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Table 2 Application of some interesting plant laccases that degrade different compounds and may be useful in water treatement

From: Laccases: structure, function, and potential application in water bioremediation

Laccase sourceApplied enzyme formType of culture, ingredientsApplicationReaction parametersResults obtainedMain putative mechanisms involvedReferences
Dye-based pollutants
 A. densiflorusP
R
Single plant having a total biomass of 70 ± 4 g in 500 mL beaker having 200 mL of 20, 40, 60, 80 and 100 mg/L by 12 h in dye solution in distilled water
Root tissue showed laccase (138%), lignin peroxidase (129%), riboflavin reductase (111%), DCIP reductase (47%), tyrosinase (26%) and azo reductase (18%) activities
Progressive dye accumulation and removal of Rubin GFL (RGFL) dyeReactors (phytoreactor of 30 L) were watered with 500 mL tap water every day for 30 daysA. densiflorus decolorized Rubin GFL (RGFL) dye (40 gm L−1) up to 91% within 48 h. RGFL at 20, 60, 80 and 100 mg/L were decolorized by 91, 82, 69% and 61%, respectivelyProposed oxidative cleavage and deamination of the dyes. Phytotoxicity study demonstrated reduced toxicity of biotransformed RGFL[85]
 Tagetes patula, Aster amellus, Portulaca grandiflora and Gaillardia grandifloraPPlants of selected species were independently planted on ridge beds and watered with normal water for first 30 daysThe textile effluent from common effluent treatment plant1000 plants were nourished with normal water (control) and remaining 1000 plants with real textile wastewater for remaining 30 days of the experiments (test)Reduction in dye by 59, 50, 46 and 73%, for each independent plant respectively within 30 days compared to dye accumulated in unplanted ridgesThe mechanisms for their degradation or detoxification in plants are poorly understood[90]
 Glandularia pulchella (Sweet) Tronc. (Moss Verbena)PPlants of approximately the same growth stage, having equal number of shoots, and almost equivalent weight
Three plants were dipped in 250 mL flasks containing solution of various dyes for 96 h
Decolorization of pollutant dyesThree plants were dipped in each of the 250-mL SF containing 100 mL solution of the synthetic dye mixture for 96 h. Those are: reactive orange HE2R, reactive yellow MEG4, reactive yellow GR, blue 2GL, remazol red, green HE4B, brown 3REL, blue 2RNL, patent blue, and malachite green
Cell free extract were used for enzyme assays
Plants of G. pulchella were exposed to solutions of ten different dyes and promoted the decolorization of all the dyes to varying extentBiodegradation in living cells is realized by multiple enzymes (laccases and peroxidases mainly) to mineralize synthetic dyes[88]
 Brumea malcolmiiC
F
Cell suspension cultures on modified Murashuge and Skoog’s medium pH 5.8 and 25 °C. The cultures were maintained at 100 rpm under 16:8 h light:darkness photoperiod during 10 days. Filtrates obtained were used as sources of extracellular enzymes for enzyme assaysDecolorization of pollutant dyes: brilliant blue R (BBR), malachite green, reactive red 2, direct red 5B and methyl orangeThe respective dyes at 40 mg/L, 0.2 M sodium acetate buffer (pH 4.8) and 0.5 mL enzyme and 35 μM ABTS. The reaction mixture was incubated at 30 °C under static as well as shaking conditions at 100 rpmSuspension cells and purified laccase showed the ability to decolorize different dyes completely. In the case of purified laccase, the addition of ABTS to BBR, increase decolorization and degradationWhole cell cultures involved a asymmetric cleavage of BBR followed by a demethylation with laccase[86]
 Alternanthera philoxeroidesPPlants were exposed to textile industry effluent in rhizofiltration reactor system for 6 daysPhytoremediation of sulfonated remazol red dye and textile effluentsPlants were put in contact with each effluent sample was monitored for a retention time of 6 days (144 h) and effluent samples were analyzed
Cell free extract from roots, stem, leaves and plants as enzyme source
A. philoxeroides could completely decolorize remazol red dye and demonstrated potential in real textile industry effluent at laboratory and pilot scaleUnknown[89]
Herbicide compounds
 Recombinant LAC1 from Gossypium arboreum in Pichia pastoris or transgenic Arabidopsis thalianaPSeeds of A. thaliana (ecotype Columbia) express LAC1 were germinated in a pot with either a syringic acid solution (2 mM) or a TCP solution (1 mM). Two weeks after germination, seedlings were sprayed with either the syringic acid solution every 3 days for 3 weeks, or with the TCP solution twice with a 5 days intervalTransformation of sinapic acid, to other phenolic compounds like 2,4,6-trichlorophenol (TCP)LAC1 in presence of 60 nmol of ABTS/min/mg protein
In transformed plants, expressing LAC1, 10–20 μM of TCP, syringic acid 2 mM or 0.5 mM of sinapic acid
Laccase activity was responsible for the conversion of sinapic acid into mono-lactone type dimer and the transformation of TCPConversion of sinapic acid into monolactone-type dimer[84]
 Recombinant laccases from Oryza sativa expressed in Pichia pastorisCS48 h cultures in YPD medium induced with 1% methanol at 30 °CModification and detoxification of herbicides atrazine (ATR) and isoproturon (IPU)Transformants were add in YPD medium containing 1% methanol and 0.4 mg/L ATR or 2.0 mg/L IPU at 30 °C for 48 h. The ATR or IPU conversion rates were calculatedThe heterologous expression of the two rice laccase genes in P. pastoris led to the cells resistant to ATR and IPU. This suggests that laccase could be involved in detoxification or degradation of ATR or IPU in plantMechanisms poorly understood[91]
  1. P whole plant, R plant roots, CS cell suspension, C crude culture supernatant, F free purified enzyme, RGFL rubin GF, DCIP 2,6-dichloroindophenol, TCP 2,4,6-trichlorophenol, AzBTS-(NH4)2 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, ABTS diammonium 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate), BBR brilliant blue R, ATR atrazine, IPU isoproturon, YPD yeast extract–peptone–dextrose