriculture. The industries such as energy, steel, and fertilizers play a significant role in improving the social, and economic status of human beings. The industrial production of energy (that involves combustion of coal), production of steel items and diammonium ammonium fertilizer generate a huge amount of wastes such as fly ash (FA), steel slag (SS) and phosphogypsum (PG), respectively. Inappropriate dumping of any kind of waste poses a threat to the environment, therefore, scientific management of waste is required to reduce associated environmental risks. These wastes i.e. SS, FA, and PG being rich sources of oxides of calcium (CaO), silicon (SiO2), iron (FeO), and aluminum (Al2O3), etc. may affect the release of greenhouse gases from the soil. The information associated with the application of FA, SS, and PG onto the paddy fields and their impacts on methane and nitrous oxide emissions are highly fragmented and scarce. The present review extensively and critically explores the available information with respect to the effective utilization of FA, SS, and PG in paddy cultivation, their potential to mitigate greenhouse gases emission and their associated mechanisms. The fine grid assessment of these waste management provides new insight into the next level research and future policy options for industries and farmers.

An overview on bioethanol production from lignocellulosic feedstocks.

Lignocellulosic ethanol has been proposed as a green alternative to fossil fuels for many decades. However, commercialization of lignocellulosic ethanol faces major hurdles including pretreatment, efficient sugar release and fermentation. Several processes were developed to overcome these challenges e.g. simultaneous saccharification and fermentation (SSF). This review highlights the various ethanol production processes with their advantages and shortcomings. Recent technologies such as singlepot biorefineries, combined bioprocessing, and bioenergy systems with carbon capture are promising. However, these technologies have a lower technology readiness level (TRL), implying that additional efforts are necessary before being evaluated for commercial availability. Solving energy needs is not only a technological solution and interlinkage of various factors needs to be assessed beyond technology development.

Algae as green energy reserve: Technological outlook on biofuel production.

Depletion of fossil fuel sources and their emissions have triggered a vigorous research in finding alternative and renewable energy sources. In this regard, algae are being exploited as a third generation feedstock for the production of biofuels such as bioethanol, biodiesel, biogas, and biohydrogen. However, algal based biofuel does not reach successful peak due to the higher cost issues in cultivation, harvesting and extraction steps. Therefore, this review presents an extensive detail of deriving biofuels from algal biomass starting from various algae cultivation systems like raceway pond and photobioreactors and its bottlenecks. Evolution of biofuel feedstocks from edible oils to algae have been addressed in the initial section of the manuscript to provide insights on the different generation of biofuel. Different configuration of photobioreactor systems used to reduce contamination risk and improve biomass productivity were extensively discussed. Photobioreactor performance greatly relies on the conditions under which it is operated. Hence, the importance of such conditions alike temperature, light intensity, inoculum size, CO2, nutrient concentration, and mixing in bioreactor performance have been described. As the lipid is the main component in biodiesel production, several pretreatment methods such as physical, chemical and biological for disrupting cell membrane to extract lipid were comprehensively reviewed and presented. This review article had put forth the recent advancement in the pretreatment methods like hydrothermal processing of algal biomasses using acid or alkali. Eventually, challenges and future dimensions in algal cultivation and pretreatment process were discussed in detail for making an economically viable algal biofuel.

Microalgal consortia for municipal wastewater treatment - Lipid augmentation and fatty acid profiling for biodiesel production.

The present study investigates the phycoremediation potentials of two microalgal consortia (MAC1 and MAC2) for treating sewage water and producing biomass with high lipid, protein and chlorophyll contents. During the study, the microalgal strains were tested for lipid enhancement, biomass production and contaminant removal from wastewater. The microalgal consortia showed prolific growth in wastewater with 75% dilution and accumulated higher lipid content of 31.33% dry cell weight in MAC1. The maximum biomass (50% diluted wastewater) for both the consortia was 1.53 and 1.04 gL-1. Total chlorophyll (19.17-25.17 µg mL-1) and protein contents (0.12-0.16 mg mL-1) for both the consortia were found to be maximum in 75 WW. MAC1 was capable of removing 86.27% of total organic carbon and 87.6% of chemical oxygen demand. Approximately, 94% of nitrate and phosphate contents were removed from the initial contents of wastewater. Heavy metal removal efficiency was also found to be better and showed 85.06% Cu, 75.2% Cr, 98.2% Pb, and 99.6% Cd removal by the algal consortia. Pyrolytic decomposition of algal consortia was observed using thermogravimetric analysis. The stepwise decomposition of algae indicated distinct losses of functional groups. The gas chromatography-mass spectrometric analysis revealed the majority of saturated fatty acids followed by monounsaturated and polyunsaturated fatty acids. Thus, the present study proved that both the consortia show tremendous potential for the treatment of domestic wastewaters with successive lipid enhancement for biodiesel production.

