Simultaneous production of 1,3‐propanediol and n‐butanol by Clostridium pasteurianum: In situ gas stripping and cellular metabolism

Abstract

Clostridium pasteurianum is a promising producer of the bulk chemicals 1,3‐propanediol and n‐butanol (BuOH), with significantly different product patterns and physiology from other typical Clostridia. Nevertheless, its growth and product formation are ultimately limited by the accumulation of inhibiting products, especially by BuOH. In this study, we implemented in situ gas stripping for BuOH removal and compared the stripping performance of external nitrogen (N2) and fermentation effluent gas (FG) from the process itself. Gas stripping was studied in fermentations of glycerol and a mixture of glycerol and glucose. In general, N2 exhibits favourable physical properties to strip out BuOH from an aqueous phase. However, in situ removal of butanol in C. pasteurianum culture with N2 stripping strongly perturbs the culture conditions such as the redox potential and thus the physiology of the microorganism, leading to enhanced formation of organic acids, especially in cosubstrate fermentation, whereas the use of FG does not show such perturbations. In an effort to explore the use of FG for gas stripping the effects of FG circulation rate and stirring speed of the bioreactor on BuOH stripping efficiency and the fermentation performance were studied in more detail. Mass transfer coefficient (kSa) of BuOH in the bioreactor was also characterized at different gas circulation rates and stirring speeds. In a fermentation of glycerol with FG stripping at a relatively high gas flow rate (7 vvm) as high as 39.2 g/L BuOH (total) and 53.7 g/L 1,3‐PDO can be simultaneously produced. The results are discussed in view of further process optimization and scale up.

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

“…using Clostridia [12][13][14][15][16][17]. Clostridium pasteurianum (C. pasteurianum) stands out owing to its ability to utilize and valorize glycerol by production of PDO and n-butanol [18,19] with completely different patterns from the well-studied C. butyricum for PDO production [20] or C. acetobutylicum for the classic aceton-butanol-ethanol process [21]. Recently, we have studied C. pasteurianum fermentation for butanol production [22,23].…”

Metabolic and proteomic analyses of product selectivity and redox regulation in Clostridium pasteurianum grown on glycerol under varied iron availability

“…Recently, C. pasteurianum was shown to accept electrons from the cathode by direct electron transfer [7], which make it an attractive candidate for new bioelectrical systems. Therefore, C. pasteurianum has received considerable interests for the production of chemicals and fuels such as 1,3-propanediol (1,3-PDO) and n -butanol (BuOH), which represents attractive bioprocesses for the use of renewable resources, like biodiesel-derived glycerol or glucose from biomass hydrolysates [8–14]. In such bioprocesses, several other fermentation products like gases (carbon dioxide and hydrogen), ethanol as well as acetic, butyric and lactic acid are produced [2, 4, 15], in addition to 1,3-PDO and BuOH.…”

Metabolomic and kinetic investigations on the electricity‐aided production of butanol by Clostridium pasteurianum strains

“…Cell growth was tracked by measuring the OD 600 and correlated with bio dry mass by multiplying the OD values with the constant factor 0.337, according to Groeger et al. [28].…”