Purification and biochemical characterization of two laccase isoenzymes isolated from Trichoderma harzianum S7113 and its application for bisphenol A degradation

Ionic liquid-assisted pretreatment of lignocellulosic biomass using purified Streptomyces MS2A cellulase for bioethanol production

In recent years, the process of producing bioethanol from lignocellulosic biomass through biorefining has become increasingly important. However, to obtain a high yield of ethanol, the complex structures in the feedstock must be broken down into simple sugars. A cost-effective and innovative method for achieving this is ionic liquid pre-treatment, which is widely used to efficiently hydrolyze the lignocellulosic material. The study aims to produce a significant profusion of bioethanol via catalytic hydrolysis of ionic liquid-treated lignocellulose biomass. The current study reports the purification of Streptomyces sp. MS2A cellulase via ultrafiltration and gel permeation chromatography. The kinetic parameters and the biochemical nature of the purified cellulase were analyzed for the effective breakdown of the EMIM[OAC] treated lignocellulose chain. The two-step cellulase purification resulted in 6.28 and 12.44 purification folds. The purified cellulase shows a Km value of 0.82 ± 0.21 mM, and a Vmax value of 85.59 ± 8.87 μmol min-1 mg-1 with the catalytic efficiency of 1.027 S-1. The thermodynamic parameters like ΔH, ΔS, and ΔG of the system were studied along with the thermal deactivation kinetics of cellulase. The optimal temperature and pH of the purified cellulase enzyme for hydrolysis was found to be 40 °C and 7. The rice husk and wheat husk used in this study were pretreated with the EMIM [OAC] ionic liquid and the change in the structure of lignocellulosic biomass was observed via HRSEM. The ionic liquid treated biomass showed the highest catalytic hydrolysis yield of 106.66 ± 0.19 mol/ml on the third day. The obtained glucose was fermented with Saccharomyces cerevisiae to yield 23.43 g of ethanol/l of glucose from the rice husk (RH) and 24.28 g of ethanol/l of glucose from the wheat husk (WH).

Kinetic studies on optimized extracellular laccase from Trichoderma harzianum PP389612 and its capabilities for azo dye removal

BACKGROUND

Azo dyes represent a common textile dye preferred for its high stability on fabrics in various harsh conditions. Although these dyes pose high-risk levels for all biological forms, fungal laccase is known as a green catalyst for its ability to oxidize numerous dyes.

METHODS

Trichoderma isolates were identified and tested for laccase production. Laccase production was optimized using Plackett-Burman Design. Laccase molecular weight and the kinetic properties of the enzyme, including Km and Vmax, pH, temperature, and ionic strength, were detected. Azo dye removal efficiency by laccase enzyme was detected for Congo red, methylene blue, and methyl orange.

RESULTS

Eight out of nine Trichoderma isolates were laccase producers. Laccase production efficiency was optimized by the superior strain T. harzianum PP389612, increasing production from 1.6 to 2.89 U/ml. In SDS-PAGE, purified laccases appear as a single protein band with a molecular weight of 41.00 kDa. Km and Vmax values were 146.12 μmol guaiacol and 3.82 μmol guaiacol/min. Its activity was stable in the pH range of 5-7, with an optimum temperature range of 40 to 50 °C, optimum ionic strength of 50 mM NaCl, and thermostability properties up to 90 °C. The decolorization efficiency of laccase was increased by increasing the time and reached its maximum after 72 h. The highest efficiency was achieved in Congo red decolorization, which reached 99% after 72 h, followed by methylene blue at 72%, while methyl orange decolorization efficiency was 68.5%.

CONCLUSION

Trichoderma laccase can be used as an effective natural bio-agent for dye removal because it is stable and removes colors very well.

Potential fungicidal and antiaflatoxigenic effects of cinnamon essential oils on Aspergillus flavus inhabiting the stored wheat grains

