Lipaz üreten Yarrowıa lipolytica alt kültürleri arasındaki işbirliği ve hilekarlığın oyun teorisi ile analizi

Game theory is a mathematical tool for understanding social dilemmas and solving conflicts of interest between agents with set of strategies and goal of maximizing personal interests (payoffs). Among microorganisms, different phenotypes, such as complete or partial failure in exoenzyme production, can be regarded as strategies in a game where growth rates of cells represent fitnesses of each strategy. Consequently, the productivity of the population is determined by the interplay between the exoenzyme producer "Cooperator" and the exoenzyme non-producer "Cheater" sub-cultures. Among non-conventional yeasts, Yarrowia lipolytica can efficiently produce extracellular lipases to degrade hydrophobic substrates such as fats and fatty acids. In this thesis a game theoretical model is constructed to analyze the evolutionary dynamics and the lipase productivity of the Y. lipolytica population in terms of structured mathematical models. Fermentation model results indicate that fed-batch mode simultaneously promoted the Cheating and the lipolytic activity compared to batch mode which signifies the importance of the specific productivity independent from sub-culture frequencies. The evolutionary stability of the "Cooperator" and the "Cheater" sub-cultures are analyzed with a "stable state finder algorithm". Two distinct game regimes were identified. When the lipase production cost is low, Cooperators dominate the population. At intermediate and higher costs, Cooperators coexist with Cheaters. These regimes correspond to "No-Conflict" and "Snowdrift" regimes respectively. The evolutionary stable states of the "multi-player fermentation game" is affected by the initial conditions. At higher initial cell densities equilibrium frequency of the Cooperators decreases. Cooperators benefit from higher initial olive oil concentrations and consequently the lipolytic activity increases. Also, Cheaters benefit from higher initial oleic acid concentrations and as a result the lipolytic activity decreases. The methodology of finding the Evolutionary stable state can also be applied to scenarios where different species are considered as players. In growing biotechnological literature, co-cultures are becoming prominent examples of such scenarios.