Gary M. Scott

Modeling xylan solubilization during autohydrolysis of sugar maple wood meal: reaction kinetics.

Abstract The objective of this work was to study the kinetics of hemicelluloses extraction during hydrothermal pretreatment of sugar maple wood meal. Pretreatment was conducted in a batch reactor at 145–185°C with reaction times up to 8 h and with liquor to solid ratio of 20:1. Under these conditions, hemicelluloses were selectively solubilized and little degradation (approximately 6–9% of the initial amount) of cellulose and lignin was observed. A kinetic model was developed. It was supposed that there are no diffusion limitations and that the reaction rate constants have first-order kinetics with Arrhenius-type temperature dependence. The model proposes the formation of xylose directly from wood xylan as well as from xylooligomers formed in the liquid phase by the hydrolysis of xylan. The model is able to correlate satisfactorily experimentally measured yields of residual xylan, xylooligomers, xylose, and furfural obtained during the pretreatment.

Quantitative analysis of sugars in wood hydrolyzates with 1H NMR during the autohydrolysis of hardwoods

The focus of this work was to determine the utility of (1)H NMR spectroscopy in the quantification of sugars resulting from the solubilization of hemicelluloses during the autohydrolysis of hardwoods and the use of this technique to evaluate the kinetics of this process over a range of temperatures and times. Yields of residual xylan, xylooligomers, xylose, glucose, and the degraded products of sugars, i.e., furfural and HMF (5-hydroxymethyl furfural), were determined. The monosaccharide and oligomer contents were quantified with a recently developed high resolution (1)H NMR spectroscopic analysis. This method provided precise measurement of the residual xylan and cellulose remaining in the extracted wood samples and xylose and glucose in the hydrolyzates. NMR was found to exhibit good repeatability and provided carbohydrate compositional results comparable to published methods for sugar maple and aspen woods.

Biomechanical pulping: a mill-scale evaluation

Mechanical pulping process is electrical energy intensive and results in low paper strength. Biomechanical pulping, defined as the fungal treatment of lignocellulosic materials prior to mechanical pulping, has shown at least 30% savings in electrical energy consumption, and significant improvements in paper strength properties compared to the control at a laboratory scale. In an effort to scale-up biomechanical pulping to an industrial level, 50 tons of spruce wood chips were inoculated with the best biopulping fungus in a continuous operation and stored in the form of an outdoor chip pile for 2 weeks. The pile was ventilated with conditioned air to maintain the optimum growth temperature and moisture throughout the pile. The control and fungus-treated chips were refined through a thermomechanical pulp mill (TMP) producing lightweight coated paper. The fungal pretreatment saved 33% electrical energy and improved paper strength properties significantly compared to the control. Since biofibers were stronger than the conventional TMP fibers, we were able to reduce the amount of bleached softwood kraft pulp by at least 5% in the final product. Fungal pretreatment reduced brightness, but brightness was restored to the level of bleached control with 60% more hydrogen peroxide. The economics of biomechanical pulping look attractive.

Recombinant manganese peroxidase (rMnP) from Pichia pastoris. Part 1: Kraft pulp delignification.

Abstract Manganese peroxidase (MnP) is the main enzyme implicated in the biobleaching of kraft pulps by white-rot fungi. However, potential commercial applications of this enzyme have been limited by its availability in large quantities. Advances have been made to produce high-yield concentrated recombinant MnP (rMnP). The objective of this study was to evaluate the ability of rMnP to delignify and brighten kraft pulps. The rMnP, produced from the yeast Pichia pastoris – in high-cell density and in fed-batch fermentations – was found to be effective in lignin removal in both hardwood and softwood unbleached kraft pulps. The rMnP applied at 30 U g-1 pulp for 24 h followed by alkali extraction caused significant kappa number reductions for all the pulps tested with different initial lignin contents and structures. Softwood and hardwood pulps showed similar delignification rates during rMnP treatments. Highly delignified pulps with kappa number less than 10 are less susceptible to delignification by rMnP compared with the pulps with higher lignin content. The rMnP-treated pulp was also shown to be more susceptible to subsequent peroxide bleaching compared with the control pulp. More than 60% of the kappa number reduction was achieved by sequential rMnP treatments combined with alkaline extraction. Sequential treatment with xylanase and rMnP also resulted in more extensive delignification than in each enzyme treatment alone or in the case of simultaneous application of the enzymes.

