title: Intensification of β-poly(L: -malic acid) production by Aureobasidium                      pullulans ipe-1 in the late exponential growth phase.
abstract: β-Poly(malic acid) (PMLA) has attracted industrial interest because this polyester can be used as a prodrug or for drug delivery systems. In PMLA production by Aureobasidium pullulans ipe-1, it was found that PLMA production was associated with cell growth in the early exponential growth phase and dissociated from cell growth in the late exponential growth phase. To enhance PMLA production in the late phase, different fermentation modes and strategies for controlling culture redox potential (CRP) were studied. The results showed that high concentrations of produced PMLA (above 40 g/l) not only inhibited PMLA production, but also was detrimental to cell growth. Moreover, when CRP increased from 57 to 100 mV in the late exponential growth phase, the lack of reducing power in the broth also decreased PMLA productivity. PMLA productivity could be enhanced by repeated-batch culture to maintain cell growth in the exponential growth phase, or by cell-recycle culture with membrane to remove the produced PMLA, or by maintaining CRP below 70 mV no matter which kind of fermentation mode was adopted. Repeated-batch culture afforded a high PMLA concentration (up to 63.2 g/l) with a productivity of 1.15 g l(-1) h(-1). Cell-recycle culture also confirmed that PMLA production by the strain ipe-1 was associated with cell growth.
authors.affiliation: National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China.
authors.forename: Weifeng
authors.initials: W
authors.lastname: Cao
authors.forename: Jianquan
authors.initials: J
authors.lastname: Luo
authors.forename: Juan
authors.initials: J
authors.lastname: Zhao
authors.forename: Changsheng
authors.initials: C
authors.lastname: Qiao
authors.forename: Luhui
authors.initials: L
authors.lastname: Ding
authors.forename: Benkun
authors.initials: B
authors.lastname: Qi
authors.forename: Yi
authors.initials: Y
authors.lastname: Su
authors.forename: Yinhua
authors.initials: Y
authors.lastname: Wan
mesh_terms: D001203:Ascomycota / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D005285:Fermentation; D007218:Industrial Microbiology; D008293:Malates / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism*
chemical_list: D008293:Malates; D011108:Polymers; C121060:poly(malic acid)