Laccase production in solid‐state and submerged fermentation by Pleurotus ostreatus

A solid‐state fermentation (SSF) system for production of an industrially important enzyme laccase by Pleurotus ostreatus was developed by using potato dextrose yeast extract medium and polyurethane foam as a supporting material. The maximum laccase production in the SSF system was as high as 3×10⁵ U/L. Addition of inducers, such as copper and ferulic acid, further enhanced the laccase production in SSF. Moreover, the time required for the maximum laccase production was reduced to 6 days compared to 10 days reported earlier. The improvement achieved by the SSF system was investigated by comparing it to a submerged fermentation system (SmF), both experimentally and by using a standard theoretical model along with a parameter sensitivity analysis. Laccase production in SSF was found to be twice of that in SmF. One of the main reasons for higher laccase production in SSF compared to SmF was possibly due to the presence of higher proteolytic activity in SmF. Strong proteolytic activity in SmF presumably caused subsequent laccase degradation, which lowered the ultimate laccase production in SmF compared to SSF.     

Laccase, cellulase and xylanase activities during growth ofPleurotus sajor-caju on sagohampas

Sagohampas, the fibrous pith residue left after starch extraction from sago palm, is abundant at sago-processing factories and can be used as a substrate for the production of laccase by solid substrate fermentation (SSF) withPleurotus sajorcaju, an edible mushroom. The fungus grown onhampas with an adjusted carbon : nitrogen ratio of 35:1, exhibited high laccase activity together with variable cellulase (0.3-2.8 U/g) and xylanase (0.9-10.1 U/g) activity. The maximum amount of laccase produced was approximately 17.7 U/g after 6 days of SSF using 4-week-old inoculum at a density of 10%. With the mature four-week inoculum, laccase activity increased 12-fold compared to that achieved with two-week-old inoculum. The optimum pH and temperature of the crude laccase were 6.0 and 50‡C, respectively. The apparent K_m and V_max values obtained were 0.073 mM and 0.962 U/min, respectively. The maximum laccase activity could be almost doubled after 6 days of fermentation by addition of 0.2 mM vanillin or ferulic acid; the cellulose to lignin ratio increased significantly during the 12 days of SSF, from 2.74 in the control to 3.3, when 0.2 mM of either vanillin or ferulic acid was added to the substrate.     

Productivity of laccase in solid substrate fermentation of selected agro-residues by Pycnoporus sanguineus

A comparative study on solid substrate fermentation (SSF) of sago 'hampas', oil palm frond parenchyma tissue (OPFPt) and rubberwood sawdust with Pycnoporus sanguineus for laccase production was carried out. Optimal mycelial growth of Pyc. sanguineus was observed on all the substrates studied over a 21 days time-course fermentation. Laccase productivity was highest during degradation of sago 'hampas' and OPFPt and a range from 7.5 to 7.6 U/g substrate on the 11th day of fermentation compared to degradation of rubberwood sawdust with a maximum laccase productivity of 5.7 U/g substrate on day 11 of SSF. Further optimization of laccase production was done by varying the inoculum age, density and nitrogen supplementation. SSF of OPFPt by Pyc. sanguineus gave maximum productivity of laccase of 46.5 U/g substrate on day 6 of fermentation with a 30% (w/w) of 4 weeks old inoculum and 0.92% nitrogen in the form of urea supplemented in the substrate. The extraction of laccase was also optimized in this study. Recovery of laccase was fourfold higher at 30.6 U/g substrate on day 10 of SSF using unadjusted tap water at pH 8.0 as extraction medium at 25+/-2 degrees C compared to laccase recovery of 7.46 U/g substrate using sodium acetate buffer at pH 4.8 at 4 degrees C. Further optimization showed that laccase recovery was increased by 50% with a value of 46.5 U/g substrate on day 10 of SSF when the extraction medium was tap water adjusted to pH 5.0 at 25+/-2 degrees C.     

