Description
The modern environmental sound pulp manufacture processes where chorine bleaching have been substituted by elemental chorine-free or totally chorine-free processes have produced new problems relates with lipophilic compounds present in wood extractives. These compounds are involved in pitch deposition and cause problems during pulp and paper manufacture. The composition of extractives is different in hardwoods and softwoods. Some microbial lipases are being studied for their application in pulping processes from softwood to decrease pitch problems, where triglycerides are the main problematic compounds. However, lipases are not effective on pulps from hardwoods (as Populus tremula and Eucalyptus globulus) and some softwoods (as Picea abies) with a high content of esterified sterols.
We propose to perform the molecular characterization of a new fungal esterase, and to study its possible application, in the degradation of lipophilic compounds causing pitch deposits in pulp and paper manufacture from wood with high levels of sterols. The esterase to be used in this project is a newly characterized enzyme from the ascomycete Ophiostoma piceae. This enzyme is able to hydrolyze both triglycerides and sterol esters. These lipophilic compounds are present in both softwood and hardwood extractives. The Pleurotus eryngii peroxidase is a new ligninolytic enzyme with a wide substrate specificity and could cooperate to decrease the pitch problem by degrading the reaction products of esterase hydrolysis via lipid peroxidation. Both enzymes were isolated and characterized by us in the CIB. The peroxidase has been cloned and expressed and its production is being currently optimized in bioreactors. The present project includes: i) Cloning and sequencing the esterase from O. piceae and comparison with other lipases and esterases previously reported; ii) the expression of this new esterase in organisms used for industrial enzyme production; iii) the study of the properties of the recombinant enzymes comparing them to those of the native enzyme and other commercial lipases and esterases; iv) the optimization and scale up production of native and recombinant esterases; v) the evaluation of P. eryngii peroxidase in the degradation, via peroxidation, on the fatty acids and free sterols produced by esterase hydrolysis of triglycerides and sterol esters; vi) the treatment of softwood and hardwood pulps and water process with esterases and peroxidases and vi) evaluation of the enzymatic treatments on the properties of pulps. The application of esterases and peroxidases in the pulp and paper manufacture process could improve the pulp quality and reduce the economic loss caused by pitch in paper pulp industries.
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