Influence of Carbon Source Pre-Adaptation on Clostridium ljungdahlii Growth and Product Formation

Oscar Tirado-Acevedo,Mari S Chinn,Jacqueline L Cotter,Amy M Grunden

doi:10.4172/2155-9821.s2-001

Abstract

Syngas fermentation is considered an alternate processing method for biofuel and biochemical production as part of thermochemical biomass conversion. Exposure of syngas fermenting microorganisms to sugars, either in the primary syngas fermentation or through pre-adaptation in the seed culture, has the potential to enhance overall fermentation performance and stress tolerance. In this rapid communication, Clostridium ljungdahlii was grown on different carbon sources including syngas only, syngas-fructose and fructose only to identify ideal pre-adaptation conditions for ethanol and acetate production from subsequent cultures grown in reactors containing syngas only or fructose-syngas substrates. In syngas only reactors, cultures pre-adapted to fructose had faster cell production rates (2X) and at least 83% higher ethanol and 16% higher acetate formation than cells pre-adapted on syngas or syngas-fructose. In syngas- fructose reactors, cultures did not show significant growth or acetate production differences under pre-adaptation treatments. Nevertheless, in these syngas-fructose reactors, cultures pre-adapted on syngas and syngas-fructose had nearly 20% higher ethanol production than those pre-adapted on fructose. Among pre-adaptation treatments, fructose had better results in syngas only reactors than syngas-fructose reactors. However, the presence of syngas in pre- adaptation cultures was better overall for ethanol production.

Highlights

Conversion of synthesis gas to liquid fuels by biological catalysts has been suggested as a promising technology to achieve oil independence [1]
C. ljungdahlii cultures were pre-adapted on three different carbon source combinations
These cells were transferred to fermentation reactors with either syngas or syngas-fructose medium

Summary

Introduction

Conversion of synthesis gas to liquid fuels by biological catalysts has been suggested as a promising technology to achieve oil independence [1]. Growth and product formation were evaluated for the fermentations that were initiated using cells pre-adapted to fructose, syngas, and mixed fructose-syngas substrates. Fermentation reactors containing medium-syngas and medium-syngas-fructose at a working volume of 250 ml were inoculated with the three different seed cultures (472 mg dry cells/L in inoculum; 5% v/v addition).

Results

Conclusion