Immobilization of laccase from Streptomyces psammoticus and its application in phenol removal using packed bed reactor

Laccase was produced from Streptomyces psammoticus under solid-state fermentation. The enzyme was partially purified by ammonium sulphate precipitation and was immobilized in alginate beads by entrapment method. Calcium alginate beads retained 42.5% laccase activity, while copper alginate beads proved a better support for laccase immobilization by retaining 61% of the activity. Phenol and colour removal from a phenol model solution was carried out using immobilized laccase. Batch experiments were performed using packed bed bioreactor, containing immobilized beads. Reusability of the immobilized matrix was studied for up to 8 successive runs, each run with duration of 6 h. The system removed 72% of the colour and 69.9% of total phenolics from the phenol model solution after the initial run. The immobilized system maintained 50% of its efficiency after eight successive runs. The degradation of phenolic compounds by immobilized laccase was evaluated and confirmed by Thin layer chromatography and nuclear magnetic resonance spectroscopy.     

Laccase from Trametes hirsuta Grown on Paper Cuttings: Application to Synthetic Dye Decolorization at Different pH Values

The potential of paper cuttings to produce laccase from Trametes hirsuta grown under solid‐state conditions was investigated. In addition, cultures were also grown on barley bran, a support commonly used in solid‐state fermentation (SSF), for comparison. Paper cutting cultures showed a maximum individual laccase activity of 7695 U/L on day 9. In addition, the ability to decolorize two structurally different dyes (Indigo Carmine and Lissamine Green B) by the extracellular liquid from both paper and barley bran cultures at pH values between 2 and 11 was analyzed. Laccase‐containing enzyme preparations from both cultures decolorized the dyes tested at pH values between 4 and 7 and, in addition, the laccase‐containing enzyme preparation from paper cutting cultures was also able to decolorize the dyes tested at alkaline pH values. This is a very interesting and novel result, since no decolorization by fungal laccases has been reported until recently at pH values higher than pH 7.     

Solid state fermentation of a Mycelia Sterilia laccase using steam-exploded wheat straw

Mycelia Sterilia YY-5, an endophytic fungus isolated from Rhus Chinensis Mill, was used in SSF for laccase production using steam-exploded wheat straw (SEWS). The fermentation period of YY-5 in solid state fermentation (SSF) shortened to 4 days compared with 5 days of submerged liquid fermentation (SmF) and the maximum laccase activity was 678.1 IU g⁻¹ substrate. The steam-explosion intensity (Log₁₀ R ₀) of SEWS had a significant effect on the growth of YY-5 and laccase activity, since SEWS could provide enough carbon source for YY-5 and inducers for laccase. The optimum SSF conditions using SEWS with Log₁₀ R ₀ = 3.597 as substrate were: inoculating with liquid inocula, keeping the solid-to-liquid ratio (S/L) for 1:4 and cultivating at 26°C. Under the optimum fermentation condition the laccase activity of YY-5 reached 849.5 ± 42.5 IU g⁻¹ substrate. The enzyme composition analysis indicated that laccase was the dominant enzyme of YY-5. Assayed with SDS-PAGE and active PAGE electrophoresis, the molecular weight of YY-5 laccase was approximately 45 kDa.     

Enhanced production of laccase activity by <Emphasis Type="Italic">Trametes versicolor </Emphasis>immobilized into alginate beads by the addition of different inducers

In the present paper the effect of adding veratryl alcohol and copper sulphate on laccase activity production by Trametes versicolor immobilized into alginate beads has been investigated. Employing copper sulphate as laccase inducer or supplementing the culture medium with veratryl alcohol, led to maximum values of laccase activity. However, the highest laccase activity (around 4,000 U l⁻¹) was obtained in cultures simultaneously supplemented with copper sulphate (3 mM) and veratryl alcohol (20 mM). These values implied a considerable enhancement in relation to␣control cultures without any inducer (around 200 U l⁻¹). The production of laccase by immobilized T. versicolor in a 2-l airlift bioreactor with the optimized inducer has been evaluated. Laccase activities around 1,500 U l⁻¹ were attained. The bioreactor operated for 44 days without operational problems and the bioparticles (fungus grows in alginate beads) maintained their shape throughout the fermentation. Moreover, the extracellular liquid obtained was studied in terms of pH and temperature activity and stability. On the other hand, anthracene was added in two-repeated batches in order to determine the efficiency of this process to degrade pollutants. Near complete degradation was reached in both batches. Moreover, in vitro degradation of several polycyclic aromatic hydrocarbons by crude laccase was also performed.     

