Abstract:

Factorial design and central composite design were applied to optimize the yield of γ-aminobutyric acid (GABA)
produced by cultured Lactococcus lactis cells from monosodium glutamate in a buffer solution. A full factorial design was used to
optimize the conversion conditions as 40 ℃, pH 3.5 and 24 h. Using single factor designs, sodium glutamate, corn steep powder
and glucose concentration were identified as major factors affecting GABA production. The interaction effect of the major factors
at three levels each was analyzed by central composite design. The results showed that the optimal medium for Lactococcus
lactis consisted of 9.5 g/L sodium glutamate, 5.74 g/L glucose, 12.50 g/L corn steep powder, 5.00 g/L yeast extract, 1.20 g/L
K2HPO4 and 0.60 g/L MgSO4. Under these conditions, the yield of GABA was 9.06 g/L, which was increased by 88.8%
when compared with that (4.80 g/L) before optimization.

Key words: γ-aminobutyric acid, Lactococcus lactis, factorial design, screening design, central composite design