The mode of interaction of the constituents of a microbial system determines the attainable exergy utilisation
by Bahar Değerli; Mustafa Özilgen
International Journal of Exergy (IJEX), Vol. 25, No. 2, 2018

Abstract: The typical text book definition of exergy is the "maximum work that this system can produce if it is brought to thermal, mechanical and chemical equilibrium with its surroundings via reversible processes". In microbial systems, this ability depends on the interaction, e.g., collaboration, competition or antagonism, between the constituents of the system. Leavening of dough with mixed cultures of microorganisms is a typical example, where the microbial constituents of a system may present different modes of interaction depending on the temperature and their relative amounts. Data pertinent to leavening at four different temperatures and six different inoculum ratio of Saccharomyces cerevisiae and Lactobacillus plantarum were processed. The maximum carbon dioxide production (42.7 g CO₂/kg dough), expansion work (0.334 kJ/kg dough) and dough volume increase (3,300 cm³/kg dough) were obtained at 35°C with the inoculum consisting of 80% S. cerevisiae and 20% L. plantarum. The system achieved the highest exergy utilisation (2000 kJ/kg dough) under these conditions, demonstrating that the microbiological and the exergy optima were not independent and achieved under the same conditions.

Online publication date: Tue, 30-Jan-2018

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