Ian D. Reid

Solid-state fermentations for biological delignification

Abstract Biological delignification, using white-rot fungi to liberate cellulose and hemicellulose from their complex with lignin, can aid the use of lignocellulose as ruminant animal feed, a source of sugars, and pulp. Solid-state fermentation is the method of choice for biological delignification. Lignin-degrading fungi, their ecophysiological requirements, and the design of solid-state fermenters for delignification are discussed. Capital and operating costs for solid-state fermentation can be kept low, and the lignocellulosic substrate is likely to be the major component of the cost of the delignified product. Experience in the operation of biological delignification processes at pilot plant or larger scale is needed to establish realistic process costs.

Pectinase in papermaking: solving retention problems in mechanical pulps bleached with hydrogen peroxide

Treatment with the enzyme pectinase has been reported to lower the cationic demand of thermomechanical pulp (TMP) bleached with alkaline peroxide in the laboratory. We have extended this discovery to bleached TMP produced industrially, and shown that commercial enzyme preparations can treat pulp within 15 min at the temperature and pH values prevalent in paper mills. About half of the cationic demand in the bleached pulp can be destroyed by pectinase. Dynamic drainage jar experiments show that the enzyme treatment improves the effectiveness of several cationic polymers to increase retention of fines and filler particles. It does not increase retention in the absence of retention aids or with nonionic polymers, and does not damage the strength properties of the pulp. Pectinase could be easily incorporated into paper machine stock preparation systems to lower the charges of cationic retention aids needed in furnishes containing peroxide-bleached mechanical pulp.

Optimization of solid-state fermentation for selective delignification of aspen wood with Phlebia tremellosa

Abstract The white-rot fungus Phlebia tremellosa can delignify aspen wood and increase the accessibility of its polysaccharides to enzymatic hydrolysis, under solid-state fermentation conditions. Fermentations at the 50 g scale were conducted to provide information for the design of larger fermentations. Agitation was not required. Forced aeration was needed for delignification of wood layers more than a few millimeters thick, but air circulation between the particles was not blocked by mycelium. Shavings were the best particles size. Sterilization of the wood was essential, but preadaptation of the inoculum to growth in wood was not. Inoculum levels as low as 2% were adequate.

Suitability of aspenwood biologically delignified with Pheblia tremellosus for fermentation to ethanol or butanediol

SummaryEnzymatic conversion of lignocellulosic material to fuels and chemicals depends on a initial pretreatment to render the cellulose more susceptible to enzymatic attack. Biological delignification of aspenwood with the fungus Phlebia tremellosus was compared to steaming as a pretreatment method.The biologically delignified aspenwood (BDA) had a high pentosan content and did not contain inhibitors of enzymatic hydrolysis or subsequent fermentation. In contrast, the steamed aspenwood required a water extraction step to remove the inhibitory material and this step also removed most of the pentosan. The yield of treated material was 90% from biological delignification and 70% from steaming.The cellulose in the BDA was less accessible to the cellulase enzymes than the steamed aspenwood. Combined hydrolysis and fermentation with Saccharomyces cerevisiae gave a lower yield of ethanol from BDA than from the steamed aspenwood, but the yields based on the weight of substrate before pretreatment were comparable. Combined hydrolysis and fermentation with Klebsiella pneumoniae gave higher yields of butanediol from BDA than from steamed aspenwood, because Klebsiella can ferment the xylose which was present in the biologically treated aspenwood. Trichoderma harzianum produced lower levels of cellulase enzymes when grown on BDA than when grown on steamed aspenwood and this was related to the xylan found in the biologically treated material.

Effect of polydimethylsiloxane oxygen carriers on the biological bleaching of hardwood kraft pulp by Trametes versicolor

SummaryImproving the availability of oxygen by adding polydimethylsiloxanes (PDMS) oxygen carriers to Trametes versicolor cultures increased pulp brightening. The presence of the oxygen carriers in cultures of T. versicolor with hardwood kraft pulp increased the growth rate of the fungus, but not the ultimate biomass yield. The PDMS also stimulated brightening of hardwood kraft pulp by it T. versicolor immobilized in polyurethane foam. A threefold increase in the oxygen uptake rate in T. versicolor cultures with PDMS was observed. This increase can be explained by elevated oxygen transfer rate and attributed to the surfactant properties of PDMS.

Biological Bleaching of Kraft Paper Pulp

The manufacture of pulp and paper from wood is an important industry; worldwide annual production is about 125 million metric tons. Paper products are used for printing and writing, packaging, and a wide variety of special purposes (Nordman, 1989).

Determining molecular weight distributions of lignins and their biodegradation products by gel filtration on a high-performance acarose column with a mixed ethanol-aqueous alkali solvent

Molecular weight distributions of 14C-labelled alkali-soluble lignins and their biodegradation products can be quickly and conveniently determined by gel filtration on a Pharmacia Superose 12 column. Elution with a 1:1 mixture of ethanol and 0.1 M NaOH prevents adsorption of the lignins on the gel.

Anthracenediethanol inhibits lignin degradation by Phanerochaete chrysosporium by competing for oxidation by lignin peroxidase, and not by trapping singlet oxygen

The biodegradation of anthracene-9, 10-diethanol by the ligninolytic fungus Phanerochaete chrysosporium, previously though to involve singlet oxygen, is shown to be catalyzed by lignin peroxidases. Veratryl alcohol stimulated the enzymatic degradation of anthracenediethanol, and anthracenediethanol inhibited enzymatic oxidation of veratryl alcohol. Competition for oxidation by lignin peroxidase is suggested as the mechanism of the inhibition of lignin biodegradation by anthracenediethanol and related anthracene derivatives.