Modeling and simulation of clean fuel production by Enterobacter cloacae IIT-BT 08

Abstract

Cell growth and substrate degradation kinetics of newly isolated Enterobacter cloacae IIT-BT 08 were investigated with the help of Monod model. The values of μ_max, K_S and Y_X/S of the cell were 0.568 h⁻¹, 3.658 g l⁻¹ and 0.0837, respectively, using glucose as a substrate. The simulated profiles of the substrate concentration and cell mass concentration had significant variance with respect to the experimental values. This might be due to the substrate inhibition as the product is a gas. A modified Andrew’s model for substrate inhibition was suggested and found to have good resemblance with the experimental results. In other studies, hydrogen production was found to be growth associated.

Introduction

The economic growth of modern industrialized society has been based on the utilization of fossil fuels like natural gas, coal, and petroleum as the energy sources. However, limited fossil fuel resources have led to a search for alternative sources of energy. Hydrogen is a potent alternative because there are no liabilities like emissions, spills, CO₂, global warming, acid rains, etc. which are associated with traditional fossil fuels. Hydrogen is a very important molecule with an enormous extent of applications and uses. It is currently being used in many industries ranging from chemical and refining to metallurgical, glass, and electronics. Hydrogen is primarily used as reactant and it is also being used as fuel, particularly in space application for the last 40 years. Various ways of producing hydrogen are available e.g., steam reforming of natural gas, thermal cracking, electrolysis of water, etc.

Many authors have investigated biological hydrogen production [1], [2], [3], [4], [5], [6], [7]. In general, there are two ways to produce hydrogen using living organisms, first, by photosynthetic organisms (such as photosynthetic bacteria, cyanobacteria, and green algae), and second, by fermentative organisms (strict anaerobes and facultative anaerobes). Comparative studies on different micro-organisms with respect to hydrogen production show that the rate of fermentative hydrogen production is always faster than the other biological methods. The other advantages of fermentative hydrogen production are mainly to produce it all day long without light and also able to clean environment by using industrial and agricultural waste thus facilitating waste recycling.

It was observed that hydrogen production rates and yields were comparatively higher in case of Enterobacter cloacae IIT-BT08 than those reported in literature for similar processes [8], [9], [10]. To realize the complete advantages of the proposed system, modeling of the system has to be done, so that scale-up of the process can be accomplished. Therefore, a kinetic model representing the cell mass growth, substrate degradation, and product formation, is sought to be developed.