Wheat is one of the essential crops for the human and animal nutrition, however, contamination with aflatoxigenic fungi, due to the improper storage conditions and high humidity, was the main global threats. So, preventing the growth of aflatoxigenic fungi in stored wheat grains, by using different essential oils was the main objective of this work. Aspergillus flavus EFBL-MU12 PP087400, EFBL-MU23 PP087401 and EFBL-MU36 PP087403 isolates were the most potent aflatoxins producers inhabiting wheat grains. The effect of storage conditions of wheat grains "humidity, temperature, incubation period, and pH" on growth of A. flavus, was assessed by the response surface methodology using Plackett-Burman design and FCCD. The highest yield of aflatoxins EFBL-MU12 B1 and B2 by A. flavus grown on wheat grains were 145.3 and 7.6 μg/kg, respectively, at incubation temperature 35°C, 16% moisture contents, initial pH 5.0, and incubated for 14 days. The tested oils had a powerful antifungal activity for the growth and aflatoxins production by A. flavus in a concentration-dependent manner. Among these oils, cinnamon oil had the highest fungicidal activity for A. flavus at 0.125%, with about 85-90 % reduction to the aflatoxins B1 and B2, conidial pigmentation and chitin contents on wheat grains. From the SEM analysis, cinnamon oils had the most deleterious effect on A. flavus with morphological aberrations to the conidial heads, vegetative mycelia, alteration in conidiophores identity, hyphae shrank, and winding. To emphasize the effect of the essential oils on the aflatoxins producing potency of A. flavus, the molecular expression of the aflatoxins biosynthetic genes was estimated by RT-qPCR. The molecular expression of nor-1, afLR, pKsA and afLJ genes was suppressed by 94-96%, due to cinnamon oil at 0.062% compared to the control. Conclusively, from the results, cinnamon oils followed by the peppermint oils displayed the most fungicidal activity for the growth and aflatoxins production by A. flavus grown on wheat grains.

Promoter engineering of natural product biosynthetic gene clusters in actinomycetes: concepts and applications

Covering 2011 to 2022Low titers of natural products in laboratory culture or fermentation conditions have been one of the challenging issues in natural products research. Many natural product biosynthetic gene clusters (BGCs) are also transcriptionally silent in laboratory culture conditions, making it challenging to characterize the structures and activities of their metabolites. Promoter engineering offers a potential solution to this problem by providing tools for transcriptional activation or optimization of biosynthetic genes. In this review, we summarize the 10 years of progress in promoter engineering approaches in natural products research focusing on the most metabolically talented group of bacteria actinomycetes.

Optimization and characterization of laccase (LccH) produced by Hexagonia hirta MSF2 in solid-state fermentation using coir pith wastes (CPW)

The accumulation of coir pith waste, a byproduct of coconut husk processing, poses environmental and logistical challenges. An innovative and sustainable solution involves using coir pith as a substrate for solid-state fermentation (SSF). In SSF, coir pith can be converted into valuable products, such as enzymes, organic acids, and bioactive compounds. The present study aimed to evaluate laccase production by Hexagonia hirta MSF2 through SSF using the coir pith waste as substrate. Physico-chemical parameters like moisture, pH, temperature, C source, N source, and CuSO4 concentrations were pre-optimized, and optimized through RSM. Laccase activity of 1585.24 U g-1 of dry substrate was recorded by H. hirta MSF2 on coir pith containing 1 % C source, 0.5 % N source, 0.25 mM of CuSO4 concentration, moisture content of 75 % at pH 4.6 and temperature 28 °C. Subsequently, the enzyme extraction parameters including, extraction buffer, mode of extraction, and temperature were optimized. The molecular weight of laccase was 66 kDa as observed by SDS-PAGE and native-PAGE. The optimum activity of partially purified laccase was achieved at 40 °C, and pH 4.0. Increasing salt concentration and use of different inhibitors affected the laccase activity. Organic solvents like dimethyl sulphoxide (DMSO) and methanol, and metal ions like BaCl2, CaCl2, CuSO4, and MnCl2 stimulated the laccase activity. Hence, coir pith used in SSF offers a dual benefit of waste management and enzyme synthesis through an eco-friendly and cost-effective approach.

Laccase-Conjugated Nanostructured ZnFe2O4/rGO-Modified Electrode-Based Interfaces for Electrochemical Impedance Monitoring of Adrenaline: A Promising Biosensor for Management of Neurodegenerative Disorders

A propitious biosensor for adrenaline (AD) detection in bovine serum albumin (BSA) real samples, which can be used for diagnosis and treatment of neurodegenerative disorders, is reported here. The biosensor consists of a La/ZF/rGO/ITO bioelectrode, which is fabricated by electrophoretic deposition of zinc ferrite/reduced graphene oxide (ZF/rGO) nanohybrid followed by drop casting of laccase (La) enzymes. The material characterization and electrochemical studies revealed that the ZF/rGO nanohybrid enhanced the electroactive surface and facilitated direct electron transfer between the electrode and electrolyte interface, resulting in enhanced electrocatalytic performance. The cyclic voltammetry and electrochemical impedance spectroscopy results asserted that the ZF/rGO nanohybrid decreased the charge-transfer resistance (Rct) and increased the surface adsorption, leading to a high diffusion coefficient (D) of 0.192 cm2/s. The biosensor exhibited a high sensitivity of 0.71 Ω/μM cm2, a good linear range (0.1 to 140 μM with R2 = 0.98), and a low limit of detection (LOD) is 12.5 μM, demonstrating the synergic effect of ZF and rGO in the La/ZF/rGO/ITO bioelectrode with AD. The biosensor also exhibited high selectivity and stability (55 days) in the presence of interfering substances and in BSA samples, with a recovery percentage close to 100 ± 5% RSD, indicating its potential biosensing applications for real-world applications in disease diagnostics, monitoring, and treatment.

