An economical biorefinery process for propionic acid production from glycerol and potato juice using high cell density fermentation.

An economically sustainable process was developed for propionic acid production by fermentation of glycerol using Propionibacterium acidipropionici and potato juice, a by-product of starch processing, as a nitrogen/vitamin source. The fermentation was done as high-cell-density sequential batches with cell recycle. Propionic acid production and glycerol consumption rates were dependent on initial biomass concentration, and reached a maximum of 1.42 and 2.30 g L(-1) h(-1), respectively, from 50 g L(-1) glycerol at initial cell density of 23.7 gCDW L(-1). Halving the concentration of nitrogen/vitamin source resulted in reduction of acetic and succinic acids yields by ~39% each. At glycerol concentrations of 85 and 120 g L(-1), respectively, 43.8 and 50.8 g L(-1) propionic acid were obtained at a rate of 0.88 and 0.29 g L(-1) h(-1) and yield of 84 and 78 mol%. Succinic acid was 13 g% of propionic acid and could represent a potential co-product covering the cost of nitrogen/vitamin source.

Pilot-scale extraction of an intracellular recombinant cutinase from E. coli cell homogenate using a thermoseparating aqueous two-phase system.

A thermoseparating aqueous two-phase system for extraction of a recombinant cutinase fusion protein from Escherichia coli homogenate has been scaled up to pilot scale. The target protein ZZ-cutinase-(WP)(4) was produced in a fed batch process at 500 l to a concentration of 12% of the total protein and at a cell concentration of 19.7 g l(-1). After harvest and high-pressure homogenisation a first extraction step was performed in an EO(50)PO(50) (50% (w/w) ethylene oxide and 50% (w/w) propylene oxide) thermopolymer/amylopectin rich Waxy barley starch system. The (WP)(4) tag was used for enhanced target protein partitioning to the EO(50)PO(50) phase while the cell debris was collected in the starch phase. A second extraction step followed where the recovered EO(50)PO(50) phase from the first step was supplemented with a non-ionic detergent (C(12-18)EO(5)) and heated to the cloud point (CP) temperature (45 degrees C). One polymer-rich liquid phase and one almost pure aqueous phase were formed. The target protein could be obtained in a water phase after the thermal phase separation at a total recovery over the extraction steps of 71% and a purification factor of 2.5. We were able to demonstrate that a disk-stack centrifugal separator could be adapted for rapid separation of both primary and thermoseparated phase systems.