Advances in enzymatic conversion of biomass derived furfural and 5-hydroxymethylfurfural to value-added chemicals and solvents.

The progress of versatile chemicals and bio-based fuels using renewable biomass has gained ample importance. Furfural and 5-hydroxymethylfurfural are biomass-derived compounds that serve as the cornerstone for high-value chemicals and have a myriad of industrial applications. Despite the significant research into several chemical processes for furanic platform chemicals conversion, the harsh reaction conditions and toxic by-products render their biological conversion an ideal alternative strategy. Although biological conversion confers an array of advantages, these processes have been reviewed less. This review explicates and evaluates notable improvements in the bioconversion of 5-hydroxymethylfurfural and furfural to comprehend the current developments in the biocatalytic transformation of furan. Enzymatic conversion of HMF and furfural to furanic derivative have been explored, while the latter has substantially overlooked a foretime. This discrepancy was reviewed along with the outlook on the potential usage of 5-hydroxymethylfurfural and furfural for the furan-based value-added products' synthesis.

Evaluating the potential of engineered Trichoderma atroviride and its laccase-mediated system for the efficient bioconversion of 5-hydroxymethylfufural.

5-Hydroxymethylfurfural (HMF) is a fermentation inhibitor which is formed during acid-based thermochemical pre-treatment of biomass. The present study involves two approaches for HMF conversion; the first includes screening and identification of fungal strains which produce oxidoreductases for HMF bioconversion, and thereafter evaluating their roles in HMF conversion. Out of the ten fungal strains screened, genetically engineered Trichoderma atroviride (Lac+) showed maximum HMF bioconversion and the activities of ligninolytic enzymes produced were noted. Maximum HMF conversion of 99% was achieved at pH 5.0 and 30 °C when 72 h old 10% inoculum of T. atroviride (Lac+) was utilized for 6 days. Based on the fungal bioconversion of HMF to 2, 5 diformylfuran with 58% yield, laccase was observed to influence the conversion process. Thus, a comparative study was established on HMF conversion by 100 U/mL of commercial laccases and partially purified laccase from T. atroviride (Lac+). In the presence of TEMPO, T. atroviride laccase showed comparable HMF conversion to commercial laccases, which establishes the efficiency of fungi and ligninolytic enzymes in bioconversion of HMF to value-added products.

Utilization of surface-active compounds derived from biosolids to remediate polycyclic aromatic hydrocarbons contaminated sediment soil.

In the present study, surface-active compounds (SAC) were extracted from biosolids using an alkaline treatment process. They were tested for their remediation efficiency of crude oil-contaminated sediment soil and was compared with Triton x-100. The SAC exhibited a similar soil washing efficiency to that of the commercial Triton x-100, and under the optimized soil washing parameters, SAC exhibited a maximum of 91% total polycyclic aromatic hydrocarbons removal. Further, on analysing the toxicity of the soil residue after washing, it was observed that SAC from biosolids washed soil exhibited an average of 1.5-fold lesser toxicity compared to that of Triton x-100 on different test models-earthworm, a monocot, and dicot plants. The analysis of the key soil parameters revealed that the commercial surfactant reduced the soil organic matter and porosity by an average of 1.3-fold compared to SAC. Further, the ability of surfactants to induce toxicity was confirmed by the adsorption of the surfactants on the surface of the soil particles which was in the order of Triton x-100 > SAC. Thus, this study suggests that SAC can be applied as an effective bioremediation approach for contaminated soil for a greener and sustainable ecosystem.

Laccase production by Pleurotus ostreatus using cassava waste and its application in remediation of phenolic and polycyclic aromatic hydrocarbon-contaminated lignocellulosic biorefinery wastewater.

The treatment of contaminants from lignocellulosic biorefinery effluent has recently been identified as a unique challenge. This study focuses on removing phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) from lignocellulosic biorefinery wastewater (BRW) applying a laccase-assisted approach. Cassava waste was used as a substrate to produce the maximum yield of laccase enzyme (3.9 U/g) from Pleurotus ostreatus. Among the different inducers supplemented, CuSO4 (0.5 mM) showed an eight-fold increase in enzyme production (30.8 U/g) after 240 h of incubation. The catalytic efficiency of laccase was observed as 128.7 ± 8.47 S-1mM-1 for syringaldazine oxidation at optimum pH 4.0 and 40 °C. Laccase activity was completely inhibited by lead (II) ion, mercury (II) ion, sodium dodecyl sulphate, sodium azide and 1,4 dithiothretiol and induced significantly by manganese (II) ion and rhamnolipid. After treating BRW with laccase, the concentrations of PAHs and phenolic contaminants of 1144 µg/L and 46160 µg/L were reduced to 96 µg/L and 16100 µg/L, respectively. The ability of laccase to effectively degrade PAHs in the presence of different phenolic compounds implies that phenolic contaminants may play a role in PAHs degradation. After 240 h, organic contaminants were removed from BRW in the following order: phenol >2,4-dinitrophenol > 2-methyl-4,6-dinitrophenol > 2,3,4,6-tetrachlorophenol > acenaphthene > fluorine > phenanthrene > fluoranthene > pyrene > anthracene > chrysene > naphthalene > benzo(a)anthracene > benzo(a)pyrene > benzo(b)fluoranthene > pentachlorophenol > indeno(1,2,3-cd)pyrene > benzo(j) fluoranthene > benzo[k]fluoranthène. The multiple contaminant remediation from the BRW by enzymatic method, clearly suggests that the laccase can be used as a bioremediation tool for the treatment of wastewater from various industries.

