Utilization of laccase immobilized CdO nanoparticles in synthesis of industrially potent organics and their molecular docking studies

In the present study, Tricholoma giganteum AGHP laccase was immobilized on amino-functionalized cadmium oxide nanoparticles (CdO NPs) which was carried out by glutaraldehyde. The synthesized CdO NPs were characterized by using transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) analysis which reflected the NPs had an average size of 35 nm with hexagonal and irregular shapes. Fourier transform infra-red (FTIR) study of laccase with amino-functionalized CdO (lac-CdO) NPs confirmed the crosslinking of laccase with CdO NPs. With immobilized laccase, a shift in pH (5.5) and temperature (35 ℃) optima was observed, when compared to free laccase (pH 4.5, 30 ℃). Lac-CdO NPs displayed 1.15 times higher stability (90 ± 0.47%) than free laccase (78 ± 0.69%) at optimum pH of 5.5. Immobilized laccase showed 1.19-fold improvement in thermal stability and 2.25-fold increment in half-life after 3 h of incubation at 50 ℃ as compared to free laccase. Recycling capability study demonstrated that lac-CdO NPs were able to retain 85 ± 0.68% of relative activity at the end of 20th 2,2-azinobis-3-ethylbenzthiozoline-6-sulfonic acid (ABTS) oxidation cycle. In addition, lac-CdO NPs showed remarkable reusability in catalysing various organic synthesis reactions even after several cycle of catalysis. Furthermore, the interactions of organic synthesis reactions and interacted residues were observed by assessing the molecular docking poses of T. giganteum laccase with substrates. The obtained results would be advantageous to develop a biocatalyst over a chemical catalyst for effective synthesis of potent organics having industrial importance.

Fungal-Assisted Bioremediation of Agricultural Organic Pollutants (Pesticides and Herbicides)

Abstract:

Extensive use of pesticides and herbicides in the agricultural fields for the safeguard of crops engenders the huge concern regarding pollution of these agricultural fields as well as directly or indirectly linked to aquatic environment. In order to find out the apt bioremediation techniques that could be potentially used against these highly noxious agricultural pollutants, utilization of fungi and their associated enzymes like laccases and others may be an imperative tool against these pesticides, insecticides, and herbicides. Fungal system including fungal enzymes have proved their efficacy in the degradation studies of malathion (1), acetamiprid (2), 2, 4-D (3), chlorimuron-ethyl, imidacloprid (4), flubendiamide (5), thiamethoxam (6), pyrimethanil (7), cypermethrin (8), nicosulfuron (9), chlorpyrifos (10), isoproturon (11), chlorothalonil (12), DDT (13), atrazine (14), and alachlor (15) like agricultural organic pollutants which have been meritoriously and succinctly conferred here. There are limited recent works on fungal system-mediated bioremediation of pesticides and herbicides in compare to bacterial system that is why; authors have objectively decided to compile the recent promising researches on the topic to provide an effective and informative update on the significant applicability of fungal system in the removal of such organic pollutants. Herein, authors have best tried to present a clear, subject-centric and compact picture on the operative contribution of fungal systems (fungi and associated enzymes) in the biodegradation of different pesticides/insecticides or herbicides.

Rapid decomposition of rice straw by application of a novel microbial consortium and study its microbial community dynamics

Rice straw decomposition is an attractive solution to open-field burning but the traditional method has slow kinetics and takes 60-90 days to obtain mature compost. In this study, we propose to boost up the decomposition process by addition of a novel microbial consortium rich in lignocellulolytic microbes. C: N ratio of the compost reached 11.69% and degradation efficiency of cellulose and hemicellulose was found to be 64 and 87% respectively within 25 days. Lignocellulolytic activity of the microbial consortium was confirmed by plate and activity assay. These parameters clearly indicated that a mature compost was obtained in 25 days. The 16S rRNA gene amplicon sequencing and functional analysis of predicted genes indicated amino acid and carbohydrate metabolism as the major metabolic pathway during composting. The tertiary level of functional analysis revealed the major metabolic pathways in the bacterial communities as pentose phosphate pathway, glycolysis and tricarboxylic acid cycle.

