Performance of wood-rotting fungi-based enzymes on enzymic saccharification of rice straw.

BACKGROUND: For effective saccharification of rice straw we focused on enzyme preparations from wood-rotting fungi that have the ability to degrade cell wall polysaccharides and lignin. We tested extracellular enzyme preparations from 14 species of fungi for saccharification activity and examined the factor for saccharification by statistical analysis. RESULTS: An enzyme preparation from Schizophyllum commune had the highest saccharification activity of rice straw. This preparation contained highly active endo-ß-xylanase, endo-ß-glucanase (CMCase), ß-d-glucosidase and acetylxylan esterase. Correlation analysis of the 14 enzyme preparations demonstrated that acetylxylan esterase was closely related to saccharification activity in rice straw. Multiple regression analysis also showed that acetylxylan esterase had an important role in saccharification. Ligninolytic enzymes, which are characteristic of white-rot fungi, did not contribute to saccharification activity of rice straw. CONCLUSION: Deacetylation is an essential factor for saccharification of rice straw and enzyme preparations for saccharification need to contain highly active acetylxylan esterase as well as highly active cellulolytic and xylanolytic enzymes, but not ligninolytic ones.

A protein from Pleurotus eryngii var. tuoliensis C.J. Mou with strong removal activity against the natural steroid hormone, estriol: purification, characterization, and identification as a laccase.

A protein with strong removal activity against the natural estrogen estriol was purified from a culture supernatant of Pleurotus eryngii var. tuoliensis C.J. Mou. The protein was characterized as a laccase and had a molecular mass of 60kDa on SDS-PAGE. The enzyme was most active at pH 7.0 and 50°C. The partial N-terminal amino acid sequence of the enzyme showed homology with laccases from mushrooms, such as Pleurotus ostreatus, Coriolus versicolor (current name: Trametes versicolor), Pycnoporus cinnabarinus, and P. eryngii. A recombinant yeast assay confirmed that laccase treatment was very efficient for removing the estrogenic activity of steroid estrogens. Our results suggest that the enzyme may be applicable as a potential factor for removing natural steroid hormones.

Biodegradation of polyvinyl alcohol by Flammulina velutipes in an unsubmerged culture.

To examine the biodegradation of polyvinyl alcohol (PVA), Flammulina velutipes (Enokitake) was cultivated in both liquid and quartz sand cultures. After incubation, discoloration of an iodide solution was observed in the filtrate recovered from the quartz sand culture, whereas discoloration was not observed in the filtrate recovered from the liquid culture. Gel permeation chromatography showed that the PVA recovered from the quartz sand culture was depolymerized and yielded low-molecular-weight portions. Infrared and ultraviolet spectrometry indicated that there was formation of carbonyl groups, and NMR analysis showed that the syndiotactic portions of PVA were preferably attacked. Based on these results, an unsubmerged cultivation of F. velutipes was considered suitable for the biodegradation of PVA, probably because the mycelium was sufficiently developed to produce PVA-degrading enzymes.

Production of cellulolytic enzymes containing cinnamic acid esterase from Schizophyllum commune.

To develop enzyme preparations capable of digesting plant biomass, we examined the production of cinnamic acid esterase as well as cellulolytic and xylanolytic enzymes in cultures of Schizophyllum commune. The cinnamic acid esterase was produced in the cultures containing solid cellulosic substrates, with production being enhanced by delignifying the wood powder. This indicates that these esterases are produced by cellulose, despite their substrates being phenolic compounds. Cellulolytic and xylanolytic enzymes, with the exception of α-arabinofuranosidase, were also produced in cultures containing cellulosic substances. These results show that enzyme preparation can have high activity of cinnamic acid esterase and cellulolytic and xylanolytic enzymes when S. commune is incubated in the presence of cellulose. These enzyme preparations will be useful for digesting plant biomass and for releasing cinnamic acid derivatives from plant cell walls.

Bioconversion of cinnamic acid derivatives by Schizophyllum commune.

To investigate the production of useful phenols from plant resources, we examined the metabolism of cinnamic acid derivatives by a wood-rotting fungus, Schizophyllum commune. Four cinnamic acid derivatives (cinnamic, p-coumaric, ferulic, and sinapic acids) were tested as substrates. Two main reactions, reduction and cleavage of the side chain, were observed. Reduction of the side chain was confirmed in cinnamic acid and p-coumaric acid metabolism. The side chain cleavage occurred in p-coumaric acid and ferulic acid metabolism but the initial reactions of these acids differed. Sinapic acid was not metabolized by S. commune. p-Hydroxybenzaldehyde accumulation was observed in the culture to which p-coumaric acid was added. This suggests that S. commune is a useful agent for transforming p-coumaric acid into p-hydroxybenzaldehyde.

Formation of 4-vinyl guaiacol as an intermediate in bioconversion of ferulic acid by Schizophyllum commune.

In order to utilize phenolic compounds in unused biomass resources, the metabolic pathway of ferulic acid by way of a white-rot fungus, Schizophyllum commune, was investigated. Ferulic acid was immediately degraded, and the formation of 4-vinyl guaiacol was confirmed by GC-MS analysis. The metabolic test of ferulic acid and its degradation products indicated that S. commune converted ferulic acid into 4-vinyl guaiacol by decarboxylation. This was then oxidized to vanillin and vanillic acid. This result indicates that S. commune distinguished ferulic acid from lignins and metabolized it specifically.