Thomas W. Joyce

Increasing ligninolytic enzyme activities in several white-rot basidiomycetes by nitrogen-sufficient media

Ligninolytic enzyme activities were monitored in five white-rot fungi cultivated on nitrogen (N)-limited glucose-BIII medium and were compared with the activities obtained in media supplemented with 56 mm peptone-N. Only Phanerochaete chrysosporium and two Bjerkandera strains produced detectable lignin peroxidase (LiP) activity. LiP was stimulated by either N-limitation or N-sufficiency in P. chrysosporium and Bjerkandera spp., respectively. All of the fungal strains tested produced manganese-dependent peroxidase (MnP) activity, which was consistently stimulated by the peptone supplementation. Both the manganese-independent peroxidase (MiP) activities, which were detected only in Bjerkandera spp., and the laccase activities, which were detected only in Lentinula edodes and Pleurotus ostreatus, were also enhanced by peptone. In several fungal strains, the activity of ligninolytic enzymes was likewise stimulated by supplying 56 mm NH+4-N at an initial pH of 7·3. This study indicates that several commercially important and commonly occurring white-rot fungi produce higher ligninolytic enzyme activities in response to a nitrogen-rich medium, in contrast to the physiological model proposed for P. chrysosporium.

Kinetics of bleach plant effluent decolorization by Phanerochaete chrysosporium

Abstract Decolorization of the first alkaline extraction stage (E 1 ) effluent from a pulp mill bleach effluent using the white-rot fungus Phanerochaete chrysosporium was conducted in a rotating biological contactor (RBC) under improved conditions. The kinetic model developed for both 1 d and 2 d retention times showed a characteristic pattern. The overall decolorization process can be divided into three distinct stages, viz., a rapid color reduction in the first hour of contact between the effluent and fungus, followed by a zero order reaction, and then a first order reaction. The color removal rate on the second day of the 2 d batch treatment was less than that on the first day. The decolorization in a continuous flow reactor achieved approximately the same daily color removal rate, but had a longer working lifetime as compared to the batch reactor, thereby removing more color over the fungal lifetime.

Cellulase binding to cellulose fibers in high shear fields

Abstract Cellulase binding onto cellulose fiber was investigated in a turbulent mixing environment created by an axial flow impeller. The binding of the enzyme was found to be associated with various process variables studied, e.g., intensity of agitation, reaction time, pulp consistency, pH, temperature, and concentration of enzyme. The similarity between trends in enzyme binding and enzyme activity confirmed that the reduction of binding with increasing intensity of agitation over time was due to denaturation of the enzyme by shear. Physical forces like shear can disrupt the structure of the enzyme resulting in the loss of binding ability and activity. It also appeared that mild mixing did not denature the enzyme, but rather the enzyme dispersed better into the pulp slurry, resulting in a higher percentage of enzyme bound to fiber. However, increasing shear resulted in a reduction in binding and activity. At a low rpm, the binding increased initially with time, reached a peak at about 3 to 5 min, and then decreased gradually. With respect to time and shear rate, the reduction in binding and activity was much more significant at 10 min of mixing. It is concluded that a high shear and/or a prolonged exposure to a low shear can disrupt the structure of enzyme resulting in the loss of binding ability and activity. At low enzyme concentrations, the binding of enzyme onto fiber increases with increasing concentration of enzyme. Similarly, the percentage of enzyme bound increased with increasing pulp consistency. Since cellulase needs mild temperatures and acidic environments to maintain its activity, high temperature and pH caused a reduction in binding. A pH of 4 and a temperature of 30°C yielded the highest percent binding among the conditions studied.

Treatment of chlorine bleaching effluent using a white-rot fungus

This study was undertaken to better understand the reactions related to fungal treatment of pulp bleaching effluents. Color, COD (chemical oxygen demand), glucose, chloride and ammonium concentration were monitored during the course of treatment of alkali extraction stage liquor (E1) with a white-rot fungus Phanerochaete chrysosporium. The color removal rate was independent on the initial glucose concentration. The earlier used glucose concentration of 10 g l−1 was found to be unnecessary high as the residual glucose accounted for about 50% of the final COD of the effluent. The lowest practical glucose concentration was 2 g l−1. Below this the fungus lost its decolorizing activity in a few days. The lignin-related COD decreased 32% and up to 16.5 mM inorganic chloride was liberated (being 34% increase from the original concentration) from the chlorinated organic material in the effluent in 2 d. The observed rapid depletion of added ammonium nitrogen is believed to indicate a switch of a part of the mycelium to primary growth which leads to higher activity and longer active period of time due to renewal of the cells.

