Abstract:

Theγ-aminobutyric acid (GABA) synthesis was conducted through biotransformation of Streptococcus salivarius subsp. thermophilus Y-2 cells to explore the effects of pH, reaction temperature, salts, surfactant, substrate concentration, strain concentration and addition of pyridoxal phosphate (PLP) on the production of GABA. Results indicated that the optimal reaction system included 25 g/L wet cells, 40 mmol/L BaCl2, 0.02% Triton X-100, 47.5 g/L L-monosodium glutanate, and 90.0 g/L L-glutamic acid. The optimal reaction conditions of this reaction system were reaction temperature of 40 ℃, reaction pH of 4.5, stirring speed of 100 r/min and reaction time of 72 h. Under these optimal conditions, the yield of GABA was up to (87.16 ± 4.33) g/L and biotransformation rate of GABA in moles was (97.60 ± 4.71)%. The total productivity of the cells was (48.42 ± 2.41) mg/(h·g).

Key words: Streptococcus salivarius subsp. thermophilus, glutamate decarboxylase, γ–aminobutyric acid, biotransformation