Middle-redox potential laccase from Ganoderma sp.: its application in improvement of feed for monogastric animals

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.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

Agitation role (Dissolved Oxygen) in production of laccase from newly identified Ganoderma multistipitatum sp. nov. and its effect on mycelium morphology

BACKGROUND

Agitation speed influenced the production rate of laccase. Orbital speed not only influenced the enzyme production, but was also effective to dissolve the oxygen during growth of mycelium, spores, and chlamydospores. Shear effects of speed greatly influenced the morphology of mycelium.

METHODS

Ganoderma multistipitatum was identified by ITS marker. Phylogenetic tree was constructed for species identification. Qualitatively by plate method contained guaiacol indicator, while quantitatively by submerged fermentation and Central Composite Design applied on agitation parameter for maximum laccase potential of this species. The effects of agitation speed on mycelium morphology were observed under compound and scanning electron microscope.

RESULTS

Statistical optimization of agitation conditions were performed by using response surface methodology to enhance the production of laccase from Ganoderma multistipitatum sp. nov. Maximum laccase yield (19.44 × 105 ± 0.28 U/L) was obtained at 150 rpm grown culture, which was higher than predicted value of laccase production (19.18 × 105 U/L) under aerobic conditions (150 rpm). The 150 rpm provided the continuous flush of oxygen. The DO (dissolved oxygen) was maximum (65%) for "27 h" incubation at 150 rpm during laccase synthesis. The statistical value of laccase production was minimum under anaerobic or nearly static condition of 50 rpm. The predicted (12.78 × 105 U/L) and obtained (12.82 × 105 U/L) yield was low at 50 rpm. Optimization of orbital shaking for aeration conditions were performed by the use of "Response Surface Methodology". The submerged shaking flasks were utilized as a nutrients growth medium to maximize the production of laccase from G. multistipitatum. The minimum incubation time highly influenced the laccase yield from 7 to 15 days via utilization of less cost-effective medium under a promising and eco-friendly method. The morphological effects of rpm on mycelium were examined under compound and scanning electron microscopy. Higher rpm (200, 230) shear the mycelium, while 150 to 200 rpm exhibited smoother and highly dense branches of mycelia.

CONCLUSION

The shear forces of 200 rpm caused the damages of mycelium and cells autolysis with less laccase production. This study concluded that 150 rpm saved the life of mycelium and enhanced the production rate of enzymes.

Optimization, purification and characterization of laccase from Ganoderma leucocontextum along with its phylogenetic relationship

The aim of this work to study an efficient laccase producing fungus Ganoderma leucocontextum, which was identified by ITS regions of DNA and phylogenetic tree was constructed. This study showed the laccase first-time from G. leucocontextum by using medium containing guaiacol. The growth cultural (pH, temperature, incubation days, rpm) and nutritional (carbon and nitrogen sources) conditions were optimized, which enhanced the enzyme production up to 4.5-folds. Laccase production increased 855 U/L at 40 °C. The pH 5.0 was suitable for laccase secretion (2517 U/L) on the 7th day of incubation at 100 rpm (698.3 U/L). Glucose and sucrose were good carbon source to enhance the laccase synthesis. The 10 g/L beef (4671 U/L) and yeast extract (5776 U/L) were the best nitrogen source for laccase secretion from G. leucocontextum. The laccase was purified from the 80% ammonium sulphate precipitations of protein identified by nucleotides sequence. The molecular weight (65.0 kDa) of purified laccase was identified through SDS and native PAGE entitled as Glacc110. The Glacc110 was characterized under different parameters. It retained > 90% of its activity for 16 min incubation at 60 °C in acidic medium (pH 4.0). This enzyme exerted its optimal activity at pH 3.0 and temperature 70 °C with guaiacol substrate. The catalytic parameters K_m and V_max was 1.658 (mM) and 2.452 (mM/min), respectively. The thermo stability of the laccase produced by submerged fermentation of G. leucocontextum has potential for industrial and biotechnology applications. The results remarked the G. leucocontextum is a good source for laccase production.

