Degradation of Polycyclic Aromatic Hydrocarbons and Aroma Oxidation of Fermented Locust Bean Seeds ‘Iru’ by Laccase Enzyme Produced by Kluyveromyces dobzhanskii DW1 and Pichia manshurica DW2

Abstract

Laccases (EC.1.10.3.2 are multi-phenolics and non-phenolic oxidizing enzymes) have received much attention in their use for environmental bioremediation, food quality and functionality improvement. This work was aimed at degrading polycyclic aromatic hydrocarbons and aroma oxidation of fermented locust beans seeds ‘iru’ by laccase produced by yeast strains. Kluyveromyces dobzhanskii DW1 and Pichia manshurica DW2 were the yeast strains employed for the production of laccase enzyme. The enzymes were used in the crude, partially purified and agar-gel immobilized forms. The percentage laccase immobilization of Kluyveromyces dobzhanskii DW1 and Pichia manshurica DW2 were 65.2% and 73.1% respectively. The PAHs degraded were Naphthalene and Phenanthrene which were degraded by 50.1%, 23.3%, 18.2% and 65.0%, 54.4%, 39.1% respectively by the crude, partially purified and immobilized laccases fromKluyveromyces dobzhanskii DW1 while the following degradation percentages; 43.6%, 14.6%, 37.1% and 62.5%, 40.4%, 60.1% for the respective compounds were obtained for Pichia manshurica DW2 laccase. The use of the crude, partially purified and immobilized laccases from Kluyveromyces dobzhanskii DW1 and Pichia manshurica DW2 resulted in aroma oxidation by 78.6%, 51.4%, 31.4% and 62.8%, 57.2%, 45.7% respectively. Chemical analysis of flavour-oxidized ‘iru’ by crude laccase from Kluyveromyces dobzhanskiiDW1 showed an increase in protein and tocopherol contents by 9.38% and 30.46% respectively. From this study, the crude laccase from strains worked best in the degradation of Naphthalene and Phenanthrene as well as the aroma flavour oxidation of ‘iru’ which confers economic benefit to the laccase as additional cost of purification and immobilization of enzyme is not required.