Biobleaching of high quality pulps with laccase mediator system: Influence of treatment time and oxygen supply

Abstract

In this study we examined the influence of the treatment time and addition of oxygen on the efficiency of a laccase mediator system (L) applied to flax pulp at atmospheric pressure. The redox potential and the dissolved oxygen concentration during L tests are measured. After L stage, an alkaline extraction (E) is carried out. The pulp properties (kappa number, brightness and viscosity) and the effluents properties (color and COD) were measured in order to evaluate the environmental impact of this enzymatic treatment.The biotreatment involves two distinct stages in both L and LE sequences; in the beginning the pulp exhibits a fast delignification and a slow viscosity decrease that is followed by slow delignification in the second. Pulp brightness changed differently during L stage and LE sequence.Initially brightness after the L stage decreased with respect to the initial pulp; then, it increased rapidly and eventually leveled off. After the LE sequence, brightness increased rapidly in the beginning and more gradually afterwards. The results show that supplying the medium with oxygen and increasing the oxygen concentration in it, influence the kinetics of the process.Based on CIE L*a*b* color coordinates study, the enzyme treatment not only removes lignin, but also alters the structure of the pulp by causing the formation of chromophoric groups giving color.Such groups are removed in an E stage.

Kinetics of Adsorbable Organic Halides (AOX) Reduction in Laccase-Aided Chlorine Dioxide Bleaching of Bagasse Pulp

“…When the AOX reduction was more than 0.14, the change in the rate of AOX reduction was small. This was similar to the results obtained in previous studies (Balakshin et al 2000(Balakshin et al , 2001aFillat and Roncero 2009), which revealed that the reaction of AOX reduction could be separated into two stages. In the initial stage, when the AOX reduction was less than 0.14, the lignin was degraded rapidly.…”

Assessing the use of xylanase and laccases in biobleaching stages of a TCF sequence for flax pulp

“…The Po stage was performed in a hot, strongly alkaline medium, which may have resulted in modified cellulose being more markedly degraded than during the viscosity measurements. 33 Therefore, the viscosity differences between L and Po may have resulted from degradation of cellulose modified by the LMS. On the other hand, cellulose was probably not oxidized to carbonyl groups by the MtL.…”

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

“…Recently, xylanase and laccase enzymes were reported to decolourise and detoxify the effluent generated by pulp and paper industry [1,2]. Both these enzymes have shown the ability to bleach kraft pulp [3,4] as well as to deink the recycled paper [5]. Application of xylanase and laccase together can considerably decrease the load of chemicals on environment caused by pulp and paper industry.…”