Microbial screening and process optimization for the production of ligninase
1995
del Rosario, E.J.
Eleven wild-type strains (local isolates and accessions) and isolated microorganisms from rotten wood chips of Paraserianthes falcataria (syn. Albizzia falcataria) and Eucalyptus deglupta were screened for ligninolytic activity using a rapid screening method. Four promising mutant strains, namely: Pc 6370 M-66; Pc 24725 m-78, m-87 and m-95, were selected as having ligninolytic activity on Bavendamm test plates. Initial experiments revealed that ligninase-treated fibers gave the lowest residual gum content compared to that of the untreated fibers. Biopulping by white-rot microorganism (Pc 63-70) and alkali-pulping conditions improved the physical properties of the pulp handsheets in terms of freeness, tear index, burst index, and brightness, thus, producing pulp of quality sufficient for paper making with Kappa number of 15.4. Biopulping of wood chips using the NTG-mutant showed 33.70 percent lignin loss based on whole wood basis and 11.42 percent on extractiveness-free basis by Klason method. Immobilization of the 6370 NTG-005 on polyurethane foam prevented genetic reversion of the mutant by allowing indefinite mycelial propagation with spore formation. Ligninase pre-treatment (20 percent) at room temperature with minimal chlorination (1 percent calcium hypochlorite) resulted in much higher degree of delignification (1.04 to 1.35 kappa number) compared to the chemically bleached samples (control) from CPMC. Physical properties of the enzyme treated pulp handsheets has higher density, thickness, burst factor, tear factor and tensile breaking length at 70 mins beating time and high freeness at 0 min beating time compared to the control. Energy cost analysis revealed a much higher operational value due to high cost of the produced enzyme
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