Gamma-aminobutyric acid (gaba) is a non-protein amino acid that is widely present in organisms. gaba is a kind of pharmacological and biological component and its application is wide and useful. several important physiological functions of gaba have been characterized, such as neurotransmission, induction of hypotension, gaba is also a strong secretagogue of insulin from the pancreas and effectively inhibit small airway-derived lung adenocarcinoma and tranquilizer. many microorganisms can produce gaba, and lactic acid bacteria have been a focus of research in recent years, because lactic acid bacteria possess special physiological activities and are generally regarded as safe. among them the lb. brevis produced the highest amount of gaba. the gaba-producing ability is affected significantly by culture conditions and medium composition. therefore, it is important to optimize these conditions for enhancing the gaba production. the major factors affecting the gaba production have been characterized, including carbon sources and glutamate concentration. lab’s high gaba production is related to the activity of the glutamic acid decarboxylase (gad) enzyme in the cells. the concentration of glutamic acid in the food matrix should be high enough. the use of food industry waste to produce valuable products such as amino acids seems to be a good way to reduce production costs and prevent waste of food resources. in a dairy factory, a high volume of sludge is produced from a separator that contains useful compounds such as growth factors, carbon, nitrogen, and organic matter that can be used by different microorganisms such as lb.brevis as carbon and nitrogen sources. therefore, it is a good source for gaba production.

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