Efficient butanol production under aerobic conditions by coculture of Clostridium acetobutylicum and Nesterenkonia sp. strain F

Abstract

Clostridium acetobutylicum is widely used for the microbial production of butanol in a process known as acetone–butanol–ethanol (ABE) fermentation. However, this process suffers from several disadvantages including high oxygen sensitivity of the bacterium which makes the process complicated and necessitate oxygen elimination in the culture medium. Nesterenkonia sp. strain F has attracted interests as the only known non‐Clostridia microorganism with inherent capability of butanol production even in the presence of oxygen. This bacterium is not delimited by oxygen sensitivity, a challenge in butanol biosynthesis, but the butanol titer was far below Clostridia. In this study, Nesterenkonia sp. strain F was cocultivated with C. acetobutylicum to form a powerful “coculture” for butanol production thereby eliminating the need for oxygen removal before fermentation. The response surface method was used for obtaining optimal inoculation amount/time and media formulation. The highest yield, 0.31 g/g ABE (13.6 g/L butanol), was obtained by a coculture initiated with 1.5 mg/L Nesterenkonia sp. strain F and inoculated with 15 mg/L C. acetobutylicum after 1.5 hr in a medium containing 67 g/L glucose, 2.2 g/L yeast extract, 4 g/L peptone, and 1.4% (vol/vol) P2 solution. After butanol toxicity assessment, where Nesterenkonia sp. strain F showed no butanol toxicity, the coculture was implemented in a 2 L fermenter with continual aeration leading to 20 g/L ABE.

Advances and Applications of Clostridium Co-culture Systems in Biotechnology

“…The fourth advantage is the improvement of system robustness. On the one hand, co-cultures with facultative anaerobic or aerobic bacteria will consume oxygen during the co-culture and provide anaerobic conditions for Clostridium (Zuroff et al, 2013;Wushke et al, 2015;Mai et al, 2016;Ebrahimi et al, 2019;Oliva-Rodríguez et al, 2019). On the other hand, metabolites that inhibit Clostridium growth may be removed by co-culture partners.…”

“…On the one hand, the Clostridium co-culture system can utilize cheaper renewable substrates. On the other hand, co-culturing Clostridium with Bacillus or other facultative anaerobic or aerobic bacteria that are able to consume oxygen, providing an anaerobic environment for Clostridium, precludes the need for expensive reductants or anaerobic operating conditions or equipment (Mai et al, 2016;Srivastava et al, 2018;Ebrahimi et al, 2019;Oliva-Rodríguez et al, 2019). And growth needs can also be met without the addition of exogenous nutrients (Mori, 1990).…”

“…Moreover, C. tyrobutyricum was also co-cultured with C. beijerinckii ATCC6014 to increase butanol production (Zhang et al, 2016a). Recently, Ebrahimi et al (2019) found the coculture of C. acetobutylicum and Nesterenkonia sp. strain F gave an efficient yield of 13.6 g/L butanol under aerobic conditions, which further made it possible to avoid control of anaerobic conditions.…”

“…It has been reported that many types of associated bacteria such as Bacillus, Enterobacter, Saccharomyces cerevisiae ( Figure 1B) (Zuroff et al, 2013), Candida molischiana (Zuroff et al, 2013), Caldibacillus debilis (Wushke et al, 2015), and Nesterenkonia sp. F (Ebrahimi et al, 2019) have the ability to remove oxygen, creating anaerobic conditions for Clostridium. In addition to removing oxygen to maintain an anaerobic environment, the removal of other metabolic inhibitors plays a critical role in the stability of a co-culture.…”

Development of optimal steam explosion pretreatment and highly effective cell factory for bioconversion of grain vinegar residue to butanol

“…In the future study, many established methods could be employed to further improve our study, which includes (i) metabolic engineering of C. tyrobutyricum for n-butanol production through co-utilization of glucose and xylose [52]; (ii) co-culture strategy [53] and (iii) process reinforcement strategy, including gas stripping [54] and new bioreactors [55,56].…”