Fermentation of syngas to biofuels

Abstract

This thesis is focused on syngas fermentation, syngas fermentative microorganisms and products from syngas fermentation process. The aim of this thesis is to find out the information about fermentation of syngas to biofuels. The main biofuels are acetate, ethanol and hydrogen. They can be produced by the syngas fermentation process. Microorganisms such as clostridium ljungdahlii, clostridium autoethanogenum and clostridium carboxidivorans play a very important role during the syngas fermentation process. Microorganisms use syngas in different fermentation methods to produce biofuels.

There are several syngas fermentations. Batch fermentation and continuous fermentation are the most significant methods. The strains of microorganism have various functions; different microorganism can produce different products during syngas fermentation. For example, anaerobic carboxydotrophic microorganisms can produce acetate and ethanol. Non-sulphur bacteria can produce hydrogen under tungsten lamps.

Syngas fermentation also needs special conditions. Acetate and ethanol are produced by clostridium ljungdahlii fermentation. During this syngas fermentation, the highest carbon dioxide concentration is obtained at short fermentation time with 1.6 atm and 1.8 atm gas pressure. Under clostridium aceticum syngas fermentation, optimizing reducing agents and optimizing nutrient are needed in order to poise and depress oxidation-reduction potential. In butyribacterium methylotrophicum syngas fermentation, supplement carbon dioxide can obtain more acetate comparing with non-supplement carbon dioxide. Finally non-sulphur bacteria was used for producing hydrogen, the growths of bacteria are effected by tungsten lights.