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Jou rn al of Scientifi c & Industrial Research Vol. 6 1. May 2002, pp 376-38 1 Biopulping and Biobleaching by White Rot Fungi Samia M He lmy* and Magda EI-Me li gi Mi crobial Chem istry Depa rtm ent . Cel lul ose and Paper Departme lll , Nati onal Research Celller, Dokki , Cai ro. Egy pt Received: 2 1 August 200 I: acce pt ed: 19 February 2002 The potentials of whit e-rot fungi namel y Co ri ol/ls versicolor NRRL 6102, Ph anerochaele chrysosporiul/1 NRRL 6359, P. chn' soSlloril/lII NRRL 636 1 and P. chrvsosporilllli NRRL 6370 are eva lu ated fo r bri ghtness of banana waste. The banana fruit sta lk is used as a sa le carbo n source under ste rili zed so lid state ferment ation (SSF) at 35°C for one mon th . Of th ese. P. C hl )'.\·osfiorilllll NRRL 6370 cultured supported max imum bri g htn ess (3 0.5 per cent th an under COlli ro I 17. 8 per cen t ). Thi s fun gus degrades li gnin and he mi cel lul ose with does not e ffect on cellulose fibres (55.4 per celli th an LInd er co ntrol 40.0 1 per cent). Th e three usef ul types of paper are prepar ed from biopu ling banana fruit sta lk . The two types f th em are bleached by hydrogen perox id e (writing and printing 40 SOR and greasy paper 80-82 SOR). Whil e th e boa rd is pr pa r ed from unbleached biopulping ill 25 SOR. Th e streng th properties of biopu lping in creases from 15-20 per cent for the ha nd-m ade sheet. Also th e brightness is hi gher. i.e. , > 2{) per cent th an under control. Results show th at biop ul pi ng cOlllro ls yield and avo ids losses in viscosity a nd streng th properties . Introduction Us in g agricultural residues is replacement source for wood raw materials for manufacturing paper pulp, th ereby avoiding serious risks of deforestation and decreas in g environmental problems a ri si ng from fires and pes t. Sa iki a el al . 1 have used th e three wi ld ban a na spec ies in th e formation of paper sheet from pulp (pulp freeness 45 SOR) has hi gh strength prope rti es fo r writing and printing paper, while paper shee ts prepared to a pulp freeness of 90 SOR showed good greasy prope rti es. Yamaza ki el al. 2 ha ve shown that th e additi on of banana stem wastes to th e straw improves th e strength prope rti es of th e res ultin g pulp. Th e bi ological pulping has th e potential to improve th e quality of pulp and th e prope rti es of paper a nd to redu ce th e energy cos ts and enviro nmental impact relative to traditi onal pulping operation,·7. The technology focuses on th e white rot fungi, which have co mpl ex ex tra- cellul ar li gninolytic enzyme syste ms that can se lec ti ve ly remove or a lt er li gnin and produces cellulose fibres. These enzy me systems are li gnin peroxidase, manganese peroxidase, a nd laccase). Arbeloa el al . R ha ve eva lu ated th e potencies of li gnin perox id ase from Ph{/nemchaete cllIysosporillll/ impro ve bl eac habi lit y of kraft pu lps. * Author for correspondence In th e prese nt study th e bi odegradation of banana waste was used to produce di ffere nt types of use ful papers such as boa rd , writin g, printing, and greasy pape r. Whereas th e biopu lping mainta in ed pulp yie ld and avoided losses in viscosity a nd streng th prope rti es . Materials and Methods (i) Raw Mat erial Banana fruit sta lk s were co ll ected from market and kaolin , a nd rosin size were de ri ved form Rakta company in Al ex. (ii) Organisms and ClIlll/res Four white-rot basidiomycetes, na me ly Coriollls I 'e rsicolor NRRL 6 102, Phan eme/wete chr yso- sporium NRRL 6359, P. chrvs()sp orilll11 NRRL 6361 and P. c hrvsosporillll1 NRRL 6370 were obtained from Departme nt of Agriculture, Research Service. Peoria, Illino is , USA. The or ga ni sms were mainta in ed on yeast ex tract-ma lt ex tract agar. The med ium co nt a in (giL) malt agar. Difi co, 4.0, glucose 4.0, yea st ex tract 4.0, di still ed water up to IL, a nd agar 20.0 th e pH (6.4)9 The four white-rot fungi were co mp ared for th eir potential as de li gnifi cation agricu ltural waste to obtain maximum brightness. They brew on banana fruit sta lk under SSF and sterilized conditions. On milliliter of each heavy spore's fun gus was us ed to inocul ate steri le test tube (30 mm x 190) containing ,.
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Page 1: 377 - NISCAIR

