Formation of aminium lactates in lactic acid fermentation - Fermentative production of 1,4-piperazinium-(L,L)-dilactate and its use as a starting material for the synthesis of dilactide (part 2)

A fermentation process for manufacturing 1,4-piperazinium-(L,L)-dilactate f rom renewable raw materials and a method for processing this product into L ,L-dilactide are described. Lactic acid fermentation with Lactobacillus par acasei was modified in such a way that pH control occurred by using an aque ous solution of piperazine as a correcting agent instead of sodium hydroxid e solution. The production of a stoichiometrically composed piperazinium la ctate was possible when the pH was 5.0, From 5.0 kg of glucose and 2.15 kg of piperazine, 6.65 kg of 1,4-piperazinium-(L,L)-dilactate were formed in t he fermentation process. Separation from fermentation broth, purification a nd concentration of the product in aqueous solutions were carried out by me ans of ultrafiltration, nanofiltration and electrodialysis. Total product r etention by the membranes used was about 33%. The crystal line salt was obt ained by vacuum evaporation. Processing of the 1,4- piperazinium-(L,L)-dila ctate into L,L-dilactide was performed in a special glass reactor. A produc t yield of 70% was achieved. The purified product was characterized by elem entary analysis, as well as solubility behaviour, polarity and spectroscopi c data. An overall process consisting of the stages fermentation, purificat ion and concentration of piperazinium dilactate as well as cyclization of t he latter to dilactide is described.