Enhanced biogas production from municipal solid waste via co-digestion with sewage sludge and metabolic pathway analysis.

The present study intends to evaluate the potential of co-digestion for utilizing Organic fraction of Municipal Solid Waste (OFMSW) and sewage sludge (SS) for enhanced biogas production. Metagenomic analysis was performed to identify the dominant bacteria, archaea and fungi, changes in their communities with time and their functional roles during the course of anaerobic digestion (AD). The cumulative biogas yield of 586.2 mL biogas/gVS with the highest methane concentration of 69.5% was observed under an optimum ratio of OFMSW:SS (40:60 w/w). Bacteria and fungi were found to be majorly involved in hydrolysis and initial stages of AD. Probably, the most common archaea Methanosarsina sp. primarily followed the acetoclastic pathway. The hydrogenotrophic pathway was less followed as indicated by the reduction in abundance of syntrophic acetate oxidizers. An adequate understanding of microbial communities is important to manipulate and inoculate the specific microbial consortia to maximize CH4 production through AD.

A comprehensive review on enzymatic degradation of the organophosphate pesticide malathion in the environment.

A comprehensive review of available bioremediation technologies for the pesticide malathion is presented. This review article describes the usage and consequences of malathion in the environment, along with a critical discussion on modes of metabolism of malathion as a sole source of carbon, phosphorus, and sulfur for bacteria, and fungi along with the biochemical and molecular aspects involved in its biodegradation. Additionally, the recent approaches of genetic engineering are discussed for the manipulation of important enzymes and microorganisms for enhanced malathion degradation along with the challenges that lie ahead.

Clinically important microbial diversity and its antibiotic resistance pattern towards various drugs.

BACKGROUND: Increased use of antibiotics in poultry leads to the development of antimicrobial resistance among the commensal bacterium of broiler chickens. OBJECTIVE: In this study, we aimed at studying the effect of periodic administration of therapeutic antibiotics against the bacterial diversity in poultry litters collected from broiler chickens. METHODS: Poultry litters were collected randomly at regular intervals after administration of antibiotics (1st, 12th and 22nd day) to the chicken. Bedding material without litters served as control. Phenotypic observations showed that there is a difference in the bacterial richness isolated at regular intervals. A total of 32 bacteria were isolated from poultry letters and are grouped into ten different genus. Isolated bacterial species were further confirmed by16S rRNA sequencing. RESULTS: Antibiotic susceptibility profile of isolated bacterial species exhibited strong resistance towards 13 selected antibiotics. These results substantiate that administration of antibiotics leads to the alterations in bacterial diversity and development of antimicrobial resistance among the commensal bacteria of poultry litter. CONCLUSION: This high selection pressure of therapeutic antibiotics may lead to species selection and development of antibiotic resistance among bacterial population. Development of such species selection may access the human and other organisms via food chain and can cause severe health defects.

Screening and enrichment of high lipid producing microalgal consortia.

Lipid content is the main parameter for the evaluation of microalgae towards biodiesel production. The present study was aimed at the screening of desirable algal consortia based on lipid content for further processing into biofuel. Twenty different algal consortia were investigated for lipid content qualitatively by Nile Red and quantitatively by gravimetric method and FTIR. Nile Red is used as a fluorophore for physically characterizing the lipid body in algal cultures. The yellow fluorescence in all the samples confirmed the presence of lipid content when observed under a fluorescent microscope. Lipid contents of algal consortia estimated by gravimetry varied from 3.53-16.21%, which was higher than that assessed by FTIR analysis. FTIR spectroscopy can be used for the quantitative estimation of lipid content, protein and carbohydrate concentration. FTIR analysis of the samples revealed the presence of lipid content by virtue of methylene and methyl stretching peaks at 2800-3000 cm-1. The appearance of stretching vibrations at 1600-1700 cm-1 and 1000-1200 cm -1 obtained by FTIR spectra confirmed the presence of protein contents and carbohydrate, respectively in all the samples. Two algal consortia SM 4 and SM13 were screened out on the basis of high lipid concentration. These algal samples can be further optimized for enhanced biofuel production.