Effect of nitrogen source on lignocellulolytic enzyme production by white-rot basidiomycetes under solid-state cultivation

Summary The effect of additional nitrogen sources on lignocellulolytic enzyme production by four species of white-rot fungi (Funalia trogii IBB 146, Lentinus edodes IBB 363, Pleurotus dryinus IBB 903, and P. tuberregium IBB 624) in solid-state fermentation (SSF) of wheat straw and beech tree leaves was strain- and substrate-dependent. In general, the yields of hydrolytic enzymes and laccase increased by supplementation of medium with an additional nitrogen source. This stimulating effect of additional nitrogen on enzyme accumulation was due to higher biomass production. Only xylanase specific activity of P. dryinus IBB 903 and laccase specific activity of L. edodes IBB 363 increased significantly (by 66% and 73%, respectively) in SSF of wheat straw by addition of nitrogen source to the control medium. Additional nitrogen (20 mM) repressed manganese peroxidase (MnP) production by all fungi tested. The study of the nitrogen concentration effect revealed that 10 mM peptone concentration was optimal for cellulase and xylanase accumulation by P. dryinus IBB 903. While variation of the peptone concentration did not cause the change in MnP yield, elevated concentrations of this nutrient (20–40 mM) led to a 2–3-fold increase of P. dryinus IBB 903 laccase activity. About 10–20 mM concentration of NH₄NO₃ was optimal for cellulase and xylanase production by F. trogii IBB 146. However, neither the laccase nor the MnP yield was significantly changed by the additional nitrogen source.     

Lignocellulose-degrading enzyme production by white-rot <Emphasis Type="Italic">Basidiomycetes</Emphasis> isolated from the forests of Georgia

The production of lignocellulolytic enzymes by eleven basidiomycetes species isolated from two ecosystems of Georgia was investigated for the first time under submerged (SF) and solid-state fermentation (SSF) of lignocellulosic by-products. Notable intergeneric and intrageneric differences were revealed with regard to the extent of hydrolase and oxidase activity. Several fungi produced laccase along with hydrolases in parallel with growth during the trophophase, showing that the synthesis of this enzyme is not connected with secondary metabolism. The lignocellulosic substrate type had the greatest impact on enzyme secretion. Some of the substrates significantly stimulated lignocellulolytic enzyme synthesis without supplementation of the culture medium with specific inducers. Exceptionally high carboxymethyl cellulase (CMCase, 122 U ml⁻¹) and xylanase (195 U ml⁻¹) activities were revealed in SF of mandarin peelings by Pseudotremella gibbosa IBB 22 and of residue after ethanol production (REP) by Fomes fomentarius IBB 38, respectively. The SSF of REP by T. pubescens IBB 11 ensured the highest level of laccase activity (24,690 U l⁻¹), whereas the SSF of wheat bran and SF of mandarin peels provided the highest manganese peroxidase activity (570–620 U l⁻¹) of Trichaptum biforme IBB 117. Moreover, the variation of lignocellulosic growth substrate provides an opportunity to obtain enzyme preparations containing different ratios of individual enzymes.     

Screening of a fungus capable of powerful and selective delignification on wheat straw

Aims: To screen and characterize a novel fungus with powerful and selective delignification capability on wheat straw. Methods and Results: A fungus capable of efficient delignification under solid‐state fermentation (SSF) conditions on wheat straw was screened. After 5 days of incubation, 13·07% of the lignin was removed by fungal degradation, and 7·62% of the holocellulose was lost. Furthermore, 46·53% of the alkali lignin was removed after 2 days of liquid fermentation. The fungus was identified as Fusarium concolor based on its morphology and an analysis of its 18S rDNA gene sequence. The molecular weight distribution of lignin was evaluated by gel permeation chromatography. Enzyme assay indicated that the fungus produced laccase, cellobiose dehydrogenase, xylanase and cellulase during the incubation period. Intracellular lignin peroxidase, manganese peroxidase and laccase were produced during liquid fermentation. Conclusions: We have successfully screened a fungus, F. concolor, which can efficiently degrade the lignin of wheat straw, with slight damage to the cellulose, after 5 days of SSF. Significance and Impact of the Study: The newly isolated strain could be used in pretreatment of lignocellulose materials prior to biopulping, bioconversion into fuel and substrates for the chemical industry.     