Fungal lignocellulolytic enzymes and lignocellulose: A critical review on their contribution to multiproduct biorefinery and global biofuel research

The continuous increase in the global energy demand has diminished fossil fuel reserves and elevated the risk of environmental deterioration and human health. Biorefinery processes involved in producing bio-based energy-enriched chemicals have paved way to meet the energy demands. Compared to the thermochemical processes, fungal system biorefinery processes seems to be a promising approach for lignocellulose conversion. It also offers an eco-friendly and energy-efficient route for biofuel generation. Essentially, ligninolytic white-rot fungi and their enzyme arsenals degrade the plant biomass into structural constituents with minimal by-products generation. Hemi- or cellulolytic enzymes from certain soft and brown-rot fungi are always favoured to hydrolyze complex polysaccharides into fermentable sugars and other value-added products. However, the cost of saccharifying enzymes remains the major limitation, which hinders their application in lignocellulosic biorefinery. In the past, research has been focused on the role of lignocellulolytic fungi in biofuel production; however, a cumulative study comprising the contribution of the lignocellulolytic enzymes in biorefinery technologies is still lagging. Therefore, the overarching goal of this review article is to discuss the major contribution of lignocellulolytic fungi and their enzyme arsenal in global biofuel research and multiproduct biorefinery.

Production, partial purification and characterization of ligninolytic enzymes from selected basidiomycetes mushroom fungi

In recent years, many research on the quantity of lignocellulosic waste have been developed. The production, partial purification, and characterisation of ligninolytic enzymes from various fungi are described in this work. On the 21st day of incubation in Potato Dextrose (PD) broth, Hypsizygus ulmarius developed the most laccase (14.83 × 10⁻⁶ IU/ml) and manganese peroxidase (24.11 × 10⁻⁶ IU/ml), while Pleurotus florida produced the most lignin peroxidase (19.56 × ⁻⁶ IU/ml). Laccase (Lac), lignin peroxidase (LiP), and manganese peroxidase (MnP), all generated by selected basidiomycetes mushroom fungi, were largely isolated using ammonium sulphate precipitation followed by dialysis. Laccase, lignin peroxidase, and manganese peroxidase purification findings indicated 1.83, 2.13, and 1.77 fold purity enhancements, respectively. Specific activity of purified laccase enzyme preparations ranged from 305.80 to 376.85 IU/mg, purified lignin peroxidase from 258.51 to 336.95 IU/mg, and purified manganese peroxidase from 253.45 to 529.34 IU/mg. H. ulmarius laccase (376.85 IU/mg) with 1.83 fold purification had the highest specific activity of all the ligninolytic enzymes studied, followed by 2.13 fold purification in lignin peroxidase (350.57 IU/mg) and manganese peroxidase (529.34 IU/mg) with 1.77-fold purification. Three notable bands with molecular weights ranging from 43 to 68 kDa and a single prominent band with a molecular weight of 97.4 kDa were identified on a Native PAGE gel from mycelial proteins of selected mushroom fungus. The SDS PAGE profiles of the mycelial proteins from the selected mushroom fungus were similar to the native PAGE. All three partially purified ligninolytic isozymes display three bands in native gel electrophoresis, with only one prominent band in enzyme activity staining. The 43 kDa, 55 kDa, and 68 kDa protein bands correspond to laccase, lignin peroxidase, and manganese peroxidase, respectively.

