A bacterium capable of utilizing pyrethroid pesticide cypermethrin as sole source of carbon was isolated from soil and identified as a Micrococcus sp. The organism also utilized fenvalerate, deltamethrin, perimethrin, 3-phenoxybenzoate, phenol, protocatechuate and catechol as growth substrates. The organism degraded cypermethrin by hydrolysis of ester linkage to yield 3-phenoxybenzoate, leading to loss of its insecticidal activity. 3-Phenoxybenzoate was further metabolized by diphenyl ether cleavage to yield protocatechuate and phenol as evidenced by isolation and identification of metabolites and enzyme activities in the cell-free extracts. Protocatechuate and phenol were oxidized by ortho-cleavage pathway. Thus, the organism was versatile in detoxification and complete mineralization of pyrethroid cypermethrin.
In this study we report the purification of laccase produced by Trichoderma harzianum strain HZN10 (using wheat bran under solid state fermentation) and its application in decolorization of synthetic dyes. Extracellular laccase was purified to homogeneity by DEAE-Sepharose and Sephadex G-100 chromatography with specific activity of 162.5 U/mg and 25-fold purification. Purified laccase was immobilized in various entrapments like calcium alginate, copper alginate, calcium alginate–chitosan beads and sol–gel matrix. Optimization results revealed that the laccase immobilized in sol–gel was optimally active in wide pH range (4.0–7.0) and thermo-stable (50–70 °C) than free enzyme which was optimum at 50 °C and pH 6.0. Kinetic analysis showed Km of 0.5 mM and 2.0 mM and Vmax of 285 U/mg and 500 U/mg by free laccase and sol–gel immobilized laccase respectively with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] substrate. Free and immobilized laccase was employed for decolorization of three different synthetic dyes (malachite green, methylene blue and congo red). High performance liquid chromatography (HPLC) analysis results revealed that approximately 100% of malachite green, 90% of methylene blue and 60% of congo red dyes at initial concentration of 200 mg/L were decolorized within 16, 18 and 20 h, respectively by laccase immobilized in sol–gel matrix in the presence of 1-hydroxybenzotriazole (HBT) mediator. During the decolorization all three synthetic dyes showed various peaks on HPLC chromatogram indicating different by-products formation. Finally, phytotoxicity analysis results revealed that the by-products of synthetic dyes (formed during decolorization) showed less toxicity against Phaseolus mungo compared to untreated synthetic dyes.
A bacterium capable of utilizing carbaryl as sole source of carbon was isolated from garden soil and identified as a Micrococcus species. The organism also utilized carbofuran, naphthalene, 1-naphthol, and several other aromatic compounds as growth substrates. The organism degraded carbaryl by hydrolysis to yield 1-naphthol and methylamine. 1-Naphthol was further metabolized via salicylate by a gentisate pathway, as evidenced by oxygen uptake and enzymatic studies.
An acidophilic-solvent-thermostable endo β-1,4-d-glucanase produced from a potential Trichoderma harzianum strain HZN11 was purified to homogeneity by DEAE-Sepharose and Sephadex G-100 chromatography with 33.12 fold purification with specific activity of 66.25 U/mg and molecular mass of ~55 kDa. The optimum temperature and pH were 60 °C and 5.5 retaining 76 and 85 % of activity after 3 h, respectively. It showed stability between pH 4.5–6.0 and temperature between 50–70 °C indicating thermostability. Endo β-1,4-d-glucanase was activated by Ca2+ and Mg2+ but inhibited by Hg2+, Pb2+ and Cd2+. The effect of thiol reagents, metal chelators, oxidizing agents and surfactants on enzyme activity has been studied. Purified endo β-1,4-d-glucanase exhibited highest specificity towards carboxymethyl cellulose. Kinetic analysis showed the K m, V max and K i (cellobiose inhibitor) of 2.5 mg/mL, 83.75 U/mg and 0.066 M, respectively. The storage stability of purified endo β-1,4-d-glucanase showed a loss of mere 13 % over a period of 60 days. The hydrolysis efficiency of purified endo β-1,4-d-glucanase mixed with cocktail was demonstrated over commercial enzyme. Optimized enzymatic hydrolysis of sweet sorghum and sugarcane bagasse released 5.2 g/g (36 h) and 6.8 g/g (48 h) of reducing sugars, respectively. Separate hydrolysis and fermentation of sweet sorghum bagasse yielded 4.3 g/L bioethanol (16 h) confirmed by gas chromatography–mass spectrometry (GC–MS). Morphological and structural changes were assessed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Elemental analysis was carried out by SEM equipped with energy dispersive X-ray technique. These unique properties prove the potentiality of enzyme for biomass conversion to biofuel and other industrial applications.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0421-y) contains supplementary material, which is available to authorized users.
A bacterium capable of utilizing p-cresol as sole source of carbon and energy was isolated from soil and identified as a Bacillus species. The organism also utilized phenol, o-cresol, m-cresol, 4-hydroxybenzoic acid, and gentisic acid as growth substrates. The organism degraded p-cresol to 4-hydroxybenzoic acid, which was further metabolized by a gentisate pathway, as evidenced by isolation and identification of metabolites and enzyme activities in the cell-free extract. Such a bacterial strain can be used for bioremediation of environments contaminated with phenolic compounds.
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