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AKAMATSU, Yasumi

HATTORI, Takefumi

SHIMADA, Mikio

TANAKA, Norifumi

Kyoto University Research Information Repository

Title<Preliminary>Effect of Oxalic Acid on the OxidativeBreakdown of Cellulose by the Fenton ReactionAuthor(s)TANAKA, Norifumi; AKAMATSU, Yasumi; HATTORI,Takefumi; SHIMADA, MikioCitationWood research : bulletin of the Wood Research Institute KyotoUniversity (1994), 81: 8-10Issue Date1994-09-30URL http://hdl.handle.net/2433/53252RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityPreliminaryEffect of Oxalic Acid on the Oxidative Breakdownof Cellulose by the Fenton Reaction*lNorifumi TANAKA*2, Yasumi AKAMATSU*3,Takefumi HATTORI*2 and Mikio SHIMADA*2(Received June 1, 1994)Keywords: Oxalic acid, Fenton oxidation, cellulose, viscosity, brown-rot decay.The drastic decrease in viscosity of cellulose at the incipient step of brown-rot wooddecay process was first reported by Cowlingl) and later by Ishihara2). The rapid decreasesin mechanical strengths observed during the brown-rot decal) have been ascribed to therapid breakdown of cellulose in wood.Halliwell first observed that cellulose is rapidly depolymerized by the Fenton oxidation(Fe2+ + H 20 2-Fe3+ + HO- + HO·)4). Koenigs reproduced a similar depolymerization ofcellulose in wood which had been treated with the Fenton reaction and proposed thatbrown-rot fungi attack wood with Fenton type oxidation at an earlier step5). Schmidt et al.proposed that oxalic acid plays a key role in reduction ofFe3+ to Fe2+, which increased thecellulolytic activity (cellulose-C02) of the iron-H20 2 non-enzymatic decay system6 ).However, the higher concentration of oxalic acid inhibited the Fenton reaction; almostconplete inhibition was observed when oxalate/Fe ratio = 10 at I mM Fe6 ). Recently, Barret al. have also reported that oxalate scavenges OH radical produced in a lignin peroxidasesystem7) .Alternatively, the cellulose chain was first demonstrated to be hydrolytically brokendown by a dilute oxalic acid solution8 ). We have reported a possible participation of acidhydrolysis in the faster degradation of cellulose during brown-rot decay since brown-rotterssecrete significant amounts of oxalic acid, thereby lowering the pH in the medium9 ).Recently, Green III et al. have also reported a significant effect of the acid on the breakdownof cotton celluloselO,ll).We report here the effects of various organic acids as physiological metabolites on thehydrolytic and oxidative depolymerization of pulp cellulose. Table 1 shows decreases inviscosity of the cellulose samples which were separately treated with 1% acetic, formic,*1 A part of this work was presented at the 43rd Annual Meeting of the Japan Wood Research Society inMorioka, Aug. 1993.*2 Laboratory of Biochemical Control.*3 The Fukui Prefectural General Green Center, Maruoka, Fukui 910-02.8 -TANAKA et al.: Effect of Oxalic Acid on Fenton OxidationTable 1. Changes in viscosity of pulp cellulose after treatment withvarious organic acids for 4 weeks at 33°C.Organic acid used (pH) Viscosity (cP) (%)Control (5.6) 29.6 (100)Acetic acid (2.8) 26.8 (91)Formic acid (2.2) 27.0 (91)Malic acid (2.4) 27.4 (93)Citric acid (2.3) 27.3 (92)Oxalic acid ( 1.3) 22.0 (75)Note: Coniferous wood pulp (20 g) each was aseptically incubated inI % organic acid solution at 33°C for 4 weeks and viscosities of therecoverd pulp samples were measured by the Tappi standard methodwith cupriethylenediamine hydroxide (TAPPI T230 om-82).malic, citric, and oxalic acid solutions. The results clearly indicate that oxalic acid is thestrongest for depolymerization of cellulose among the organic acids tested, althoughdepolymerization speed is not as fast as that observed with the Fenton degradation (Fig. 1).Fig. 1 shows viscosities of the pulp which was treated with the Fenton type oxidation in>......(/)oc.J(/)>10 L..-.........--J.__--'-__.L..-.........---1.