Multi-Objective Optimization for Enhanced Ethanol Production during Whey Fermentation

Whey fermentation is an important anaerobic fermentation process to produce lactic and alcoholic beverages like ethanol from by-products of cheese and dairy industries using various microorganisms like lactic acid bacteria and yeast. One of the significant parameters affecting the quality and quantity of ethanol yield is Dissolved Oxygen(DO) etc. In this paper, a multi-objective control scheme is proposed for achieving quality and cost of ethanol yield by optimizing DO in fed-batch fermentation of Kluyveromyces Marxianus. Firstly, the DO is controlled by manipulating substrate feed rate with conventional Proportional Integral (PI) controller. Secondly, a multi-objective control problem is formed to optimize PI controller parameters to achieve minimum Integral Error (ISE) to improve quality of ethanol product and minimum control effort to minimize cost of product and successfully solved by NSGA-II. The performance of the proposed controller is analysed under servo and regulatory operations It is found experimentally that the proposed NSGA-II algorithm gives optimal solutions to the DO problem.