Biogenesis of copper oxide nanoparticles (CuONPs) using Sida acuta and their incorporation over cotton fabrics to prevent the pathogenicity of Gram negative and Gram positive bacteria.

Textile industry is a major sector providing global financial and employment support to different countries of the world. The major problems of the textile industry are dirt and microbial contaminants affecting the quality of cotton fabrics. Recently, nanoparticles such as silver, chitosan, silicon dioxide, titanium dioxide and zinc oxide have gained attraction in textile industries to avoid the contamination of fabrics through microbes. The necessity to develop an ecofriendly, efficient and cost effective method for the synthesis of nanoparticles is under the radar. Plant extracts serve as potential reducing and coating agents due to the presence of bioactive molecules such as phenols, lipids, carbohydrates, enzymes, protein molecules etc., which endow effective antimicrobial activity to the nanoparticles. In the present study, biological synthesis of Copper oxide nanoparticles (CuONPs) was performed using S. acuta leaf extract. CuONPs were synthesized and characterized using UV-vis, FTIR, SEM and TEM analyses. The antimicrobial property of CuONPs was tested against Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Staphylococcus aureus) pathogens, which showed zones of inhibition at different concentrations. As the final part of the study, CuONPs were coated over cotton fabrics showing longer stability, which prevented the growth of infectious pathogens. Apart from the antimicrobial activity, CuONPs synthesized using S. acuta possessed effective photocatalytic activity against commercial dyes.

Photocatalytic properties and antimicrobial efficacy of Fe doped CuO nanoparticles against the pathogenic bacteria and fungi.

Pathogenic microbes are becoming a potential threat to human beings and environment. Owing to the biofilm forming ability, multidrug resistant pathogens have emerged, which has led to increased death and mortality rate. CuO is a transition metal oxide with high captivating property used for various technological applications such as superconductors, gas sensors, photocatalytic applications etc. CuO in the form of nanoparticles (NPs) is a potential candidate against microbial pathogens. Recently, the antimicrobial and antibiofilm properties of CuO have been tested against various pathogenic bacteria and fungi. In the present study, Fe doped CuO synthesized using sol-gel method was tested against pathogenic bacteria and fungus. The synthesized NPs were characterized using XRD, FTIR, SEM and EDAX analysis. The photocatalytic activity of the Fe doped CuO NPs was analysed using UV-Vis and fluorescent light spectroscopic analysis (FL). In vitro analysis was performed to analyze the antimicrobial and antibiofilm potentials of Fe doped CuO NPs against the pathogenic bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and fungus (Candida albicans). Therefore, the present study is the first report showing both antibiofilm and antibacterial activities of Fe doped CuO NPs against bacterial and fungal pathogens.

Biological approaches to tackle heavy metal pollution: A survey of literature.

Pollution by heavy metals has been identified as a global threat since the inception of industrial revolution. Heavy metal contamination induces serious health and environmental hazards due to its toxic nature. Remediation of heavy metals by conventional methods is uneconomical and generates a large quantity of secondary wastes. On the other hand, biological agents such as plants, microorganisms etc. offer easy and eco-friendly ways for metal removal; hence, considered as efficient and alternative tools for metal removal. Bioremediation involves adsorption, reduction or removal of contaminants from the environment through biological resources (both microorganisms and plants). The heavy metal remediation properties of microorganisms stem from their self defense mechanisms such as enzyme secretion, cellular morphological changes etc. These defence mechanisms comprise the active involvement of microbial enzymes such as oxidoreductases, oxygenases etc, which influence the rates of bioremediation. Further, immobilization techniques are improving the practice at industrial scales. This article summarizes the various strategies inherent in the biological sorption and remediation of heavy metals.