Kinetic Study on the Effect of Substrate and Micronutrient Inhibition during Anaerobic Fermentation of Biohydrogen

Nurul Sakinah Engliman

doi:10.47191/ijcsrr/v5-i1-03

Abstract

There are several factors that influence the production of biohydrogen by dark fermentation including inoculum seeds, type and concentration of substrate, pH, temperature, presence of micronutrient and reactor configuration. Previous research has proven that the concentration of substrate and the presence of micronutrient will influence the yield and productivity of biohydrogen production. However, improvement of yield and productivity of the process can only be achieved once the system is under the optimum amount of substrate and micronutrient. Therefore, the best way to determine the effect of substrate concentration and presence of micronutrient is through kinetic study that was done using Monod model along with Andrews model. Besides that, the substrate inhibition effect also will be evaluated to determine the maximum substrate that needs to be supplied for maximum hydrogen production, and thus supplied the information for economic feasibility for fermentation process. In the meantime, the inhibition effect of adding the iron nanoparticles also had been evaluated in order to understand the interaction effect between iron nanoparticles and bacteria in term of catabolism reaction. It was found that increasing the substrate concentration more than 10 g/l will cause the inhibition to the system, in which it will slow down the reaction process and reduced the production of hydrogen. While the presence of iron NPs more than its optimum value (200 mg/l) will inhibit the bacterial growth and hence, affect the hydrogen production. For both cases, when the inhibition occurred at the respective concentration, it was found that the metabolic pathway was shifted to produce more hydrogen-consuming metabolite such as propionate acid, and thus, dropped the hydrogen production.

Highlights

Biohydrogen production involves mixed community of bacteria that bring about an ecological pattern that is different from pure culture in which the growth rate and microbial activity was affected by diurnal variation of substrate, pH, DO and temperature [1]
As we can see that the substrate concentration above 10 g/l will cause the inhibition to the system, investigation on the inhibition effect of the addition of iron NPs were done by using fixed amount of substrate (10 g/l) while varying the concentration of NPs
Since all experiments were run using the optimum condition such as the fixed pH and temperature, it is better to observed the inhibition effect of substrate concentration as well as iron NPs when changing the fermentation condition as the results might be different with the finding from this study

Summary

Introduction

Biohydrogen production involves mixed community of bacteria that bring about an ecological pattern that is different from pure culture in which the growth rate and microbial activity was affected by diurnal variation of substrate, pH, DO and temperature [1]. Substrate concentration and addition of micronutrients are among the crucial factors that will affect the productivity and yield of the process. Ginkel and his co-worker has demonstrated that the presence of the appropriate concentration of substrate during hydrogen fermentation could increase the ability of the hydrogen-producing bacteria to produce maximum amount of hydrogen [2]. In order to understand the substrate utilization by the microorganism during the fermentation process, kinetic model such as Monod equation is commonly used to describe the correlation of microbial growth with substrate intake [4]. Monod equation is the adaptation from Michaelis-menten kinetic model that had been used in enzymatic reaction, but when applied to cellular system, it is known as Monod equation

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Conclusion