Partial purification and characterization of a thermophilic and alkali-stable laccase of Phoma herbarum isolate KU4 with dye-decolorization efficiency

Production of an extracellular thermophilic and alkali stable laccase from Phoma herbarum isolate KU4 was reported for the first time, both in submerged fermentation (SmF, highest 1590 U/mL) and solid state fermentation (SSF, highest 2014.21 U/mL) using agro-industrial residues. The laccase was partially purified to 7.93 fold with the apparent molecular weight of 298 kDa. The enzyme had pH optimum at 5.0 and temperature optimum at 50 °C, with maximum stability at pH 8.0. It showed activity towards various phenolic and non-phenolic compounds. The kinetic parameters, K_m, V_max and K_cat of the laccase for DMP were 0.216 mM, 270.27 U/mg and 506.69 s^-1, respectively. Laccase activity was inhibited by various metal ions and conventional inhibitors, however, it was slightly increased by Zn²⁺. The laccase showed good decolorization efficiency towards four industrial dyes, namely, methyl violet (75.66%), methyl green (65%), indigo carmine (58%) and neutral red (42%) within 24 h. FTIR analysis of the decolorized products confirmed the degradation of the dyes. The decolorization efficiency of the enzyme suggests that the partially purified laccase could be used to decolorize synthetic dyes present in industrial effluents and for waste water treatments. The thermophilic and alkali stable laccase may also have wider potential industrial applications.

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.

Nanoencapsulated Laccases Obtained by Double-Emulsion Technique. Effects on Enzyme Activity pH-Dependence and Stability

One primary drawback of enzyme catalysis at industrial scale is the short-term service life of the enzymes, they lose their activity due to oxidation or other processes which results in less stability and a shorter lifetime thereby rendering them less efficient. An effective way to increase the stability of the enzymes is to attach them to nanoparticles. In this work, the polymer Eudragit® L 100-55 sensitive to pH was used to prepare laccase polymeric nanoparticles by the double-emulsion solvent evaporation approach. The size and morphology of the nanoparticles obtained were evaluated—as well as the encapsulation efficiency and zeta potential. pH effect on activity and stability was compared between free and immobilized laccase. Their stability was also determined in a sequential assay involving acidic pHs up to alkaline ones. The nanoparticles had a spherical shape with a mean size of 147 nm, zeta potential of −22.7 mV at pH 7.0 and load efficiency of 87%. The optimum pH of both free and immobilized laccases was 3.0, being the nanoparticles more stable at acidic pHs. Thus, this would be the first report of obtaining laccase nanoparticles with potential application in animal feed due to the stability conferred to enzymatic activity at pHs similar to those present in the gastrointestinal tract of rabbits, which would allow their potential use in animal feed.

From agro-waste to tool: biotechnological characterization and application of Ganoderma lucidum E47 laccase in dye decolorization

The culture of fungal species from agro-waste allows for the sustainable preparation of valuable biotechnological products and contributes to establish the Circular Economy concept. The Ganoderma lucidum species is well known as producer of laccases (EC 1.10.3.2), which serves as a tool to oxidize chemicals. When producing G. lucidum E47 basidiomes with edible purposes out of rice crop residues, its laccase remains as by-product. In this work, we report the biotechnological characterization and application of the laccase recovered from spent cultures of the G. lucidum E47 strain. We detected at least one polypeptide (ca. 59 kDa) which displays attractive activity and stability values when used in the range of 18-45 °C in mildly acidic environment (pH 4.8-5.8). These parameters can be enhanced in the presence of organic cosolvents such as butyl acetate and methyl iso-butyl ketone, but the opposite effect is observed with solvents of lower log P. The best activity-stability performance is reached when the biocatalyst is used in pH 4.8 buffer with 5% (v/v) butyl acetate at 37 °C. The laccase was capable of decolorizing xanthene, azo and triarylmethane dyes, exhibiting excellent selectivity on bromocresol green and bromocresol purple. Furthermore, the biocatalyst displayed an attractive activity when assessed for the decolorization of bromocresol green in a proof-of-concept effluent biotreatment.

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.

