Ian Cullis

Predicting the regenerative capacity of conifer somatic embryogenic cultures by metabolomics

Somatic embryogenesis in gymnosperms is an effective approach to clonally propagating germplasm. However, embryogenic cultures frequently lose regenerative capacity. The interactions between metabolic composition, physiological state, genotype and embryogenic capacity in Pinus taeda (loblolly pine) somatic embryogenic cultures were explored using metabolomics. A stepwise modelling procedure, using the Bayesian information criterion, generated a 47 metabolite predictive model that could explain culture productivity. The model performed extremely well in cross-validation, achieving a correlation coefficient of 0.98 between actual and predicted mature embryo production. The metabolic composition and structure of the model implied that variation in culture regenerative capacity was closely linked to the physiological transition of cultures from the proliferation phase to the maturation phase of development. The propensity of cultures to advance into this transition appears to relate to nutrient uptake and allocation in vivo, and to be associated with the tolerance and response of cultures to stress, during the proliferation phase.

Optimized delignification of wood-derived lignocellulosics for improved enzymatic hydrolysis.

One of the major bottlenecks in the bioconversion of lignocelluosic feedstocks to liquid ethanol is the recalcitrance of residue following pretreatment, specifically softwood derived residues. Peroxide delignification has previously been shown to effectively aid in the removal of condensed lignaceous moieties from substrates following pretreatment, and thereby improve the hydrolyzability of the polymeric carbohydrates to their monomeric constituents. Despite the effectiveness of peroxide, drawbacks in this system still remain, as the concentration of peroxide required for adequate hydrolysis performance is currently uneconomical. In an attempt to improve the efficacy of the delignification process, we evaluated other post‐treatment operations and concurrently attempted to limit the decomposition of peroxide loading; with the over arching aim to improve the efficiency of the bioconversion process. By employing several peroxide stabilizers and pre‐chelating the steam exploded recalcitrant substrates, we were able to substantially improve the delignification treatment of Douglas‐fir wood chips, and to reduce peroxide loading by more than 50% without negative effects on the hydrolysis rates and yield. Biotechnol. Bioeng. 2010;106: 884–893.

Checking of Profiled Southern Pine and Pacific Silver Fir Deck Boards

This study tests the hypothesis that the effectiveness of surface profiling at reducing the checking of deck boards exposed to weathering varies with wood species and profile type. Southern pine (Pinus sp.) and Pacific silver fir (Abies amabilis) deck boards were machined to produce three different types of surface profiles: flat (control), ribbed (V-shaped grooves), and rippled (U-shaped grooves). Boards were exposed to accelerated weathering for 5 days, and the number and sizes of checks that developed in boards were quantified. Surface profiling reduced the total number and total width of checks in both Pacific silver fir and southern pine deck board specimens, but it had a greater effect at reducing checking in Pacific silver fir than in southern pine. The ribbed profile, in particular, was much more effective at reducing checking of Pacific silver fir than it was at reducing the checking of southern pine. Therefore, we conclude that the effectiveness of surface profiling at reducing checking of deck boards depends on wood species and the type of profile machined into wood surfaces. Checks developed in the grooves between the ribs of profiled boards and appeared to be constrained from becoming wider to a greater extent than becoming longer. Therefore, we conclude that the beneficial effect of profiling on the appearance of boards arises because checks are much narrower than those on flat boards and are located in the grooves, where they are difficult to see.

A note on the effect of wood moisture content and clear coating on the color of veneer panels stained with solvent-borne stain.

Red alder, mahogany, maple, white oak, and pine veneer panels conditioned to 6, 12, or 20 percent moisture content (MC) were stained with red solvent-borne stain, partially coated with clear lacquer, and air dried. All of the hardwood panels stained at an MC of 20 percent were either significantly redder or darker than panels stained at lower MCs. Clear coating made panels darker and redder (except oak). We conclude that large departures from the recommended MC for staining (6% to 8%) can significantly alter the color of hardwood veneer panels stained with solvent-borne stain.