Description
Lipases belong to one of the enzymatic families most widely used in industry because of their high versatility. In aqueous solvents they hydrolyze triglycerides but, in organic solvents, they can carry out esterification and transesterification reactions. The enzyme stability under the last conditions is very important. Sterol esterases are enzymes that hydrolyze sterol esters. They share several properties with lipases, since they also perform hydrolysis reactions in aqueous solutions and transesterification reactions in alcoholic solvents. In fact, the classification of this group of enzymes is somewhat confusing, since there are lipases and sterol esterases with catalytic activity specific on triglycerides or sterol esters and others with preferential activity on one of these compounds although, in the appropriate conditions, they can hydrolyze both substrates.
The fungus Ophiostoma piceae secretes a sterol esterase able to hydrolyze efficiently model triglycerides, sterol esters and the complex mixtures of both, present in extractives and paper pulp from softwoods and hardwoods. We have recently observed that this esterase is active in presence of detergents, a characteristic that has not been reported or observed for other commercial lipases and sterol esterases analysed in our laboratory. At the present time, we are characterising the recombinant sterol esterase from O. piceae expressed in Pichia pastoris. The recombinant enzyme is strongly glycosylated but it showed more efficiency than the native form degrading triglycerides and sterol esters (3-4 times) since, in spite of having a similar affinity for the substrates, the velocity of the substrate hydrolysis was higher.
On the other hand, we are also studying the ability of an anamorph of the basidiomycete fungus Bjerkandera adusta to degrade polycarbonate, an ester obtained from polymerization of bisphenol A and phosgene. This fungus secretes to the culture medium an esterase (inducible by olive oil) which could take part on the polycarbonate degradation. These results, together with the recent sequencing of the basidiomycete Pleurotus ostreatus (now in the annotation phase), fostered us to the search new lipases/sterol esterases in basidiomycetes, a fungal group in which these enzymes has not been characterized. It must be pointed that our group has been studying for more than a decade several enzymes secreted by these fungi which are implicated in the degradation of lignin and other aromatic compounds responsible of environmental problems.
There are many bottlenecks for using lipases/sterol esterases in industrial processes, and we would like to contribute to the search of new and more efficient biocatalysts for their use in some biotechnological applications. To reach this goal, we propose: i) Continue structure-function studies with the sterol-esterase from O. piceae, ii) Study new esterases (from new fungi and also those obtained from genomes recently sequenced), iii) Express and characterize the genes of interest, iv) Compare the catalytic properties of selected esterases with those from O. piceae esterase and, v) Check the activity of these enzymes on industrially interesting substrates (related to paper, food and biofuel industries).
The fungus Ophiostoma piceae secretes a sterol esterase able to hydrolyze efficiently model triglycerides, sterol esters and the complex mixtures of both, present in extractives and paper pulp from softwoods and hardwoods. We have recently observed that this esterase is active in presence of detergents, a characteristic that has not been reported or observed for other commercial lipases and sterol esterases analysed in our laboratory. At the present time, we are characterising the recombinant sterol esterase from O. piceae expressed in Pichia pastoris. The recombinant enzyme is strongly glycosylated but it showed more efficiency than the native form degrading triglycerides and sterol esters (3-4 times) since, in spite of having a similar affinity for the substrates, the velocity of the substrate hydrolysis was higher.
On the other hand, we are also studying the ability of an anamorph of the basidiomycete fungus Bjerkandera adusta to degrade polycarbonate, an ester obtained from polymerization of bisphenol A and phosgene. This fungus secretes to the culture medium an esterase (inducible by olive oil) which could take part on the polycarbonate degradation. These results, together with the recent sequencing of the basidiomycete Pleurotus ostreatus (now in the annotation phase), fostered us to the search new lipases/sterol esterases in basidiomycetes, a fungal group in which these enzymes has not been characterized. It must be pointed that our group has been studying for more than a decade several enzymes secreted by these fungi which are implicated in the degradation of lignin and other aromatic compounds responsible of environmental problems.
There are many bottlenecks for using lipases/sterol esterases in industrial processes, and we would like to contribute to the search of new and more efficient biocatalysts for their use in some biotechnological applications. To reach this goal, we propose: i) Continue structure-function studies with the sterol-esterase from O. piceae, ii) Study new esterases (from new fungi and also those obtained from genomes recently sequenced), iii) Express and characterize the genes of interest, iv) Compare the catalytic properties of selected esterases with those from O. piceae esterase and, v) Check the activity of these enzymes on industrially interesting substrates (related to paper, food and biofuel industries).
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