Mycoremediation of lignocellulosic biorefinery sludge: A reinvigorating approach for organic contaminants remediation with simultaneous production of lignocellulolytic enzyme cocktail.

This research work aims to valorize lignocellulosic biorefinery sludge with genetically engineered Trichoderma atroviride for simultaneous removal of organic contaminants, fermentation inhibitors, and lignocellulolytic enzyme cocktail production. Upon analysis, three phenolic compounds (42.6 ± 3.6 µg/g), two polycyclic aromatic hydrocarbons (0.42 ± 0.06 µg/g) and five fermentation inhibitors (2.5 ± 0.3 mg/g) were detected in the sludge. Bioaugmentation of sludge with 72 h-old T. atroviride (5%) results in the production of cellulase (21 U/g), xylanase (84 U/g), laccase (20 U/g), lignin peroxidase (14 U/g) and aryl alcohol oxidase (116 U/g), along with the concomitant removal of organic contaminants (phenol, 2, 4-dinitrophenol, pentchlorophenol, phenanthrene, benzo(a)pyrene) and fermentation inhibitors (furfural, 5-hydroxymethylfurfural, levulinic acid, ferulic acid, and catechol). Subsequently, the enrichment of sludge with nutrients and rhamnolipids enhanced the enzyme production by 5-6-fold and resulted in the removal of 85-95% of organic contaminants and fermentation inhibitors, which constitutes an eco-friendly process.

Surfactant-aided mycoremediation of soil contaminated with polycyclic aromatic hydrocarbons.

Remediation of persistent polycyclic aromatic hydrocarbons (PAHs) contaminated soil has become a major challenge in recent years. Further, conventional application of bioaugmentation strategies for PAHs remediation require continuous supply of microbial specific nutrients, which makes these processes less feasible. Hence, the present study focused on PAHs remediation using surfactants along with wood assisted fungal system in a microcosm set up. In this study, in absence of surfactants, a saturation in PAHs degradation was noted in bioaugmentation with wood assisted fungal system (BAW) with 61 ± 1.25% degradation, followed by bioaugmentation with free fungi system (BAF) (54 ± 0.46%). However, with addition of 1500 mg/L of surface-active compounds (SAC), a maximum PAHs degradation in BAW (100%) and BAF (86 ± 1.30%) strategies were noted on 21st day. Irrespective of the strategies, presence of SAC and rhamnolipids enhanced PAHs degradation by increasing the enzymes production in Trametes hirsuta when compared to Triton x-100 and sodium dodecyl sulphate (SDS). Among the detected PAHs, 100% degradation within 17 days was noted for naphthalene and acenaphthene in SAC-supplemented BAW system. Further, ecotoxicity analysis established showed the LC50 of sediment soil at 26.5 ± 0.24%, which was reduced by an average of 71% after soil remediation. Hence, the current microcosm system proved that the application of SAC with BAW enhanced the PAHs remediation rate, which supports its application in real time soil remediation.

Insolubilization of Tramates versicolor laccase as cross-linked enzyme aggregates for the remediation of trace organic contaminants from municipal wastewater.

The novelty of this study deals with the biocatalytic treatment of trace organic contaminants (TrOCs) from municipal wastewater by insolubilized laccase. Laccase from Trametes versicolor was aggregated by three-phase partitioning technique followed by cross-linking with glutaraldehyde to produce insolubilized laccase as cross-linked enzyme aggregates (CLEAs). The optimal conditions for CLEAs preparation include ammonium sulphate concentration of 83% (w/v), crude to t-butanol ratio of 1.00: 1.05 (v/v), pH 5.3, and glutaraldehyde concentration of 20 mM obtained via statistical design. The efficiency of insolubilization of the CLEAs laccase based on the kcat/km ratio was approximately 4.8-fold greater than that of free laccase. The developed CLEAs showed greater resistance to product inhibition mediated by ABTS than the free enzyme and exhibited excellent catalytic activity even after the tenth successive cycle. Further, free laccase and the synthesized CLEAs laccase were utilized to treat five analgesics, two NSAIDS, three antibiotics, two antilipemics, and three pesticides in the municipal wastewater. Under the batch process with operating conditions of pH 7.0 and 20 °C, 1000 U/L of CLEAs, laccase removed 11 TrOCs in the range of about 20-99%. However, the inactivated CLEAs only adsorbed 2-25% of TrOCs. It was observed that acetaminophen, mefenamic acid, trimethoprim, and metolachlor depicted almost complete removal with CLEAs laccase. The performance of CLEAs laccase in a perfusion basket reactor was tested for the removal of TrOCs from municipal wastewater.

