Production of Trametes pubescens laccase under submerged and semi-solid culture conditions on agro-industrial wastes

A systematic study on the characteristics and applications of laccases produced by fungi: insights on their potential for biotechnologies

Laccases are polyphenol oxidase enzymes and form the enzyme complex known for their role in wood decomposition and lignin degradation. The present study aimed to systematically review the state-of-the-art trends in scientific publications on laccase enzymes of the last 10 years. The main aspects checked included the laccase-producing fungal genera, the conditions of fungal growth and laccase production, the methods of immobilization, and potential applications of laccase. After applying the systematic search method 177 articles were selected to compound the final database. Although various fungi produce laccase, most studies were Trametes and Pleurotus genera. The submerged fermentation (SmF) has been the most used, however, the use of solid-state fermentation (SSF) appeared as a promising technique to produce laccase when using agro-industrial residues as substrates. Studies on laccase immobilization showed the covalent bonding and entrapment methods were the most used, showing greater efficiency of immobilization and a high number of enzyme reuses. The main use of the laccase was in bioremediation, especially in the discoloration of dyes from the textile industry and the degradation of pharmaceutical waste. Implications and consequences of all these findings in biotechnology and environment, as well as the trends and gaps of laccase research were discussed.

Wheat bran as an efficient agro-process waste for enhanced yellow laccase production by Lentinus tigrinus SSB_W2 and its application in anthraquinone dye degradation

Lentinus tigrinus SSB_W2, isolated from Mahabaleshwar in the Western Ghats of Maharashtra, India, was employed to enhance laccase production in solid-state fermentation (SSF). The spectral analysis indicated that the laccase produced by L. tigrinus is a typical yellow laccase, exhibiting no absorption at 600 nm. Notably, this yellow laccase demonstrated exceptional catalytic activity, as confirmed by electrochemical analysis. Four agricultural processing wastes were evaluated as substrates for SSF, and the results showed that L. tigrinus effectively utilized wheat bran. Initial testing by one-factor-at-a-time method showed 3.79-fold increase in yellow laccase production, which subsequently increased to 6.51-fold after Plackett-Burman design. Moreover, employing response surface methodology resulted in 11.87-fold increase (108,472 IU gds-1) in laccase production. The utilization of yellow laccase for the biotransformation of various textile dyes was investigated, and it exhibited the highest degradation efficiency toward Reactive blue 4, a recalcitrant anthraquinone dye, with a rate of 18.36 mg L-1 h-1, for an initial concentration of 1000 mg L-1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03881-9.

Activity of Lignin-Modifying Enzyme of Selected Medicinal Mushrooms in Submerged Fermentation of Lignocellulosic Materials

In the present study, wide diversity in the set and activity of lignin-modifying enzymes (LME) was revealed during submerged fermentation of mandarin peel with 15 strains of white rot Basidiomycetes. Among them, Trametes pubescens BCC153 was distinguished by the simultaneous production of laccase, manganese peroxidase (MnP), and lignin peroxidase (LiP). Supplementation of CuSO4 at a concentration of 1 mM in the media for the cultivation of four Trametes species manifold increased the production of laccase. The diverse effects of chemically different lignocellulosic growth substrates and nitrogen sources on the production of individual LME have been established. The maximum laccase activity of T. pubescens was observed when the fungus was cultivated on media containing mandarin peel and wheat bran, whereas the highest MnP and LiP activities were detected in the submerged fermentation of tobacco residue. Peptone and casein hydrolysate appeared to be the best sources of nitrogen to produce laccase and both peroxidases by T. pubescens BCC153 whereas KNO3 was the worst nitrogen-containing compound for the production of all enzymes.

Evaluating the efficacy of wood decay fungi and synthetic fungal consortia for simultaneous decolorization of multiple textile dyes

Wastewater from the textile industry dyeing process containing high loads of synthetic dyes leads to pollution of water with these toxic and genotoxic dyes. Much effort has been put towards developing biological systems to resolve this issue. Mycoremediation is a well-known approach using fungi to remove, degrade, or remediate pollutants and can be applied to decolorize textile dyes in industrial effluent. Fungal strains from four genera of Polyporales, namely Coriolopsis sp. TBRC 2756, Fomitopsis pinicola TBRC-BCC 30881, Rigidoporus vinctus TBRC 6770, and Trametes pocas TBRC-BCC 18705, were studied for decolorization efficiency, and R. vinctus was found to exhibit the greatest activity in removing all seven tested reactive dyes and one acid dye with a decolorization efficiency of 80% or more within 7 days under limited oxygen. This fungus simultaneously degraded multiple dyes in synthetic wastewater as well as industrial effluent from the dyeing process. To enhance the decolorization rate, various fungal consortia were formulated for testing. However, these consortia only trivially improved efficiency compared with using R. vinctus TBRC 6770 alone. Evaluation of R. vinctus TBRC 6770 decolorization ability was further performed in a 15-L bioreactor to test its ability to eliminate multiple dyes from industrial effluent. The fungus took 45 days to adapt to growth in the bioreactor and subsequently reduced dye concentration to less than 10% of the initial concentration. The following six cycles required only 4-7 days to reduce dye concentrations to less than 25%, demonstrating that the system can run efficiently for multiple cycles without the need for extra medium or other carbon sources.