Jou rnal of Scientifi c & Industrial Research

Vol. 6 1. May 2002, pp 376-38 1

Biopulping and Biobleaching by White Rot Fungi Samia M Helmy* and Magda EI-Meligi

Mi crobial Chemistry Department . Cel lulose and Paper Departmelll , Nati onal Research Celller, Dokki , Cai ro. Egypt

Received: 2 1 August 200 I: accepted: 19 February 2002

The potentials of white-rot fungi namel y Coriol/ ls versicolor NRRL 6102, Phanerochaele chrysosporiul/1 NRRL 6359, P. chn'soSl lo ril/lII NRRL 636 1 and P. chrvsosporil llli NRRL 6370 are eva luated fo r bri ghtness of banana waste. The banana fruit sta lk is used as a sale carbon source under sterili zed so lid state fermentation (SSF) at 35°C for one mon th . Of these. P. Chl)'.\·osfiorilllll NRRL 6370 cultured supported max imum brightness (30.5 per cent th an under COlli ro I 17.8 per cent). Thi s fun gus degrades li gnin and hemi cel lulose with does not effect on cellulose fibres (55.4 per celli th an LInder control 40.0 1 per cent). The three useful types of paper are prepared from biopu ling banana fruit stalk . The two types f them are bleached by hydrogen perox ide (writi ng and printing 40 SOR and greasy paper 80-82 SOR). Whil e th e board is pr pa red from unbleached biopulping ill 25 SOR. The strength properties of biopu lping increases from 15-20 per cent for the hand-made sheet. Also the brightness is hi gher. i.e. , > 2{) per cent than under control. Results show that biopul pi ng cOlllro ls yield and avoids losses in viscosity and strength properties .

Introduction

Us ing agr icultural res idues is replacement source for wood raw materials for manufacturing paper pulp, thereby avoiding serious risks of deforestation and decreas ing environmental problems ari si ng from fires and pes t.

Saiki a el al .1 have used the three wi ld banana spec ies in the formation of paper sheet from pulp (pulp freeness 45 SOR) has hi gh strength properties fo r writing and printing paper, while paper sheets prepared to a pulp freeness of 90 SOR showed good greasy properties. Yamazaki e l al. 2 ha ve shown that the additi on of banana stem wastes to the straw improves the strength properti es of the resulting pulp.

The bi ologica l pulping has the potential to improve the quality of pulp and the properties of paper and to reduce the energy costs and environmental impact relative to traditi onal pulping operation,·7. The technology focuses on the white rot fungi, which have complex ex tra- cellul ar li gninolytic enzyme systems that can se lecti vely remove or alter li gnin and produces ce llulose fibres. These enzyme systems are li gnin peroxidase, manganese peroxidase, and laccase). Arbeloa el al .R have eva luated the potencies of li gnin perox idase from Ph{/nemchaete cllIysosporillll/ improve bleac habi lity of kraft pu lps.

* Author for correspondence

In the present study the biodegradation of banana waste was used to produce di fferent types of useful papers such as board , writing, printing, and greasy paper. Whereas the biopu lping maintained pulp yield and avoided losses in viscosity and strength properties .

Materials and Methods

(i) Raw Material

Banana fruit sta lks were co ll ected from market and kaolin , and rosin s ize were deri ved form Rakta company in Alex.

(ii) Organisms and ClIlll/res

Four white-rot basidiomycetes, namely Co riollls I'ersicolor NRRL 6 102, Phaneme/wete chryso­sporium NRRL 6359, P. chrvs()sporilll11 NRRL 6361 and P. chrvsosporillll1 NRRL 6370 were obtained from Department of Agriculture, Research Service. Peoria , Illinois , USA. The organisms were maintained on yeast extract-malt extract agar. The med ium contain (giL) malt agar. Difico, 4.0, glucose 4.0, yeast extract 4.0, distilled water up to I L, and agar 20.0 the pH (6.4)9

The four white-rot fungi were co mpared for their potential as deli gnifi cation agricu ltural waste to obtain maximum brightness . They brew on banana fruit stalk under SSF and sterilized conditi ons. On milliliter of each heavy spore's fun gus was used to inoculate steri le test tube (30 mm x 190) containing

,.