The phenoloxidases of the ascomycete Podospora anserina: The three forms of the major laccase activity

In Podospora anserina three laccase activities (I, II and III) were identified. Present results show the existence of an additional lacaase (an anodic protein; MW 80,000; R_f 0.07). Laccase IV derived from the dissociation at acid pH (4.5) of a protein which showed identical molecular weight (390,000) and R_f (0.1) to the oligomeric laccase I. The recovery of laccase I activity when starting from laccase IV (purified by means of isoelectric focusing) suggests that laccase I itself was the source of laccase IV. In turn, laccase IV gave rise to the laccase III after electrophoresis or dialysis at basic pH (8.5).     

In vivo enzymatic digestion, in vitro xylanase digestion, metabolic analogues, surfactants and polyethylene glycol ameliorate laccase production from Ganoderma sp. kk-02

AIMS: The effect of in vivo enzymatic digestion (IVED), in vitro xylanase digestion (IVXD), metabolic analogues, surfactants and polyethylene glycol (PEG) on laccase production from Ganoderma sp. kk-02 was studied. METHODS AND RESULTS: An acidic laccase producing Ganoderma sp. kk-02 produced 16.0 U ml(-1) and 365.0 U g(-1) of laccase, when grown under submerged (SmF) and solid state (SSF) fermentation conditions, respectively. Modification of the substrate (wheat bran) molecular architecture by IVED and IVXD increased subsequent laccase production from Ganoderma sp. kk-02 by 1.31-fold (21.0 U ml(-1)) (SmF); 2.21-fold (810.0 U g(-1)) (SSF) and 1.10-fold (18.0 U ml(-1)) (SmF); 1.78-fold (650.0 U g(-1)) (SSF) when compared with untreated wheat bran. Further enhancement in laccase yield under SmF and SSF was obtained when IVED treated wheat bran was used in conjunction with amino acids [DL-tryptophan, 2.66-fold (56.0 U ml(-1)) SmF; 2.86-fold (2324.0 U g(-1)) SSF], vitamins [biotin, 1.71-fold (36.0 U ml(-1)) SmF; 3.06-fold (2483.0 U g(-1)) SSF], surfactants [Tween-40, 1.85-fold (39.0 U ml(-1)) SmF; 2.25-fold (1828.0 U g(-1)) SSF], and PEG [PEG 6000, 1.93-fold (40.0 U ml(-1)) SmF; 1.58-fold (1284.0 U g(-1)) SSF]. CONCLUSIONS: The IVED of substrate (wheat bran) facilitated hyper laccase production in presence of additives from Ganoderma sp. kk-02. SIGNIFICANCE AND IMPACT OF THE STUDY: The study highlights a new methodology viz. IVED for concomitant and economic production of diverse enzymes using the same substrate. The hyper laccase levels obtained could improve the economic competitiveness of environmentally benign processes applied in varied industries. The work also provides an insight into the regulation of complex metabolic pathways governing the expression of extra cellular proteins from white-rot fungi.     