Biological pretreatment of sugarcane bagasse for the production of fungal laccase and bacterial cellulase

Sugarcane bagasse (SB) is a promising source of appreciable quantities of fermentable sugars. However, the presence of lignin hinders utilization of these carbohydrates and hence pretreatment to remove lignin is necessarily carried out. Here, a biological pretreatment method was synchronized with the production of a thermostable cellulase using SB as a raw material. Initially, bagasse was fermented by a laccase producing fungus, Trametes pubescens MB 89 under solid state fermentation (SSF) and a titer of 1758 IU mL^-1 of laccase was obtained. Investigations of nine factors affecting laccase production through Plackett Burman design improved the titers to 6539 IU mL^-1 . Five factors (incubation period, concentration of CuSO₄ , temperature, moisture content, and particle size) were found significant which were optimized through Central Composite design leading to an improvement in the titers by ~5 folds (8841 IU mL^-1 ). Biologically pretreated SB was fermented by a thermophilic bacterium, Neobacillus sedimentimangrovi UE25, that yielded 8.64 IU mL^-1 of cellulase. Delignification and cellulose utilization were affirmed by structural analysis through FTIR and SEM. The synchronized process yielded higher titers of laccase and cellulase under SSF of SB with the minimum use of corrosive chemicals.

Microaerobic conditions enhance laccase production from Rheinheimera sp. in an economical medium

Statistical optimization of aeration conditions viz. aerobic, microaerobic and anaerobic, was performed using response surface methodology (RSM) utilizing soybean meal as medium to enhance the production of laccase from Rheinheimera sp. Maximum laccase yield (18.48 × 10⁵ U/L) was obtained under microaerobic (static) conditions sustained for 12 h in tandem with 26 h aerobically (150 rpm) grown culture, which was 17.03-fold higher than laccase production in the starting M162 medium under aerobic conditions (150 rpm). The reduction in incubation time from 72 to 38 h and utilization of cost-effective soybean meal as medium, which is easily available from local market, have provided a promising, eco-friendly method of laccase enzyme production. Enhanced expression of laccase gene under microaerobic conditions corresponded to the increased expression of fnr (fumarate nitrate reductase) gene, the oxygen sensing global regulator. The putative FNR-binding site upstream of laccase transcription initiation site was predicted to play an imperative role in Rheinheimera sp. adaptation from aerobic to microaerobic conditions and for enhanced laccase production.

Studies on production and evaluation of biopigment and synthetic dye decolorization capacity of laccase produced by A. oryzae cultivated on agro-waste

The present study investigated the screening of mono and co-culture fungal cultivations for laccase production using extracted lignin as the substrate obtained from cauliflower wastes by two different pretreatment methods. Amongst mono and mixed culture fungal cultivations, monoculture of Aspergillus oryzae exhibited the highest enzymatic activity of 29.7 ± 0.6 U mL^-1 under submerged conditions and using alkali extracted lignin as substrate. Under the optimal conditions (pH 4.5, 30 °C, 12 days, 1% (w/v) lignin and 0.5 mM Cu²⁺ concentration) the maximum laccase activity was estimated to be 41.3 ± 2.8 U mL^-1 and production yield of 153.3 ± 2.4 mg L^-1. Maximum decolorization of pigment extracted from Aspergillus heteromorphus CBS 117.55 cultivated culture media was achieved by administration of 40 U g^-1 of crude enzyme concentration. Thermal and pH stability of crude laccase was observed over wide ranges. The dye decolorization efficiency of crude A. oryzae laccase was studied and Congo Red exhibited maximum decolorization percentage (64 ± 1.3%) at 15 µM, 50 °C and pH 4.5. The kinetic study of different dye (Congo Red) concentrations obtained V_max and K_m values of 0.123 × 10^-3 M and 0.724 mol L^-1 min^-1, respectively.

