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•This review focused on the methane generation using micro and macroalgae.•Discussed key issues and pretreatment strategies to improve AD and methane yield.•Summarized co-digestion ...process using algal biomass to enhance methane yield.•Enlightened future perspectives and challenges for algal methane production.
Biogas production using algal resources has been widely studied as a green and alternative renewable technology. This review provides an extended overview of recent advances in biomethane production via direct anaerobic digestion (AD) of microalgae, macroalgae and co-digestion mechanism on biomethane production and future challenges and prospects for its scaled-up applications. The effects of pretreatment in the preparation of algal feedstock for methane generation are discussed briefly. The role of different operational and environmental parameters for instance pH, temperature, nutrients, organic loading rate (OLR) and hydraulic retention time (HRT) on sustainable methane generation are also reviewed. Finally, an outlook on the possible options towards the scale up and enhancement strategies has been provided. This review could encourage further studies in this area, to intend and operate continuous mode by designing stable and reliable bioreactor systems and to analyze the possibilities and potential of co-digestion for the promotion of algal-biomethane technology.
In recent years, the use of nanoparticle-based antimicrobials has been increased due to many advantages over conventional agrochemicals. This study investigates the utilization of common medicinal ...plant dandelion,
Taraxacum officinale
, for the synthesis of silver nanoparticles (TOL-AgNPs). AgNPs were evaluated for antimicrobial activity against two important phytopathogens,
Xanthomonas axonopodis
and
Pseudomonas syringae.
The morphology, size, and structure of TOL-AgNPs were characterized using UV-visible spectroscopy and X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FT-IR) showed the presence of phytochemicals involved during synthesis of NPs. High-resolution transmission electron microscopy (HR-TEM) analysis shed light on the size of monodispersed spherical AgNPs ranging between 5 and 30 nm, with an average particle size of about 15 nm. The TOL-AgNPs (at 20 μg/mL concentration) showed significant antibacterial activity with significant growth inhibition of phytopathogens
X. axonopodis
(22.0 ± 0.84 mm) and
P. syringae
(19.5 ± 0.66 mm). The synthesized AgNPs had higher antibacterial activity in comparison with commercial AgNPs. Synergistic assays with standard antibiotics revealed that nanoformulations with tetracycline showed better broad-spectrum efficiency to control phytopathogens. They also possessed significant antioxidant potential in terms of ABTS (IC
50
= 45.6 μg/mL), DPPH (IC
50
= 56.1 μg/mL), and NO (IC
50
= 55.2 μg/mL) free radical scavenging activity. The TOL-AgNPs showed high cytotoxic effect against human liver cancer cells (HepG2). Overall, dandelion-mediated AgNPs synthesis can represent a novel approach to develop effective antimicrobial and anticancer drugs with a cheap and eco-friendly nature.
This study first time reports the novel synthesis of silver nanoparticles (AgNPs) using a Punica granatum leaf extract (PGE). The synthesized AgNPs were characterized by various analytical techniques ...including UV-Vis, Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy and energy-dispersive spectra (FESEM-EDS) and high-resolution transmission electron microscopy (HRTEM). FTIR analysis revealed that the involvement of biological macromolecules of P. granatum leaf extract were distributed and involved in the synthesis and stabilization of AgNPs. A surface-sensitive technique of XPS was used to analyse the composition and oxidation state of synthesized AgNPs. The analytical results confirmed that the AgNPs were crystalline in nature with spherical shape. The zeta potential study revealed that the surface charge of synthesized AgNPs was highly negative (−26.6 mV) and particle size distribution was ranging from ∼35 to 60 nm and the average particle size was about 48 nm determined by dynamic light scattering (DLS). The PGE-AgNPs antidiabetic potential exhibited effective inhibition against α-amylase and α-glucosidase (IC
50
; 65.2 and 53.8 μg/mL, respectively). The PGE-AgNPs showed a dose-dependent response against human liver cancer cells (HepG2) (IC
50
; 70 μg/mL) indicating its greater efficacy in killing cancer cells. They also possessed in vitro free radical-scavenging activity in terms of ABTS (IC
50
; 52.2 μg/mL) and DPPH (IC
50
; 67.1 μg/mL) antioxidant activity. PGE-AgNPs displayed strong antibacterial activity and potent synergy with standard antibiotics against pathogenic bacteria. Thus, synthesized PGE-AgNPs show potential biomedical and industrial applications.
