Purification of oligosaccharides from a fermentation broth by using filtration

A method for purification of an oligosaccharide of interest from a fermentation broth, wherein the method comprises:

• (i) providing a fermentation broth which comprises the oligosaccharide of interest, biomass, microbial cells and carbohydrates other than the oligosaccharide of interest;
• (ii) removing the microbial cells from the fermentation broth, thereby providing a process stream;
• (iii) subjecting the process stream to a first filtration using a nanofiltration membrane, thereby providing a filtrate which contains the oligosaccharide of interest, wherein the nanofiltration membrane used in the first filtration has a molecular weight cut-off of between about 700 Dalton and about 3,000 Dalton;
• (iv) subjecting the filtrate to a second filtration using a nanofiltration membrane, thereby providing a retentate which contains the oligosaccharide of interest, wherein the nanofiltration membrane used in the second filtration has a molecular weight cut-off between 100 Dalton and 1,000 Dalton;
• and
• (v) removing one or more salts from the process stream using electrodialysis thereby providing a purified preparation of the oligosaccharide of interest
• wherein the method does not comprise an ion exchange step.