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Aims:  Naphthenic acids (NAs) are naturally occurring, linear and cyclic carboxylic surfactants associated with the acidic fraction of petroleum. NAs account for most of the acute aquatic toxicity of oil sands process‐affected water (OSPW). The toxicity of OSPW can be reduced by microbial degradation. The aim of this research was to determine the extent of NA degradation by sediment microbial communities exposed to varying amounts of OSPW. Methods and Results:  Eleven wetlands, both natural and process‐affected, and one tailings settling pond in Northern Alberta were studied. The natural wetlands and process‐affected sites fell into two distinct groups based on their water chemistry. The extent of degradation of a 14C‐labelled monocyclic NA surrogate [14C‐cyclohexane carboxylic acid (CCA)] was relatively uniform in all sediments (approximately 30%) after 14 days. In contrast, degradation of a bicyclic NA surrogate [14C‐decahydronaphthoic acid (DHNA)]was significantly lower in non process‐affected sediments. Enrichment cultures, obtained from an active tailings settling pond, using commercially available NAs as the sole carbon source, resulted in the isolation of a co‐culture containing Pseudomonas putida and Pseudomonas fluorescens. Quantitative GC–MS analysis showed that the co‐culture removed >95% of the commercial NAs, and partially degraded the process NAs from OSPW with a resulting NA profile similar to that from ‘aged wetlands’. Conclusions:  Exposure to NAs induced and/or selected micro‐organisms capable of more effectively degrading bicyclic NAs. Native Pseudomonas spp. extensively degraded fresh, commercial NA. The recalcitrant NAs resembled those found in process‐affected wetlands. Significance and Impact of the Study:  These results suggest that it may be possible to manipulate the existing environmental conditions to select for a microbial community exhibiting higher rates of NA degradation. This will have significant impact on the design of artificial wetlands for water treatment.

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Mountain pine beetle-killed lodgepole pine (Pinus contorta) chips were pretreated using the organosolv process, and their ease of subsequent enzymatic hydrolysis was assessed. The effect of varying pretreatment chemicals and solvents on the substrate's physicochemical characteristics was also investigated. The chemicals employed were MgCl2, H2SO4, SO2, and NaOH, and the solvents were ethanol and butanol. It was apparent that the different pretreatments resulted in variations in both the chemical composition of the solid and liquid fractions as well in the extent of cellulolytic hydrolysis (ranging from 21% to 82% hydrolysis after 12 h). Pretreatment under acidic conditions resulted in substrates that were readily hydrolyzed despite the apparent contradiction that pretreatment under alkaline conditions resulted in increased delignification (approximately 7% and 10% residual lignin for alkaline conditions versus 17% to 19% for acidic conditions). Acidic pretreatments also resulted in lower cellulose degree of polymerization, shorter fiber lengths, and increased substrate porosity. The substrates generated when butanol/water mixtures were used as the pretreatment solvent were also hydrolyzed more readily than those generated with ethanol/water. This was likely due to the limited miscibility of the solvents resulting in an increased concentration of pretreatment chemicals in the aqueous layer and thus a higher pretreatment severity.

Organosolv-pretreated Lodgepole pine substrates were physically and chemically treated to increase their hydrophilicity and swelling as these are two substrate attributes which have been shown to improve cellulolytic hydrolysis. Surprisingly, mechanical treatment of the organosolv-treated substrates by PFI-mill refining did not significantly increase hydrolysis yields despite decreases in particle size and crystallinity and increases in swelling. However, sulfonation of the substrate did, significantly, increase enzymatic hydrolysis at loadings of both 5 and 2.5 FPU g(-1) cellulose (from 80% to 95% and from 35% to 80%, respectively). In addition, sulfonation resulted in an increase in the amount of free enzymes detected during the course of hydrolysis to a maximum of 80% after 72 h. This suggested that the beneficial effects of sulfonation were primarily due to a decrease in the non-specific binding of the cellulases to the lignin.