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HELM Y & EL-MELlGI: BIOPULPING & BIOTECHNOLOGY BY WHITE ROT FUNGI 377

2.0 mL di stilled water and 15 .5g of banana fruit sta lk as substrate . The inoculated tubes were incubated at 35°C for one month and the brightness degree was examined every week to find out the optimum durati on of effic ient funga l incubati on.

(iii) Chemical Analysis of Banana Waste

The banana waste was chemicall y ana lyzed before and after bi opulping and bleaching fo r

ho ll owcellul ose 'o and average molecular weight ". u­cellul ose and extractible hemicellul ose, kl ason li gnin , and ash content were tested , according to method suggested by Caseyl 2.

(iv) Bleaching

Biopulping and contro l of banana fruit sta lk were bl eached by hydrogen perox ide in two stages . The bleachi ng mixture in each stage is contained 4 per cent hydrogen peroxide, 0 .5 sodium silicate, and 0 .1 Mg S04, the pH ( 10- 1 I ) was adjusted additi on by NaOH. It was furth er kept at 75°C for 1.5 h. The pul p was was hed thoroughl y with water after each stage.

(v) Details nf Paper Manufacture

(a) Prepar ation of Board ( ISO g/m2) - Unbleached pul p was beaten in Jordan beate r at 3.6 consistency till it atta ined 25 SOR . (b) Preparation of Writing and Printing Paper (60glml) -

Bleached pulp was beate n till it reached 40 SOR and during sheet fo rmation so me additi ves were added such as, 10 per cent kao lin and 2 per cent ros in size 10 per cent alu minum sulphate was added till pH 4.5 was obtained.

(c) Preparatioll of Greasy Paper (45g/ml) - B leached pulp was beaten till it reached 80-82 SOR.

The paper sheets were prepared accord ing to T APPI standard methods using the sheet fo rmer of A B Lorentzen und Wett re (Stockholm, Sweden). T he produced papers were cond iti oned for 24 h at 20°C and SOper cent RH .

(v i) Examination of Physica l Properties

T he optica l properties suc h as , brightness and opac ity were examined by Hu nterlab co lour/di fference Meter 025-2. Also the strength properties such as tensil e strength were measured by Ametek Ll oyd inst ruments 1996, bursting st rength by Mullen tester B F P Perkins and tearing res istance by Elmendorf Tearing Tester. T he tensi le strength can be converted to the break ing length by cons idering the basis we ight and strip length . Whereas the strength

properties optica l properties, and sizeability were measured according to method of Casey l2.

Results and Discussion

(i) Screen ing of Whi te-rot Fungi for Ability to Remove Lignin

A comparati ve study was undertaken us ing fo ur stra ins of white-rot fung i to obta in the highest percentage of brightness. T hese stra ins were screened on banana fruit stalk as a so le carbon source under SSF, incubated at 35°C fo r one month. We examined the ir susceptibility fo r biopul pling peri odicall y during I to 4 weeks. It showed that the brightness increased corresponding to increase time of incubati on except in the case of C. versicolor NRRL 636 1, as shown in Figu re I . The time work agreed with experimental work by Gary et al." Phanerochaete chrysosfJorium NRRL 6370 was observed to be the most effic ient in per cent of bri ghtness 30.5per cent than cont ro l 17.5 per cent. Figure I . Tabl e I shows that P.chrysosfJorium RRL 6370 degraded lignin ( 10 per cent) as compared with contro l ( 17.6 per cent). Thi s result was confirmed by Arbeloa el.al. 8 who evalu ated the potenc ies of lignin perox idase fro m P.chrysosfJorium in red uced lignin content. The most mi croorgani sms fo r ligni n degradation are those that can produce xy lanases and phenylox idases. The fo rmer degrade xy lane to xy lose (a sugar req uired to sa ti s fy microb ial energy requirements) and the latter take part in lignin degradati on '4 . The xy lose is one of the structure of hemicellul ose, thi s is sugar requ irement to microb ial

120.0

P.chrysosporfum P.ctvysosporium P.cllrysosporlum c.v8f'31co1or

NRRl6359 NRRl6.36f NRRl6370 NRRl6f02

MiCloorganisms

o 4th week

0 3rdweek m2nd week . 1st week

Fi g. I - Screening of white- ro t fu ng i fo r th e ir effi cacy of bri ght ne,s on banana waste (ss t) incubaleci

Page 3: 377 - NISCAIR

378 J SCIIND RES VOL 6 1 MAY 2002

energy attributed to degrade li gninl5

. T his results in decrease in the he micellulose ratio compared with control ( 19 .2 per cent to 28 per cent). The fungus degraded li gnin and hemicelluloses did not have any effect on cellul ose fibres bound by them (55.4 per cent inocul ated , 40.1 per cent control). Also ash content of inocul ated was less than contro l (6.2 per cent , 11 .8 per cent respective ly) which gave a bri tt le pulpl 2.

