Effect of nitrogen, carbon sources and agitation speed on acetoin production of Bacillus subtilis SF4-3

Background: Currently, microbial fermentation method has become the research hotspot for acetoin production. In our previous work, an acetoin-producing strain, Bacillus subtilis SF4-3, was isolated from Japanese traditional fermented food natto. However, its conversion of glucose to acetoin was relatively low. In order to achieve a high-efficient accumulation of acetoin in B. subtilis SF4-3, main medium components and fermentation conditions were evaluated in this work. Results: The by-products analysis showed that there existed reversible transformation between acetoin and 2,3-butanediol that was strictly responsible for acetoin production in B. subtilis SF4-3. The carbon sources, nitrogen sources and agitation speed were determined to play crucial role in the acetoin production. The optimal media (glucose-H2O 150 g/L, yeast extract 10 g/L, corn steep dry 5 g/L, urea 2 g/L, K2HPO4 0.5 g/L, MgSO4 0.5 g/L) were obtained. Furthermore, the low agitation speed of 300 r/min was found to be beneficial to the reversible transformation of 2,3-butanediol for acetoin production in B. subtilis SF4-3. Eventually, 48.9 g/L of acetoin and 5.5 g/L of 2,3-butanediol were obtained in a 5-L fermenter, and the specific production of acetoin was 39.12% (g/g), which accounted for 79.90% of the theoretical conversion. Conclusions: The results indicated acetoin production of B. subtilis SF4-3 was closely related to the medium components and dissolved oxygen concentrations. It also provided a method for acetoin production via the reversible transformation of acetoin and 2,3-butanediol.

Production of 2,3-Butanediol from Sucrose by Klebsiella pneumoniae NRRL B199 in Batch and Fed-Batch Reactors

In batch mode, Klebsiella pneumoniae growth and 2,3-butanediol/acetoin formation are increasingly inhibited by initial sucrose concentrations (S0) over 60 g/L. At non inhibitory conditions, a maximum sucrose consumption rate of 1,5 g/L/h was measured. With S0=204 g/L however, this rate decreased to 0.15 g/L/h. K. pneumoniae fermented 204 g/L sucrose to produce 84.3 g/L of a mixture 2,3-butanediol/acetoin with a yield of 0.41 g/g and a productivity of 1.06 g/L/h. Higher oxygen transfer rates improved the overall process rate but the product yield was reduced. Avoiding substrate inhibition, by performing the fermentation in fed-batch mode, a final 2,3-butanediol/acetoin concentration of 80.0 g/L was achieved. In this case, a productivity of 2.63 g/L/h and a product yield of 0.37 g/g were calculated.

Em regime descontínuo, o crescimento celular e a formação de 2,3-butanodiol/acetoína por Klebsiella pneumoniae sofrem inibição por concentrações iniciais de sacarose (S0) acima de 60 g/L. Sob condições não inibidoras, uma velocidade máxima de consumo de sacarose de 1,5 g/L/h foi observada. Entretanto, com S0 = 204 g/L, esta velocidade decresceu para 0,15 g/L/h. A fermentação de 204 g/L de sacarose por K. pneumoniae levou à formação de 84,3 g/L de mistura 2,3-butanodiol/acetoína, com uma conversão de 0,41 g/g e uma produtividade de 1,06 g/L/h. Um maior suprimento de oxigênio aumentou a velocidade global do processo mas reduziu a conversão em produto. Em regime descontínuo alimentado, a inibição foi evitada, tendo sido atingida uma concentração final de produtos de 80,0 g/L, com uma produtividade de 2,63 g/L/h e uma conversão de 0,37 g/g.

Analysis of the UV absorbing constituents of the metabolites from UV-B tolerance bacteria and study on its anti-ultraviolet mechanism / 中国海洋药物

Objective The anti-UV-B radiation mechanism of UV-B tolerance strain KFS-9 was studied from the profile of metabolites.Methods The compounds were separated by column chromatography and their structures were elucidated based on GC-MS,LC-TOF-MS,EI-MS and NMR analyses.Results Three unsaturated fatty acids(identified as 9-hexadecenoic acid,9,12-octadecadienoic acid and 11-octadecenoic acid) and 1,2-benzenedicarboxylic acid able to absorb ultraviolet were isolated from the petroleum ether extract of the fermentation liquid of Pantoea agglomerans KFS-9.Fraction(Ⅱ) was isolated from the ethyl acetate extract and was composed of 2,3-butanediol and a series of high unsaturated aroma compounds.Fraction(Ⅱ) had a wide absorption peak,and it could protect E.coli from UV-B damage in some sense.Conclusion Strain KFS-9 produced metabolites that were able to absorb UV to build a natural barrier and so improved the tolerance to UV radiation.The UV-B radiation protection test to the E.coli also showed fraction(Ⅱ) was not the only protector,and there definitely existedother materials and mechanism to protect the strain.