Efficient poly(β-L-malic acid) production from cassava hydrolysate by cell recycle of Aureobasidium pullulans

Poly(β-L-malic acid) (PMLA) is a water-soluble, biodegradable, and biocompatible polymer with broad prospective applications and can be hydrolyzed to produce widely used acidulant L-malic acid. In order to meet an increasing demand of PMLA, we employed two effective cell-recycling strategies to produce PMLA from raw cassava hydrolysate by Aureobasidium pullulans ZD -3d. In fed-batch fermentation with raw cassava hydrolysate, 101.9 g/L PMLA was obtained with the productivity and yield of 0.77 g/L/h and 0.40 g/g, respectively. Further, three times of membrane filtration–based cell recycling fermentation was carried out, with a high productivity and yield of 1.04–1.64 g/L/h and 0.5–0.84 g/g achieved, respectively. While harnessing centrifugation-based cell recycling fermentation for five times, the productivity and yield approached 0.98–1.76 g/L/h and 0.78–0.86 g/g, respectively. To our knowledge, the processes showed the highest average PMLA productivity compared with others using low-cost biomass, which offered efficient and economical alternatives for PMLA production. Graphical abstract Key points • PMLA production from raw cassava hydrolysate by Aureobasidium pullulans was studied • High PMLA productivity and yield were obtained via two cell recycling strategies • The highest average PMLA productivity from low-cost biomass to date was achieved