Screening of Novel Laccase Producers-Isolation and Characterization of Cold-Adapted Laccase from Kabatiella bupleuri G3 Capable of Synthetic Dye Decolorization

Psychrophilic laccases catalyzing the bond formation in mild, environmentally friendly conditions are one of the biocatalysts at the focus of green chemistry. Screening of 41 cold-adapted strains of yeast and yeast-like fungi revealed a new laccase-producing strain, which was identified as Kabatiella bupleuri G3 IBMiP according to the morphological characteristics and analysis of sequences of the D1/D2 regions of 26S rDNA domain and the ITS1-5,8S-ITS2 region. The extracellular activity of laccase in reaction with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) at the optimal pH 3.5 was 215 U/L after 15 days of growth in a medium with waste material and 126 U/L after 25 days of cultivation in a defined medium. Copper (II) ions (0.4 mM), Tween 80 (1.0 mM) and ascorbic acid (5.0 mM) increased the production of laccase. The optimum temperature for enzyme operation is in the range of 30-40 °C and retains over 60% of the maximum activity at 10 °C. New laccase shows high thermolability-half-life at 40 °C was only 60 min. Enzyme degradation of synthetic dyes was the highest for crystal violet, i.e., 48.6% after 1-h reaction with ABTS as a mediator. Outcomes of this study present the K. bupleuri laccase as a potential psychrozyme for environmental and industrial applications.

Mechanism of Laccase Induction via Emodin in Trametes versicolor

Secondary metabolites of traditional Chinese herbs can prominently stimulate the production of laccase from white rot fungi during submerged fermentation. However, the molecular mechanism through which these natural products induce the production of laccase remains unknown. In this study, the Chinese herbal medicine Polygonum cuspidatum was used to induce laccase production in Trametes versicolor, and the best inducer was identified in emodin, even under conditions of 1000-L, large-scale fermentation. Proteomics analysis identified a selection of proteins that were differentially expressed in the presence of emodin, indicating that emodin may affect the expression of laccase genes through three mechanisms: reducing bioenergy productivity, the aryl hydrocarbon receptor (AHR)/xenobiotic response element (XRE) pathway, and the nuclear erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. Combined with protoplast flow cytometry and fluorescence, it is revealed that emodin might reduce the synthesis of ATP by lowering the mitochondrial membrane potential, leading to the subsequent responses.

Valorization of Lignocellulosic Wastes to Produce Phytase and Cellulolytic Enzymes from a Thermophilic Fungus, Thermoascus aurantiacus SL16W, under Semi-Solid State Fermentation

Agricultural wastes are lignocellulosic biomasses that contain high mineral and nutrient contents. This waste can be used as a raw material in industrial enzyme production by microbial fermentation. Phytase is an important enzyme used in animal feed to enhance the amount of phosphorus available for the growth and overall health improvement of monogastric animals. Fungi offer high potential as an effective source in the production of various extracellular enzymes. In this study, the production of lignocellulolytic enzymes (endoglucanase and xylanase) and phytase by a thermophilic fungus, namely Thermoascus aurantiacus strain SL16W, was evaluated using sixteen different Thai agricultural forms of waste under conditions of high temperature (45 °C). Semi-solid state fermentation was used in the production experiments. The results of this study reveal that the highest phytase activity (58.6 U/g substrate) was found in rice bran, whereas the highest degrees of activity of endoglucanase and xylanase were observed in wheat bran and red tea leaves at 19 and 162 U/g substrate, respectively. Consequently, the optimal conditions for phytase production of this fungus using rice bran were investigated. The results indicate that the highest phytase yield (58.6 to 84.1 U/g substrate) was observed in rice bran containing 0.5% ammonium sulfate as a nitrogen source with 10 discs of inoculum size at a cultivation period of 9 days at 45 °C and moisture content of 95%. Notably, the phytase yield increased by 1.71-fold, while endoglucanase and xylanase were also increased by 1.69- and 1.12-fold, respectively. Furthermore, the crude enzyme obtained from the optimal condition was extracted. The crude enzyme extract was then separately added to red tea leaves, rice straw, corncobs, palm residue, and peanut husks. Subsequently, total reducing sugar and phosphorus contents were determined. The results indicate that the highest level of reducing sugar (122.6 mg/L) and phosphorus content (452.6 mg/L) (p < 0.05) were obtained in palm residue at 36 and 48 h, respectively, after the addition of the crude enzyme extract. This study has provided valuable information on a potentially eco-friendly way to valorize agricultural waste into value-added products as industrial enzymes.

Optimization and kinetic modeling of Trametes maxima IIPLC-32 laccase and application in recalcitrant dye decolorization

Enhanced laccase production by the Trametes maxima fungus and its use for decolorization of the textile dye RBBR.

