| Biosurfactants(BS)can be widely used due to their wide variety and complex structure.The main reason for high-limit large-scale production is low product yield and high production cost.At present,the production is mainly reduced by mutagenizing strains,changing fermentation conditions and optimizing the composition of the medium.Bacillus licheniformis DGG-1-3-F was studied by measuring the cell density(OD600),surface tension(ST),emulsifying activity(EI24)and BS yield of the fermentation broth using different metal ions(MgSO4,MnSO4 and Fe SO4)and amino acids(Glu or Gln)effects of fermentation,in order to increase yield by changing the composition of the medium.The results showed that the addition of different concentrations of(0,0.2,0.3,0.6,0.8m M)MgSO4 or MnSO4 could promote the growth of bacteria and the formation of products.The growth of the cells in the 0.3mM MgSO4 group was slow but the yield of BS was the highest(29.6 mg / L),which was 8 times higher than that of the control group(3.5 mg / L),and the decrease of ST(65.5%)was significantly higher than that of the other groups(P<0.05).The yield and ST decrease of BS in the 0.6mM MnSO4 group were higher than those in the other groups(P<0.05),but the growth of the cells was also slower,indicating that limiting the cell growth rate favored the synthesis of the product.The results of TLC analysis were consistent with the results of the product yield determination.The BS components were all glycoproteins and there was no change in the composition during fermentation.The fermentation of BS was carried out by mixing MgSO4 and MnSO4(0,0.1,0.2,0.3,0.4mM)in different proportions.The results showed that the 0.3mM MgSO4 and MnSO4 groups were more favorable for the production of BS,but the growth of the strain was slow,indicating that cell growth was restricted to product synthesis.The growth of the cells and the decrease of ST(67.2%)in the mixed fermentation of MgSO4 and Fe SO4 were significantly higher than those in the other groups(P<0.05),and the amount of BS produced was increased by 20.4 times(79.6 mg / L).Studies have shown that the mixed addition of MgSO4,MnSO4 and Fe SO4 can promote BS synthesis.The results of thin layer chromatography are consistent with the results of BS yield measurement.The mixed components of MgSO4,MnSO4 and Fe SO4 and the BS components of MgSO4 and MnSO4 alone may be glycoproteins.And there is no change in the composition during the fermentation.The results showed that at the same nitrogen concentration(0.047 M),the ST decline(71.3% and 70.2%)and the increase in BS yield(21.8 and 19.5)of the strains using Glu and Na NO3,Gln and Na NO3 were significantly higher than Glu and Gln(P<0.05).The results of thin layer chromatography are the same as those of BS.The BS component fermented by Glu and Gln may be a single glycolipid or lipopeptide,but the BS component fermented by Glu and Na NO3,Gln and Na NO3 may be a complex glycolipid or lipopeptide.It indicated that Glu and Gln can accelerate the metabolism of inorganic nitrogen in the medium and promote the synthesis of lipopeptides.The foam stability coefficient of the fermentation supernatant was 0.94~0.98.The bubbling separation of 100 m L fermentation supernatant could obtain 55% foam extraction rate at p H 1~8 and gas flow rate of 1.8 L/min.As the extraction time increases,the concentration of sugar,protein and lipid in the extract gradually decreases,at p H 1-5.In the first 12 min,the concentrations of sugar and protein(65 mg / L and 44.3 mg / L)were higher at p H 2,and the concentration of lipid(5.4 mg / L)was smaller.The concentration of sugar and protein decreased to the same level,and the lipid concentration decreased to 0 at 12-21 min.The composition and content of the foam in the foam obtained by different p H separations at different stages were different. |
PDF Full Text Request