Analyses of long-term fungal degradation of spruce bark reveals varying potential for catabolism of polysaccharides and extractive compounds

The bark represents the outer protective layer of trees. It contains high concentrations of antimicrobial extractives, in addition to regular wood polymers. It represents a huge underutilized side stream in forestry, but biotechnological valorization is hampered by a lack of knowledge on microbial bark degradation. Many fungi are efficient lignocellulose degraders, and here, spruce bark degradation by five species, Dichomitus squalens, Rhodonia placenta, Penicillium crustosum, Trichoderma sp. B1, and Trichoderma reesei, was mapped, by continuously analyzing chemical changes in the bark over six months. The study reveals how fungi from different phyla degrade bark using diverse strategies, regarding both wood polymers and extractives, where toxic resin acids were degraded by Basidiomycetes but unmodified/tolerated by Ascomycetes. Proteome analyses of the white-rot D. squalens revealed several proteins, with both known and unknown functions, that were specifically upregulated during growth on bark. This knowledge can accelerate improved utilization of an abundant renewable resource.

Effect of ferrate pretreatment on anaerobic digestibility of primary sludge spiked with resin acids

Resin acids are mixtures of high molecular weight carboxylic acids found in tree resins. Due to higher hydrophobicity and low solubility, they tend to adsorb on the suspended solids in pulp and paper (P&P) mill wastewater and accumulate in primary sludge through settling. Anaerobic digestion (AD) is a common practice stabilizing sludge; however, high concentration of resin acids affects the AD process. The aim of this research was mainly to determine the impact of ferrate (Fe (VI)) oxidation on selected resin acids and anaerobic digestibility of ferrate-treated primary sludge (PS) spiked with the resin acids. First, batch control oxidation of model resin acids with Fe (VI) was conducted to identify an optimum dosage, pH and contact time using a Box-Behnken design approach. Thereafter, anaerobic treatability studies of primary sludge spiked with resin acids both under control condition and optimum ferrate pretreatment were conducted. Up to 97% oxidation of resin acids occurred in pure water, while only 44%-62% oxidation of resin acids occurred in PS with an increasing Fe (VI) dosage from 0.034 to 0.137 mg Fe (VI)/mg tCOD_fed. The pretreatment did not affect the anaerobic biodegradability of resin acids; however, it lowered their negative influences on the PS digestibility. About 0.076 mg Fe (VI) dosage/mg tCOD_fed solubilized the sludge increasing the methane production by 40% compared to the untreated digester. The potential benefits of ferrate pretreatment of P&P primary sludge include resin acids oxidation and subsequent toxicity reduction, higher sludge solubilization enhancing methane production and enabling anaerobic digestion at higher COD loading.

Anaerobic digestibility of resin acids in primary sludge: Effect of ozone pretreatment

Resin acids in pulp and paper mills wastewater are potentially partitioned in the solids in post-primary clarification due to higher hydrophobicity with log K_ow ∼1.74-5.80. They are known to adversely affect anaerobic digestion (AD) process, although the effect has not been quantified deterministically in control studies. The objective of the present work was to determine the effect of untreated and ozonated spiked resin acids on AD of primary sludge. Batch adsorption tests were conducted to determine the solid-liquid partition coefficient (K_d) of resin acids on the primary sludge. Higher K_d was obtained at pH 4; however, it was decreased by 78-98% at pH 8. Thereafter, batch AD of model resin acids in primary sludge using food to microorganism ratio (S₀/X) of 0.5gtCOD/gVSSindicated only 15-20% removal of resin acids in the liquid phase anaerobically. While, ozonation in pure water using 0.74-1.48 mg O₃/mg tCOD showed >90% reduction of the test resin acids, an ozone dose of 0.52 mg O₃/mg tCOD reduced 50-70% spiked resin acids' load to the digester. However, no further removal of resin acids occurred during AD over 30 days. About 42% reduction in methane production compared to the control digestor occurred in the presence of 150 mg/L of resin acids. When treated with 0.52 mg O₃/mg tCOD, methane production improved and was comparable to the control digestor, indicating that resin acids may not be detrimental to AD at a concentration range of 45-75 mg/L.

