Immobilized laccase: an effective biocatalyst for industrial dye degradation from wastewater.

Environmental concerns due to the release of industrial wastewater contaminated with dyes are becoming more and more intense with the increasing industrialization. Decolorization of industrial effluents has become the top priority due to the continuous demand for color-free discharge into the receiving water bodies. Different dye removal techniques have been developed, among which biodegradation by laccase enzyme is competitive. Laccase, as a green catalyst, has a high catalytic activity, generates less toxic by-products, and has been extensively researched in the field of remediation of dyes. However, laccase's significant catalytic activity could only be achieved after an effective immobilization step. Immobilization helps strengthen and stabilize the protein structure of laccase, thus enhancing its functional properties. Additionally, the reusability of immobilized laccase makes it an attractive alternative to traditional dye degradation technologies and in the realistic applications of water treatment, compared with free laccase. This review has elucidated different methods and the carriers used to immobilize laccase. Furthermore, the role of immobilized laccase in dye remediation and the prospects have been discussed.

Innovative strategies in algal biomass pretreatment for biohydrogen production.

Biohydrogen is one of the cleanest renewable energies with a high calorific value. Algal biomass can be utilized as a sustainable feedstock for biohydrogen production via dark fermentation. However, the recovery of fermentable sugar from algal biomass is challenging because of the diversity and complex cell wall composition and therefore, requires an additional pretreatment step. However, most of the conventional pretreatment strategies suffer from limited technological feasibility and poor economic viability. In this context, this review aims to present the structural complexities of the cell wall of algae and highlight the innovative approaches such as the use of hybrid technologies, biosurfactants, nanoparticles, and genetic engineering approaches for the hydrolysis of algal biomass and improved biohydrogen production. Additionally, a comprehensive discussion of the comparative evaluation of various pretreatment methods, and the techno-economic and life cycle assessment of algal biohydrogen production is also presented in this review.

Enhanced adsorption of Congo red dye onto polyethyleneimine-impregnated biochar derived from pine needles.

Biochar derived from waste pine needles was chemically modified using polyethyleneimine (PEI) to increase its adsorptive potential for withdrawal of anionic dye Congo red from aqueous solution. PEI impregnation on biochar was confirmed from scanning electron microscopy and energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The surface area of biochar decreased after PEI treatment, but the amine groups increased on biochar surface. PEI-treated biochar displayed considerable increase in adsorption at acidic conditions. Adsorption isotherm was best explained by Langmuir model (R2 > 99) and the adsorption kinetics agrees well with pseudo-second-order model. The maximum adsorption capacity of PEI-treated biochar was observed to be 294.11 mg g-1 and 30.76 mg g-1 for pristine biochar displaying a 9.5-fold increase. The positive value of standard enthalpy of adsorption (∆H° = 14.96 KJmole-1) indicated the endothermic nature of adsorption, and positive value of entropy (∆S° = 74.43 Jmole-1 K-1) revealed the affinity of biochar towards dye molecules. Negative value of Gibb's free energy ∆G° (- 7.2 KJmole-1) revealed that the process was spontaneous. Electrostatic interaction appeared to be the key mechanism governing the adsorption process. Thus, PEI-impregnated biochar represents novel low-cost sorbent that can effectively remove anionic dyes which are poorly removed by pristine biochar.

Bioremoval of toxic malachite green from water through simultaneous decolorization and degradation using laccase immobilized biochar.

