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.

Batch- and continuous propionic acid production from glycerol using free and immobilized cells of Propionibacterium acidipropionici

Propionic acid production from glycerol was studied using Propionibacterium acidipropionici DSM 4900 cells immobilized on polyethylenimine-treated Poraver (PEI-Poraver) and Luffa (PEI-Luffa), respectively. Using PEI-Luffa, the average productivity, yield and concentration of propionic acid from 40 g L(-1) glycerol were 0.29 g L(-1) h(-1), 0.74 mol(PA) mol(Gly)(-1) and 20 g L(-1), respectively, after four consecutive recycle-batches. PEI-Poraver supported attachment of 31 times higher amounts of cells than PEI-Luffa and produced 20, 28 and 35 g L(-1) propionic acid from 40, 65 and 85 g L(-1) glycerol, respectively (0.61 mol(PA) mol(Gly)(-1)). The corresponding production rates were 0.86, 0.43 and 0.35 g L(-1) h(-1), which are the highest reported from glycerol via batch or fed-batch fermentations for equivalent propionic acid concentrations. Using a continuous mode of operation at a dilution rate of 0.1 h(-1), cell washout was observed in the bioreactor with free cells; however, propionic acid productivity, yield and concentration were 1.40 g L(-1) h(-1), 0.86 mol(PA) mol(Gly)(-1), and 15 g L(-1), respectively, using immobilized cells in the PEI-Poraver bioreactor. The choice of the immobilization matrix can thus significantly influence the fermentation efficiency and profile. The bioreactor using cells immobilized on PEI-Poraver allowed the fermentation of higher glycerol concentrations and provided stable and higher fermentation rates than that using free cells or the cells immobilized on PEI-Luffa.

Improving the productivity of propionic acid with FBB-immobilized cells of an adapted acid-tolerant Propionibacterium acidipropionici

Propionic acid is an important short-chain fatty acid with many applications, but its large-scale bioproduction was hindered by the low productivity. An adapted acid-tolerant Propionibacterium acidipropionici CGMCC 1.2230 strain was selected to produce propionic acid with a relatively high productivity (0.29 g/(Lh)) in the free-cell fermentation. Further immobilized-cell fermentation in fibrous-bed bioreactor (FBB) supported high-level repeated batch fermentations with a high productivity of 0.96 g/(Lh). The FBB also presents the potential to increase final propionic acid concentration by using glucose feeding strategy. The propionic acid concentration was increased to 51.2g/L in the fed-batch fermentation with the productivity of 0.71 g/(Lh). By adopting the above strategies, sugarcane bagasse hydrolysate could support the production of propionic acid with high productivity in the repeat-batch and fed-batch fermentations. The present work would pave one road to the accomplishment of large-scale bioproduction of propionic acid from renewable resources.

[A positive effect of Propionibacterium freudenreichii on the growth of Saccharomyces cerevisiae during their cocultivation]

The growth pattern of Saccharomyces cerevisiae and Propionibacterium freudenreichii ssp. shermanii (P. shermanii; propionic acid bacteria, PABs) during cocultivation in liquid media depended on the ratio of the cells in the inoculum. An increase in the growth rate of S. cerevisiae was observed at a PAB to yeast ratio of approximately 3 : 1; higher ratios exerted adverse effects on yeast growth. The culture liquid of 18- to 24-h (young) cultures of PABs stimulated yeast growth. Although yeast growth-stimulating exometabolites of PABs were not high-molecular-weight compounds, they were thermolabile. When present in the medium at concentrations of up to 1.5%, the antimicrobial agent sodium propionate did not interfere with S. cerevisiae growth; however, it completely inhibited the growth of B. subtilis at a concentration of 0.2%.

Behaviour of Propionibacterium shermanii in alkaline medium

Physiological and morphological properties of Propionibacterium shermanii were estimated in a liquid semisynthetic medium of initial pH between 7-10. Prolongation of the lag phase and a shift of the stationary phase occurred at higher initial pH values of the medium. The growth response of the strain depended on the way of glucose addition (either sterilized in the medium or added aseptically after sterilization). At pH 8.5 and higher the cells begin to form slime and capsules. The strain exhibited growth activity even at initial pH values of the medium 11.5

[Protective effect of P40 fraction of C. granulosum against leukemia L1210 in mice]

Administration of glutaraldehyde treated L1210 leukemia cells, either alone or coupled with tetanus toxoid by means of glutaraldehyde as well as L1210 cells inactivated by mitomycin, did not induce appreciable protection against a tumorigenic dose of L1210 cells. On the other hand, injection of P40 fraction of C. granulosum induced non-specific resistance to L1210 leukemia and increased the efficiency of specific immunization by either glutaraldehyde treated L1210 cells or cells coupled with tetanus toxoid. Injection of Freund's complete adjuvant resulted in increase of rate of mortality after challenge with L1210 cells.