__-Jo 2 4 6 8 10Organic acid (mY).: Oxalate added. 0: Citrate added.6.: Succinate added. 0: Acetate added.- - -: Untreated-pulp viscosity.Fig. I. Effects of various organic acids on changes in viscosity of cellulose during theFenton type oxidation. Note: The reaction mixture (40 ml of distilled water)contained I g of beech pulp (Kappa value; 16.8), 1.5 mM ofH20 2 added, ferricchloride (0.1 mM), and each organic acid (0.1, 0.5, 1.0,2.0,5.0, and 10mM).The Fenton oxidation was initiated by the addition of H 20 2 solution and themixture was incubated for 24 hrs at 30°C with occasional stirring. The cellulosesamples were recovered, washed with distilled water, and treated with NaBH4(50 mg in 33 ml of water). After drying the treated pulps (250 mg dry wt. each)were dissolved in the cupriethylenediamine hydroxide solution and the viscositieswere measured by the T APPI standard method (TAPPI T230 om-82).-9-WOOD RESEARCH No. 81 (1994)the presence of varying amounts of each organic acid in the reaction mixtures. The resultsindicate that although a control system (no addition of an organic acid) reduced the viscositysignificantly (to 85% of the original value), the organic acids affected the degradation ofcellulose by the Fenton oxidation in different ways as follows: a) Citric acid inhibited thedecrease in viscosity with an increase in concentrations of the acid. b) Both acetic andsuccinic acids accelerated the degradation of cellulose. c) Oxalic acid most effectivelyaccelerated the degradation around the region of I mM concetration, whereas it begins tosignificantly inhibit the degradation at the 3 mM concentration, causing a completeinhibition over the range of 5 mM of oxalic acid.The maximal decrease in viscosity, or about 60% of the original value, was observed atI mM oxalic acid (oxalate/Fe = 10), whereas at 5 mM oxalic acid (oxalate/Fe ratio=50) nodecrease in the viscosity was observed. The present results indicate that if the oxalate/Feratio exceeds 50, the Fenton oxidation is inhibited, which is consistent with the previousfindings6 ,7). Alternatively, we observed that the reduction ofFe3 + to Fe2 + by oxalate is notprerequiste for causing the Fenton reaction, as can be seen in the control sytem withoutoxalate added (Fig. 1). However, since the oxalic acid-mediated hydrolysis of cellulose(Table 1) is a very slow step, it is also important to investigate the breakdown ofhemicellulose and lignin carbohydrate complex during the brown-rot wood decay process toaccount for the rapid loss of the mechanical strengths of brown-rotting wood. Thus, theamount of oxalic acid produced in the decaying wood may control the oxidative degradationof wood components in either a positive or negative way.References1) E.B. COWLING: USDA, Forest Servo Tech. Bull., No. 1258, 1-79 (1961).2) M. ISHIHARA: Ph.D. Thesis (Kyoto University), pp.107 (1986).3) W.W. WILCOX: Wood and Fiber, 9, 247-252 (1978).4) G. HALLIWELL: Biochem. j., 95, 35--40 (1965).5) j.W. KOENIGS: Wood and Fiber, 6, 66-80 (1974).6) CJ. SCHMIDT, B.K. WHITTEN and D.D. NICHOLAS: Am. Wood Preserv. Assoc., 77, 157-164 (1981).7) D.B. BARR, M.M. SHAH. T.A. GROVER and S.D. AUST: Arch. Biochem, Biophys., 298, 480--485 (1992).8) M. SHIMADA, Y. AKAMATSU, A. OHTA and M. TAKAHASHI: Intern. Res. Group/Wood Preserv. Document, No.IRG/WP 1472 (1991).9) H. SHIMAZONO, H:j.Jpn. For. Soc., 33, 393-396 (1951).10) F. GREEN III, MJ. LARSEN, j.E. WINANDY and T.L. HIGHLEY: Material und Organismen, 26, 191-213(1991).11) F. GREEN III,j.M. HACKNEY, C.A. CLALUSEN, MJ. LARSEN and T.L. HIGHLEY: Intern. Res. GrouplWoodPreserv. Document, No. IRG/WP/10028 (1993).- 10-

<Preliminary>Effect of Oxalic Acid on the Oxidative Breakdown of Cellulose by the Fenton Reaction

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<Preliminary>Effect of Oxalic Acid on the Oxidative Breakdown of Cellulose by the Fenton Reaction

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