Effects of acetic acid, furfural and p-hydroxybenzoic acid on succinic acid fermentation by Escherichia coli BSS133
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
During hemicellulose hydrolysis, a mandatory step prior to fermentation, degradation products are formed from sugars and lignin In the case of hardwood hemicellulose, acetate is also released from xylan deacetylation. Those compounds might be inhibitory for both Escherichia coli growth and the succinic acid production. In the present work, E. coli growth was first tested on both glucose and xylose in the presence of different inhibitors: sodium acetate [0-12 g/L]; furfural [0-3 g/L] and 4-hydroxybenzoic acid [0-2 g/L]. This investigation was performed in shake flasks, using small size inocula. Afterwards, eleven fermentations in batch mode were carried out in 1-L fermentors, following a full factorial design with three centred points. The ranges of inhibitors studied were: acetic acid [0-10 g/L], furfural [0-2 g/L] and p-hydroxybenzoic acid [0-2 g/L]. Finally, hemicellulose was extracted from birch wood, hydrolysed with 2.7% sulfuric acid and used as a substrate for fermentation. The results showed that furfural was the most toxic compound. Besides, its association with acetic acid was synergistic since no growth occurred when furfural and acetic acid were present in the media at 2 and 10 g/L, respectively. Nevertheless, E. coli was able to hydrolyse these two compounds to some extent. Low POH concentrations did not have any significant effect on the growth and fermentation performance of E. coli. Acetic acid at high concentrations affected both the growth and the succinic acid production. Indeed, lower succinic acid concentrations were obtained when there was an initial concentration of 10 g/L of acetic acid in the media. Acetic acid, furfural and phenols were found in the hydrolysates at concentration of 13.3 g/L, 2.2 g/L and 1.5 g/L respectively. As expected from the experimental model E. coli was thus not able to grow on undetoxified birtchwood hemicellulose hydrolysates when using a batch process.
Place, publisher, year, edition, pages
2014. , 84 p.
Technology, Succinic acid, E. coli fermentation, lignocellulose, fermentation inhibitors
IdentifiersURN: urn:nbn:se:ltu:diva-53692Local ID: ab1dc10c-2d03-4646-b9f7-5c33e0293856OAI: oai:DiVA.org:ltu-53692DiVA: diva2:1027068
Subject / course
Student thesis, at least 30 credits
Chemical Engineering, master's level
Validerat; 20140326 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved