Capability of Immobilized Clostridium beijerinckii TISTR 1461 on Lotus Stalk Pieces to Produce Butanol from Sugarcane Molasses

Patthranit Narueworanon,Pattana Laopaiboon,Lakkana Laopaiboon

doi:10.3390/pr9040573

Abstract

Immobilized Clostridium beijerinckii TISTR 1461 was used to enhance the butanol production efficiency from sugarcane molasses. Lotus stalk (LS) pieces were used as carriers for cell immobilization. Sugarcane molasses containing 50 g/L of sugar supplemented with 1 g/L of yeast extract was found to be an appropriate medium for bacterial cell immobilization on the LS pieces. Carrier size (4, 12 and 20 mm in length) and carrier loading (1:15, 1:30 and 1:45, w/v) were optimized for high levels of butanol production using response surface methodology (RSM). The batch fermentation was carried out under anaerobic conditions in 1 L screw-capped bottles at 37 °C and an agitation rate of 150 rpm. It was found that the optimum conditions for the butanol production were the carrier size of 4 mm and carrier loading of 1:31 (w/v). Under these conditions, the butanol concentration (PB) was 12.89 g/L, corresponding to the butanol productivity (QB) of 0.36 g/L∙h and butanol yield (YB/S) of 0.36 g/g. These values were higher than those using free cells (PB, 10.20 g/L, QB, 0.28 g/L∙h and YB/S, 0.32 g/g). In addition, it was found that a 24 h incubation time for cell immobilization was appropriate for the immobilization process, which was confirmed by the results of the scanning electron microscope (SEM) and atomic force microscopy (AFM) images and specific surface area measurement. When the fermentation using the immobilized cells was carried out in a stirred-tank reactor (STR), column reactor (CR) and CR coupled with STR, the results showed that all reactors could be used to produce butanol production from the immobilized cells on LS pieces. However, the PB using CR and CR coupled with STR were only 75% and 45% of those using the screw-capped bottle and STR.

Highlights

The results showed that the batch profiles of ABE fermentation by the immobilized cells in tryptone-glucose-yeast extract (TGY) medium were similar to those in the sugarcane molasses medium (Figure 2)
The pH of the fermentation broth decreased sharply during the 12 h fermentation, corresponding to acetic and butyric acid production (Figure 2b). This indicated that acidogenesis occurred in this period, implying that cells were very active. pH in the fermentation broth slightly increased after 12 h, and acetone, butanol and ethanol were detected (Figure 2a), indicating the occurrence of solventogenesis
Other parameters measured during butanol fermentation were not significantly different, indicating that sugarcane molasses added with 1 g/L of YE could be used as a low-cost immobilization medium for butanol fermentation

Summary

Introduction

It is employed as a solvent in the production of plastics, polymers, lubricants, hydraulic fluids, hormones, drugs, antibiotics, cosmetics and vitamins [1]. It is a potential renewable biofuel and fuel additive for use in internal combustion engines. These include a greater energy content along with lower volatility, hydroscopicity, corrosivity and flammability than ethanol [2]. Butanol can serve as a fuel in gasoline engines with no engine modifications necessary. It is considered an exciting alternative to first generation biofuels that can serve as a starting material to make a wide variety of bio-based products [3]

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