Bleach Enhancement of Mixed Wood Pulp by Xylanase–Laccase Concoction Derived Through Co-culture Strategy

Abstract

Mixed enzyme preparation having both xylanase and laccase activity was evaluated for its bleach enhancing ability of mixed wood pulp. The enzyme was produced through co-cultivation of mutant Penicillium oxalicum SAU(E)-3.510 and Pleurotus ostreatus MTCC 1804 under solid-state fermentation. Bleaching of pulp with mixed enzyme had resulted into a notable decrease in kappa number and increased brightness as compared to xylanase alone. Analysis of bleaching conditions had denoted that 8 IU g(-1) of mixed enzyme preparation (xylanase/laccase, 22:1) had led into maximal removal of lignin from pulp when bleaching was performed at 10% pulp consistency (55 degrees C, pH 9.0) for 3 h. An overall improvement of 21%, 8%, 3%, and 5% respectively in kappa number, brightness, yellowness, and viscosity of pulp was achieved under derived bleaching conditions. Process of enzymatic bleaching was further ascertained by analyzing the changes occurring in polysaccharide and lignin by HPLC and FTIR. The UV absorption spectrum of the compounds released during enzymatic treatment had denoted a characteristic peak at 280 nm, indicating the presence of lignin in released coloring matter. The changes in fiber morphology following enzymatic delignification were studied by scanning electron microscopy.

Production of thermo-alkali-stable laccase and xylanase by co-culturing of Bacillus sp. and B. halodurans for biobleaching of kraft pulp and deinking of waste paper

“…Thakur et al [33] and Valls et al [9] investigated the sequential xylanase and laccase prebleaching effect on kraft pulp by using either commercial or fungal enzymes having different optimum conditions. Combined biobleaching effect of xylanase and laccase, coproduced using Penicillium oxalicum SAU E -3.150 and Pleurotus ostreatus MTCC 137, on mixed wood pulp was reported with 21 % reduction in kappa number, 8 % increase in brightness, and 5 % increase in pulp viscosity [34]. No report is known on combined effect of xylanase and laccase on kraft pulp.…”

Mixed Enzyme Systems for Delignification of Lignocellulosic Biomass

“…Xylanase and laccase are readily commercially available and thus are the primary focus of this discussion. Xylanase exposes lignin which can be degraded by laccase with a mediator [16]. The simultaneous application of the two classes of enzymes, in the context of pulp delignification, could be incorporated into most bleach plants without significant capital investment.…”

“…Penicillium oxalicum and Pleurotus ostreatus were co-cultured for xylanase and laccase, respectively, via solid-state fermentation in an intermittent rotating bioreactor [16]. The obtained laccase-xylanase mixture was applied at 8 units/g od pulp in a ratio of 22:1 xylanase:laccase to a 60:40 eucalyptus:poplar pulp mix.…”

“…In contrast, a xylanase only treatment provided just a 4% reduction in kappa (to 13.4) and a 4% increase in brightness (to 37.0 ISO). The investigators proposed that the synergistic action of xylanase and laccase caused simultaneous dissociation and degradation of lignin into smaller phenolic compounds, resulting in more effective delignification of pulp [16]. The action of xylanase and laccase also resulted in improved fiber quality: the fiber morphology after enzyme treatment exhibited greater porosity, swelling, separation, and peeling of pulp fibers in comparison to the smooth surface of untreated pulp [16].…”

Delignification Process of Agro-Industrial Wastes an Alternative to Obtain Fermentable Carbohydrates for Producing Fuel

“…Finally, the use of crude extracts from ligninolytic fungi has shown to be a promissory alternative for delignification. Crude extracts from Aspergillus niger, A. niveus, and A. ochraceus, containging xylanases, allowed a 20% delignification of cellulase pulp in 2 h (Betini et al, 2009), while a crude extract of Penicillium oxalicum and Pleurotus osteatus, containg xylanase and laccase enzymes, produced a 21% delignification of wood pulp in 3 h (Dwivedi et al, 2010).…”