It has been thought that when different strains of Aureobasidium spp. were grown in sucrose, the produced fructooligosaccharides (FOSs) by β-D-fructofuranosidase were beneficial for their cell growth and pullulan biosynthesis. However, it is still unknown about how β-D-fructofuranosidases activity and synthesized FOSs influence on pullulan biosynthesis. It was found that the genomic DNA of Aureobasidium melanogenum P16, a high pullulan producing yeast, contained three genes encoding β-D-fructofuranosidase1, β-D-fructofuranosidase2 and β-D-fructofuranosidase3. The FTR1 factor, a transcriptional activator, activated expression of the three β-D-fructofuranosidase genes and invertase gene. Disruption of the FTR1 gene rendered a disruptant DF3 to produce less FOSs (12.1 ± 0.4 g/L), less β-D-fructofuranosidase activity (1.1 ± 0.2 U/mL), lower Mw (380000) of the pullulan and more pullulan titer (77.0 ± 2.6 g/L) than the yeast strain P16. Similarly, removal of both the two genes encoding β-D-fructofuranosidase1 and β-D-fructofuranosidase3 resulted in a double mutant DF4-7 producing 77.5 ± 3.1 g/L pullulan with Mw of 340000, 0.2 ± 0.0 U/mL of β-D-fructofuranosidase activity and the trace amount of FOSs while its wild type strain P16 yielded 65.7 ± 3.5 g/L pullulan with Mw of 440000, 6.8 ± 0.0 U/mL of β-D-fructofuranosidase activity and 6.2 ± 0.5 g/L of FOSs. These confirmed that high β-D-fructofuranosidase activity, the presence of high level of FOSs negatively influenced pullulan biosynthesis, but positively increased Mw of the produced pullulan. However, the β-D-fructofuranosidase2 had no such function. Furthermore, complementation of the FTR1 gene, β-D-fructofuranosidase1 gene and β-D-fructofuranosidase3 gene enabled the corresponding transformants to restore β-D-fructofuranosidase activity, FOSs and pullulan biosynthesis and Mw of the pullulan.

pullulan, fructooligosaccharides, β-D-fructofuranosidase, Aureobasidium melanogenum, transcriptional activator

• Compound ID: 22163
  

  -6)-a-D-Glcp-(1-4)-a-D-Glcp-(1-4)-a-D-Glcp-(1-

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  Structure type: polymer chemical repeating unit ; 380000-440000
  Trivial name: pullulan
  Compound class: glucan, polysaccharide
  Reference(s) to other database(s): GTC:G71532WE, GenDB:XM_001396532
  
   
  
  Aureobasidium melanogenum P16, Aureobasidium melanogenum DG41, Aureobasidium melanogenum DF3, Aureobasidium melanogenum DF1-52, Aureobasidium melanogenum DF3-9, Aureobasidium melanogenum DF4-7 EF8, Aureobasidium melanogenum EF1-33, Aureobasidium melanogenum EF3-42
  CSDB ID 49979 (all data & tools)