The effects of hydrolysed sorghum on growth performance and meat quality of rabbits

<p class="Articletitle">The effect of sorghum hydrolysed by <em>Trametes maxima</em> CU1 and <em>Pycnoporus sanguineus</em> CS2 was evaluated on growth performance traits and rabbit meat quality. A total of 24 unsexed New Zealand rabbits, weaned at 20 d of age, were allocated to 2 treatments: T1 (diet including 300 g/kg of non-hydrolysed sorghum) and T2 (diet including 300 g/kg of hydrolysed sorghum by <em>Trametes maxima</em> CU1 and <em>Pycnoporus sanguineus</em> CS2). Rabbits of group T2 did not have significantly different (<em>P</em>&gt;0.05) feed intake compared to those in T1. Carcass traits were also not significantly different (<em>P</em>&gt;0.05) between the 2 groups. The pH, water-holding capacity, colour and cooking loss of the longissimus lumborum were not different (<em>P</em>&gt;0.05) between treatments, whereas the pH of the rabbits biceps femoris was higher in T2 (6.21; <em>P</em>&lt;0.05) than in T1 (6.14). Meat hardness and gumminess in T2 were lower (<em>P</em>&lt;0.05) in comparison to meat from T1. Thus, sorghum hydrolysed by <em>Trametes maxima</em> CU1 and <em>Pycnoporus sanguineus</em> CS2 contributed to a better rabbit meat texture.</p>

Gel-Based Purification and Biochemical Study of Laccase Isozymes from Ganoderma sp. and Its Role in Enhanced Cotton Callogenesis

Basidiomycetous fungi, Ganoderma lucidum MDU-7 and Ganoderma sp. kk-02 secreted multiple laccase isozymes under diverse growth condition. Aromatic compounds and metal salts were also found to regulate the differential expression of laccase isozymes from both the Ganoderma sp. Laccase isozymes induced in the presence of copper from G. lucidum MDU-7 were purified by gel-based (native-PAGE) purification method. The purity of laccase isozymes was checked by zymogram and SDS-PAGE. The SDS-PAGE of purified proteins confirmed the multimeric nature of laccase isozymes. The molecular mass of isozymes was found to be in the range of 40–66 kDa. Further, the purified laccase isozymes and their peptides were confirmed with the help of MALDI-TOF peptide fingerprinting. The biochemical characterization of laccase isozymes viz. Glac L2, Glac L3, Glac L4, and Glac L5 have shown the optimum temperature in the range of 30°–45°C and pH 3.0. The K_m values of all the laccase isozymes determined for guaiacol were (96–281 μM), ABTS (15–83 μM) and O-tolidine (78–724 μM). Further, laccase isozymes from G. lucidum whole genome were studied using bioinformatics tools. The molecular modeling and docking of laccase isozymes with different substrates showed a significant binding affinity, which further validates our experimental results. Interestingly, copper induced laccase of 40 U/ml in culture medium was found to significantly induce cotton callogenesis. Interestingly, all the laccase isozymes were found to have an antioxidative role and therefore capable in free radicals scavenging during callogenesis. This is the first detailed study on the biochemical characterization of all the laccase isozymes purified by a gel-based novel method.

Enhanced candicidal compound production by a new soil isolate Penicillium verruculosum MKH7 under submerged fermentation

BACKGROUND

Microorganisms are a rich source of structurally diverse secondary metabolites that exert a major impact on the control of infectious diseases and other medical conditions. The biosynthesis of these metabolites can be improved by manipulating the nutritional or environmental factors. This work evaluates the effects of fermentation parameters on the production of a lactone compound effective against Candida albicans by Penicillium verruculosum MKH7 under submerged fermentation. Design-Expert version8.0 software was used for construction of the experimental design and statistical analysis of the experimental data.

RESULTS

The important factors influencing antibiotic production selected in accordance with the Plackett-Burman design were found to be initial pH, temperature, peptone, MgSO4.7H2O. Orthogonal central composite design and response surface methodology were adopted to further investigate the mutual interaction between the variables and identify the optimum values that catalyse maximum metabolite production. The determination coefficient (R2) of the fitted second order model was 0.9852. The validation experiments using optimized conditions of initial pH 7.4, temperature 27 °C, peptone 9.2 g/l and MgSO4.7H2O 0.39 g/l resulted in a significant increase (almost 7 fold from 30 to 205.5 mg/l) in the metabolite production which was in agreement with the prediction (211.24 mg/l). Stability of the compound was also assessed on the basis of its response to physical and chemical stresses.

