Improved n-butanol production by a non-acetone producing Clostridium pasteurianum DSMZ 525 in mixed substrate fermentation

Wael Sabra,An-Ping Zeng,C Groeger,P N Sharma

doi:10.1007/s00253-014-5588-8

Abstract

The kinetics of growth, acid and solvent production in batch culture of Clostridium pasteurianum DSMZ 525 were examined in mixed or mono-substrate fermentations. In pH-uncontrolled batch cultures, the addition of butyric acid or glucose significantly enhanced n-butanol production and the ratio of butanol/1,3-propanediol. In pH-controlled batch culture at pH = 6, butyric acid addition had a negative effect on growth and did not lead to a higher n-butanol productivity. On the other hand, mixed substrate fermentation using glucose and glycerol enhanced the growth and acid production significantly. Glucose limitation in the mixed substrate fermentation led to the reduction or inhibition of the glycerol consumption by the growing bacteria. Therefore, for the optimal growth and n-butanol production by C. pasteurianum, a limitation of either substrate should be avoided. Under optimized batch conditions, n-butanol concentration and maximum productivity achieved were 21 g/L, and 0.96 g/L × h, respectively. In comparison, mixed substrate fermentation using biomass hydrolysate and glycerol gave a n-butanol concentration of 17 g/L with a maximum productivity of 1.1 g/L × h. In terms of productivity and final n-butanol concentration, the results demonstrated that C. pasteurianum DSMZ 525 is well suitable for n-butanol production from mixed substrates of biomass hydrolysate and glycerol and represents an alternative promising production strain.

Highlights

Before the 1950s, acetone-butanol-ethanol (ABE) fermentations using Clostridia ranked second to ethanol in importance and scale of bioproduction processes
Despite the high potential of C. pasteurianum for the production of n-butanol (Biebl 2001; Malaviya et al 2012; Khanna et al 2013a, b), only a few publications have dealt with the optimization of n-butanol production with this microorganism
With C. pasteurianum, instability and great variation in the formation of the two major products 1,3-PDO and butanol was revealed after growth on glycerol (Biebl 2001)

Summary

Introduction

Before the 1950s, acetone-butanol-ethanol (ABE) fermentations using Clostridia ranked second to ethanol in importance and scale of bioproduction processes. There are still three major hurdles for fermentative n-butanol to compete with the petroleum-based one (Biebl 2001; Jang et al 2012; Lee et al 2012; Tracy 2012). Glycerol as a byproduct from biodiesel production has recently attracted much attention as a potential substrate for bio-based production of chemicals and fuels Their abundance and cost competitiveness make both substrates excellent candidates for n-butanol production. Clostridium pasteurianum, on the other hand, is known as a potentially promising producer of n-butanol This microorganism normally does not produce acetone and ethanol, but organic acids such as acetic and butyric acids as major fermentation products from sugars. Biebl (2001) first reported the production of 17 g/L n-butanol in batch cultures with C. pasteurianum grown in semi-synthetic media containing glycerol as the sole carbon source. The use of BH was evaluated in the co-substrate bioprocess for n-butanol production

Materials and methods

Analytical methods

Results

Discussion