High Production of 2,3-Butanediol (2,3-BD) by Raoultella ornithinolytica B6 via Optimizing Fermentation Conditions and Overexpressing 2,3-BD Synthesis Genes

Abstract

Biological production of 2,3-butandiol (2,3-BD) has received great attention as an alternative to the petroleum-based 2,3-BD production. In this study, a high production of 2,3-BD in fed-batch fermentation was investigated with a newly isolated bacterium designated as Raoultella ornithinolytica B6. The isolate produced 2,3-BD as the main product using hexoses (glucose, galactose, and fructose), pentose (xylose) and disaccharide (sucrose). The effects of temperature, pH-control schemes, and agitation speeds on 2,3-BD production were explored to optimize the fermentation conditions. Notably, cell growth and 2,3-BD production by R. ornithinolytica B6 were higher at 25°C than at 30°C. When three pH control schemes (no pH control, pH control at 7, and pH control at 5.5 after the pH was decreased to 5.5 during fermentation) were tested, the best 2,3-BD titer and productivity along with reduced by-product formation were achieved with pH control at 5.5. Among different agitation speeds (300, 400, and 500 rpm), the optimum agitation speed was 400 rpm with 2,3-BD titer of 68.27 g/L, but acetic acid was accumulated up to 23.32 g/L. Further enhancement of the 2,3-BD titer (112.19 g/L), yield (0.38 g/g), and productivity (1.35 g/L/h) as well as a significant reduction of acetic acid accumulation (9.71 g/L) was achieved by the overexpression of homologous budABC genes, the 2,3-BD-synthesis genes involved in the conversion of pyruvate to 2,3-BD. This is the first report presenting a high 2,3-BD production by R.ornithinolytica which has attracted little attention with respect to 2,3-BD production, extending the microbial spectrum of 2,3-BD producers.

Technological development of the bio‐based 2,3‐butanediol process

“…Metabolic engineering can also control the formation of NADH‐dependent by‐products, prioritizing the major pathway for 2,3‐BDO formation over the parallel metabolic pathways 30 . The main modified and recently isolated microorganisms reported in the evaluated documents were: Klebsiella pneumoniae , 31,32 K. oxytoca , 33–35 Paenibacillus polymyxa , 23,36,37 Bacillus subtillis , 38 Clostridium sp., 39,40 Enterobacter cloacae , 41,42 Escherichia coli , 43,44 Raoultella sp., 45,46 Zymobacter sp., 47 Pichia pastoris sp., 24 B. licheniformis , 48 B. amyloliquefaciens , 49,50 Serratia marcescens , 51,52 and Saccharomyces cerevisiae 3,53 . Cellular modifications also aim at process safety, which is considered to be another important requirement for large‐scale 2,3‐BDO production.…”

The current strategies and parameters for the enhanced microbial production of 2,3-butanediol

“…However, accumulation of acetic acid reached up to 23.32 g/l. In addition, the overexpression of homologous budABC genes improved the 2,3-BD production up to 112.19 g/l and 1.35 g/l.h productivity, whereas accumulation of acetic acid decreased to 9.71 g/l [50].…”

“…As a solution to scarcity of nonrenewable energy resources, biofuel is the only sustainable solution to satisfy ever-growing energy demands [[2], [3], [4]]. One of the examples is microbial production of 2, 3-butanediol by different microorganisms including bacteria and yeast trains [1,5], and it is now widely used in the industry [[6], [7], [8]]. 2,3-BD is a valuable chemical feedstock due to its potential applications [9], including its use as a liquid fuel and for the production of various chemicals, foods, and pharmaceuticals (Fig.…”

Rapid Production of a Novel Al(III) Dependent Bioflocculant Isolated From Raoultella ornithinolytica 160-1 and Its Application Combined With Inorganic Salts

“…Raoultella strains with potential biotechnological application have been reported with pullulanase and peroxidase production ( Hii et al, 2012 ; Freitas et al, 2017 ). Recently, in contrast with petroleum-based 2,3-butanediol (2,3-BD) production, the biological production of 2,3-BD by R. ornithinolytica is an environmentally friendly method and has received much attention ( Kim et al, 2016 ). To date, few literatures have reported on the production of bioflocculants from Raoultella strains.…”