Continuous Butanol Fermentation of Dilute Acid-Pretreated De-oiled Rice Bran by Clostridium acetobutylicum YM1

Najeeb Kaid Nasser Al-Shorgani,Abdualati Ibrahim Al-Tabib,Mohd Fauzi Zanil,Abudukeremu Kadier,Mohd Sahaid Kalil,Kiat Moon Lee

doi:10.1038/s41598-019-40840-y

Najeeb Kaid Nasser Al-Shorgani, Abdualati Ibrahim Al-Tabib + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-40840-y

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Abstract

Continuous fermentation of dilute acid-pretreated de-oiled rice bran (DRB) to butanol by the Clostridium acetobutylicum YM1 strain was investigated. Pretreatment of DRB with dilute sulfuric acid (1%) resulted in the production of 42.12 g/L total sugars, including 25.57 g/L glucose, 15.1 g/L xylose and 1.46 g/L cellobiose. Pretreated-DRB (SADRB) was used as a fermentation medium at various dilution rates, and a dilution rate of 0.02 h−1 was optimal for solvent production, in which 11.18 g/L of total solvent was produced (acetone 4.37 g/L, butanol 5.89 g/L and ethanol 0.92 g/L). Detoxification of SADRB with activated charcoal resulted in the high removal of fermentation inhibitory compounds. Fermentation of detoxified-SADRB in continuous fermentation with a dilution rate of 0.02 h−1 achieved higher concentrations of solvent (12.42 g/L) and butanol (6.87 g/L), respectively, with a solvent productivity of 0.248 g/L.h. This study showed that the solvent concentration and productivity in continuous fermentation from SADRB was higher than that obtained from batch culture fermentation. This study also provides an economic assessment for butanol production in continuous fermentation process from DRB to validate the commercial viability of this process.

Highlights

The worldwide energy demand is continuously increasing over time due to the expected decline of petrol and due to environmental issues that are related to the use of petrol as a source of energy[1]
The results of this study showed that C. acetobutylicum YM1 has high efficiency for butanol production in continuous fermentation from both substrates, glucose and SADRB hydrolysate
Pretreatment of de-oiled rice bran followed by detoxification was a necessary process for the enhancement of butanol production

Summary

Introduction

The worldwide energy demand is continuously increasing over time due to the expected decline of petrol and due to environmental issues that are related to the use of petrol as a source of energy[1]. Clostridium acetobutylicum YM1 is a solvent-producing strain that was isolated from local agricultural soil in Malaysia and has been used for butanol and hydrogen production[2,3]. The use of low cost and sustainable feedstocks for butanol production can minimize the cost of this process[4]. Some Clostridium strains have been engineered using systematic or mutagenesis approaches to improve butanol productivity and overcome the butanol toxicity. CRISPR-Cas provided large-scale genome editing of Clostridium over than mutagenesis and genetic manipulation techniques. CRISPR-Cas-based editing tool kits is a promising biotechnology which can be used for efficient Clostridium cell engineering for improving butanol production[6]. A comprehensive review on recent strategies for strain development and advanced downstream process techniques for butanol production by Clostridium acetobutylicum is detailed by Xue et al.[6]

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