CONCLUSIONS

So far as our knowledge goes, till date there are no reports available on the production of antibiotics by Penicillium verruculosum through media optimization using RSM. Optimization not only led to a 7 fold increase in metabolite yield but the same was achieved at much lesser time (8-10 days compared to the earlier 12-15 days). The enhanced yield of the antibiotic strongly suggests that the fungus P. verruculosum MKH7 can be efficiently used for antibiotic production on a large scale.

Isolation and Physicochemical Characterization of Laccase from Ganoderma lucidum-CDBT1 Isolated from Its Native Habitat in Nepal

At present, few organisms are known to and capable of naturally producing laccases and white rot fungi are one such group. In the present study, three fungal species, namely, Ganoderma lucidum-CDBT1, Ganoderma japonicum, and Lentinula edodes, isolated from their native habitat in Nepal were screened for laccase production, and G. lucidum-CDBT1 was found to express highest levels of enzyme (day 10 culture media showed 0.92 IU/mg total protein or 92 IU/mL laccase activity with ABTS as substrate). Lignin extracted from rice straw was used in Olga medium for laccase production and isolation from G. lucidum-CDBT1. Presence of lignin (5 g/L) and copper sulfate (30 μM) in the media increased the extracellular laccase content by 111% and 114%, respectively. The laccase enzyme produced by G. lucidum-CDBT1 was fractionated by ammonium sulfate and purified by DEAE Sepharose anion exchange chromatography. The purified enzyme was found to have a molecular mass of 43 kDa and exhibits optimal activity at pH 5.0 and 30°C. The isolated laccase was thermally stable for up to 70°C for 1 h and exhibited broad pH stability. The kinetic constants, K_m, V_max, and K_cat, determined using 2,2′-azinobis-(-3-ethylbenzothiazoline-6-sulfonic acid) as substrate were found to be 110 μM, 36 μmol/min/mg, and 246 min⁻¹, respectively. The isolated thermostable laccase will be used in future experiments for delignification process.

Degradation of Synthetic Dyes by Laccases – A Mini-Review

Laccases provide a promising future as a tool to be used in the field of biodegradation of synthetic dyes with different chemical structures. These enzymes are able to oxidize a wide range of phenolic substrates without the presence of additional co-factors. Laccases have been confirmed for their potential of synthetic dye degradation from wastewater and degradation products of these enzymatic reactions become less toxic than selected dyes. This study discusses the potential of laccase enzymes as agents for laccase-catalyzed degradation in terms of biodegradation efficiency of synthetic dyes, specifically: azo dyes, triphenylmethane, indigo and anthraquinone dyes. Review also summarizes the laccase-catalyzed degradation mechanisms of the selected synthetic dyes, as well as the degradation products and the toxicity of the dyes and their degradation products.

High Level Secretion of Laccase (LccH) from a Newly Isolated White-Rot Basidiomycete, Hexagonia hirta MSF2

Newer and novel laccases attract considerable attention due to its promising and valuable multiple applications in biotech industry. This present investigation documents, for the first time, on high level extracellular secretion of laccase (LccH) in newly isolated wood-degrading basidiomycete Hexagonia hirta MSF2. LccH was optimally active at 40°C in citrate phosphate buffer with a pH of 3.4. Optimized Cu(2+) in glucose yeast extract (GY) medium enhanced the LccH production by H. hirta to 1944.44 U.ml(-1). A further increment in LccH activity of 5671.30 U.ml(-1) was achieved by the addition of a phenolic inducer, 2,5 Xylidine. Zymogram and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of LccH revealed that LccH is a monomer with a molecular mass of 66 kDa. MALDI-TOF-MS based peptide mass fingerprinting and comparative modeling of the amino acid sequence of LccH showed that it was closer to Trametes sp. AH28-2 (PDB: 3KW7) with 48% identity, 95% coverage, 0.011 alignment score and RMSD of 0.497Å. Crude LccH delignified lignocellulosic biomass such as wood and corncob, to a level of 28.6 and 16.5%, respectively. Such high level secretion, thermal and solvent stability of LccH make H. hirta a potential candidate not only for LccH production and biodelignification but also generation of lignin derived aromatic feed stock chemicals for industrial and environmental applications.