New antibacterial hydrophobic assay reveals Abies balsamea oleoresin activity against Staphylococcus aureus and MRSA

ETHNOPHARMACOLOGICAL RELEVANCE

Oleoresin of Abies balsamea (L.) Mill. was used by Native Americans of the boreal forest of Canada and French Canadians to treat various infections, suggesting that oleoresin has antibacterial properties.

AIM OF THE STUDY

In this study, the antibacterial activity of whole oleoresin from A. balsamea was investigated against E. coli, S. aureus and two methicillin-resistant S. aureus (MRSA) strains using a new sensitive assay developed to evaluate hydrophobic matrix and compounds.

MATERIALS AND METHODS

Antibacterial activity of oleoresin was first investigated using dilution and disk diffusion methods against E. coli and S. aureus, and compared to a new sensitive assay for hydrophobic matrix. Moreover, whole oleoresin was analyzed by GC-MS to characterize the composition and to identify the compounds responsible of the antibacterial activity.

RESULTS

The results showed that whole oleoresin was inactive against Gram-negative E. coli (MIC₉₀ >90µg/ml) but active against Gram-positive S. aureus and MRSA with MIC₉₀ ranging from 18.2 to 30µg/ml. The oleoresin is mainly composed of monoterpene (28%), sesquiterpenes (2%), and diterpenes (45%). Resin acids were found, in part, responsible for the antibacterial activity of whole oleoresin. Isopimaric acid and levopimaric acid are the most active with a MIC₉₀ of respectively 9.7µg/ml and 10µg/ml.

CONCLUSION

This study supports the use of oleoresin of A. balsamea by the Native Americans and French Canadians to treat bacterial infections due to S. aureus.

Biophysical study of resin acid effects on phospholipid membrane structure and properties

Hydrophobic resin acids (RAs) are synthesized by conifer trees as part of their defense mechanisms. One of the functions of RAs in plant defense is suggested to be the perturbation of the cellular membrane. However, there is a vast diversity of chemical structures within this class of molecules, and there are no clear correlations to the molecular mechanisms behind the RA's toxicity. In this study we unravel the molecular interactions of the three closely related RAs dehydroabietic acid, neoabietic acid, and the synthetic analogue dichlorodehydroabietic acid with dipalmitoylphosphatidylcholine (DPPC) model membranes and the polar lipid extract of soybeans. The complementarity of the biophysical techniques used (NMR, DLS, NR, DSC, Cryo-TEM) allowed correlating changes at the vesicle level with changes at the molecular level and the co-localization of RAs within DPPC monolayer. Effects on DPPC membranes are correlated with the physical chemical properties of the RA and their toxicity.

Chemical Composition and Content of Lipophilic Seed Extractives of Some Abies and Picea Species

The chemical content and composition of the lipophilic extracts from seeds of some fir species: Abies alba, A. cephalonica, A. concolor, and A. koreana, as well as of a few spruce species: Picea abies, P. orientalis, and P. pungens, were examined. The amount of lipophilic extractives is diverse among the tree species and it varies from 9.8% to 41% of seeds. The chemical characterization showed significant differences, not only in the content, but also in the composition of extractives. However, most of the identified compounds like resin alcohols, -aldehydes, and -acids, as well as fatty acids, were detected in the seed extracts of all the examined tree species. The dominating identified compound group was esterified fatty acids (2.5 - 55.4% w/w of dry extract), occurring mainly as tri- and diglycerides, as well as free acids. The main representatives of this group were linoleic and oleic acids. The resin acids, among which the main were abietic, neoabietic, dehydroabietic, and palustric acids, were also detected at high levels, from 1.8% to 16.9% of the dry seed extracts. Phytosterols, tocopherols, resin hydrocarbons, and resin esters, as well as fatty alcohols were also identified. The coniferous tree seeds, as a renewable natural material, could represent a prospective raw material for producing valuable chemicals.