Electrolytic stimulation in aid of poly(β-L-malic acid) production by Aureobasidium melanogenum ipe-1

Poly (β-L-malic acid) (PMLA) is attracting industrial interest for its potential application in medicine and other industries. In this study, electrolytic stimulation assisted PMLA production was developed. Firstly, it was found that the pentavalent nitrogen source (i.e., NO₃^-) was more suitable for PMLA production. Secondly, a usual single-chamber bioelectric-fermentation system (BES) cannot improve PMLA production, which can only promote cell growth. Then, a new single-chamber BES with an external circulation was developed, where the PMLA metabolism was further intensified. Finally, the integration of NO₃^- addition and electrolytic stimulation mode (c) showed a positive synergy on the PMLA production. Compared to the case without NO₃^- addition and electrolytic stimulation, the PMLA production was increased by 22.9 % using the integrated process. Moreover, compared to the case without the electrolytic stimulation mode (c), it was revealed that the different genes involved in 12 metabolic subsystems using the integrated process, where 31 and 177 genes were up-regulated and down-regulated, respectively. The up-regulated genes were mainly participated in melanin metabolic process, catalase activity, and oxidoreductase activity. Hence, the integration of electrolytic stimulation represents a novel approach to improve PMLA production.