Reduced toxicity of malachite green decolorized by laccase produced from Ganoderma sp. rckk-02 under solid-state fermentation

Statistical designs were applied for optimizing laccase production from a white-rot fungus, Ganoderma sp. rckk-02 under solid-state fermentation (SSF). Compared to unoptimized conditions [2,154 U/gds (Unit per gram of dry substrate)], the optimization process resulted in a 17.3-fold increase in laccase production (37,423 U/gds). The laccase produced was evaluated for its potential to decolorize a recalcitrant synthetic dye, malachite green. Laccase at dosage of 30 U/ml in presence of 1 mM of 1-hydroxybenzotriazole (HBT) almost completely decolorized 100 and 200 mg/l of malachite green in 16 and 20 h, respectively, at 30 °C, pH 5.5 and 150 rpm. While, higher dyes concentrations of 300, 400 and 500 mg/l were decolorized to 72, 62 and 55 % in 24, 28 and 32 h, respectively, under similar conditions. Furthermore, it was observed that the decolorized malachite green was less toxic towards the growth of five white-rot fungi tested viz. Crinipellis sp. RCK-1, Ganoderma sp. rckk-02, Coriolopsis Caperata RCK 2011, Phanerochaete chrysosporium K3 and Pycnoporous cinnabarinus PB. The present study demonstrates the potential of Ganoderma sp. rckk-02 to produce high titres of laccase under SSF, which can be exploited in conjunction with redox mediator for the decolorization of high concentrations of malachite green from water bodies.

Identification of a laccase Glac15 from Ganoderma lucidum 77002 and its application in bioethanol production

BACKGROUND

Laccases have potential applications in detoxification of lignocellulosic biomass after thermochemical pretreatment and production of value-added products or biofuels from renewable biomass. However, their application in large-scale industrial and environmental processes has been severely thwarted by the high cost of commercial laccases. Therefore, it is necessary to identify new laccases with lower cost but higher activity to detoxify lignocellulosic hydrolysates and better efficiency to produce biofuels such as bioethanol. Laccases from Ganoderma lucidum represent proper candidates in processing of lignocellulosic biomass.

RESULTS

G. lucidum 77002 produces three laccase isoenzymes with a total laccase activity of 141.1 U/mL within 6 days when using wheat bran and peanut powder as energy sources in liquid culture medium. A new isoenzyme named Glac15 was identified, purified, and characterized. Glac15 possesses an optimum pH of 4.5 to 5.0 and a temperature range of 45°C to 55°C for the substrates tested. It was stable at pH values ranging from 5.0 to 7.0 and temperatures lower than 55°C, with more than 80% activity retained after incubation for 2 h. When used in bioethanol production process, 0.05 U/mL Glac15 removed 84% of the phenolic compounds in prehydrolysate, and the yeast biomass reached 11.81 (optimal density at 600 nm (OD600)), compared to no growth in the untreated one. Addition of Glac15 before cellulase hydrolysis had no significant effect on glucose recovery. However, ethanol yield were improved in samples treated with laccases compared to that in control samples. The final ethanol concentration of 9.74, 10.05, 10.11, and 10.81 g/L were obtained from samples containing only solid content, solid content treated with Glac15, solid content containing 50% prehydrolysate, and solid content containing 50% prehydrolysate treated with Glac15, respectively.

CONCLUSIONS

The G. lucidum laccase Glac15 has potentials in bioethanol production industry.