Modulation of crude glycerol fermentation by Clostridium pasteurianum DSM 525 towards the production of butanol

Abstract

High production yields and productivities are requisites for the development of an industrial butanol production process based on biodiesel-derived crude glycerol. However, impurities present in this substrate and/or the concentration of glycerol itself can affect the microbial metabolism. In this work, the effect of crude glycerol concentration on the production of butanol and 1,3-propanediol (1,3-PDO) by Clostridium pasteurianum DSM 525 is studied. Also, the effect of acetate and butyrate supplementation to the culture medium and the culture medium composition are evaluated. The results showed a marked effect of crude glycerol concentration on the product yield. The competitive nature of butanol and 1,3-PDO pathways has been evident, and a shift to the butanol pathway once using higher substrate concentrations (up to 35 g l À1) was clearly observed. Butyrate supplementation to the culture medium resulted in a 45% higher butanol titre, a lower production of 1,3-PDO and it decreased the fermentation time. Acetate supplementation also increased the butanol titre but the fermentation was longer. Even though glycerol consumption could not be increased over 32 g l À1 , when the concentrations of NH 4 Cl and FeCl 2 were simultaneously increased, the results obtained were similar to those observed when butyrate was supplemented to the culture medium; a 35% higher butanol yield at the expense of 1,3-PDO and a shorter fermentation. The results herein gathered suggest that there are other factors besides butanol inhibition and nutrient limitation that affect the glycerol consumption.

Impact of butyric acid on butanol formation by Clostridium pasteurianum

“…Butyric acid uptake in shake flasks and stirred tank reactors is typically shown under pH buffered conditions, using CaCO 3 as a buffering agent (Gallardo et al, 2014). The experimental results of a similarly configured system are shown in Fig.…”

“…The standard Gibbs free energy of formation (at 25°C and 101.3 kPa) of butyric acid (D f G°= À352.63 kJ mol À1 ) is very close to butanol (D f G°= À171.84 kJ mol À1 ), especially in comparison to the substrate glycerol (D f G°= À488.52 kJ mol À1 ) (Thauer et al, 1977). However, successful uptake and further conversion of butyric acid will directly increase butanol yield (Gallardo et al, 2014) and hence is a desired metabolic pathway to activate.…”

Improved electrocompetence and metabolic engineering of Clostridium pasteurianum reveals a new regulation pattern of glycerol fermentation

“…Bioproduction of fuels and chemicals has become a research field of increasing interest, as rising CO 2 levels in the atmosphere and growing awareness of its consequences indicate the need for more sustainable alternatives compared to the petroleum-based industries. Among others the microbial production of 1,3-propanediol (PDO) and n-butanol has received particular attention and is industrially used [1][2][3][4][5][6][7][8]. They can Abbreviations: C. pasteurianum, Clostridium pasteurianum; PDO, 1,3-propanediol; gRNA, guide RNA; MFA, metabolic flux analysis; SNPs, single-nucleotide polymorphisms be produced from fermentations of glycerol -a byproduct from biodiesel production [9][10][11] -and sugars, e.g.…”

Anaerobic and micro-aerobic 1,3-propanediol production by engineered Escherichia coli with dha genes from Klebsiella pneumoniae GLC29

“…Glucose is a high cost feedstock, and biodieselderived glycerol is becoming an abundant alternative feedstock, due to the increasing biodiesel production (Pyne, 2014). The price of corn-derived glucose is approximately US$ 0.28/kg (Gallardo et al, 2014) while the current price of biodiesel-derived glycerol varies from US$ 0.04 to 0.11/kg (Quispe et al, 2013). Some processes of biodiesel production generate crude glycerol a byproduct considered as waste, generally with no commercial value or acceptance, and its disposal costs is attributed to the biodiesel producers (Yazdani and Gonzalez, 2007).…”