New Pulp Biobleaching System Involving Manganese Peroxidase Immobilized in a Silica Support with Controlled Pore Sizes

Abstract

Attempts have been made to use manganese peroxidase (MnP) for chlorine-free pulp biobleaching, but they have not been commercially viable because of the enzyme's low stability. We developed a new pulp biobleaching method involving mesoporous material-immobilized manganese peroxidase from Phanerochaete chrysosporium. MnP immobilized in FSM-16, a folded-sheet mesoporous material whose pore size is nearly the same as the diameter of the enzyme, had the highest thermal stability and tolerance to H 2 O 2 . MnP immobilized in FSM-16 retained more than 80% of its initial activity even after 10 days of continuous reaction. We constructed a thermally discontinuous two-stage reactor system, in which the enzyme (39°C) and pulp-bleaching (70°C) reactions were performed separately. When the treatment of pulp with MnP by means of the two-stage reactor system and alkaline extraction was repeated seven times, the brightness of the pulp increased to about 88% within 7 h after completion of the last treatment.

Proteins in Mesoporous Silicates

“…Others have also advocated that a snug fit inside the pores was desirable. [63][64][65][66] Smaller pore entrances can also improve overall catalytic activity by reducing leaching; for example, MCF materials with smaller pore entrances exhibited better stability, activity, and recycling properties than materials with larger entrances for an immobilized antibody in organic solvents. [67] However, there must be room for the substrate to have access to the protein, as limitations on the substrate diffusion rate can reduce the overall activity of the immobilized enzyme.…”

“…[64,68] The hydrophobicity or hydrophilicity and size of the substrate will have a very strong influence on the catalytic activity of the immobilized enzyme. [46,64,66] If the substrate is hydrophobic, diffusion through the channels of a hydrophilic mesoporous silica structure may be slow. Larger pore sizes may compensate for this mismatch, with higher diffusion rates than for smaller pores.…”

“…Of the enzymes immobilized on mesoporous materials, only approximately one third have been examined for their ability to be recycled, and activity losses occur in each cycle in many of these cases. [b] Reuse cytochrome c [64,73,108] no higher enhancedmicroperoxidase-11 [118] no less --lysozyme [84,86] no ---trypsin [41,112,114,126,127] no higher higher [c] enhanced enhanced [c] yes organophosphorus hydrolase [45,91,92] no higher enhanceda-chymotrypsin [57,63,116] no less enhanced yes horseradish peroxidase [62,73] higher [c] enhancedchloroperoxidase [65,90,93,94,106] no less [c] enhanced yes manganese peroxide [66] active enhanced yes papain [27,117] no less enhanced yes pepsin [73] ----bovine serum albumin [71,73] ----subtilisin [62,73] higher [c] enhancedmyoglobin [71,127] ----metmyoglobin [128] higher [c] --hemoglobin [109,110] higher [d] enhanced yes [c]…”

“…If not, it will adsorb only [66] --FSM-16 3-9 papain [27,117] 8. 75 3.7 3.7 5.0 MCM-41, MCM-48 4, 6.2 pepsin [73] < 1 33 kDa…”

New families of mesoporous materials

“…Adsorption of proteins to mesoporous materials, especially to mesoporous silica, has been rapidly paid attentions [169][170][171][172][173][174][175][176][177][178][179][180][181][182][183][184][185]. As shown below, Vinu et al provide systematic researches on protein adsorption onto mesoporous materials [96,[186][187][188][189][190][191][192][193][194][195][196].…”