Australasian Biotechnology (backfiles) AusBiotech ISSN: 1036-7128 Vol. 11, Num. 5, 2001, pp. 38-39

Australasian Biotechnology, Vol. 11 No. 5, 2001, pp. 38-39

BIOPRODUCT DEVELOPMENT

UTILIZATION OF USED PAPER MATERIALS AS A RENEWABLE RESOURCE FOR BIOPRODUCT DEVELOPMENT

J.P.H. van Wyk and M. Mohulatsi

Box 225, Department of Pharmacology and Therapeutics, Medical University of Southern Africa, South Africa, 0204. Email: vanwykz@yahoo.com

Code Number: au01065

Enzymatic catalyzed saccharification of used foolscap paper, filter paper, newsprint, office paper as well as microcrystalline cellulose was performed with the cellulase from Penicillium funiculosum. Glucose, the major reaction product, showed different formation tendencies during biodegradation of these cellulose materials. Foolscap paper exhibited the highest susceptibility for hydrolysis by this enzyme followed by filter paper, newspaper, microcrystalline cellulose and office paper. These different susceptibilities of cellulose materials for cellulase activity have been confirmed by degrading all materials with changing enzyme and substrate concentrations.

Introduction

Environmental pollution, especially in densely populated areas, needs more attention and issues such as waste prevention and recycling as well as bioproduct development are thus topical (Block, 1999). The elaboration of biofuels is encouraged due to the depletion of fossil fuel reserves and increased pollution as a result of its combustion. With almost 80% of dry municipal solid waste described as organic materials, many cities and countries experience difficulties in managing this biodegradable part of household refuse, market garbage, yard rubbish, animal and human waste. Used paper is the largest component of these organic waste with cellulose the major structural component of it (Gupta, 1998). The biodegradation of waste cellulose materials to fermentable sugars would assist in the limitation of waste as well as with the development of sustainable bioenergy (Jeffries and Schartmann, 1999) and bioproducts like lactic acid (Venkatesh, 1997). Cellulose, a beta- 1,4-glucosidic linked glucose polymer, can undergo biodegradation into glucose by the hydrolytic action of a multi-component enzyme system called cellulase (Walker and Wilson, 1991) that is mostly manifested in fungi (Perrson et.al, 1991) and bacteria (Gilkes, et.al, 1991). Different waste cellulose materials (Wood et.al, 1997) have already been treated with cellulase resulting in varying degrees of bioconversion. The susceptibility of used foolscap paper, filter paper, office paper, newsprint as well as microcrystalline cellulose towards saccharification by P. funiculosum cellulase has been determined in the current study.

MATERIALS AND METHODS

Cellulase and cellulose materials

Filter paper (Whatman No. 1), foolscap paper (unglazed ruled manuscript paper), office paper (used for photocopying and printing), newspaper as well as powdered microcrystalline cellulose (Merck) were biodegraded. All paper materials have been prepared as pieces of 1.0 cm x 1.0 cm before cellulase treatment.

Cellulase assay

P. funiculosum cellulase (E.C. 3.2.1.4 ; Sigma) prepared at a concentration of 10.0 mg / mL in 0.05 M Tris-HCl buffer, pH 4.5 was incubated with the different cellulose materials (10.0 mg / mL enzyme solution) during a 10 h period with regular sugar determinations to construct the glucose formation patterns. Enzyme concentrations ranging from 0.25 - 14.0 mg / mL were used to degrade a fixed cellulose mass while varying substrate amounts (0.25 - 25.0 mg / mL) were incubated with a constant enzyme concentration. Triplicate incubations with a total volume of 1.0 mL were performed at 45ºC and the biocatalytic action was terminated by leaving the incubation mixtures in boiling water for 15 min and these cooled reaction mixtures were then filtered (0.45 µm) with the filtrate used for hplc analyses.

Hplc-analyses

Glucose resulted from cellulase acting on different cellulose materials was determined by hplc using a Supelcosil- NH2 column (Sigma). A 1.0 % H2SO4 solution prepared in hplc-grade water identification and quantification.

RESULTS AND DISCUSSION

Cellulose is described as the most abundant organic source of food, fuel and chemicals with its usefulness depending on its ability to be hydrolyzed to glucose (Henrissat, 1994). P. funiculosum cellulase, a multi-component enzyme system high in beta-glucosidase activity, results in a relative high glucose formation during biodegradation of cellulose materials (Mishra, 1984). During the 10 h incubation period this cellulase showed the highest relative glucose formation when acted on foolscap paper followed by degradation of filterpaper, newspaper, microcrystalline cellulose and office paper. Figure 1 illustrates the relative saccharification trends for the various cellulose materials with no glucose increase after 5 h of enzymatic treatment. At this time of degradation, foolscap paper exhibited 470% more glucose than the amount calculated for office paper with filter paper producing 340 %, newsprint 130 % and microcrystalline cellulose 50 % more glucose than obtained from office paper.

These saccharification curves exhibit distinctive features of cellulose hydrolysis (Wald, et. al, 1984) with the first period characterizing a rapid production of glucose that occurs during the first 3-5 h of hydrolysis. The differentiation in saccharification patterns results from variation in accessibility of the substrates for the enzyme caused by varying crystalline and amorphous sections of cellulose materials (Gharpurray, et. al, 1983).

Increasing paper amounts (Fig. 2) also resulted in increased glucose formation with the maximum glucose production from all cellulose materials observed at a substrate concentration of 20.0 mg / mL. The differentiation in susceptibility of these cellulose materials for the cellulase is supported by the increasing substrate concentration investigation and was proved during the treatment with changing cellulase concentrations (Fig. 3). The high resistance of office paper towards P. funiculosum cellulase catalyzed biodegradation was well illustrated with changing enzyme concentration investigation as no cellulase concentration lower than 8 mg / mL could cause glucose formation from this cellulose material.

From this investigation it can be concluded that waste paper materials are susceptible for cellulase catalyzed saccharification and the differentiation in glucose producing patterns an important variable to consider when tend to optimize the biodegradation process. Besides structural differences the non-similar glucose releasing patterns could also be ascribed to the different manufacturing processes to which each paper product was exposed. Waste paper could thus be utilized as a feedstock for bioproduct(s) development through fermentation of the resulting glucose into bioethanol. The saccharification of wastepaper can be enhanced by the use of cellulase from other resources (Van Wyk, 1998) as well as through the pretreatment of these cellulose materials (Van Wyk, 1997) prior to cellulase catalyzed degradation.

REFERENCES

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