Comparison of the efficiency of bacterial and fungal laccases in delignification and detoxification of steam-pretreated lignocellulosic biomass for bioethanol production

This study evaluates the potential of a bacterial laccase from Streptomyces ipomoeae (SilA) for delignification and detoxification of steam-exploded wheat straw, in comparison with a commercial fungal laccase from Trametes villosa. When alkali extraction followed by SilA laccase treatment was applied to the water insoluble solids fraction, a slight reduction in lignin content was detected, and after a saccharification step, an increase in both glucose and xylose production (16 and 6%, respectively) was observed. These effects were not produced with T. villosa laccase. Concerning to the fermentation process, the treatment of the steam-exploded whole slurry with both laccases produced a decrease in the phenol content by up to 35 and 71% with bacterial and fungal laccases, respectively. The phenols reduction resulted in an improved performance of Saccharomyces cerevisiae during a simultaneous saccharification and fermentation (SSF) process, improving ethanol production rate. This enhancement was more marked with a presaccharification step prior to the SSF process.     

Purification and characterization of laccase from <Emphasis Type="Italic">Pycnoporus sanguineus</Emphasis> and decolorization of an anthraquinone dye by the enzyme

The white rot fungus Pycnoporus sanguineus produced high amount of laccase in the basal liquid medium without induction. Laccase was purified using ultrafiltration, anion-exchange chromatography, and gel filtration. The molecular weight of the purified laccase was estimated as 61.4 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme oxidized typical substrates of laccases including 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate), 2,6-dimethoxyphenol, and syringaldazine. The optimum pH and temperature for the purified laccase were 3.0 and 65°C, respectively. The enzyme was stable up to 40°C, and high laccase activity was maintained at pH 2.0–5.0. Sodium azide, l-cysteine, and dithiothreitol strongly inhibited the laccase activity. The purified enzyme efficiently decolorized Remazol Brilliant Blue R in the absence of added redox mediators. The high production of P. sanguineus laccase as well as its decolorization ability demonstrated its potential applications in dye decolorization.     

High production of laccase by a new basidiomycete, <Emphasis Type="Italic">Trametes</Emphasis> sp

A new basidiomycete, Trametes sp. 420, produced laccase at 6,810 U l⁻¹ (268 mg, 25.4 U mg⁻¹ protein for guaiacol) in glucose medium and 7,870 U l⁻¹ (310 mg) in cellobiose medium with induction by 0.5 mM Cu²⁺ and 6 mM o-toluidine. Laccase isozyme E (LacE) was the sole laccase in the fermentation products. It was stable at pH 5–9 and below 70°C over 30 min. The K _m values of LacE for four substrates (guaiacol ABTS, 2,6-dimethoxyphenol and syringaldazine) varied from 5 to 245 μM. The activity of LacE was strongly inhibited by NaN₃ but not by EDTA or dimethylsulfoxide. LacE at 0.5 U l⁻¹ could decolorize industrial dyes. The open reading frame of the lacE gene was 2,130 bp and was interrupted by 10 introns. It displayed a high homology to laccases from other fungi. Pingui Tong and Yuzhi Hong contributed equally to the study     

Novel Characteristics of Bifidobacterium bifidum in Solid State Fermentation System

Summary The characteristics of Bifidobacterium bifidum grown in solid state fermentation (SSF) system (water content of media 54.5 and 68.8%) was compared with the submerged fermentation (SmF) system (water content of medium: 89.8%). Besides lactic acid (lactate) and acetic acid (acetate), the bacterium was able to secrete propionic acid (propionate) and butyric acid (butyrate) under SSF conditions. However, it only produced lactate and acetate under SmF conditions. The ratio of lactate to acetate was 1.26–1.62:1 in SSF but it was 1:2 in SmF. A higher content of C16:0 and C18:1 as well as a lower content of C18:0 cell membrane fatty acids were observed in SSF than in SmF. There was a lower growth rate, a lower viable count and a longer logarithmic growth phase for B. bifidum cultivated in SSF than in SmF.     

