Self-cycling fermentation for 1,3-propanediol production: Comparative evaluation of metabolite flux in cell recycling, simple batch and continuous processes using Lactobacillus brevis N1E9.3.3 strain

- 1,3-PDO titers of 51.51 g/l in batch mode and 78.33 g/l in repeated batch mode was observed.
- A higher yield of 0.64 g1,3-PDO/gGlycerol was established with a non pathogenic strain in batch and repeated batch fermentation.
- Strain was observed to be efficient in suspended or immobilized form.

The microbial conversion of biodiesel derived crude glycerol to 1,3-propanediol (1,3-PDO) has attained high industrial value due to the broad range of applications as a monomer (1,3-PDO) in textile, cosmetic and polymer industries. This fine chemical through biological production addressed several limitations of the chemical process like high temperatures, pressure and expensive catalysts. In this study 1,3-propanediol production was achieved from a non-pathogenic lactic acid bacterial strain Lactobacillus brevis N1E9.3.3 in suspended and immobilized form under batch, sequential batch and continuous modes of fermentation. The microorganism was immobilized in polyurethane foam cubes. The effects of initial glycerol concentration on suspended and immobilized cells were investigated in stirred tank reactor. The maximum 1,3-PDO titers of 51.5 g1,3-PDO/l and 42.59 g1,3-PDO/l with a yield of 0.64 g1.3-PDO/gGlycerol and 0.53 g1.3-PDO/gGlycerol using suspended and immobilized cells respectively was observed in batch fermentation with an initial glycerol concentration of 80 g/l. In repeated batch (self-cycling) fermentation 78.3 g/l 1,3-PDO with 0.65 g1.3-PDO/gGlycerol yield and 0.65 g/l/h productivity was observed at the end of 5th cycle. A constant yield between 0.3-0.65 g1.3-PDO/gGlycerol was observed with cell recycling using suspended and immobilized cells. The highest productivity of 1.735 g1,3-PDO/l/h was observed in chemostat with immobilized cells.