(ii) Mechanical Properties of Boardfrom Banana Pulp and Other Wastes ( 150g/m2)

Figures 2-4 show that the strength properties of biopulping were hi gher than untreated pulp, similar trends are reported by Oriaran et al.

16. This result was

Tab le 1- Analysis of pu lpi ng banana waste before and after inoculated by P. cllI}'sosporiUlu NRRL 6370 at 35°C for one

month

Experiment Untreated Treated

Holloweellulose per cent 68.1 74.6

u- Cellu lose per cent 40.1 55.4

Extractible hemicellulose per cent 28 19.2

Kl ason li gnin per cent 17.6 10

Ash content per cent I 1. 8 6.2

Note: The brightness of untreated banana waste was 17.8 per cent but the brightness of treated banana waste was 30.5 per cent

"e e;, :i. :c-o, c ~ iii ~ 'iii c CI)

t-

16

14

12

10

Samples

DTensile sample .Tensile control

Fi g. 2 - Tensile strength of board from banana waste & other wastes ( 150 g/m2)

attributed to decrease in ash and lign in content (Table 2). The board from blended banana waste with pulp of magazine waste had good strength properties (Tens ile strength 7.3, burst strength 3, and tear resistance 125) compared with other different board patterns. Since the pulp of magazine waste is a chemical pulp and this contains some percentage of

2 3 4 5

Samples

Fig. 3 - Burst strength of board from banana waste & other wastes (150 g/m2)

250

200

OJ W u s:: CIl iii 'iii CIl .... .... CIl CIl t-

50

a 2 3 4 5

Samples

Fig. 4 - Tear resistance of board from bana waste & other wastes ( 150 glm2

)

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HELM Y & EL-MELlGI: BIOPULPI NG & BIOTECHNOLOGY BY WHITE ROT FUNGI 379

lignin and higher percentage of cellul ose if compared with a pulp of cotton stalk and Rossella . Also the pulp of newsprint contains hi gher percentage of li gnin compared with pulp of magazine. The blended board from banana waste with newsprint waste is higher than board from banana waste with Rosse ll a or cotton stalk, as shown in Table 2.

From these results, we observed that the additi on of banana waste to di ffe rent wastes improved the strength properties of these res idues

2.

(ii i) Hand-made Sheetsfor Writing and Printing Paper (60g/nl)

Banana waste, e ither inocul ated or uninoculated, was bleached in orde r to obtain a suitable paper fo r writ ing and printing. We used hydrogen perox ide fo r bleaching after biopulping in order to bri ght character of paper. T able 3 illustrates that decrease in li gnin , hemicellulose and ash content of bi opulping banana waste after bleaching (2.8 per cent , 13.9 per cent, and 18 per cent , respecti ve ly) . The hydrogen perox ide under certain conditi ons formed perhydroxy l ion (-OOH-) which was capable of further degrading quin oid lignin structures and c hanging li gnin into small fragments di sso lved in it bleachi ng mi xture l 7

Also, hydrogen perox ide had severely degraded to the

hemicellulose ( low-molecul ar weight) to a certain ex tent' 8.

E nzymatic pretreatment with xy lanase from P. chrysosporium NRLL 6370 improves bleachab ili ty of banana waste l9

. The results have shown strong dependence of prebleaching e ffect on end products. The enzyme maintains pul p yie ld and avoid loss in viscosity and strength properties whic h was a lso confirmed by Gliese et al.20

.