In this study, decolorization and degradation of malachite green dye was studied using the laccase immobilized pine needle biochar. Successful immobilization of biochar was achieved by adsorption and confirmed through scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX), Fourier transform infrared spectroscopy (FTIR). High laccase binding of 64.4 U/g and high immobilization yield of 78.1% was achieved using 4U of enzyme at pH3 and temperature 30 °C. The immobilized laccase retained >50% relative activity in the pH range 2-7, >45% relative activity at 65 °C and >55% relative activity at 4 °C for 4 weeks. The re-usability of immobilized enzyme was checked with 2, 2'-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) substrate and enzyme retained 53% of its activity after 6 cycles. Immobilized laccase was used for the degradation and decolorization of azo dye malachite green in aqueous solution. More than 85% removal of malachite green dye (50 mg/L) was observed within 5 h. FTIR and high performance liquid chromatography (HPLC) analysis clearly indicated the breakdown of dye and presence of metabolites (leuco malachite green, methanone, [4-(dimethyl amino)pheny]phenyl and 3-dimethyl-phenyl amine) in gas chromatography-mass spectrometry (GC-MS) analysis confirmed the dye degradation. Phytotoxicity analysis indicated that the enzymatic degradation resulted in lesser toxic metabolites than the original dye. Thus, laccase immobilized biochar can be used as an efficient biocatalytic agent to remove dye from water.

Liquid wastes as a renewable feedstock for yeast biodiesel production: Opportunities and challenges.

Microbial lipids (bacterial, yeast, or algal) production and its utilization as a feedstock for biodiesel production in a sustainable and economical way along with waste degradation is a promising technology. Oleaginous yeasts have demonstrated multiple advantages over algae and bacteria such as high lipid yields, lipid similarity to vegetable oil, and requirement of lesser area for cultivation. Oleaginous yeasts grown on lignocellulosic solid waste as renewable feedstocks have been widely reported and reviewed. Recently, industrial effluents and other liquid wastes have been evaluated as feedstocks for biodiesel production from oleaginous yeasts. The idea of the utilization of wastewater for the growth of oleaginous yeasts for simultaneous wastewater treatment and lipid production is gaining attention among researchers. However, the detailed knowledge on the economic aspects of different process involved during the conversion of oleaginous yeast into lipids hinders its large-scale application. Therefore, this review aims to provide an overview of yeast-derived biodiesel production by utilizing industrial effluents and other liquid wastes as feedstocks. Various technologies for biomass harvesting, lipid extraction and the economic aspects specifically focused on yeast biodiesel production were also analyzed and reported in this review. The utilization of liquid wastes and the incorporation of cost-efficient harvesting and lipid extraction strategy would facilitate large-scale commercialization of biodiesel production from oleaginous yeasts in near future.

SARS-CoV-2 in wastewater: Challenges for developing countries.

The COVID-19 pandemic that has engulfed the world, has affected the human lives in several aspects. The detection of SARS-CoV-2 in faeces and urine of the infected person, even after viral clearance in the respiratory tract, and its presence in untreated wastewater raises the possibility of fecal-oral transmission in future. The situation is likely to be more aggravated in developing and least developed countries struggling with the problem of ineffective waste disposal system, open defecation, poor sanitation, and limited access to clean drinking water. In this review, the available data on wastewater treatment, sanitation status and healthcare infrastructure from middle- and low-income countries is collected and correlated with the risk associated with the fecal-oral transmission of SARS-CoV-2. The review also highlights the limitation of COVID-19 surveillance through sewage monitoring in these countries owing to the absence of proper sewerage system. An inclusive approach of awareness, prevention, and mitigation from global to the local levels is required to overcome this challenging situation in developing countries.

Development of a novel reporter gene vector for cell based angiogenic studies.

Angiogenesis is a promising area of research that targets key therapeutic areas like cancer; wound healing, inflammatory diseases, etc. There is an increasing demand for screening of potential angiogenic and anti-angiogenic agents using sensitive, robust cell-based assays. We have developed a reporter vector containing cis-acting elements that respond to growth factors/angiogenic ligands for use in a cell-based luciferase reporter assay. We performed transient transfection of our reporter gene vector in MCF-7 cells to establish its application for screening of potential pro/anti-angiogenic agents. Reporter gene transactivation studies with different concentrations of fetal bovine serum clearly indicated that the vector is functionally responsive to the angiogenic signals mediated by serum growth factors. We also used endostatin to inhibit transactivation and prove responsiveness to the anti-angiogenic agent. This vector is a promising tool for studying angiogenesis using cell-based reporter gene assays.