Experimental Design to Improve Cell Growth and Ethanol Production in Syngas Fermentation by Clostridium carboxidivorans

Abstract

Fermentation of gases from biomass gasification, named syngas, is an important alternative process to obtain biofuels. Sequential experimental designs were used to increase cell growth and ethanol production during syngas fermentation by Clostridium carboxidivorans. Based on ATCC (American Type Culture Collection) 2713 medium composition, it was possible to propose a best medium composition for cell growth, herein called TYA (Tryptone-Yeast extract-Arginine) medium and another one for ethanol production herein called TPYGarg (Tryptone-Peptone-Yeast extract-Glucose-Arginine) medium. In comparison to ATCC® 2713 medium, TYA increased cell growth by 77%, reducing 47% in cost and TPYGarg increased ethanol production more than four-times, and the cost was reduced by 31%. In 72 h of syngas fermentation in TPYGarg medium, 1.75-g/L of cells, 2.28 g/L of ethanol, and 0.74 g/L of butanol were achieved, increasing productivity for syngas fermentation.

Impacts of Syngas Composition on Anaerobic Fermentation

“…Syngas is a gaseous mixture of CO, H 2 and CO 2 . It also contains CH 4 while secondary components such as H 2 O, H 2 S or NH 3 or tar are often present [5,7]. It can be used to produce biofuels (gasoline, diesel oil), energy (heat and/or electricity generation) and chemicals [7].…”

“…Syngas, also named synthesis gas, is mainly composed of CO (carbon monoxide), CO 2 (carbon dioxide) and H 2 (hydrogen gas) which can be converted to alcohols such as ethanol, butanol and hexanol and other chemicals such as acetic, butyric and hexanoic acids by acetogenic bacteria through the Wood-Ljungdahl pathway or its derivatives [4,5]. Syngas fermentation is one of three major approaches to the production of second generation biofuels, along with the Fischer-Tropsch process and lignocellulosic fermentation [6].…”

“…The combination of gasification with syngas fermentation results in taking advantage of some of the relevant features of thermochemical and biochemical technologies; however, the fermentation of these gaseous substrates presents challenges that still must be overcome. Syngas fermentation depends on factors such as the microorganism, type of reactor, gas composition, medium components, operating parameters, gas-liquid mass transfer and fermentation strategies [5].…”

Physicochemical Properties of Biobutanol as an Advanced Biofuel

“…Instead of synthesis gas catalysis, another approach can be used. Syngas fermentation is carried out by microbial catalysts that are known as homo-acetogenic, such as Clostridium ljungdahlii , Clostridium carboxidivorans, Clostridium autoethanogenum, Eubacterium limosum, Clostridium ragsdalei , and Alkalibaculum bacchi [ 27 , 28 , 29 ]. When compared to chemical catalysts, syngas fermentation has the advantage of high specificity to the substrate, operation at low temperature and pressure, and high tolerance to toxic gases [ 30 , 31 ].…”

Fermentation of cellulose pyrolysis oil by a Clostridial bacterium

“…Another promising way is the fermentation of syngas produced by biomass gasification using specific Clostridial strains that are able to convert carbon monoxide and carbon dioxide into alcohols. This approach allows the valorisation of biomass wastes [37,38]. However, the fermentation using carbohydrates presents faster cell growth, more efficient mass transfer (carbohydrates are already present as a soluble molecule in the aqueous phase) and several microorganisms are able to ferment carbohydrates to produce a wide variety of chemicals and biofuels [39].…”