Stabilization-destabilization and redox properties of laccases from medicinal mushroom Ganoderma lucidum and human pathogen Yersinia enterocolitica

Laccases or benzenediol oxygen oxidoreductases (EC 1.10.3.2) are polyphenol multicopper oxidases that are known for their structural and functional diversity in various life forms. In the present study, the molecular and physico-chemical properties (redox-potential and secondary structures) of fungal laccase isozymes (FLIs) isolated from a medicinal mushroom Ganoderma lucidum were analyzed and compared with those of the recombinant bacterial laccases (rLac) obtained from different Yersinia enterocolitica strains. It was revealed that the FLIs contained His-Cys-His as the most conserved residue in its domain I Cu site, while the fourth and fifth residues were variable (Ile, Leu, or Phe). Evidently, the cyclic voltammetric measurements of Glac L2 at Type 1 Cu site revealed greater E° for ABTS/ABTS⁺ (0.312 V) and ABTS⁺/ABTS²⁺ (0.773 V) compared to the E° of rLac. Furthermore, circular dichroism-based conformational analysis revealed structural stability of the FLIs at acidic pH (3.0) and low temperature (<30 °C), while the isozymes were destabilized at neutral pH (7.0) and high-temperature conditions (>70 °C). The zymographic studies further confirmed the functional inactivation of FLIs at high temperatures (≥70 °C), predominantly due to domain unfolding. These findings provide novel insight into the evolution of the catalytic efficiency and redox properties of the FLIs, contributing to the existing knowledge regarding stress responses, metabolite production, and the biotechnological utilization of metabolites.

Decolorization of Textile Effluent by Trametes hirsuta Bm-2 and lac-T as Possible Main Laccase-Contributing Gene

The decolorization of dye and textile effluent by Trametes hirsuta was studied in both induced and non-induced media. A removal of 70-100% of the color was achieved through adsorption and the action of laccases. Laccase activity was increased significantly with the addition of grapefruit peel (4000 U/mL) and effluent with grapefruit peel (16,000 U/mL) in comparison with the basal medium (50 U/mL). Analysis of the expression of laccase isoenzymes lac-B and lac-T revealed clear differences in the expression of these genes. The low levels of expression of lac-B in all media suggest a basal or constitutive gene expression, whereas lac-T was over-expressed in the media with effluent, and showed an up/down regulation depending on culture conditions and time. The results obtained suggest that the lac-T gene of T. hirsuta is involved in the decolorization of dyes.

Laccase isoform diversity on basal medium in Cyathus bulleri and role in decolorization/detoxification of textile dyes and effluent

Laccases (EC 1.10.3.2) are multi-copper oxidases that can degrade several xenobiotics, including textile dyes. Present study investigated the nature of laccase isoforms induced by 2,6-dimethylaniline in Cyathus bulleri cultivated on basal salt medium. Two isoforms, LacI and LacII were identified and purified by a combination of ultrafiltration and ion-exchange chromatography. The MS spectrum of the two proteins displayed a number of non-identical and identical molecular peaks (m/z), and, the latter were mapped to protein originating from the previously reported Laccase (Lcc) 1 gene. The LacI isoform exhibited higher catalytic efficiency (K_cat/K_m) towards 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), 2,6-dimethoxyphenol, guaiacol and pyrogallol and was tolerant to high levels of chloride ions and resistant to EDTA. Higher decolorization of several dyes such as Direct Scarlet B (67%), Reactive Brilliant blue-R (96%), Direct Orange 34 (50%) and Reactive Red198 (95%) by the LacI isoform makes it a good candidate for degradation of synthetic dyes. The decolorization of Direct Orange 34 by laccases is being reported for the first time. Many of the properties exhibited by this isoform make it a good candidate for large scale production and applications for use in the dyeing industry.

Alternative methods for gibberellic acid production, recovery and formulation: A case study for product cost reduction

The aim of this work was to develop a new production, recovery and formulation process of gibberellic acid (GA₃). Low-cost byproducts - citrus pulp (CP) and soybean hulls (SH) - were employed as substrate for GA₃ production by Gibberella fujikuroi in semisolid fermentation. A CP/SH mixture (70%/30%) promoted high productivities both in bubble column reactor (1.66 mg L/h), and in stirred tank reactor (2.13 mg L/h). GA₃ production medium cost (US$ 6.70/m³) was reduced by 85% when compared to previously reported synthetic media (US$ 44.96/m³). It was described that GA₃ fermented extract has low stability, and that liquid and powder formulation of the fermented extract maintained the biomolecule activity over 6 months. Alginate and alginate/kefiran beads containing GA₃ showed encapsulation efficiency of 70% and 60%, respectively. This work supports good perspectives for GA₃ production using cheap substrates and simple formulation of clarified extract to favour its use in agricultural countries.

