Abstract
An optimization process with a cheap and abundant substrate is considered one of the factors affecting the price of the production of economical 2,3-Butanediol (2,3-BD). A combination of the conventional method and response surface methodology (RSM) was applied in this study. The optimized levels of pH, aeration rate, agitation speed, and substrate concentration (maltodextrin) were investigated to determine the cost-effectiveness of fermentative 2,3-BD production by metabolically-engineered Klebsiella oxytoca KMS005. Results revealed that pH, aeration rate, agitation speed, and maltodextrin concentration at levels of 6.0, 0.8 vvm, 400 rpm, and 150 g/L respectively were the optimal conditions. RSM also indicated that the agitation speed was the most influential parameter when either agitation and aeration interaction or agitation and substrate concentration interaction played important roles for 2,3-BD production by the strain from maltodextrin. Under interim fed-batch fermentation, 2,3-BD concentration, yield, and productivity were obtained at 88.1±0.2 g/L, 0.412±0.001 g/g, and 1.13±0.01 g/L/h respectively within 78 h.
Highlights
Bio-refinery systems that integrate bio-mass conversion processes and are equipped to produce fuel, power, and bio-based chemicals from renewable resources are the focus of worldwide development due to concerns about scarce crude oil reserves, gradual increases in price, and environmental pollution [1, 2]. 2,3-Butanediol (2,3-BD) is one example of bulk chemicals produced by fermentation that has raised much interest
The effects of pH in the range of 5.0 to 7.0 on 2,3-BD production by the KMS005 strain were initially investigated at the aeration rate and agitation speed of 0.5 vvm and 200 rpm respectively, and maltodextrin at the concentration of 100 g/L was used
The highest levels of by-products, mainly succinate and acetate, were accumulated at pH 7.0. This observation was in agreement with Lee et al [7] whose study stated that an increased pH led to higher proportions of fermentative metabolites such as acetate, suucinate, and ethanol, resulting in a decreased level of 2,3-BD in K. pneumoniae
Summary
Bio-refinery systems that integrate bio-mass conversion processes and are equipped to produce fuel, power, and bio-based chemicals from renewable resources are the focus of worldwide development due to concerns about scarce crude oil reserves, gradual increases in price, and environmental pollution [1, 2]. 2,3-Butanediol (2,3-BD) is one example of bulk chemicals produced by fermentation that has raised much interest. There are several micro-organisms, including Klebsiella pneumoniae, K. oxytoca, Bacillus polymyxa, Serratia marcescens, capable of naturally producing 2,3-BD [4]. Among these species, Klebsiella spp. were comprehensively studied for fermentative 2,3-BD production [5,6,7,8,9]. K. oxytoca has an advantage at the purification step over K. pneumoniae owing to less formation of capsular polysaccharide during 2,3-BD production [10]. This may make K. pneumoniae unsuitable for 2,3-BD production on a large scale
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