Effect of growth substrate,method of fermentation,and nitrogen source on lignocellulose-degrading enzymes production by white-rot basidiomycetes

The exploration of seven physiologically different white rot fungi potential to produce cellulase, xylanase, laccase, and manganese peroxidase (MnP) showed that the enzyme yield and their ratio in enzyme preparations significantly depends on the fungus species, lignocellulosic growth substrate, and cultivation method. The fruit residues were appropriate growth substrates for the production of hydrolytic enzymes and laccase. The highest endoglucanase (111 U ml⁻¹) and xylanase (135 U ml⁻¹) activities were revealed in submerged fermentation (SF) of banana peels by Pycnoporus coccineus. In the same cultivation conditions Cerrena maxima accumulated the highest level of laccase activity (7,620 U l⁻¹). The lignified materials (wheat straw and tree leaves) appeared to be appropriate for the MnP secretion by majority basidiomycetes. With few exceptions, SF favored to hydrolases and laccase production by fungi tested whereas SSF was appropriate for the MnP accumulation. Thus, the Coriolopsis polyzona hydrolases activity increased more than threefold, while laccase yield increased 15-fold when tree leaves were undergone to SF instead SSF. The supplementation of nitrogen to the control medium seemed to have a negative effect on all enzyme production in SSF of wheat straw and tree leaves by Pleurotus ostreatus. In SF peptone and ammonium containing salts significantly increased C. polyzona and Trametes versicolor hydrolases and laccase yields. However, in most cases the supplementation of media with additional nitrogen lowered the fungi specific enzyme activities. Especially strong repression of T. versicolor MnP production was revealed.     

Growth and laccase production by Pleurotus ostreatus in submerged and solid-state fermentation

Pleurotus ostreatus showed atypical laccase production in submerged vs. solid-state fermentation. Cultures grown in submerged fermentation produced laccase at 13,000 U l⁻¹, with a biomass production of 5.6 g l⁻¹ and four laccase isoforms. However, cultures grown in solid-state fermentation had a much lower laccase activity of 2,430 U l⁻¹, biomass production of 4.5 g l⁻¹, and three laccase isoforms. These results show that P. ostreatus performs much better in submerged fermentation than in solid-state fermentation. This is the first report that shows such atypical behavior in the production of extracellular laccases by fungi.     

Laccase induction by synthetic dyes in Pycnoporus sanguineus and their possible use for sugar cane bagasse delignification

The use of synthetic dyes for laccase induction in vivo has been scarcely explored. We characterized the effect of adding different synthetic dyes to liquid cultures of Pycnoporus sanguineus on laccase production. We found that carminic acid (CA) can induce 722 % and alizarin yellow 317 % more laccase than control does, and they promoted better fungal biomass development in liquid cultures. Aniline blue and crystal violet did not show such positive effect. CA and alizarin yellow were degraded up to 95 % during P. sanguineus culturing (12 days). With this basis, CA was selected as the best inducer and used to evaluate the induction of laccase on solid-state fermentation (SSF), using sugarcane bagasse (SCB) as substrate, in an attempt to reach selective delignification. We found that laccase induction occurred in SSF, and a slight inhibition of cellulase production was observed when CA was added to the substrate; also, a transformation of SCB under SSF was followed by the ¹³C cross polarization magic angle spinning (CPMAS) solid-state nuclear magnetic resonance (NMR). Results showed that P. sanguineus can selectively delignify SCB, decreasing aromatic C compounds by 32.67 % in 16 days; O-alkyl C region (polysaccharides) was degraded less than 2 %; delignification values were not correlated with laccase activities. Cellulose-crystallinity index was increased by 27.24 % in absence of CA and 15.94 % when 0.01 mM of CA was added to SCB; this dye also inhibits the production of fungal biomass in SSF (measured as alkyl C gain). We conclude that CA is a good inducer of laccase in liquid media, and that P. sanguineus is a fungus with high potential for biomass delignification.

     

Laccase and Manganese Peroxidase Activities of Phellinus Robustus and Ganoderma Adspersum Grown on Food Industry Wastes in Submerged Fermentation

Phellinus robustus produced both laccase (700–4,000 U l⁻¹) and manganese peroxidase (MnP) (1,000–11,300 U l⁻¹) in fermentation of nine food wastes, whereas Ganoderma adspersum produced only laccase (600–34,000 U l⁻¹). Glucose provided high laccase and MnP activity of P. robustus but repressed enzyme production by G. adspersum. Ammonium sulphate and ammonium tartrate increased the P. robustus laccase yield (3-fold), whereas the accumulation of MnP was not enhanced by additional nitrogen.