Comprehensive studies on optimization of ligno-hemicellulolytic enzymes by indigenous white rot hymenomycetes under solid-state cultivation using agro-industrial wastes

The disposal of oil palm biomass is a huge challenge in Malaysian oil palm plantations. The aim of this study was to develop efficient solid-state cultivated (SSC) ligno-hemicellulolytic bio-degrader formulations of indigenous white-rot hymenomycetes (Trametes lactinea FBW and Pycnoporus sanguineus FBR) utilizing oil palm empty fruit bunches (EFB), rubber wood sawdust (SD) and vermiculite (V) either alone or in combination as substrates. Based on significant laccase (849.40 U mg^-1 protein), xylanase (42.26 U g^-1 protein) and amylase (157.49 U g^-1 protein) production, SD+V (T5) and V (T3) were the optimum substrates for SSC of T. lactinea FBW. Whereas, utilizing EFB (T1) substrate for SSC of P. sanguineus FBR enhanced the production of MnP (42.51 U mg^-1 protein), LiP (103.20 U mg^-1 protein) and CMCase (34.39 U g^-1 protein), enzymes. Apparently, this is the first study reporting on the protein profiles by T. lactinea FBW, producing two isoforms of un-purified laccase (~55 and 70 kDa) and MnP (~40 and 60 kDa) and a CMCase band (~60 kDa) during SSC on SD+V (T5) substrate. Interestingly, this is also the first report to document a single isoform of un-purified laccase (~50 kDa), MnP (~45 kDa), CMCase (~60 kDa) and xylanase (~55 kDa) by P. sanguineus FBR during SSC on empty fruit bunches substrate. The computed Principal Component Analysis (PCA) Biplot analysis elucidated the relationship between the solid substrate compositions, the hymenomycete strain, ligno-hemicellulolytic enzyme profiles, and cultivation time. Therefore, it is suggested to use PCA as a tool for multivariate analysis method for comprehensive selection and optimization of ligno-hemicellulolytic enzyme cocktails by the indigenous white rot hymenomycetes. These non-toxic (acute oral toxicity) formulations are safe to be used in field applications to efficiently degrade oil palm trunks and root mass that had been felled, chipped or pulverized under zero burning waste management program. This study could also serve as an alternative method for efficient utilization of agro-industrial waste as substrates for the development of cost-effective bio-degraders formulations for agro-waste management.

Pre-treatment of a sugarcane bagasse-based substrate prior to saccharification: Effect of coffee pulp and urea on laccase and cellulase activities of Pycnoporus sanguineus

Production of second-generation bioethanol uses lignocellulose from agricultural by-products such as sugarcane bagasse (SCB). A lignocellulose pre-treatment is required to degrade lignin, ensuring further efficient saccharification. Two experimental designs were set up to define culture conditions of Pycnoporus sanguineus in mesocosms to increase laccase activities and thus delignification. The first experimental design tested the effect of phenolic complementation (via coffee pulp) and the use of urea as a simple nitrogen source and the second defined more precisely the percentages of coffee pulp and urea to enhance delignification. The responses measured were: lignocellulolytic activities, laccase isoform profiles by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the chemical transformation of the substrate using solid-state NMR of 13C. Adding 10% of coffee pulp increased laccase activities and fungal biomass (32.5% and 16% respectively), enhanced two constitutive isoforms (R_f 0.23 and 0.27), induced a new isoform (R_f 0.19) and led to a decrease in total aromatics. However, higher concentrations of coffee pulp (25%) decreased laccase and cellulase activities but no decrease in aromaticity was observed, potentially due to the toxic effect of phenols from coffee pulp. Moreover, laccase production was still inhibited even for lower concentrations of urea (0-5%). Our findings revealed that an agricultural by-product like coffee pulp can enhance laccase activity -though to a threshold- and that urea limited this process, indicating that other N-sources should be tested for the biological delignification of SCB.