Among four isolated cellulolytic microorganisms, Streptomyces sp. MDS can utilize a broad range of cellulosic substrates including: carboxymethyl cellulose, avicel, xylan, cellobiose, filter paper, ...wood straw and rice straw by producing a large amount of endoglucanase, exoglucanase, cellobiase, xylanase and glucoamylase. Effects of different physicochemical parameters to achieve maximum production of cellulolytic enzymes were systematically investigated. It was found that the cellulolytic enzyme activities were mainly located at extracellular location. It was observed that supplementation of CaCl2 (5 mM) as a metal additive significantly induced the whole enzyme system. These cellulases also have high thermal stability as evidenced by retaining 60–70% activity at 90 °C and pH 5 and alkalotolerance as more than 55–60% of the activity at pH 10 and 40 °C and 60 °C (for endoglucanase) after 1 h of incubation. The enzymes also retained up to 50–70% of its initial activity upon incubation in the presence of commercials detergents for 1 h. Finally, the efficiency of fermentative conversion of the CMC and rice straw hydrolyzate by Saccharomyces cerevisiae (KCTC 7296) resulted in 55.8 and 57.2% of maximum theoretical ethanol yield based on sugar (glucose and xylose) fermentation, respectively.
► A novel cellulolytic microorganism Streptomyces sp. MDS was isolated. ► This strain have ability to utilize pure cellulosic substrates as well as agricultural waste namely rice straw for cellulolytic enzymes production. ► The produced cellulolytic enzymes show stability at extremely thermophilic, alkaline condition. ► The produced enzymes stable in the presence of commercial detergents increases the industrial applicability of this strain. ► Finally, the cellulosic hydrolysate was used for fermentative ethanol production using S. cerevisiae.
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•Discussed intrinsic relation of algae cultivation strategies using inexpensive nutrient sources.•Advancements in cultivation techniques for enhanced biomass production.•Current ...status for microalgae biofuels at large-scale production.•Addressed challenges and future prospectives Microalgal biorefinery as feasible approach.
Scientists are grabbing huge attention as well as consciousness on non–renewable energy sources for the global energy crises because of gradual increase in oil price, fast depletion or low availability of resources, and the release of more toxic–gases (CO2, SOx, NxO) during exhaustion, etc. Due to such hitches, the key need is to find alternative biofuels or feedstocks to replace fossil fuel energy demands worldwide. Currently, microalgae have become intrigued feedstock candidates (3rd generation source of biofuel) to replace nearly 50–60 % of fossil fuels due to high production of biomass and oil, mitigating CO2 and wastewater remediation. The present work demonstrated the current developments and future perspectives on large–scale algal cultivation strategies for the biorefinery economy. In addition, various advanced cultivation techniques adopted for enhanced biomass production and cost-effective methods for bioenergy production were detailly discussed.
A novel bacterium was isolated from the soil of Ichalkaranji textile industrial area. Through 16S rRNA sequence matching and morphological observation it was identified as Lysinibacillus sp. RGS. ...This strain has ability to decolorize various industrial dyes among which, it showed complete decolorization and degradation of toxic sulfonated azo dye C.I. Remazol Red (at 30°C, pH 7.0, under static condition) with higher chemical oxygen demand (COD) reduction (92%) within 6 h of incubation. Various parameters like agitation, pH, temperature and initial dye concentrations were optimized to develop faster decolorization process. The supplementation of cheap co-substrates (e.g., extracts of agricultural wastes) could enhance the decolorization performance of Lysinibacillus sp. RGS. Induction in oxidoreductive enzymes presumably indicates involvement of these enzymes in the decolorization/degradation process. Analytical studies of the extracted metabolites confirmed the significant degradation of Remazol Red into various metabolites. The phytotoxicity assay (with respect to plants Phaseolus mungo and Sorghum vulgare) revealed that the degradation of Remazol Red produced nontoxic metabolites. Finally Lysinibacillus sp. RGS was applied to decolorize mixture of dyes and actual industrial effluent showing 87% and 72% decolorization (in terms of decrease in ADMI value) with 69% and 62% COD reduction within 48 h and 96 h, respectively. The foregoing result increases the applicability of the strain for the treatment of industrial wastewaters containing dye pollutants.
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.