Microalgal-based bioremediation of emerging contaminants: Mechanisms and challenges

Emerging contaminants (ECs) in different ecosystems have consistently been acknowledged as a global issue due to toxicity, human health implications, and potential role in generating and disseminating antimicrobial resistance. The existing wastewater treatment system is incompetent at eliminating ECs since the effluent water contains significant concentrations of ECs, viz., antibiotics (0.03-13.0 μg L-1), paracetamol (50 μg L-1), and many others in varying concentrations. Microalgae are considered as a prospective and sustainable candidate for mitigating of ECs owing to some peculiar features. In addition, the microalgal-based processes also offer cost and energy-efficient solutions for the bioremediation of ECs than conventional treatment systems. It is pertinent that, microalgal-based processes also provides waste valorization benefits as microalgal biomass obtained after ECs treatment can be potentially applied to generate biofuels. Moreover, microalgae can effectively utilize alternative metabolic (cometabolism) routes for enhanced degradation of ECs. Additionally, the ECs removal via the microalgal biodegradation route is highly promising as it can transform the ECs into less toxic compounds. The present review comprehensively discusses different mechanisms involved in removing ECs and various factors that affect their removal. Also, the technoeconomic feasibility of microalgae than other conventional wastewater treatment methods is summarised. The review also highlighted the different molecular and genetic tools that can augment the activity and robustness of microalgae for better removal of organic contaminants. Finally, we have summarised the challenges and future research required towards microalgal-based bioremediation of emerging contaminants (ECs) as a holistic approach.

Computational explorations of the interaction between laccase and bisphenol A: influence of surfactant and different organic solvents

Bisphenol A (BPA), as an environmental endocrine disruptor can cause damage to the reproductive, nervous and immune systems. Laccase can be used to degrade BPA. However, laccase is easily deactivated, especially in organic solvents, but the specific details are not clear. Molecular dynamics simulations were used to investigate the reasons for changes in laccase activity in acetonitrile (ACN) and dimethyl formamide (DMF) solutions. In addition, the effects of ACN and DMF on the activity of laccase and surfactant rhamnolipid (RL) on the degradation of BPA by laccase were investigated. Results showed that addition of ACN changed the structure of the laccase, not only decreasing the van der Waals interaction that promoted the binding of laccase with BPA, but also increasing the polar solvation free energy that hindered the binding of laccase with BPA, so it weakened the laccase activity. DMF greatly enhanced the van der Waals interaction between laccase and BPA, and played a positive role in their binding. The addition of surfactant RL alleviated the effect of organic solvent on the activity of laccase by changing the polar solvation energy. The mechanism of surfactant RL affecting laccase activity in ACN and DMF is described, providing support for understanding the effect of organic solvents on laccase.

Biochemical, molecular and anti-tumor characterization of L-methionine gamma lyase produced by local Pseudomonas sp. in Egypt

A soil inhabiting Pseudomonas sp. has been examined for producing L- methionine gamma-lyase enzyme. The identity of the tested bacteria was verified by VITEK2, and MALDI-TOF analysis in addition to molecular confirmation by 16S rDNA sequence and submitted in Genbank under accession number ON993898.1. Production of the targeted enzyme was done using a commercial medium including L-methionine, as the main substrate. This obtained enzyme was precipitated using acetone (1:1v/v) followed by purification with Sephadex G100 and sepharose columns. The specific activity of the purified enzyme (105.8 µmol/ mg/min) increased by 1.89 folds after the purification steps. The peptide fingerprint of the native MGL was verified from the proteomics analysis, with identical conserved active site domains with database-deposited MGLs. The molecular mass of the pure MGL denatured subunit was (>40 kDa) and that of the native enzyme was (>150 kDa) ensuring their homotetrameric identity. The purified enzyme showed absorption spectra at 280 nm and 420 nm for the apo-MGL and PLP coenzyme, respectively. Amino acids suicide analogues analysis by DTNB, hydroxylamine, iodoacetate, MBTH, mercaptoethanol and guanidine thiocyanate reduced the relative activity of purified MGL. From the kinetic properties, the catalytic effectiveness (K_cat/k_m) of Pseudomonas sp. MGL was 10.8 mM ^-1 S^-1 for methionine and 5.51 mM ^-1 S^-1 for cysteine, respectively. The purified MGL showed highly significant antiproliferative activity towards the liver carcinoma cell line (HEPG-2) and breast carcinoma cell line (MCF-7) with half inhibitory concentration values (IC₅₀) 7.23 U/ml and 21.14 U/ml, respectively. No obvious signs of toxicity on liver and kidney functions in the examined animal models were observed.