Coproduction of hydrogen and volatile fatty acids via integrated two-step fermentation of sweet sorghum stalks by alkaline and enzymatic treatment

doi:10.1016/j.biombioe.2020.105923

Biomass and Bioenergy

Volume 145, February 2021, 105923

https://doi.org/10.1016/j.biombioe.2020.105923 Get rights and content

Highlights

•
C. thermosaccharolyticum was used for coproduction of H₂ and VFA.
•
Alkaline and enzymatic treatment enhanced the yields of H₂ and VFA.
•
A promising approach for sweet sorghum biorefining was developed.

Abstract

Coproduction of H₂ and volatile fatty acids from sweet sorghum stalks was successfully developed via two-step fermentation process involving alkaline and enzymatic treatment of the residual slurry obtained from the first step fermentation of the raw material. The optimum treatment conditions to obtain the highest yield of the end products included 2% (w/v) alkali at 120 °C for the residual slurry and 32 FPU cellulase per gram of the alkali-treated materials. The two-step fermentation using Clostridium thermosaccharolyticum increased the end product yields of H₂ (6.37 mmol/g-substrate) by 95%, acetic acid (2.33 g/L) by 97% and butyric acid (2.36 g/L) by 143% compared with those obtained in the single step fermentation without any treatment. As a result, the H₂ energy recovery efficiency of the two-step fermentation process with commercially attractive butyric acid as a coproduct reached 10.54%. These results provide a promising approach for sweet sorghum biorefining.

Introduction

The conversion of lignocellulosic biomass into fuels and chemicals is strategic, environmental, and economically important. However, the bioconversion efficiency is not high because of low biodegradability of lignocellulosic biomass that is mainly composed of cellulose, hemicellulose, and lignin [[1], [2], [3], [4]]. Therefore, various efficient pretreatment processes, such as acid or alkaline pretreatment, steam explosion and ammonia fiber explosion, have been investigated to reduce cellulose crystallinity and increase the porosity of the biomass to enhance the H2/methane/ethanol fermentation production from lignocellulosic biomass [[5], [6], [7]].

The alkaline treatment is one of the pretreatment methods, which has been extensively studied in delignification of lignocellulosic biomass because it is effective and inexpensive [8,9]. The bonds between lignin and carbohydrates can be broken by low alkaline load leading to a partial dissolution of lignin and hemicellulose without producing high level phenolic inhibitors, such as furfural and 5-hydroxymethyl furfural (HMF) [10,11]. The enzymatic hydrolysis of lignocellulosic biomass is considered an energy-saving and environmentally friendly treatment process. After lignin removal by mild alkaline treatment, the resulting cellulose and hemicellulose substrates can be easily used in enzymatic hydrolysis [[12], [13], [14]].

Sweet sorghum is a high-yielding sugar crop that has been considered a particularly important energy plant for biofuel production [15]. Recently, biological H₂ production from the sweet sorghum has attracted significant attention [16,17]. Soluble sugars in sweet sorghum can be easily utilized by the H₂-producing bacteria; however, the majority of structural carbohydrates remain underutilized in the microbial reaction [[18], [19], [20], [21], [22], [23]]. The current study aimed to achieve efficient coproduction of H₂ and volatile fatty acids (VFA) from the sweet sorghum stalks. Clostridium thermosaccharolyticum, a highly efficient H₂-producing thermophilic stain, was used to consume soluble sugars from the raw materials in the initial fermentation process; thereafter, the resulting residue obtained in the first fermentation process was treated with NaOH for delignification followed by cellulase treatment for subsequent release of soluble sugars. In the second step, the treated slurry was used to produce H₂ and VFA using the microbial cultures from the first step fermentation process.

Section snippets

Materials and chemicals

Sweet sorghum stalks were from Sonid Youqi Farm, Inner Mongolia, China. Stalks were dried at 60 °C and ground to ≤1 mm powder for all experiments [18]. All chemicals were obtained from Chemical Reagents Company, Beijing.

