Evaluation of Fungal Xylanase and Lignin Peroxidase in Bio-bleaching of Sugar Cane Bagasse Biopulping

FUNGAL xylanase and lignin peroxidase enzymes were used as pretreatment for biobleaching of bagasse biopulping treated with a mixed culture of Ophiostoma piliferum and Ceriporiopsis subvermispora SS- 33 at 27ºC for one week in MV medium as a static culture before the pulping with propylene glycol ( PG). Some agricultural wastes such as corn cobs, wheat bran, and bagasse powder were used as a sole carbon source for xylanase production. The maximum production of fungal xylanase was attained after 7 days fermentation period on corn cobs medium at 30C on rotary shake flasks at 150 rpm. The enzyme production by Trichoderma reesie NRRL 6156 increased 1.17 fold as compared with that obtained by Trichoderma viride NRRL 13034.Using 10.30 IU xylanase/g bagasse biopulp, produced by Trichoderma reesie NRRL 6156, for 4 h at 50ºC was the best xylanase pretreatment which reduced klason lignin% and increased the brightness % of bagasse biopulp. The solid-state HC- LN medium supplemented with tween 60 and veratryl alcohol in addition to 10 grams of bagasse pulp was the best one for lignin peroxidase production by Phanerochaete chrvsosporium NRRL 6361, the enzyme activity of this treatment (77.75 IU/L) was higher than that obtained using semi-solid (47.75 IU/L) and liquid (36.50 IU/L) state, after 6 days incubation period. The optimum lignin peroxidase dose, for the best biobleaching of unbleached bagasse biopulp at 37C for 8 h was 1.54 IU/g. Using these enzyme pretreatments led to increasing the brightness %, breaking length and tear factor 6.7, 18.89 and 12.7 % by xylanase bleached bagasse (XBB) and 8.94 %, 34.92 and 30.82 %, by lignin peroxidase bleached bagasse (LBB), respectively. The enzyme treatment of LBB and XBB led to a decrease of chlorine consumption 40% and 26.67 % as compared to control. Scanning electron microscope (SEM) of bleached bagasse pulp clearly showed fiber that exposed to enzymes treatment had a more open surface and it becomes more accessible to subsequent bleaching agents. The biological pretreatment of bagasse pulp with xylanase orlignin peroxidase enzymes led to increasing in the crystallinity by 11.29 and 8.3 %, respectively.