(iv) Physical Properties of Hand-made Sheet from Bleached Banana Was te (60g/n/)

T able 4 shows th at the strength prope rties of

inocul ated pulp are hi ghe r th an uninocul ated pul p

Tab le 3 - Analysis of bleaching biopu lping banana waste by hydrogen perox ide

Experi ment Uninoculated Inocu lated

Holl owcellulose per cent 84.2 90

a- Cellulose per cent 63.2 76.1

Extractible hemicellulose per cent 2 1 13.9

Kl ason li gnin per cent 5.2 2.8

Ash content per cent 3.7 1.8

A vcrage mo lecular weight 795 .6 818

Waste

Table 2 - Analysis of using wastes blend with banana waste

Analysis

Magazine wast e

ewsprint waste

Colton stal k

Rosel le stalk

a-cellulose per cent

75

59

56.6

50.4

Hemi cellul ose per cent

12.5

18.5

22.2

24

Li gn in per cent

1.4

20

24

22

Ash co ntent per cent

8

1.3

2

2.6

Table 4 - Physical properti es of hand- made sheets (60g/1112) of bleaching hi opulpi ng wit h or without additives

Test

Brightness per cent

Opacity per cen t

Tensile strength (kg)

Breaking lengt h (m)

Tearing resistance (g)

Burst strength (kglcm2)

Sizeabi lity (~ec )

Blank

70.5

85.7

6

2358.5

92

2.4

Inocu lated

With add it ives

70.5

87. 1

4.5

1767X

80

1.9

12- 13

ote: The addi ti ves were 10 per cent kao li n and2 per cent rosi n size

Uni nocu lated

Bl an k With dditives

48.6 48.6

90.3 92. 1

5.1 3.4

2002.2 1336.9

76 70

2 1.5

12- 13

Page 5: 377 - NISCAIR

380 J SCI IND RES VOL 6 1 MAY 2002

Table 5 - Ph ysical properties of greasy paper (45g/m2) from bleached biopulp banana waste

Test Uninocul ated Inocu lated

SOR 80-82 80-82

Brightness per cent 48 70.5

Opacity per cent 75 .6 71.4

Tensi Ie strength (kg) 3.5 4.7

(tens il e strength 6, 5.1 ; burstin g strength 2.4, 2.0; tearin g res istance 92 and 76, res pect ive ly). These results are in agreement with th ose obtained by Myers et. 0/

2 1. The inoc ul ated sample gave more

brightness th an unin oc ul ated ones (70 .5 per ce nt and 48.6 per cent , respect ive ly) which is confirmed by Lu ef a I . 22 . The strength properties dec rease a fter addition of add iti ves (Tab le 4). Since the addition of fill er (Kaolin) cann ot form hydrogen bonds, hence it reduces th e strength by bl ockin g fibre to fibre bonds and ros in s ize wh ich gives brittl e pUlpl 7 Simil arl y th e opac ity increases after additio n of add iti ves , s ince th e fi ll er (Ka olin ) fill s the space betwee n fibre fo rmin g fibre-fill er bo ndin g and th e s izeab ility inc reases due to add iti on of ros in size whi ch gets prec ipitated as a luminum res in ate at pH 4.5 which makes the paper parti a ll y hydrophobic, and thus prevents the

d· f' k 17 sprea Ing 0 In . Generall y, banana waste has hi gher strength

properti es due to its hi gher fibre length. The fibre length of banana pulp range between 4.5 to 5 em, while the long fibre of bl eaching wood pulp range betw~en 1.2 to 1.5 cm2

.1 .

(v) Production of Greasy Paperfrom Bleached Banana Waste (45g/I1/)

The banana pl ant has a specia l character compared with other agri culture residues at hi gher beating, whereas it produces greasy paperl.

Tn thi s study greasy paper (45 g/1ll1) was produced from bleached banana waste (e ither inoculated or uninocu lated) at 80-82 SDR. The tensil e strength of banana (4.7 kg than cont ro l 3.5 kg) cannot be affected by hi gher beating due to its content hi gher long fibre21

. The opac ity ranged from 71.4 per cent-75 .6 per cent of inocul ated and uninocul ated pulp, respec ti vely (Table 5).

The production of greasy paper from biopulping banana waste reduced costs and env ironmental impact, compared to traditional pUlping operations.

References

Saiki a 0 C, Goswami T & Saikia C N, Wild banana plants (Musa spp.) as source of liber for pa er and cordage industri es , J Sci Ill d Res. 56 (7) ( 1997) 408-4 13.

2 Yamazak i H, Kuril a T, Miyazak i K, Yokomizo H & M orimoto M, Pu lping and papermaking properti es o f the libers from abaca (Musa tex til es) and other Musa species, Kalll i Pa Cik\'oshi, 34 (4) ( 1980) 299-3 15.

3 Nishida T & Tsutsumi Y , Lignin biodegradati on by wh ite­ro t fungi and it s app li ca tion , recent research . Del' Microbiol, I ( 1997) 23 1-253.

