Giovanni Giovannozzi Sermanni

Oxirane-immobilized Lentinula edodes laccase: stability and phenolics removal efficiency in olive mill wastewater.

Immobilization of Lentinula edodes laccase on Eupergit C increased pH, thermal and proteolytic stability with slight modifications in laccase oxidation efficiency. Immobilized laccase proved to be efficiently stable in removing olive mill wastewater phenolics.

Characterization of immobilized laccase from Lentinula edodes and its use in olive-mill wastewater treatment

This study is mainly concerned with the characterization of an immobilized laccase from the white-rot fungus Lentinula edodes for use in wastewater treatment. The enzyme was immobilized on chitosan by adsorption and subsequent cross-linking with glutaraldehyde. The immobilized laccase displayed a lower specific activity and a lower substrate affinity than the free enzyme. Nevertheless, the immobilized catalyst exhibited an appreciable catalytic capability (520 units g−1 support) along with remarkably improved stability properties to various parameters, such as temperature, pH and storage time. The treatment of olive mill wastewater with immobilized laccase led to a partial decolorization as well as to significant abatements in its content in polyphenols, ortho-diphenols combined with a decreased toxicity of the effluent.

Submerged and solid-state production of laccase and Mn-peroxidase by Panus tigrinus on olive mill wastewater-based media.

The possible use of olive-mill wastewater (OMW) as a growth medium for the production of extracellular laccase and manganese peroxidase (MnP) from the white-rot fungus Panus tigrinus (P. tigrinus) CBS 577.79 was studied using a properly formulated OMW-based medium (2-fold diluted OMW supplemented with 0.5% sucrose and 0.1% yeast extract) either in a stirred-tank or an air-lift reactor. Solid-state fermentation (SSF) was also performed in a rotary drum reactor using maize stalks moistened with the OMW-based medium. Highest levels of laccase and manganese peroxidase activity were obtained in the stirred-tank reactor (4600+/-98 U l(-1) on day 13) and in the air-lift reactor (410+/-22 on day 7), respectively. Based on total enzyme activities, SSF appears to be more suitable than LSF but the latter exhibits better volumetric productivities.

The biodegradation of recalcitrant effluents from an olive mill by a white-rot fungus

Biodegradation of olive-mill wastewater (OMW) was performed by the polyurethane-immobilized mycelium of Lentinula edodes. Throughout three consecutive treatment cycles of the effluent significant abatements of its polluting characteristics were observed. In fact, its contents in total organic carbon, total phenols, total ortho-diphenol were dramatically reduced. In addition, a significant effluent decolorization was evident.

Correlated effects during the bioconversion of waste olive waters by Lentinus edodes

Waste-olive-waters arising from the solid-liquid processing system were degraded in agitated liquid cultures of the white-rot fungus Lentinus edodes. About 45% of biodecolouration and 75% of total organic carbon reduction were achieved within 4 days. Over the same period, the content of total phenols was reduced by 66%. The release of exo-enzymes involved in the metabolism of phenolic compounds (phenol-oxidases and Mnperoxidase) was greatly enhanced with respect to the control. A highly-significant correlation was observed between decolourization, total organic carbon and total phenols.

The production of exo-enzymes by Lentinus edodes and pleurotus ostreatus and their use for upgrading corn straw

Abstract The influence of the growth of two white-rot fungi, Pleurotus ostreatus and Lentinus edodes , on the composition and on the digestibility of corn straw ( Zea mais ) was evaluated. P. ostreatus and L. edodes showed a different pattern of release of extracellular enzymes, including phenol-oxidases, cellulases and xylanases. The best results in terms of delignification and increase in digestibility were obtained in L. edodes cultures. When the two fungi were grown in submerged fermentation conditions in the presence of a water-soluble lignin-rich copolymer, a crude filtrate containing phenol-oxidases but no cellulolytic enzymes was obtained. Corn straw, treated with the above mentioned crude filtrate and subjected to paper pulping, gave paper handsheets with improved technical properties (freenes, breaking length and burst index).

Structural modifications induced during biodegradation of wheat lignin by Lentinula edodes

The structural modifications occurring during wheat straw lignin biodegradation were evaluated by the concerted use of 31P-, 1H- and 2D homo- and heteronuclear NMR spectroscopies. Straw lignin was found to be oxidatively degraded via stereoselective side-chain oxidation as evidenced by a lower erythro/threo ratio. Significantly lower amounts of phenolic hydroxy and methoxy groups in the decayed lignin may be indicative that its structure after the fungal treatment contained a lower amount of aromatic units. In addition an increase in carboxylic acids content, that cannot be explained only on the basis of side-chain oxidation reactions, was also apparent. This evidence, coupled with pertinent data collected during this effort, suggests the occurrence of aromatic ring cleavage reactions. In fact the oxidative degradation of lignin model compounds by fungi has been reported to occur via the 3-oxoadipate pathway which is known to cause aromatic ring cleavage with the formation of aliphatic chains. The presence of aliphatic moieties in the decayed lignin was confirmed by detailed 1H- and 2D NMR spectroscopic analyses.

Aromatic ring oxidation of vanillyl and veratryl alcohols by Lentinus edodes : possible artifacts in the lignin peroxidase and veratryl alcohol oxidase assays

Abstract The degradation pathway of vanillyl and veratryl alcohol by Lentinus edodes extracellular enzymes was studied. In both cases several products of side chain oxidation and aromatic ring cleavage were isolated and characterized. We have observed that the products from veratryl alcohol degradation by Lentinus edodes are quite different from those isolated from incubations with other white-rot fungi which have veraraldehyde as the major product, in fact, this compound is not produced as final metabolite in L. edodes incubations. This behaviour could explain the apparent absence of lignin peroxidase and veratryl alcohol oxidase activities in L. edodes cultures, since such activities are usually measured by monitoring veratraldehyde formation during the veratryl alcohol oxidation; thus, it is suggested that additional assay methods should be developed, with preferably direct observation of aromatic ring oxidation products.

Oxidation and aromatic ring cleavage of 4-methoxy and 3,4-dimethoxycennamic acid by Lentinus edodes

Several products of metabolism and aromatic ring cleavage of 3-methoxy and 3,4-dimethoxycinnamic acid from ligninolytic cultures of Lentinus edodes were isolated and identified.

Aspects of Design of Bioreactors in SSF

It is well known that the solid-state fermentation (SSF) is a new technology with which antibiotics, enzymes, fine chemicals can be obtained by new bioprocesses with improved efficiency (Giovannozzi-Sermanni & Porri 1989; Pandey et al., 2000) if compared to the classical submerged fermentations. SSF processes can be defined as “the growth of microorganisms, mainly fungi, on moist solid materials in the absence of free-flowing water”(Cannel & Moo-Young 1980). In the last few decades SSF has grown quickly in interest and importance and has been used for the production of antibiotics, alkaloids, aroma compounds, plant growth factors, enzymes, biofuel, and also for the bioremediation of polluting compounds.