Biobleaching of Acacia kraft pulp with extracellular enzymes secreted by Irpex lacteus KB-1.1 and Lentinus tigrinus LP-7 using low-cost media

Abstract

The white-rot fungi Irpex lacteus KB-1.1 and Lentinus tigrinus LP-7 have been shown in previous studies to have high biobleaching activity in vivo. The aim of this study was to investigate the activities and stabilities of extracellular enzymes, prepared from I. lacteus and L. tigrinus culture grown in three types of economical media of agricultural and forestry wastes, for biobleaching of Acacia oxygen-delignified kraft pulp using kappa number reduction as an indicator of delignification. After 3 days of incubation, the extracellular enzymes preparations from I. lacteus and L. tigrinus cultures in media of Acacia mangium wood powder supplemented with rice bran and addition 1 % glucose (WRBG), resulted in significant decrease of 4.4 and 6.7 %, respectively. A slightly higher kappa number reduction (7.4 %) was achieved with the combine extracellular enzymes from I. lacteus and L. tigrinus. One of the strategies for reducing the cost of enzyme production for treatment processes in the pulp and paper industry is the utilization of agricultural and forestry waste. Thus, WRBG has potential as a culture medium for producing stable lignolytic enzymes simply and economically.

Comparison of the Ability of Several White-rot Fungi to Biobleach Acacia Oxygen-delignified Kraft Pulp

“…From the three types of media, incubation with the WRBG culture supernatant resulted in a greater than expected Kappa number reduction, as compared with the WRB and WRBM culture media. The previous study has been shown that I. lacteus and T. tigrinus produces high organic acids (malonate and oxalate) in WBRG [16]. We suggest that the presence of organics acids in culture media containing glucose could be correlated with performance of lignolytic enzymes of white-rot fungi to degrade lignin residues in A-OKP.…”

“…1. Meanwhile, time-L. tigrinus refer to report previously [16]. We compared the production of lignolytic enzymes among the white-rot fungi, the results showed that versicolor, I. lacteus and L. tigrinus MnP, MIP, and Lac, but no LiP.…”

“…The single plugs of pre-inoculum (6 mm diameter) from the 1-week-old colonized plate were inoculated with 10 mL of media. Three type media was used for the experiments: the basal medium (2% of A. mangium wood powder and rice bran (3:2) in distilled water, WRB), A. mangium wood powder and rice bran in 1% of aqueous solution of glucose (WRBG), and A. mangium wood powder and rice bran in malonate buffer containing 50 mM MnSO 4 •5H 2 O (WRBM) [16]. Every 3 days for 21 days, the cultures were harvested, the solids were separated by filtration followed by centrifugation at 10,000 rpm (r = 55 mm), at 4°C for 10 min.…”

“…Lignolytic enzyme activities of Manganese peroxidase (MnP), Manganese-independent peroxidase (MIP), and Laccase (Lac) were determined by measuring the absorbance change at 470 nm related to the rate of oxidation of 2,6-dimethoxyphenol in malonate buffer (pH 4.5) [16]. Meanwhile, Lignin peroxidase (LiP) activity was determined by the oxidation of veratryl alcohol in succinate buffer (pH 3.0) at 310 nm.…”

“…The biobleaching activity of extracellular enzymes secreted by the four white-rot fungi on WRB, WRBG, and WRBM was evaluated on A-OKP, which had an International Standard (ISO) brightness of 47.6% and Kappa number of 9. The experimental treatments were performed in 25-ml screw cap bottles, stationary reactions, and incubated at 40ºC for 1, 2, 3, and 4 days [16].…”