Modification of Loblolly Pine Chips with Ceriporiopsis subvermispora Part 1: Effect of Fungal Treatment

Abstract The effect of treating loblolly pine (Pinus taeda) chips with the fungus Ceriporiopsis subvermispora was investigated by assessing the wood changes at 2 and 4 weeks incubation relative to a control (no fungal treatment). Scanning electron microscopy indicated that during the first 2 weeks of colonization, C. subvermispora had grown over the surface of the chips and also within ray cells. A mass loss of 5% occurred after 2 weeks, 6% after four weeks. The extractives were reduced 23% in the first 2 weeks of fungal treatment and 32% after 4 weeks. Lignin loss was statistically insignificant at 2 weeks but reached 8% of the original lignin after 4 weeks. The carbohydrate content of the treated wood showed no significant differences from the control after 2 weeks and only minor losses after 4 weeks. The fraction of the wood soluble in 1% NaOH was 14.9% at 2 weeks compared to 11.5% for the control chips and increased to 18.8% after 4 weeks. This indicated only a mild decay due to the fungal treatment. At 2 weeks of fungal treatment, the lignin phenolic hydroxyl content was not significantly different from the control. However, after 4 weeks of treatment the phenolic hydroxyl groups increased by 14%. Small increases in the average pore size of the wood occurred with incubation time, including a broadening in the range of pore sizes.

Recombinant manganese peroxidase (rMnP) from Pichia pastoris. Part 2: Application in TCF and ECF bleaching.

Abstract The recombinant manganese peroxidase (rMnP) produced from the yeast Pichia pastoris has been investigated in totally chlorine free (TCF) and elemental chlorine free (ECF) bleaching sequences for improving the bleachability of kraft pulps. In TCF bleaching, oxygen delignified hardwood kraft pulp was treated with rMnP, followed by a sequence combining a chelating and alkaline peroxide bleaching stage. The inclusion of the enzymatic treatment significantly improved the pulp brightness to a level that is difficult to obtain by chemical bleaching alone. Furthermore, the treatment with rMnP resulted in energy savings during pulp refining with PFI mill with a slight improvement in pulp strength properties such as tensile index and burst index. In ECF bleaching, a significant reduction in chlorine dioxide consumption was obtained. A three-stage rMnP treatment combined with alkaline extraction, followed by DED bleaching sequence for hardwood kraft pulp (HWKP) or DEDED bleaching sequence for softwood kraft pulp (SWKP), reduced the total effective chlorine by 41% and 32% for HWKP and SWKP, respectively, compared with the conventional bleaching sequences without enzymatic treatment. The strength properties of the enzyme-treated pulp were also slightly better than that of the control pulp. Further reductions in the consumption of total effective chlorine were obtained when a xylanase pretreatment was incorporated into the bleaching sequence before the repeated rMnP treatment.

Multivariable analysis, correlation, and prediction

Making best use of multi-point observations and sensor information to forecast future events in complex real time systems is a challenge which presents itself in many military and industrial problem domains. The first step in tackling these challenges is to analyze and understand the data. Depending on the algorithm used to forecast a future event, improvements to a prediction can be realized if one can first determine the nature and extent of variable correlations, and for the purposes of prediction, quantify the strength of the correlations of input variables to output variables. This is no easy task since sensor readings and operator logs are sometimes inconsistent and/or unreliable, some catastrophic failures can be almost impossible to predict, and time lags and leads in a given system may vary from one day to the next. Correlation analysis techniques can help us deal with some of these problems. They allow us to find out what variables may be strongly correlated to major events. After detecting where the strongest correlations exist, one must choose a model which can best predict the possible outcomes that could occur for a number of possible scenarios. The model must be tested and evaluated, and sometimes it is necessary to go back to the feature selection stage of the model design process and reevaluate the available sensory data and inputs. An industrial process example is adopted in this research to both highlight the issues that arise in complex systems and to demonstrate methods of addressing such issues.

Modification of Loblolly Pine Chips with Ceriporiopsis subvermispora Part 2: Kraft Pulping of Treated Chips

Abstract Loblolly pine (Pinus taeda) chips treated with Ceriporiopsis subvermispora for two or four weeks were pulped with different combinations of kraft pulping conditions to obtain a better understanding of the interaction between the fungal action and the pulping variables. Two different levels of effective alkali (18 or 22%), two times at maximum Tmax (60 or 90 min), 22% sulfidity, and a Tmax of 170°C, were used. The best delignification without adversely affecting pulp viscosity was found in pulps made from chips treated with the fungus for 2 weeks and at the mildest pulping conditions. At all pulping conditions there was a substantial decrease in the amount of rejects with 2 weeks of fungal treatment. Pulps from fungally‐treated chips refined more easily than the control pulp and strength properties of pulps of fungally‐treated chips were superior to those of the control pulp.