A novel organophosphate hydrolase from Arthrobacter sp. HM01: Characterization and applications

Bioremediation systems coupled to efficient microbial enzymes have emerged as an attractive approach for the in-situ removal of hazardous organophosphates (OPs) pesticides from the polluted environment. However, the role of engineered enzymes in OPs-degradation is rarely studied. In this study, the potential OPs-hydrolase (opdH) gene (Arthrobacter sp. HM01) was isolated, cloned, expressed, and purified. The recombinant organophosphate hydrolase (ropdH) was ∼29 kDa; which catalyzed a broad-range of OPs-pesticides in organic-solvent (∼99 % in 30 min), and was found to increase the catalytic efficiency by 10-folds over the native enzyme (k_cat/K_m: 10⁷ M^-1s^-1). The degraded metabolites were analyzed using HPLC/GCMS. Through site-directed mutagenesis, it was confirmed that, conserved metal-bridged residue (Lys-127), plays a crucial role in OPs-degradation, which shows ∼18-folds decline in OPs-degradation. Furthermore, the catalytic activity and its stability has been enhanced by >2.0-fold through biochemical optimization. Thus, the study suggests that ropdH has all the required properties for OPs bioremediation.

Black liquor: A potential moistening agent for production of cost-effective hydrolytic enzymes by a newly isolated cellulo-xylano fungal strain Aspergillus tubingensis and its role in higher saccharification efficiency

In the present study, black liquor generated during mild alkali pre-treatment was evaluated as a moistening agent to produce cost effective hydrolytic enzymes using novel cellulo-xylano fungal strain Aspergillus tubingensis M7. The fungus competently produced 21.90 and 22.46 filter paper, 1004 and 1369 endoglucanase, 117 and 142 β-glucosidase and 8188 and 7981 U/g xylanase activity by using modified Mandel & weber's and black liquor medium, respectively. The crude hydrolytic enzymes from black liquor were evaluated for saccharification of pre-treated biomass. Reducing sugar yields (mg/g substrate) and the corresponding saccharification efficiency (%) from rice straw, corncob, sugarcane bagasse and banana stem were 745.50 (86.02; 18 h); 596 (74.50; 24 h); 358.15 (42.98; 24 h) and 245.70 (33.00; 24 h), respectively. Residual biomass compositional analysis revealed that reduced onset temperature, increased activation energy and pre-exponential factor in saccharified biomass as compared to pre-treated and untreated biomass, suggesting their utilization for pyrolysis to obtain value added products.

Structural insight into the fungal β-glucosidases and their interactions with organics

Fungal β-glucosidases (BGLs) have unceasingly utilized for industrial applications and recently, they possess a crucial role in bioethanol production. To engineer the BGLs, understanding their structures, intermolecular interactions and molecular docking is requisite, which is carried out in this work based on the glycosyl hydrolase (GH) family. Among 12 BGLs, protein sequence, structure, and conserved sites of GH1 BGLs are evidently diverged to GH3 BGLs. Even biophysical and chemical features of GH1 BGLs are utterly varied from GH3 BGLs, wherein pI, instability index, aliphatic index, surface & buried area, thermostability and thermodynamics are included. On the contrary, aromatic, charged, polar, and hydrophobic residues are significantly higher in GH1 BGLs as compared to that of GH3 BGLs. Moreover, molecular docking of BGLs with 12 substrates and 5 inhibitors revealed that the GH3 BGLs efficiently bound with laminaribose, gentibiose, aryl- and cello-substrates than GH1 BGLs; however, GH3 BGLs are noticeably inhibited by glucose, glucono-δ-lactone, methanetriamine. So, structural insight of BGLs provides an explicit knowledge regarding the catalytic residues, biophysical chemistry and notable binding ligands, which are most important factors for enzyme engineering.

Biosorption Potential of Phanerochaete chrysosporium for Arsenic, Cadmium, and Chromium Removal from Aqueous Solutions

Efficient degradation of hazardous contaminants from contaminated water is the major challenge for researchers, wherein heavy metals are the prominent contaminants. Consequently, the assessment of multimetal removal is necessary using efficient biosorbant. In this work, the capability of Phanerochaete chrysosporium is evaluated for the individual and simultaneous removal of heavy metals. Individual and simultaneous removal of As, Cd, and Cr is optimized using response surface methodology based on the central composite design by changing the variables, i.e., pH, fungal biomass, and metal concentration. Optimization of the individual metal removal study reveals that fungus effectively absorbs As (29.95 mg L-1), Cd (18.1 mg L-1), and Cr (26.34 mg L-1) at 6.1, 5.64, and 4.15 of pH, respectively. Similarly, As (14.18 mg L-1), Cd (4.53 mg L-1), and Cr (9.28 mg L-1) are absorbed by fungal hyphae simultaneously within 1 h. Changes in the morphology of fungal hyphae are detected in metal absorbed samples as compared to the control hyphae. Interaction of metal-absorbed fungal hyphae is analyzed using FTIR spectroscopy, revealing that the proteins, carbohydrates, and fatty acids present in the fungal cell are interacted with metals. The model white rot fungi used in the present study can be applied efficiently for the multimetal removal in effluent treatment plants.