Response surface based optimization of laccase production from Bacillus sp. MSK-01 using fruit juice waste as an effective substrate

Laccases are multicopper oxidases containing four copper atoms per monomer distributed in three redox sites. Because of its tremendous applications in different areas, isolation of new laccases with wide range of industrial implementation. The present study focuses on the optimization of laccase production from Bacillus sp. MSK-01 under solid state fermentation conditions using fruit juice waste as the substrate. MSKLAC was produced extracellularly by the bacteria. This laccase was able to oxidize ABTS and syringaldazine. Various nutritional and environmental factors were utilized for increasing the enzyme yield. Plackett Burman was used to study the influence of input parameters on laccase yield. Tween-80, initial moisture ratio and magnesium sulphate were the major influencing factor affecting laccase yield. Central composite design of RSM was used for the modelling of experiment. Desirability approach was used to optimize laccase yield. Maximum laccase yield of 1645 IUg⁻¹ was obtained when 0.55% of tween -80, 1:2.34 initial moisture ratio and 300μM magnesium sulphate was used. A 470 fold increase in the yield of laccase from unoptimized condition was obtained.

Current advances in gibberellic acid (GA3) production, patented technologies and potential applications

Gibberellic acid is a plant growth hormone that promotes cell expansion and division. Studies have aimed at optimizing and reducing production costs, which could make its application economically viable for different cultivars. Gibberellins consist of a large family of plant growth hormones discovered in the 1930s, which are synthesized via the terpenes route from the geranylgeranyl diphosphate and feature a basic structure formed by an ent-gibberellane tetracyclic skeleton. Among them, only four have biological activity, including gibberellic acid (GA₃), which acts as a natural plant growth regulator, especially for stem elongation, seed germination, and increased fruit size. It can be obtained from plants, fungi, and bacteria. There are also some reports about microalgae GA₃ producers. Fungi, especially Gibberella fujikuroi, are preferred for GA₃ production via submerged fermentation or solid-state fermentation. Many factors may affect its production, some of which are related to the control and scale-up of fermentation parameters. Different GA₃ products are available on the market. They can be found in liquid or solid formulations containing only GA₃ or a mixture of other biological active gibberellins, which can be applied on a wide variety of cultivars, including crops and fruits. However, the product's cost still limits its large and continuous application. New low-cost and efficient GA₃ production alternatives are surely welcome. This review deals with the latest scientific and technological advances on production, recovery, formulation, and applications of this important plant growth hormone.

Laccase-mediator system produced by Trametes hirsuta Bm-2 on lignocellulosic substrate improves dye decolorization

Lignin is a source for obtaining natural phenols with high commercial value that can act as redox mediators enhancing effects in dye decolorization. In this study Trametes hirsuta Bm-2 was grown on wheat bran to produce laccases and phenol extracts (PE). Ultrafiltered phenols obtained at different times were evaluated in their potential as redox mediators of laccase activity and indigo carmin decolorization. Laccase activity (L) on ABTS increased up to 12.4 times with L/PE72 compared with laccase alone and L/PE48 showed the highest level of dye decolorization (97%) compared with laccase (12%). The chromatographic analysis by HPLC showed variation in the profile and concentration of phenols at different times of culture. Stability of the laccase mediator system (LMs) in dye decolorization was maintained over 3 months. Our results suggest the use of natural mediators as a strategy for improving efficiency in dye biodegradation by laccase-producing fungi.

Cupuaçu (Theobroma grandiflorum) residue and its potential application in the bioremediation of 17-Α-ethinylestradiol as a Pycnoporus sanguineus laccase inducer

Bioremediation is a strategy to mitigate environmental impacts of hazardous pollutants from anthropogenic sources. Natural byproducts, including agroindustrial wastes (AW) can be used to induce enzyme biosynthesis, leading up to enhancement of pollutants degradation process. Therefore, this study aimed to evaluate the use of cupuaçu, Theobroma grandiflorum AW as Pycnoporus sanguineus Laccase (Lac) inducer in order to promote 17-α-ethinylestradiol (EE2) bioremediation. The macro and micro-nutrients levels of cupuaçu AWs were evaluated in order to establish further correlations with enzymatic biosynthesis induction. The fungus was cultivated for 7 days in temperature of 28 ± 2 °C and agitation of 150 rpm. For bioremediation, Lac enzymatic extract was added to EE2 solution (10 µg mL^-1) and the percentage of removal was evaluated by HPLC after 1-24 hr of reaction. At optimized conditions, the enzyme extract production was remarkably enhanced by adding only 1% (w/v) of cupuaçu AW. Lac activity reached 1642 U mL^-1 on the 6th day of culture, which was higher than positive control (511 U mL^-1). 86% of EE2 removal was reached after 4 hr, and after 8 hr of reaction, 96.5% was removed. Analysis by direct infusion in MS-ESI-TOF exhibited intermediary compounds formed by radical hydroxilation.

