The Study On Purification Of GABA In Fermentation Broth By Membrane Techniques

Gamma-aminobutyric acid (GABA) is an important non-protein amino acid. GABA has thephysiological functions of dropping blood pressure, curing epilepsy, improving brain engineryetc. Current research is focused on its action mechanism and its production. The production ofGABA by high yield microorganism has the advantage of high security and low cost. This paperis dealt with the purification of fermentation broth by membrane techniques to increase the yieldand the purity. The article includes thee parts of researches: 1 The membrane with MWCO value of 50000 was used to purify the fermentation brothand two following dialfiltration operations was tested and compared. The influences of operationconditions were investigated and the optimization lead to the following conditions: T<40℃ ,Δp=0.15MPa, u=0.5m/s,pH=5. Results show that although the flux of continuous diafiltration(CD) is higher than that of discontinuous diafiltration (DD), it may not compensate for the extraprocessing (a concentration step) required by CD. The 'UF/Re-UF' operations can reject 43.4%protein, 62.9% polysaccharide and the content of GABA in the permeation can be increased from50.2% to 94.9%. 2 The fouling and cleaning of UF membrane was studied. The observation by SEM revealedthe existence of a layer of macromolecular compounds on the membrane surface, with thethickness of 5~10μm. The following operation can efficiently control the fouling of UFmembranes: T<40 ℃, u=0.5m/s;reversing rinse the membrane with permeate for 30secs in every10 minutes;using the solution(LAS 0.3%,Cl 200mg/L,pH=12) to rinse the system. 3 Nanofiltration (NF) with SR2 (MWCO 600-800) and SR3 (MWCO 200-300) was studiedto purify further the UF permeate. It is feasible that using SR2 to permeate GABA and using SR3to concentrate GABA by studying the simulation solution made of Met and salt. SR2 can reject43.93% protein, 88.69% polysaccharide, 30.05% ash and more than 90% pigment.SR3 can reject85.32% protein most of which are dissociation amino acids, 39.91% ash. As a whole, the membrane separations can reject 71.81% protein, 97.47% polysaccharide,71.34% ash and increase the purification of GABA from 8.87% after high-speed centrifugalmachine to 31.63%。...