Enhanced production of 2,3-butanediol from glycerol by forced pH fluctuations |
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Authors: | Kaloyan Petrov Penka Petrova |
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Institution: | (1) Institute of Chemical Engineering, Bulgarian Academy of Sciences, 103, Acad. G. Bonchev str., 1113 Sofia, Bulgaria;(2) Institute of Microbiology, Bulgarian Academy of Sciences, 26, Acad. G. Bonchev str., 1113 Sofia, Bulgaria |
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Abstract: | The glycerol fermentation by Klebsiella pneumoniae occurs by receiving more than five liquid products—organic acids, diols, and ethanol. Aiming to direct the glycerol conversion
towards predominant production of 2,3-butanediol (2,3-BD), the main influencing parameters (the aeration and the pH) were
investigated during fed-batch processes. The regime of intensive aeration (2.2 vvm air supply) was evaluated as most favorable
for 2,3-BD synthesis and ensured the decrease of all other metabolites. Thus, without pH control, 52.5 g/l 2,3-BD were produced,
as the carbon conversion of glycerol into 2,3-BD reached 60.6%. Additional enhancement in 2,3-BD production (by significant
increase of glycerol utilization) was achieved by the development of a new method of “forced pH fluctuations”. It was realized
by consecutive raisings of pH using definite ΔpH value, at exact time intervals, allowing multiple variations. Thus, the optimal
conditions for maximal glycerol consumption were defined, and 70 g/l 2,3-BD were produced, which is the highest amount obtained
from glycerol as a sole carbon source until now. The forced pH fluctuations emphasized pH as a governing factor in microbial
conversion processes. |
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