Biological delignification of pulp by Phanerochaete chrysosporium

Biological delignification of wood pulp was studied using the white-rot fungus Phanerochaete chrysosporium in liquid cultures. Kraft pulp and chemithermo-mechanical pulp (CTMP) were used as substrates. Both types of pulp could readily be delignified by the shaking cultures of the fungus: the kappa number of kraft pulp decreased from 33 to less than 10 in two weeks and the Klason lignin content of CTMP decreased from 26.5 to 21.3% in the same time. Stationary cultures did not delignify pulps effectively. During the fungal treatment, the strength of CTMP increased substantially. At a freeness level of about 350 ml, the tensile and tear indices increased by 20% and the burst index by 40% as compared to the original pulp. Unfortunately, CTMP turned dark during the treatment. The ISO brightness was originally 52.5, but after the incubation with the fungus it was only 17.9. After peroxide bleaching the brightness was still low, only 41.6.

A continuous biological process to decolorize bleach plant effluents.

Although almost every U.S. pulp mill has a biological wastewater treatment system, these systems based on bacteria, are largely ineffective in the removal of color. For this reason, we have attempted to utilize Phanerochaete chrysosporium, a fungus known to degrade lignin, as the primary organism in a novel waste treatment scheme named the MyCoR Process. Color from bleached Kraft mills originates principally from the first extraction stage of the bleach plant. It is this waste stream which is sent to the MyCoR Process reactor, a rotating biological contactor, for decolorization. We have found that under optimal conditions up to 2,000 color units/L/day can be removed from the waste stream. There is also a concomitant removal of COD and BOD. In addition, chlorolignins originating from the bleaching process were found to be dechlorinated; this is of interest to those concerned with the impact of bleach plant effluents on the environment. The process uses conventional wastewater treatment equipment. However, the use of a pure culture of fungus in a secondary metabolic state has not been attempted previously in a waste treatment scheme. Minor equipment modification and close operator attention may therefore be required. A preliminary economic analysis shows that the MyCoR Process, in its present state, would cost about US

Role of glucose in fungal decolorization of wood pulp bleaching effluents

30/metric ton of bleached Kraft pulp produced. This cost will decrease as improved or new strains of fungi are developed for the process.

Enzyme activity recovery from secondary fiber treated with cellulase and xylanase

The white-rot fungus Phanerochaete chrysosporium, when immobilized on discs in a rotating biological contactor (RBC), can effectively decolorize the first alkaline extraction stage (E1) effluent from the bleach plant of a wood pulp production facility. We have shown that to degrade lignin and lignin-derived chromophoric structures, a co-substrate such as glucose must be added.

Dechlorination and detoxification of bleach plant effluent by Phanerochaete chrysosporium

Abstract One of the major problems with implementing biotechnical processes in the recycled paper industry, such as enzyme-enhanced deinking and enzymatic enhancement of pulp drainage properties, is the cost of commercial enzyme preparations. Thus, several factorial studies were performed to determine if enzyme activity can be successfully removed from simulated recycled fiber (once-dried, bleached hardwood and softwood kraft fiber) treated with low concentrations (0.2% or 2.0% on oven-dry fiber) of cellulase or xylanase. Enzyme activity recovery was accomplished by washing treated fiber with dilute NaOH in combination with a low concentration of the nonionic surfactant Tween 80 under a variety of mild conditions. Various cellulase activities i.e., endoglucanase, exoglucanase, and filter paper, can be effectively recovered depending on the washing conditions, the cellulase charge, and the fiber type. Xylanase activity was effectively recovered from softwood, but not hardwood. The results suggest that enzyme activity recovery may be a possible means of decreasing the operating costs for biotechnical processes in the paper industry.

Effect of shear fields on hemicellulase binding to pulp fibers

Abstract Dechlorination, detoxification, and decolorization of the first alkaline extraction stage (Ep) effluent from a pulp mill bleach plant were studied during fungal treatment. The original Ep effluent and Ep effluent fractionated by ultrafiltration were treated with the white-rot fungus Phanerochaete chrysosporium under agitated conditions. The fungus was grown from spores for 4 d. Decolorization was observed 2 d after the addition of fresh media containing reduced levels of nitrogen and carbon. After 2–3 d reaction time detoxification, dechlorination and decolorization were evaluated. Color removal was most effective in the MW > 10 000 (HMW) fraction. Toxicity as measured by the MICROTOX bioassay, increased in both the HMW and MW 1000–10000 (MMW) fraction after fungal treatment. Molecular weight decreased during fungal treatment, which may have caused the increase in toxicity. The amount of chlorinated organic compounds, as measured by adsorbable organic halide analysis (AOX), decreased in each fraction.