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•Bioremediation is a promising technology for addressing the issues of heavy metal pollution.•Microbial cellular components and the enzyme secretions can effectively aid biosorption.•Immobilization of microorganisms on macro-materials improves biosorption efficiency.•Use of nanomaterials for site specific clean-up is emerging as a latest technology.
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•BES-mediated biofuels production and nutrient removal/recovery are summarized.•Bioelectrochemical systems are promising for recovering ammonium nitrogen.•Integration of biological ...and BES allows the development of new waste biorefineries.•Several bottlenecks that are preventing or delaying the commercialization of BES are discussed.•Conferred future challenges to develop a research interest in BESs.
Bioelectrochemical systems (BES) have the potential to be used in a variety of applications such as waste biorefinery, pollutants removal, CO2 capture, and the electrosynthesis of clean and renewable biofuels or byproducts, among others. In contrast, many technical challenges need to be addressed before BES can be scaled up and put into real-world applications. Utilizing BES, this review article presents a state-of-the-art overall view of crucial concepts and the most recent innovative results and achievements acquired from the BES system. Special attention is placed on a hybrid approach for product recovery and wastewater treatment. There is also a comprehensive overview of waste biorefinery designs that are included. In conclusion, the significant obstacles and technical concerns found throughout the BES studies are discussed, and suggestions and future requirements for the virtual usage of the BES concept in actual waste treatment are outlined.
A surface-engineered nano-support for enzyme laccase-immobilization was designed by grafting the surface of halloysite nanotubes (HNTs) with Fe3O4 nanoparticles and chitosan. Herein, HNTs were ...magnetized (HNTs-M) by a cost-effective reduction-precipitation method. The synthesized HNTs-M were grafted with 0.25%, 0.5%, 1%, and 2% chitosan (HNTs-M-chitosan), respectively. Synthesized HNTs-M-chitosan (0.25%), HNTs-M-chitosan (0.5%), HNTs-M-chitosan (1%) and HNTs-M-chitosan (2%) were linked with glutaraldehyde (GTA) for laccase immobilization. Among these formulations, HNTs-M-chitosan (1%) exhibited the highest laccase immobilization with 95.13% activity recovery and 100.12 mg/g of laccase loading. The optimized material was characterized thoroughly by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) analysis. The immobilized laccase (HNTs-M-chitosan (1%)-GTA-Laccase) exhibited higher pH, temperature, and storage stabilities. The HNTs-M-chitosan (1%)-GTA-Laccase possesses excellent reusability capabilities. At the end of 10 cycles of the reusability experiment, HNTs-M-chitosan (1%)-GTA-Laccase retained 59.88% of its initial activity. The immobilized laccase was utilized for redox-mediated degradation of sulfamethoxazole (SMX), resulting in 41%, 59%, and 62% degradation of SMX in the presence of 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), guaiacol (GUA), and syringaldehyde (SA), respectively. Repeated SMX degradation (57.10% after the sixth cycle) confirmed the potential of HNTs-M-chitosan (1%)-GTA-Laccase for environmental pollutant degradation. Thus, we successfully designed chitosan-based, rapidly separable super-magnetic nanotubes for efficacious enhancement of laccase biocatalysis, which can be applied as nano-supports for other enzymes.
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•Valorization of lignin towards chemicals and fuels is reviewed.•Various process routes are evaluated for efficient lignin depolymerization.•Detrimental reactions in depolymerization ...of lignin are discussed.•Biorefinery aspects for value added products generation are outlined.•Perspectives towards the biorefinery scheme is recommended.
In recent years, lignin valorization is commercially an important and advanced sustainable process for lignocellulosic biomass-based industries, primarily through the depolymerization path. The conversion of the lignin moieties into biofuels and other high value-added products are still challenging to the researchers due to the heterogeneity and complex structure of lignin-containing biomass. Besides, the involvement of different microorganisms that carries varying metabolic and enzymatic complex systems towards degradation and conversion of the lignin moieties also discussed. These microorganisms are frequently short of the traits which are obligatory for the industrial application to achieve maximum yields and productivity. This review mainly focuses on the current progress and developments in the pretreatment routes for enhancing lignin degradation and also assesses the liquid and gaseous biofuel production by fermentation, gasification and hybrid technologies along with the biorefinery schemes which involves the synthesis of high value-added chemicals, biochar and other valuable products.
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