Browsing by Author "Pihlajaniemi, Ville Juhani"

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  • New acidic fungal cutinases from Sirococcus conigenus and Aspergillus niger
    (2011) Pihlajaniemi, Ville Juhani
     School of Chemical Engineering | Master's thesis
    Cutinases are enzymes that hydrolyse cutin, protective bio polyester on the surface of plants. They are considered as intermediates between lipases and esterase's. All previously described cutinases have alkaline or neutral pH-optima. In this work, the gene of a novel acidic cutinase from the fungus Aspergillus niger was identified. The A. niger cutinase and another novel acidic cutinase from the fungus Sirococcus conigenus were heterologously produced in Pichia pastoris and characterized. The A. niger and S. conigenus cutinases both displayed acidic pH-optima roughly at pH values 5 and 4, respectively. Both cutinases were functional and thermally stable at pHs between 3.5 and 6.5 and had good thermal stabilities at high temperatures at optimum pH. The cutinases preferred rho-nitrophenyl esters of short chain fatty acids as substrates over those of long chain fatty acids, which is typical for cutinases. Both were able to hydrolyse natural apple cutin. The cutinase of S. conigenus also hydrolysed birch suberin and had minor lipase activity. The specific activity of the S. conigenus cutinase was over 500-fold higher compared to the cutinase of A. niger and it was considered to have potential for industrial use in applications, where cutinolytic activity at acidic pH is desired.