4 Christov L P& Prior B A, Research in hiot 'chnology ror the pulp and paper industry in South Afric3. Sowh Afr J Sci, 94 (4) ( 1998) 195-1 99.

5 Breen A & Singleton F I, Fungi in lignocell ulose brcakdown and biopu lping . Cllrr Opill Biotechllol, 10 (3) ( 1999) 252-258.

6 Andre F, Jaimc R, Juanita r & Jaime B, Formi c acidl acetone-organosol v pu lping of white-rotted. J Chelll Tecllllol Biotechl/ol, 25 ( 12) (2000) I 190- 1 196.

7 Andre F, Regis M & FI,\vio T dJ Si lva, Organo~o l v delignili cation of white-and brown-rolled Ellcalrplii s gralldi.\·, .! Chelll Techllol /Jiotechl/o l, 75 ( I ) (2000) 18-24.

8 Arheloa M, De Icseleuc J, Goma G & Pommier J C. An evaluation of the potentiJI of l igbnin perux idases to improve pulps, TAPPI.!, (M arch 1992) 2 15.

9 Methods manual , internati onal coopcr:1ti\'e project lor description and deposit ion of type cu ltures or Streptomycetes, ISP: 1964, 1966 and 196,'.

10 Jayme G, Preparation of hollowcellu losc with soLliul1l chlorit e, Celllliose Chi'lII , 20 ( 1942) 43.

II Brown W & Wikstrom R. Determinat ion the degree of po lymerizJ ti on, Ellr PoIYIII.I , I ( 1965) 1-10.

12 Casey J P. Paper testill g alit! cOII\ 'l'r1illg ill pllifl (Il1d papl' l" , 3. 3rd cd (Intcrsciencc Publi sher. ew York) 19RI, 171 4-1965.

13 Gary F L , Gary C M & Theodore H W. Bi omechan ical pulping or aspen chips: paper strength and opti ca l properti es result ing rrom different funga l treatments. TA PPI .! ( 1990) 249-255.

14 Eriksson K E, Reccnt developments in hiolechnology in the pulp and paper industry, lJiollla.\·s, 15 ( 19RH) 117-19.

15 Eriksson K E L & Athens G A, Biotechnology in the pul p and PJper industry, lVood Sci Techllol, 24 ( 1990) 79- 10 I .

16 Oriaran T P, Labosky P Jr & Blanken horn P R, Kraft pulp and paper making properti cs of Phancrochacte chrysospo­rium-degraded red Qak, Woot! Fiher Sci. 23 (3) ( 1991 ) 316-327.

17 Ulllllal/lI 's, ellcycl0fl edia 0/ illdllstrial chcllli.Hr" (VCH, Verlagsgeshchaft, mbH, 0 -6940, Weinheim) 199 1,6 16.

Page 6: 377 - NISCAIR

HELMY & EL-MELlGI : BIOPULPING & BIOTECHNOLOGY BY WHITE ROT FUNGI 38 1

18 Smook G A, Handbook for pulp alld paper technologists (Angus Wiled Publicati ons, Vancouver, Bellingham) 1992, 2 10-2 11.

19 Sami a M Helmy & Nadi a H Abd EI-Nasser, Enzymes produ ced by some white-rot fun gi on banana fruit stalk waste and it s appli cati ons, Arab Univ J Agric Sci, 9 (2) (200 I) 569-58 1.

20 Gli ese T & Kleemann S, Einflup ausgewahlter reakti on­sparameter enzymati scher bleichstu fe n auf bleichbarkeit und zell stoffeigenschaften, Wochenblall Papieljabrikation, 123 ( 1111 2) ( 1995) 526-532.

2 1 Myers G C, Leath am G F, Wegner T H & Blanchette R A, Fungal pretreatment of aspen chips improves strength of refin er mechanical pulp, TA PPI J, 71 (1988) 105-1 09.

22 LU X M, Jan J L, Gao P J & Liu G L, Biomechan ical pulping of Paul owni a elongata chi ps treated with Phanerochaete cll/ysosporilll/'l and its lip-negati ve mutant lip-1 4, Bioi Sci Symp , (4 17 TAPPI , Press, Atl anta Ga) 1997.

23 Maha Mohamed Ahmed Ibrahim, Effect of differellt structures of different types of banana on physical alld chemical properties of produced pllipes, Ph D Thesis, Helwan Uni versity, 1996.