Time course of fungal removal of lipophilic extractives from Eucalyptus globulus wood

Resin acids play key roles in shaping microbial communities during degradation of spruce bark

The bark is the outermost defense of trees against microbial attack, largely thanks to toxicity and prevalence of extractive compounds. Nevertheless, bark decomposes in nature, though by which species and mechanisms remains unknown. Here, we have followed the development of microbial enrichments growing on spruce bark over six months, by monitoring both chemical changes in the material and performing community and metagenomic analyses. Carbohydrate metabolism was unexpectedly limited, and instead a key activity was metabolism of extractives. Resin acid degradation was principally linked to community diversification with specific bacteria revealed to dominate the process. Metagenome-guided isolation facilitated the recovery of the dominant enrichment strain in pure culture, which represents a new species (Pseudomonas abieticivorans sp. nov.), that can grow on resin acids as a sole carbon source. Our results illuminate key stages in degradation of an abundant renewable resource, and how defensive extractive compounds have major roles in shaping microbiomes.

A statistical modeling approach based on the small-scale field trial and meteorological data for preliminary prediction of the impact of low temperature on Eucalyptus globulus trees

Eucalyptus trees are important for industrial forestry plantations because of their high potential for biomass production, but their susceptibility to damage at low temperatures restricts their plantation areas. In this study, a 6-year field trial of Eucalyptus globulus was conducted in Tsukuba, Japan, which is the northernmost reach of Eucalyptus plantations, and leaf damage was quantitatively monitored over four of six winters. Leaf photosynthetic quantum yield (QY) levels, an indicator of cold stress-induced damage, fluctuated synchronously with temperature in the winters. We performed a maximum likelihood estimation of the regression model explaining leaf QY using training data subsets for the first 3 years. The resulting model explained QY by the number of days when the daily maximum temperature was below 9.5 °C over approximately the last 7 weeks as an explanatory variable. The correlation coefficient and coefficient of determination of prediction by the model between the predicted and observed values were 0.84 and 0.70, respectively. The model was then used to perform two kinds of simulations. Geographical simulations of potential Eucalyptus plantation areas using global meteorological data from more than 5,000 locations around the world successfully predicted an area that generally agreed with the global Eucalyptus plantation distribution reported previously. Another simulation based on meteorological data of the past 70 years suggested that global warming will increase the potential E. globulus plantation area in Japan approximately 1.5-fold over the next 70 years. These results suggest that the model developed herein would be applicable to preliminary predictions of E. globulus cold damage in the field.

Debarking, pitch removal and retting: Role of microbes and their enzymes

Microbial enzymes are green and clean alternatives for several processes in the pulp and paper industry. Enzyme treatment decreases the energy requirement and minimizes the wood losses during drum debarking. Lipophilic wood extractives are known as pitch. Pitch deposition adversely affects the pulp quality and increases equipment maintenance and operating costs during paper manufacturing. Several chemical additives have been used to remove pitch deposits. Natural seasoning of wood is used to minimize pitch content in wood, but it has some disadvantages including yield losses and decreased brightness. Controlled seasoning with white-rot fungi or albino strains of sapstain fungi is an effective tool for degradation and removal of wood extractives. Enzymes including lipase, laccase, sterol esterase, and lipooxygenase have also been used to minimize pitch-related problems. Enzymatic retting has been proved an eco-friendly and economical solution for chemical degumming and traditional retting.

Review on recent developments on pulp and paper mill wastewater treatment

Economic benefits of the pulp and paper industry have led it to be one of the most important industrial sections in the world. Nevertheless, in recent years, pulp and paper mills are facing challenges with the energy efficiency mechanisms and management of the resulting pollutants, considering the environmental feedbacks and ongoing legal requirements. This study reviews and discusses the recent developments of affordable methods dealing with pulp and paper mill wastewaters. To this end, the current state of the various processes used for pulp and paper production from virgin or recovered fibers has been briefly reviewed. Also, the relevant contaminants have been investigated, considering the used raw materials and applied techniques as the subject for further discussion about the relevant suitable wastewater treatment methods. The results of the present study indicated that adopting the integrated methods, alongside a combination of biological (e.g., anaerobic digestion) and physicochemical (e.g., novel Fenton reactions) treatment methods, can be environmentally and economically preferable to minimize environmental contaminants and energy recycling.

The potential of Pleurotus-treated olive mill solid waste as cattle feed

The aims of the current study were to follow: (1) the capability of the edible mushroom Pleurotus ostreatus to degrade cell wall components and soluble phenols of the olive mill solid waste (OMSW), and improve it for ruminant nutrition (2) the fate of oil and the lipid-soluble compounds tocopherols, squalene and beta-sitosterol in the fermented OMSW. A significant decrease in oil and lipid-soluble compounds with a concomitant shift in the fatty acid profile and degradation of soluble phenols took place already after 14 d. The utilization of lipids by the fungus shifted the degradation of the structural carbohydrates to a later stage, and significantly reduced the metabolizable energy of the OMSW. We propose that edible fungi with reduced lipase activity would preserve the energy and health promoting ingredients of the oil, and force the fungus to degrade structural carbohydrates, thus improving its digestibility.

