The synthesis of n-caproate from lactate: a new efficient process for medium-chain carboxylates production

Abstract

A unique microbiome that metabolizes lactate rather than ethanol for n-caproate production was obtained from a fermentation pit used for the production of Chinese strong-flavour liquor (CSFL). The microbiome was able to produce n-caproate at concentrations as high as 23.41 g/L at a maximum rate of 2.97 g/L/d in batch trials without in-line extraction. Compared with previous work using ethanol as the electron donor, the n-caproate concentration increased by 82.89%. High-throughput sequencing analysis showed that the microbiome was dominated by a Clostridium cluster IV, which accounted for 79.07% of total reads. A new process for n-caproate production was proposed, lactate oxidation coupled to chain elongation, which revealed new insight into the well-studied lactate conversion and carbon chain elongation. In addition, these findings indicated a new synthesis mechanism of n-caproate in CSFL. We believe that this efficient process will provide a promising opportunity for the innovation of waste recovery as well as for n-caproate biosynthesis.

Production of high-concentration n-caproic acid from lactate through fermentation using a newly isolated Ruminococcaceae bacterium CPB6

“…5, with an initial fermentation cycle and a further wastewater replenishment, a final CA concentration of 16.6 g/L was obtained with rapid consumption of lactate in the wastewater. The maximum CA productivity was 5.29 g/L/day, which was nearly two times higher than the results from our previous report when mixed culture was used [18]. The control reactor with sterile wastewater showed a production of CA of 15.9 g/L with a maximum productivity of 5.63 g/L/day (Additional file 2: Figure S4).…”

“…However, in none of the above cases for CA production from endogenous lactate [14, 18, 20], M. elsdenii was detected. So, M. elsdenii was not likely the main strain that is responsible for the lactate-to-CA conversion in these processes.…”

Complete genome sequence of Ruminococcaceae bacterium CPB6: A newly isolated culture for efficient n -caproic acid production from lactate

“…Only trace amount of CA production (0.26-0.48 g/L) from lactate have been reported for the fermentation with M. elsdenii (Marounek et al, 1989). However, recently, we showed high level CA production from endogenous or exogenous lactate for the first time with a microbiome in a fed-batch reactor system (Zhu et al, 2015). Afterwards, Kucek et al (2016) also reported similar results in a continuous fermentation process.…”

“…Notably, Clostridium cluster IV is observed to be the most prominent population in the lactate-utilizing, CA-producing microbiome (Strauber et al, 2016;Zhu et al, 2015). This cluster belongs to the family Ruminococcaceae and is found to be abundant in gut microbiota, which plays an important role in host resistance against intestinal pathogens and promotion of systemic autoimmunity (Atarashi et al, 2011).…”

Waste Conversion into n-Caprylate and n-Caproate: Resource Recovery from Wine Lees Using Anaerobic Reactor Microbiomes and In-line Extraction

“…n -Caproate has been produced with reactor microbiomes from ethanol (Levy et al, 1981; Steinbusch et al, 2011; Agler et al, 2012), carbohydrates (Wang et al, 2007; Ding et al, 2010), and lactate (Zhu et al, 2015; Kucek et al, 2016a) as electron donors. Ethanol-fed bioreactors have demonstrated superior n -caproate productivities (Grootscholten et al, 2013c).…”