Microorganism and culture conditions

Clostridium thermosaccharolyticum (DSM572) was purchased from the Deutsche Sammlung von Mikroorganismen and Zellkulturen (DSMZ), Germany. The strain was cultured in modified CM4 medium composed of (g/L) 1.5 KH₂PO₄, 3.8 K₂HPO₄ · 3 H₂O, 1.3 (NH₄)₂SO₄, 1.6 MgCl₂ · 6H₂O, 0.013 CaCl₂

First step fermentation of sweet sorghum stalks using C. thermosaccharolyticum

C. thermosaccharolyticum was used to consume soluble sugars from the sweet sorghum stalks for the production of H₂, acetic acid and butyric acid. H₂ production reached 3.27 mmol/g-substrate, and acetic acid and butyric acid concentrations in the fermentation broth reached 1.18 g/L and 0.97 g/L, respectively. More than 97% of the soluble sugars from the sweet sorghum stalks were consumed in the first step fermentation process, and the above results were consistent with those reported in our

Conclusion

Two-step dark fermentation of whole sweet sorghum stalks without juice extraction and avoiding washing of the alkali-treated slurry for enzymatic hydrolysis enhanced the yields of H₂ and volatile fatty acids. The suitable NaOH treatment intensity of the slurry after the first step followed by enzymatic hydrolysis increased the release of soluble sugars with limited amount of phenolic compounds. The maximum total H₂ yield reached 6.37 mmol/g-substrate in the two-step fermentation of sweet

Acknowledgments

This work was financially supported by the State Key Laboratory of Bio-Fibers and Eco-Textiles (Qingdao University), the Key Research and Development Project of Shandong Province (2019GSF109079), the National Basic Research Program (973 Program) of China (No. 2013CB733600), the Qingdao Key Health Discipline Development Fund, and the CAS-TWAS President's Fellowship for Md. Saiful Islam.

References (50)

W.E. Mabee et al.
Bioethanol from lignocellulosics: status and perspectives in Canada, bioresour
Technol.
(2010)
X. Tao et al.
Reinforced acid-pretreatment of Triarrhena lutarioriparia to accelerate its enzymatic hydrolysis
Int. J. Hydrogen Energy
(2017)
Z. Yang et al.
Enhanced hydrogen production from lipid-extracted microalgal biomass residues through pretreatment
Int. J. Hydrogen Energy
(2010)
Z. Zhou et al.
Enhancement of enzymatic hydrolysis of sugarcane bagasse by pretreatment combined green liquor and sulfite
Fuel
(2017)
M. Wang et al.
Bioethanol production from cotton stalk: a comparative study of various pretreatments
Fuel
(2016)
Z. Yan et al.
Lignin relocation contributed to the alkaline pretreatment efficiency of sweet sorghum bagasse
Fuel
(2015)
S. Li et al.
A demonstration study of ethanol production from sweet sorghum stems with advanced solid state fermentation technology
Appl. Energy
(2013)
E. Palmqvist et al.
Fermentation of lignocellulosic hydrolysates. II: inhibitors and mechanisms of inhibition
Bioresour. Technol.
(2000)
I.A. Panagiotopoulos et al.
Effect of pretreatment severity on the conversion of barley straw to fermentable substrates and the release of inhibitory compounds
Bioresour. Technol.
(2011)
Q. Li et al.
Dynamic microwave-assisted alkali pretreatment of cornstalk to enhance hydrogen production via co-culture fermentation of Clostridium thermocellum and Clostridium thermosaccharolyticum
Biomass Bioenergy
(2014)

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¹: Md Saiful Islam and Zeju Zhang have contributed equally to this work.

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Coproduction of hydrogen and volatile fatty acids via integrated two-step fermentation of sweet sorghum stalks by alkaline and enzymatic treatment

Highlights

Abstract

Introduction

Section snippets

Materials and chemicals

Microorganism and culture conditions

First step fermentation of sweet sorghum stalks using C. thermosaccharolyticum

Conclusion

Acknowledgments

Technol.

Int. J. Hydrogen Energy

Int. J. Hydrogen Energy

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