An alkaline bacterial laccase for polymerization of natural precursors for hair dye synthesis

In the present study, an extracellular alkali stable laccase (Lac DS) from Bacillus subtilis DS which has pH optima at 8.5 using p-phenylenediamine (PPD) as substrate has been reported. Lac DS retained 70% activity for 4 h at pH 8.5 and 90% activity for 24 h at 55 °C. The enzyme yield was enhanced by optimization of fermentation conditions. A 746-fold increase in yield was observed under optimized conditions using 150 µM MgSO₄, 1.2% yeast extract, 0.35% tryptone, and 150 µM vanillic acid. Lac DS was used to polymerize natural dye precursor catechol, pyrogallol, syringaldehyde, syringic acid, ferulic acid and gallic acid to develop a range of natural hair colors such as black, golden yellow, and reddish brown. The results indicate that alkaline Lac DS is a suitable candidate to develop a user-friendly and commercially applicable hair dyeing process in the area of cosmetic industry.

Flavonoid-rich agro-industrial residues for enhanced bacterial laccase production by submerged and solid-state fermentation

Laccases have potential applications in industrial, biotechnological, and environmental set ups. Development of cost effective and efficient production technologies has gained significant attention in recent years. To enhance the laccase production from Rheinheimera sp. (Gram negative) using submerged fermentation (SmF) and from Lysinibacillus sp. (Gram positive) using solid-state fermentation (SSF), the inducing effect of various flavonoid-rich agro-industrial residues was investigated. Peels of citrus fruits, soybean meal, tofu dreg, lignin monomers, and lingo-cellulosic waste, used tea leaves and peels of onion and kiwi, paper, and dying industry effluents were tested as inducers. In SmF, 0.1% of soybean meal, tofu dreg, and powdered orange peel were best, enhancing the laccase production 2.57-, 2.11-, and 2.05-fold, respectively. In SSF, 10 mg (w/w) of used tata acti green tea leaves per 5 g of wheat bran, 1% pulp and paper industry effluent (agro based), and 1% wine made from Sygium cumini enhanced the laccase production 2.69-, 2.61-, and 2.09-fold, respectively. These results suggest the utilization of these flavonoid and phenolic-rich waste materials to be potential enhancers of industrially important laccase production.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZαA-GlucPost-Stop in Pichia pastoris. Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL⁻¹ at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a V_max of 6.87 × 10⁻⁵ mM s⁻¹, with an apparent K_m of 5.36 × 10⁻² mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges.

Purification and immobilization of laccase from Trichoderma harzianum strain HZN10 and its application in dye decolorization

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 K_m of 0.5 mM and 2.0 mM and V_max 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.

Production of Enzymes From Agricultural Wastes and Their Potential Industrial Applications

Enzymatic hydrolysis is the significant technique for the conversion of agricultural wastes into valuable products. Agroindustrial wastes such as rice bran, wheat bran, wheat straw, sugarcane bagasse, and corncob are cheapest and plentifully available natural carbon sources for the production of industrially important enzymes. Innumerable enzymes that have numerous applications in industrial processes for food, drug, textile, and dye use have been produced from different types of microorganisms from agricultural wastes. Utilization of agricultural wastes offers great potential for reducing the production cost and increasing the use of enzymes for industrial purposes. This chapter focuses on economic production of actinobacterial enzymes from agricultural wastes to make a better alternative for utilization of biomass generated in million tons as waste annually.

Biodegradation of phenolic compounds by Basidiomycota and its phenol oxidases: A review

The phylum Basidiomycota include organisms with enormous bioremediation potential. A variety of processes were proposed at the lab scale for using these fungi and their phenol oxidases in the degradation of phenolics. Here we present a survey of this topic using literature published mostly over the last 10 years. First, the sources of the enzymes are summarized. The laccase and tyrosinase were mainly from Trametes versicolor and Agaricus bisporus, respectively. Recently, however, new promising wild-type producers of the enzymes have emerged and a number of recombinant strains were also constructed, based mainly on yeasts or Aspergillus strains as hosts. The next part of the study summarizes the enzyme and whole-cell applications for the degradation of phenols, polyphenols, cresols, alkylphenols, naphthols, bisphenols and halogenated (bis)phenols in model mixtures or real wastewaters from the food, paper and coal industries, or municipal and hospital sewage. The enzymes were applied as free (crude or purified) enzymes or as enzymes immobilized in various supports or CLEAs, and optionally recycled or used in continuous mode. Alternatively, growing cultures or harvested mycelia were used instead. The products, which were characterized as quinones and their polymers in some cases, could be eliminated by filtration, flocculation or adsorption onto chitosan. The purity of a treated wastewater was monitored using a sensitive aquatic organism. It is concluded that low-cost sources of these enzymes should be searched for and the benefits of enzymatic, biological and physico-chemical methods could be combined to make the processes fit for industrial use.