Effect of bio-treatment on the lipophilic and hydrophilic extractives of wheat straw

Wheat straw, an important papermaking raw material in China, was treated with a white-rot fungus of Phanerochaete chrysosporium ME446, and the lipophilic and hydrophilic extractives from the control and bio-treated samples were analyzed by GC and GC-MS. Bio-treatment of wheat straw could alter the chemical composition of both the lipophylic and hydrophilic extractives. Sugars and phenolic substances such as coniferyl alcohol, 4-hydroxycinnamic acid, 1-guaiacylglycerol and ferulic acid were substantially degraded or consumed by the fungus. More lipophilic substances such as wax, glycerides and steryl esters were degraded into the corresponding components, resulting in much higher concentrations of fatty acids and sterols in the bio-treated samples. Obviously, the bio-treatment of wheat straw was of benefit to pitch control in pulping and papermaking processes, in the view of degradation of the more lipophilic substances. In addition, the bio-treatment could increase the lignin concentration in hot-water extractives of wheat straw.

Effect of storage time on the composition and content of wood extractives in Eucalyptus cultivated in Brazil

Lipophilic wood extractives commonly referred to as pitch, cause significant problems for the pulp and paper industries. The reduction of these extractives is an important aspect that concerns industries around the world. In the present work the change in the amount and chemical composition of lipophilic extractives from Eucalyptus spp. stored for 20, 40, 60, 100, 140 and 180 days after harvesting was investigated. The results showed a decrease in extractives content with storage time, with the most significant decrease occurring 60 days after harvesting. In addition, fatty acids and sterols were the main classes of compounds responsible for the significant decrease in extractive content. Data were analyzed by principal component analysis. PC1 explains approximately 99% of the total variance, and beta-sitosterol was the major compound responsible for the differentiation. These studies demonstrate that in terms of economical aspects, quality of the pulp and paper and minimization of pitch formation, the best period of wood storage is 60 days.

Characterization of Melanocarpus albomyces steryl esterase produced in Trichoderma reesei and modification of fibre products with the enzyme

Melanocarpus albomyces steryl esterase STE1 is considered to be an interesting tool for several industrial applications due to its broad substrate specificity. STE1 was produced in the filamentous fungus Trichoderma reesei in a laboratory bioreactor at an estimated production level of 280 mg l(-l). The properties of the purified recombinant enzyme (rSTE1), such as substrate specificity, molecular mass, pH optimum and stability and thermostability, were characterized and compared to the corresponding properties of the native enzyme. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed one band with a molecular weight of 60 kDa for rSTE1, whereas analytical gel filtration showed a dimeric structure with a molecular weight of 120 kDa. The rSTE1 was somewhat less stable under different conditions and had slightly lower activities on various substrates than the native STE1. The effects of rSTE1 on the properties of paper sheets and polyethylene terephthalate (PET) fabric were preliminarily evaluated. Due to the hydrolysis of triglycerides and steryl esters by the rSTE1 treatment, the tensile strength and hydrophilicity of the paper were increased. The rSTE1 treatment increased significantly the polarity of PET by hydrolysing the ester bonds in the polyester backbone. Dyeing of PET with methylene blue was also slightly improved after rSTE1 treatment.

Production, isolation and characterization of a sterol esterase from Ophiostoma piceae

We studied extracellular sterol esterase production by the ascomycete Ophiostoma piceae in liquid culture. Esterase activity was found in low levels in glucose medium but it was strongly induced by olive oil. An esterase was purified from the 0.5% olive oil-supplemented cultures using ultrafiltration followed by a single chromatographic step on a hydrophobic interaction column. The enzyme was a glycoprotein with 8% N-linked carbohydrate content, a molecular mass by SDS/PAGE around 56.5 kDa and an isoelectric point of 3.3. Its N-terminal sequence was TTVNVKYPEGEVV. Substrate specificity studies showed that the O. piceae esterase hydrolyzes p-nitrophenol esters, tributyrin, triolein and different cholesterol esters. Both affinity (Km) and catalytic constant (k(cat)) were positively affected by the length of the fatty acid esterifying glycerol and cholesterol. The presence of double bonds in the acyl chain increased the enzyme efficiency, although it affected the k(cat) values rather than the Km on the cholesterol esters. The O. piceae enzyme showed no interfacial activation. This enzyme could have biotechnological applications in paper manufacturing since it efficiently hydrolyzes both triglycerides and sterol esters, which form pitch deposits during manufacturing of softwood and hardwood paper pulps, respectively.

Identification of a novel series of alkylitaconic acids in wood cultures of Ceriporiopsis subvermispora by gas chromatography/mass spectrometry

A novel series of long-chain unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid has been identified by gas chromatography/mass spectrometry during in vitro decay of eucalypt wood by the white-rot basidiomycete Ceriporiopsis subvermispora. The major compounds were identified as tetradecyl-, 7-hexadecenyl- and hexadecylitaconic acids by their mass fragmentation patterns. Other members of the same compound series, identified as dodecanyl-, tridecanyl-, tetradecenyl-, pentadecanyl-, octadecenyl- and octadecanylitaconic acids, were present in very minor amounts or traces. Whereas hexadecenylitaconic acid has already been reported in cultures of C. subvermispora, to our knowledge this is the first report of the presence of the other alkylitaconic acids in fungal cultures. These new alkylitaconic-type metabolites may constitute a source for peroxidizable lipids involved in lignin degradation during wood decay by C. subvermispora and other white-rot basidiomycetes.