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This paper implies production of cellulase and xylanase enzyme using a potent strain of Trichoderma harzianum for the efficient deinking of photocopier waste papers. Different nutritional and environmental factors were optimized for higher production of cellulase along with xylanase. After fermentation, maximum enzyme extraction was achieved from fermented matter using a three-step extraction process with increased efficiency by 26.6-29.3 % over single-step extraction. Static solid state was found as the best fermentation type using wheat bran (WB) as carbon source and ammonium ferrous sulfate (0.02 M) as nitrogen source. Subsequently, inoculum size (8 × 10(6) CFU/gds), incubation days (4 days), temperature (34 °C), initial pH (6.0), and moisture ratio (1:3) significantly affected the enzyme production. Cellulase and xylanase activities were found to be maximum at pH 5.5 and temperature 55-60 °C with good stability (even up to 6 h). Furthermore, this crude enzyme was evaluated for the deinking of photocopier waste papers without affecting the strength properties with improved drainage as an additional advantage. The crude enzyme-deinked pulp showed 23.6 % higher deinking efficiency and 3.2 % higher brightness than chemically deinked pulp. Strength properties like tensile, burst indices, and folding endurance were also observed to improve by 6.7, 13.4, and 10.3 %, respectively, for enzyme-deinked pulp. However, the tear index was decreased by 10.5 %. The freeness of the pulp was also increased by 21.6 % with reduced drainage time by 13.9 %.

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The utilization of post-consumer papers in the production of new paper products is increasing all over the world in recent years. Recycling of photocopier paper is a major problem due to difficulty in removal of non-impact ink. Enzymes offer potential advantages in ecofriendly deinking of recovered paper. In this study the deinking of photocopier paper was examined using chemicals and a commercial cellulase enzyme. Parameters of deinking experiments were optimized for hydrapulping. The ink was removed by flotation and washing processes. Then these parameters were compared in terms of ink removal ability of the process, as well as optical and strength properties of the deinked paper. The application of enzymatic deinking improved ink removal efficiency by 24.6% and freeness by 21.6% with a reduction in drainage time of 11.5% in comparison to those obtained with chemical deinking. The physical properties, namely burst index and tensile index, were observed to improve by 15.3% and 2.7%, respectively and brightness and tear index decreased by 2.1% and 21.9%, respectively. Results of deinking efficiency of photocopier paper showed that the enzyme used in the present work performed better than the conventional chemicals used for deinking.