Residual Gas for Ethanol Production by Clostridium carboxidivorans in a Dual Impeller Stirred Tank Bioreactor (STBR)

Tatiana Ferreira,Marcelle Branco,Carolina Benevenuti,Mariana Do Nascimento-Correa,Alanna Botelho,Priscilla Amaral

doi:10.3390/fermentation7030199

Tatiana Ferreira, Marcelle Branco + Show 4 more

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https://doi.org/10.3390/fermentation7030199

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Abstract

Recycling residual industrial gases and residual biomass as substrates to biofuel production by fermentation is an important alternative to reduce organic wastes and greenhouse gases emission. Clostridium carboxidivorans can metabolize gaseous substrates as CO and CO2 to produce ethanol and higher alcohols through the Wood-Ljungdahl pathway. However, the syngas fermentation is limited by low mass transfer rates. In this work, a syngas fermentation was carried out in serum glass bottles adding different concentrations of Tween® 80 in ATCC® 2713 culture medium to improve gas-liquid mass transfer. We observed a 200% increase in ethanol production by adding 0.15% (v/v) of the surfactant in the culture medium and a 15% increase in biomass production by adding 0.3% (v/v) of the surfactant in the culture medium. The process was reproduced in stirred tank bioreactor with continuous syngas low flow, and a maximum ethanol productivity of 0.050 g/L.h was achieved.

Highlights

Global energy consumption has increased over the last decades, with demand forecasted to be 248 quadrillions BTU of liquid fuels by 2050, which represents an increase of50% compared to 2021 [1]
C. carboxidivorans as a preferential substrate for heterotrophic growth
The effect caused by the addition of Tween®80 to ATCC®2713 medium was evidenced by an increase in biomass and ethanol production during Clostridium carboxidivorans syngas fermentation in serum bottles and validated in a stirred tank bioreactor

Summary

Introduction

Global energy consumption has increased over the last decades, with demand forecasted to be 248 quadrillions BTU of liquid fuels by 2050, which represents an increase of50% compared to 2021 [1]. The constant fluctuation of oil prices caused by political and economic instability around the world brings insecurity to this industrial sector [3] In this scenario, there is an increasing demand for renewable and carbon-neutral fuels, especially those produced through microbial fermentation, such as ethanol and butanol [4,5]. The interest in butanol as a liquid fuel, which is less hygroscopic and provides higher caloric value in comparison to ethanol, has increased in recent years [6] Those alcohols are produced through direct fermentation of sugars extracted from food or energy crops, with pretreatment steps to hydrolyze carbohydrate polymers, increasing costs and byproduct formation [7,8]

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