Understanding the factors affecting adsorption of pharmaceuticals on different adsorbents - A critical literature update.

Remediation of emerging pharmaceutically active compounds (PhACs) as micropollutants in wastewater is of foremost importance as they can cause extremely detrimental effects on life upon bioaccumulation and generation of drug-resistance microorganisms. Presently used physicochemical treatments, such as electrochemical oxidation, nanofiltration and reverse osmosis, are not feasible owing to high operating costs, incomplete removal of contaminants along with toxic by-products formation. Adsorption with the utilization of facile and efficient nanoparticulate adsorbents having distinctive properties of high surface area, excellent adsorption capacity, ability to undergo surface engineering and good regeneration displays great potential in this aspect along with the incorporation of nanotechnology for effective treatment. The application of such nanosorbents provides optimal performance under a wide range of physicochemical conditions, decreased secondary pollution with reduced mechanical stress along with excellent organic compound sequestration capacity, which in turn improves the quality of potable water in a sustainable way compared to current treatments. The present review intends to consolidate the range of factors that affect the process of adsorption of different PhACs on to various nanosorbents and also highlights the adsorption mechanism aiding in the retrieval.

Effect of alkaline treatment on the removal of contaminants of emerging concern from municipal biosolids: Modelling and optimization of process parameters using RSM and ANN coupled GA.

The current study aimed in enhancing the efficiency of alkaline treatment for CECs remediation in biosolids through the application of RSM and ANN. Due to the seasonal variation of CECs in biosolids, a complete CECs profile over a period of three years were performed. Out of 64 targeted CECs, 13 PhACs (70.1 µg/kg) and 10 pesticides (57.2 µg/kg) were detected in biosolids. In order to enhance the remediation efficiency of CECs by alkaline treatment, process parameters - pH (9.0-13.0), time (3.0-12.0 h) and biosolids age (1-28 days) were optimized by statistical modelling. Using Box-Behnken design, experiments were designed and the resultant data was employed as input for model building using RSM and ANN. The developed mathematical model for alkaline treatment of biosolids using ANN predicted CECs removal with 3.2-fold lower MSE and exhibited high regression coefficient (R2 > 0.99) than the conventional RSM model. Further, the multiparameter model was optimized for achieving maximum of 95.7 % CECs removal using ANN-GA. On analyzing the acute toxicity of alkaline treated residual biosolids under the optimized conditions, a reduction in LC50 by an average of 2.1-fold than initial biosolids was observed. This study not only established the application of statistical modelling in the development of an efficient remediation strategy for biosolids, which can be further applied for large-scale remediation process, but also proved the reliability and efficiency of ANN-GA.

Fabrication of highly permeable and anti-fouling performance of Poly(ether ether sulfone) nanofiltration membranes modified with zinc oxide nanoparticles.

Membrane fouling is one of the challenging bottleneck problems in waste water treatment by membrane process. The present study constructed a nanofiltration membrane based on the zinc oxide nanoparticle (n-ZnO) integrated Poly(ether ether sulfone) (PEES) membranes. The developed membranes were characterized by X-ray diffraction (XRD), attenuated total reflectance - fourier transform infrared spectroscopy (AT-FTIR), atomic force microscopy (AFM) and scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) analysis. Pure water flux, contact angle, molecular weight cut-off, mean pore size and porosity were determined to investigate the influence of n-ZnO on the properties of the membranes. The characterization showed asymmetric configuration of membranes after n-ZnO incorporation. This incorporation also enhanced the hydrophilicity of PEES membrane. The fouling-resistant potential of the membranes was investigated by the model foulant humic acid (HA) and an enhanced anti-fouling irreversible property with a corresponding flux recovery rate of 92.43 % was noted for the prepared membrane. The rejection performance and permeability of HA was 98.03 % and 166.73 L m-2 h-1, respectively, owing to the hydrophilic nature of ZnO particles. Further, modified PEES membrane exhibited superior separation performance for monovalent and divalent anions. PEES/n-ZnO hybrid membrane assisted nanofiltration is an effective process for the improvement of membrane performance and anti-fouling property, demonstrating its immense use in water reclamation.