Expressão heteróloga em Saccharomyces cerevisiae de genes de Zygosaccharomyces bailii envolvidos na resistência a conservantes alimentares

• Autor(es): Almeida, Maria Madalena Carneiro de
• Data: 2014
• Identificador Persistente: http://hdl.handle.net/10400.5/8203
• Origem: Repositório da UTL
• Assunto(s): Z. bailii; resistance to weak acids; food preservatives; membrane permeability; ZbGas1
• Tipo de Documento: Dissertação de mestrado
• Idioma: Português
• Orientador(es): Prista, Catarina Geoffroy; Leandro, Maria José
• Contribuidor(es): Repositório da Universidade de Lisboa

Descrição

Mestrado em Engenharia Alimentar - Qualidade e Segurança Alimentar - Instituto Superior de Agronomia

Zygosaccharomyces bailii is one of the main spoilage yeasts and one of the biggest problems for Food Industry due to its high resistance to food preservatives, namely weak acids. In this work, we performed an evaluation of one mechanisms proposed for the increased resistance to benzoic and sorbic acid of Z. bailii: the decreased permeability to cations. More specifically, we evaluated the role of eight Z. bailii genes (OPI3, FEN1, SUR4, ISC1, ERG2, ERG4, ERG6, GAS1) on weak acid resistance. We cloned and characterized each Z.bailii genes by heterologous expression in S. cerevisiae strains without the respective gene. In order to characterize each transformant strain, we evaluated weak acid resistance (1-6 mM), intracellular pH, proton influx and extrusion through the plasma membrane and growth parameters (final biomass and yield) in YNB and in a commercial apple juice in non-adapted and in adapted cells to the acids. The most relevant results were obtained for ZbGAS1 gene, whose expression in S. cerevisiae improved growth (final biomass and cell yield) and increased proton pump activity in the presence of weak acid. These results point to possible cell wall composition changes as one of the mechanism possible involved in weak acid resistance