Fungal assisted bio-treatment of environmental pollutants with comprehensive emphasis on noxious heavy metals: Recent updates.

In the present time of speedy developments and industrialization, heavy metals are being uncovered in aquatic environment and soil via refining, electroplating, processing, mining, metallurgical activities, dyeing and other several metallic and metal based industrial and synthetic activities. Heavy metals like lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), Zinc (Zn), Cobalt (Co), Iron (Fe), and many other are considered as seriously noxious and toxic for the aquatic environment, human, and other aquatic lives and have damaging influences. Such heavy metals, which are very tough to be degraded, can be managed by reducing their potential through various processes like removal, precipitation, oxidation-reduction, bio-sorption, recovery, bioaccumulation, bio-mineralization etc. Microbes are known as talented bio-agents for the heavy metals detoxification process and fungi are one of the cherished bio-sources that show noteworthy aptitude of heavy metal sorption and metal tolerance. Thus, the main objective of the authors was to come with a comprehensive review having methodological insights on the novel and recent results in the field of mycoremediation of heavy metals. This review significantly assesses the potential talent of fungi in heavy metal detoxification and thus, in environmental restoration. Many reported works, methodologies and mechanistic sights have been evaluated to explore the fungal-assisted heavy metal remediation. Herein, a compact and effectual discussion on the recent mycoremediation studies of organic pollutants like dyes, petroleum, pesticides, insecticides, herbicides, and pharmaceutical wastes have also been presented.

Nano-reduction of gold and silver ions: A perspective on the fate of microbial laccases as potential biocatalysts in the synthesis of metals (gold and silver) nano-particles.

Nanoparticles of metals have momentous place in the field of biological as well as pharmaceutical chemistry due to which in the present scenario of the research, this field is of auspicious interest. Synthesis of metal nanoparticles via microbial assistance is a burning field for their green synthesis. In this direction, microbial enzymes play significant role, out of which microbial laccases may also be a talented biocatalyst for the synthesis of metal nanoparticles considering its efficacy and interesting promising biological applications. A very little works are known on the role of microbial laccases in the synthesis of metal nanoparticles but after effective scrutiny of their reported works on the synthesis of gold and silver nanoparticles, its fate as potential biocatalyst in the synthesis of metals nanoparticles is being automatically established. Thus, this perspective commendably appraises the active applicability of microbial laccases in the synthesis of gold and silver nanoparticles by reducing their ions in suitable reaction environment.

An alkali tolerant α-l-rhamnosidase from Fusarium moniliforme MTCC-2088 used in de-rhamnosylation of natural glycosides.

Analkali tolerant α-l-rhamnosidase has been purified to homogeneity from the culture filtrate of a new fungal strain, Fusarium moniliforme MTCC-2088, using concentration by ultrafiltration and cation exchange chromatography on CM cellulose column. The molecular mass of the purified enzyme has been found to be 36.0 kDa using SDS-PAGE analysis. The Km value using p-nitrophenyl-α-l-rhamnopyranoside as the variable substrate in 0.2 M sodium phosphate buffer pH10.5 at50 °C was 0.50 mM. The catalytic rate constant was15.6 s-1giving the values of kcat/Km is 3.12 × 104M-1 s-1. The pH and temperature optima of the enzyme were 10.5 and 50 °C, respectively. The purified enzyme had better stability at 10 °C in basic pH medium. The enzyme derhamnosylated natural glycosides like naringin to prunin, rutin to isoquercitrin and hesperidin to hesperetin glucoside. The purified α-l-rhamnosidase has potential for enhancement of wine aroma.

α-l-rhamnosidase selective for rutin to isoquercitrin transformation from Penicillium griseoroseum MTCC-9224.

An α-l-rhamnosidase secreting fungal strain has been isolated from the decaying goose berry (Emblica officinalis) fruit peel. The fungal strain has been identified as Penicillium greoroseum MTCC-9224. The α-l-rhamnosidase of this fungal strain has been purified to homogeneity using a simple procedure involving concentration by ultra filtration and an anion exchange chromatography on DEAE-cellulose. The purified enzyme gave a single protein band corresponding to molecular mass of 97kDa in SDS-PAGE analysis. The native-PAGE analysis also gave a single protein band confirming the purity of the enzyme. Using p-nitrophenyl-α-l-rhamnopyranoside as the substrate, Km and kcat values of the enzyme were 0.65mM and 43.65s-1, respectively. The pH and temperature optima of the enzyme were 6.5 and 57°C, respectively. The activation energy for the thermal denaturation of the enzyme was 27.9kJ/mol. The purified α-l-rhamnosidase hydrolyzed rutin to isoquercitrin and l-rhamnose but has no effect on naringin and hesperidin.

