Hydrogen production by Enterobacter sp. LBTM 2 using sugarcane bagasse hemicellulose hydrolysate and a synthetic substrate: understanding and controlling toxicity

Ivon M Campos,Marina Tonucci,Sérgio F Aquino,Flaviane Silva,Oscar F.H Adarme,Marilia Menegatto,Jose Augusto Zorel,Bruno E.L Baêta,Silvana Q Silva

doi:10.1590/0001-3765202120201679

Ivon M Campos, Marina Tonucci + Show 7 more

Open Access

https://doi.org/10.1590/0001-3765202120201679

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Abstract

Abstract Sugars released by thermochemical pretreatment of lignocellulosic biomass are possible substrate for hydrogen production. However, the major drawback for bacterial fermentation is the toxicity of weak acids and furan derivatives normally present in such substrate. This study aimed to investigate the metabolism involved in hydrogen production by the isolate Enterobacter LBTM2 using 10, 20 and 30-fold diluted synthetic (SH) and sugarcane bagasse hemicellulose (SBH) hydrolysates. In addition, the effects of acetic acid, formic acid and furfural on the bacterial metabolism, as well as detoxification of SBH with activated carbon and molecularly imprinted polymers on the hydrogen production were assessed. The results showed the best hydrogen yield was 0.46 mmol H2/mmol sugar for 20-times diluted SH, which was 2.3-times higher than obtained in SBH experiments. Bacterial growth and hydrogen production were negatively affected by 0.8 g/L of acetic acid when added alone, but were totally inhibited when formic acid (0.4 g/L) and furfural (0.3 g/L) were also supplied. However the maximum hydrogen production of SBH20 has duplicated when 3% of powdered activated carbon was added to the SBH experiment. The results presented herein can be helpful in understanding the bottlenecks in biohydrogen production and could contribute towards development of lignocellulosic biorefinery.

Highlights

Fossil fuel demands, population growth and environmental pollution create a need for new alternative energy sources which are both environmentally friendly and renewable
The cell wall composition, the nature of lignocellulosic material and the type of pretreatment determine the inhibiting compounds which are produced (Chandel et al 2013). These inhibitors can be classified into three main groups: furan derivatives, produced by dehydration of pentoses and hexoses; weak acids, mainly acetic acid formed by hydrolysis of acetyl groups linked to the heteropolysaccharides of hemicellulose; and phenolic compounds resulting from solubilization of lignin (Lee et al 2015)
Amongst the adsorbents that can be used for detoxifying hydrolysates, the molecularly imprinted polymers (MIPs) seem to be an interesting material due to their intrinsic features such as high selectivity, high adsorption capacity, relatively low cost and easy synthesis (Tarley et al 2005, Shahar & Mandler 2016)

Summary

Introduction

Population growth and environmental pollution create a need for new alternative energy sources which are both environmentally friendly and renewable. Hydrogen is a biofuel that can be produced by fermentative microorganisms and has several advantages, such as carbon-free biofuel and greater heat capacity (in mass terms), compared to conventional fossil fuels or even other biofuels (Bielen et al 2013) It is considered a cleaner energy, as its combustion generates only water, and can be produced from virtually any type of biomass (e.g. agricultural, forestry and food industry wastes) (Nissilã et al 2014, Gonzales et al 2016). Understanding and controlling the effects of inhibitory compounds on hydrolysate sugar fermentation is essential to improve biofuel production In this present study, the effects of furfural, formic and acetic acids on hydrogen production by dark fermentation in synthetic and real sugarcane bagasse hemicellulose hydrolysate were comparatively evaluated using the newly isolated Enterobacter sp.

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