(1) What kind of cellulase is the best for deinking, acidic, neutral, or alkaline?
There is no definitive answer to this question. With acid-sized (sulfite) paper, we obtained good results using a Trichoderma reesei cellulase (acid). With alkaline sized papers, we had to adjust the pH range to within the activity range of the enzyme. It was more economical to use an enzyme with neutral activity (Humicola insolens) in order to save acid. Recycled fibers contain large amounts of calcium carbonate, and its alkaline pKa generally necessitates the use of a neutral to alkaline enzyme. Cellulases that have their pH optima in the alkaline region are rare and also exhibit very low specific activities. Certain alkaliphilic Bacillus sp. are most commonly seen as producers of alkaline cellulases.
(2) We can get high CMCase [carboxymethylcellulase] from bacteria and FPase [filter paper activity] from fungi. Do you think that the mixture of bacterial and fungal cellulase will be the best for deinking?
It is possible. Since we do not fully understand the mechanism of enzymatic deinking, it is difficult to predict what will work best. Synergism between endo- and exo-acting cellulases generally gives the highest overall activity.
(3) Does the Novozyme 342 preparation come from bacteria or fungi?
Novozyme 342 is a cellulase product from Novo Nordisk Industri AG. It is produced by Humicola insolens. The specifics of its production and formulation are outlined in a patent. A few scientific papers have also been published on the Humicola insolens cellulase complex.
(4) Do you think the mechanism is same in enzyme deinking and enzyme detergency?
The principal enzymes used in detergents are proteinases and lipases. Cellulases are also used to reduce "pill" formation in cotton fabrics. However, cellulases may also help to release stains from amorphous cellulose or cellulose microfibrils on the fabric surface.
The mechanisms for enzymatic deinking of paper fibers may be similar, but it depends in part on the types of contaminants being removed. First, the inks do not usually stain the fibers themselves but rather form particles or microparticles that are either embedded in the paper fiber or intertwined and adherent with the fibers.
In the case of small particles that are ground into the fibers, the cellulases could release them by removing the microfibrilar matrix in which they are embedded. This can be done fairly easily. Once the microfibrils are gone, the fibers would have a lower specific surface area and would release water (and particles) more readily.
In the case of larger particles (such as toner particles) in which the fibers are trapped in the plastic matrix (rather than the particles trapped in the fiber), I think that either the fibers break off from the toner particle, or the presence of the enzyme allows the fiber to slip free from the adherent toner. We know that mechanical action is synergistic with and important to the removal of toner particles by cellulases.
For comments or further information write to Tom Jeffries: twjeffri@facstaff.wisc.edu