Azadirachta indica plant-assisted green synthesis of Mn3O4 nanoparticles: Excellent thermal catalytic performance and chemical sensing behavior.

The leaf extract of Azadirachta indica (Neem) plant was utilized as reducing agent for the green synthesis of Mn3O4 nanoparticles (NPs). The crystalline analysis demonstrated the typical tetragonal hausmannite crystal structure of Mn3O4, which confirmed the formation of Mn3O4 NPs without the existence of other oxides. Green synthesized Mn3O4 NPs were applied for the catalytic thermal decomposition of ammonium perchlorate (AP) and as working electrode for fabricating the chemical sensor. The excellent catalytic effect for the thermal decomposition of AP was observed by decreasing the decomposition temperature by 175 °C with single decomposing step. The fabricated chemical sensor based on green synthesized Mn3O4 NPs displayed high, reliable and reproducible sensitivity of ∼569.2 µA mM(-1) cm(-2) with reasonable limit of detection (LOD) of ∼22.1 µM and the response time of ∼10 s toward the detection of 2-butanone chemical. A relatively good linearity in the ranging from ∼20 to 160 µM was detected for Mn3O4 NPs electrode based 2-butanone chemical sensor.

Purification, characterization and synthetic application of a thermally stable laccase from Hexagonia tenuis MTCC-1119.

A thermally stable laccase was purified from the culture filtrate of Hexagonia tenuis MTCC-1119. The method involved concentration of the culture filtrate by ammonium sulphate precipitation and an anion-exchange chromatography on diethylaminoethyl (DEAE) cellulose. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (native-PAGE) both gave single protein bands, indicating that the enzyme preparation was pure. The molecular mass of the enzyme determined from SDS-PAGE analysis was 100 kDa. The purification fold and percentage recovery of the enzyme activity were 12.75 and 30.12%, respectively. The pH and the temperature optima were 3.5 and 45 degrees C, respectively. The enzyme was most stable at pH 4.0 when exposed for 1 h. Using 2,6-dimethoxyphenol (DMP), 2,2 [azino-bis-(3-ethylbonzthiazoline-6-sulphonic acid) diammonium salt] (ABTS) and 3,5-dimethoxy-4-hydroxybenzaldehyde azine (syringaldazine) as the substrates, the K(m), k(cat) and k(cat)/K(m) values of the laccase were 80 µM, 2.54 s(-1), 3.17 x 10(4) M(-1)s(-1), 36 µM, 2.54 s(-1), 7.05 x 10(4) M(-1)s(-1) and 87 µM, 2.54 s(-1), 2.92 x 10(4) M(-1)s(-1), respectively. The purified laccase was finally used for the selective biotransformation of aromatic methyl group to aldehyde group in presence of diammonium salt of ABTS as the mediator and products were characterized by HPLC, IR and 1H NMR. The percentage yields of these transformed products were > 91%.

Selective oxidation and N-coupling by purified laccase of xylaria polymorpha MTCC-1100.

The chemical route of oxidation of methyl group to its aldehyde is inconvenient because once a methyl group is attacked, it is likely to be oxidized to the carboxylic acid and it is very difficult to stop the reaction at the aldehyde stage. Fungal laccases can be used for such oxidation reaction and the reaction can be completed sharply within 1-2 hrs. Coupling of amines are another important reactions known forfungal laccases; coupling reactions generally take 3-7 hrs. We have used the purified laccase of molecular weight 63 kDa obtained from the fungal strainXylaria polymorpha MTCC-100 with activity of 1.95 IU/mL for selective oxidation of 2-fluorotoluene, 4-fluorotoluene, and 2-chlorotoluene to 2-fluorobenzaldehyde, 4-fluorobenzaldehyde, and 2-chlorobenzaldehyde, respectively, and syntheses of 3-(3,4-dihydroxyphenyl)-propionic acid derivatives by N-coupling of amines. In each oxidation reactions, ABTS was used as mediator molecule. All the syntheses are ecofriendly and were performed at room temperature.