Fabrication of an Amperometric Flow-Injection Microfluidic Biosensor Based on Laccase for In Situ Determination of Phenolic Compounds

We aim to develop an in situ microfluidic biosensor based on laccase from Trametes pubescens with flow-injection and amperometry as the transducer method. The enzyme was directly immobilized by potential step chronoamperometry, and the immobilization was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode response by amperometry was probed using ABTS and syringaldazine. A shift of interfacial electron transfer resistance and the electron transfer rate constant from 18.1 kΩ to 3.9 MΩ and 4.6 × 10(-2) cm s(-1) to 2.1 × 10(-4) cm s(-1), respectively, evidenced that laccase was immobilized on the electrode by the proposed method. We established the optimum operating conditions of temperature (55°C), pH (4.5), injection flow rate (200 µL min(-1)), and applied potential (0.4 V). Finally, the microfluidic biosensor showed better lower limit of detection (0.149 µM) and sensitivity (0.2341 nA µM(-1)) for ABTS than previous laccase-based biosensors and the in situ operation capacity.

An extracellular thermo-alkali-stable laccase from Bacillus tequilensis SN4, with a potential to biobleach softwood pulp

Degradation of residual lignin in kraft pulp by chemical bleaching is implicated in causing environmental pollution. The use of thermo- and alkali-tolerant bacterial laccases is considered to be important biological alternative to chemical processing. Laccases from Bacillus species have shown promise in this respect but their intracellular/spore bound presence make their industrial application economically unfeasible. We report here on a novel extracellular active thermo-alkali-stable laccase (SN4 laccase)  which is active at 90 °C and pH 8.0 using 2,6-dimethoxyphenol as substrate from Bacillus tequilensis SN4. SN4 laccase retained 27 % activity for 5 min at 100 °C and more than 80 % activity for 24 h at 70 °C. The enzyme is also stable at a higher pH (9.0-10.0). Enzyme production was optimized by submerged fermentation. Relatively high yields (18,356 nkats ml^-1) of SN4 laccase was obtained in a medium containing 650 μM MnSO₄, 350 μM FeSO₄, and 3.5 % ethanol. A 764-fold increase in laccase activity was observed under optimal conditions. In addition, reduction in kappa number and increase in brightness of softwood pulp by 28 and 7.6 %, respectively, were observed after treatment with SN4 laccase without a mediator. When N-hydroxybenzotriazole was used as a mediator, the kappa number was decreased to 47 % and brightness was increased to 12 %.

Enhanced laccase production by Trametes versicolor using corn steep liquor as both nitrogen source and inducer

A highly efficient strategy for laccase production by Trametes versicolor was developed using corn steep liquor (CSL) as both a nitrogen source and a laccase inducer. At the optimal CSL concentration of 20 gL(-1), an extracellular laccase activity of 633.3 UL(-1) was produced after a culture period of only 5 days. This represented a 1.96-fold increase relative to control medium lacking CSL. The addition of crude phenolic extracts from CSL improved laccase production to 91.8% greater than the control. Sinapinic acid, present in CSL, caused a reduction in laccase production, vanillic acid and ferulic acid (also present in CSL) synergistically induced laccase production by more than 100% greater than the control medium. Vanillic acid and ferulic acid provided the main contribution to the enhancement of laccase production. This study provides a basis for understanding the induction mechanism of CSL for laccase production.

Fungal laccases and their applications in bioremediation

Laccases are blue multicopper oxidases, which catalyze the monoelectronic oxidation of a broad spectrum of substrates, for example, ortho- and para-diphenols, polyphenols, aminophenols, and aromatic or aliphatic amines, coupled with a full, four-electron reduction of O₂ to H₂O. Hence, they are capable of degrading lignin and are present abundantly in many white-rot fungi. Laccases decolorize and detoxify the industrial effluents and help in wastewater treatment. They act on both phenolic and nonphenolic lignin-related compounds as well as highly recalcitrant environmental pollutants, and they can be effectively used in paper and pulp industries, textile industries, xenobiotic degradation, and bioremediation and act as biosensors. Recently, laccase has been applied to nanobiotechnology, which is an increasing research field, and catalyzes electron transfer reactions without additional cofactors. Several techniques have been developed for the immobilization of biomolecule such as micropatterning, self-assembled monolayer, and layer-by-layer techniques, which immobilize laccase and preserve their enzymatic activity. In this review, we describe the fungal source of laccases and their application in environment protection.