Purification and characterization of Mn-peroxidase from Musa paradisiaca (banana) stem juice.

Mn-peroxidase (MnP), a biotechnologically important enzyme was purified for the first time from a plant source Musa paradisiaca (banana) stem, which is an agro-waste easily available after harvest of banana fruits. MnP was earlier purified only from the fungal sources. The enzyme was purified from stem juice by ultrafiltration and anion-exchange column chromatography on diethylamino ethylcellulose with 8-fold purification and purification yield of 65%. The enzyme gave a single protein band in SDS-PAGE corresponding to molecular mass 43 kDa. The Native-PAGE of the enzyme also gave a single protein band, confirming the purity of the enzyme. The UV/VIS spectrum of the purified enzyme differed from the other heme peroxidases, as the Soret band was shifted towards lower wavelength and the enzyme had an intense absorption band around 250 nm. The K(m) values using MnSO4 and H2O2 as the substrates of the purified enzyme were 21.0 and 9.5 microM, respectively. The calculated k(cat) value of the purified enzyme using Mn(II) as the substrate in 50 mM lactate buffer (pH 4.5) at 25 degrees C was 6.7s(-1), giving a k(cat)/K(m) value of 0.32 microM(-1)s(-1). The k(cat) value for the MnP-catalyzed reaction was found to be dependent of the Mn(III) chelator molecules malonate, lactate and oxalate, indicating that the enzyme oxidized chelated Mn(II) to Mn(III). The pH and temperature optima of the enzyme were 4.5 and 25 degrees C, respectively. The enzyme in combination with H2O2 liberated bromine and iodine in presence of KBr and KI respectively. All these enzymatic characteristics were similar to those of fungal MnP. The enzyme has the potential as a green brominating and iodinating agent in combination with KBr/KI and H2O2.

A laccase of Fomes durissimus MTCC-1173 and its role in the conversion of methylbenzene to benzaldehyde.

A laccase has been purified from the liquid culture growth medium containing bagasse particles of Fomes durissimus. The method involved concentration of the culture filtrate by ultrafiltration and anion exchange chromatography on diethyl aminoethyl cellulose. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis both gave single protein band indicating that the enzyme preparation was pure. The molecular mass of the purified laccase determined from SDS-PAGE analysis was 75 kDa. Using 2,6-dimethoxyphenol as the substrate, the determined K (m) and k (cat) values of the laccase are 182 µM and 0.35 s(-1), respectively, giving a k (cat)/K (m) value of 1.92 × 10(3) M(-1) s(-1). The pH and temperature optimum were 4.0 and 35 °C, respectively. The purified laccase has yellow colour and does not show absorption band around 610 nm found in blue laccases. Moreover, it transformed methylbenzene to benzaldehyde in the absence of mediator molecules, property exhibited by yellow laccases.

Coal Depolymerising Activity and Haloperoxidase Activity of Mn Peroxidase from Fomes durissimus MTCC-1173.

Mn peroxidase has been purified to homogeneity from the culture filtrate of a new fungal strain Fomes durissimus MTCC-1173 using concentration by ultrafiltration and anion exchange chromatography on diethylaminoethyl (DEAE) cellulose. The molecular mass of the purified enzyme has been found to be 42.0 kDa using SDS-PAGE analysis. The K(m) values using MnSO(4) and H(2)O(2) as the variable substrates in 50 mM lactic acid-sodium lactate buffer pH 4.5 at 30(°)C were 59 µM and 32 µM, respectively. The catalytic rate constants using MnSO(4) and H(2)O(2) were 22.4 s(-1) and 14.0 s(-1), respectively, giving the values of k(cat)/K(m) 0.38 µM(-1)s(-1) and 0.44 µM(-1)s(-1), respectively. The pH and temperature optima of the Mn peroxidase were 4 and 26(°)C, respectively. The purified MnP depolymerises humic acid in presence of H(2)O(2). The purified Mn peroxidase exhibits haloperoxidase activity at low pH.