Table 1.

Effect of amino acids on biomass and γ-PGA production.

Amino acids	Amount (g/L)	Biomass (g/L)	γ-PGA (g/L)	γ-PGAincrease rate (%)
Control	0	8.99 ± 0.24	26.32 ± 0.25
Glycine	1	9.79 ± 0.21	27.10 ± 0.21	2.96
	2	10.25 ± 0.22	27.20 ± 0.18	3.34
Serine	1	8.81 ± 0.22	26.95 ± 0.12	2.39
	2	8.99 ± 0.20	27.01 ± 0.10	2.62
Glutamate	1	9.15 ± 0.33	28.32 ± 0.25	7.60
	2	11.36 ± 0.31	30.02 ± 0.21	14.06
Glutamine	1	8.45 ± 0.29	22.72 ± 0.25	−13.68
	2	8.13 ± 0.29	21.21 ± 0.15	−19.41
Histidine	1	8.51 ± 0.21	26.42 ± 0.25	0.38
	2	8.34 ± 0.20	26.23 ± 0.20	−0.34
Proline	1	8.41 ± 0.21	26.62 ± 0.25	1.14
	2	8.49 ± 0.11	26.78 ± 0.22	1.75
Tyrosine	1	8.65 ± 0.12	26.52 ± 0.25	0.76
	2	8.38 ± 0.19	26.28 ± 0.29	−0.15
Lysine	1	8.74 ± 0.22	25.92 ± 0.25	−1.52
	2	8.47 ± 0.18	25.74 ± 0.21	−2.20
Aspartic acid	1	9.75 ± 0.20	29.52 ± 0.25	12.16
	2	12.03 ± 0.29	31.09 ± 0.20	18.12
Asparagine	1	8.51 ± 0.21	26.42 ± 0.20	0.38
	2	8.78 ± 0.20	26.39 ± 0.20	0.26
Isoleucine	1	8.51 ± 0.21	26.22 ± 0.25	−0.38
	2	8.48 ± 0.18	26.37 ± 0.18	0.19
Phenylalanine	1	9.71 ± 0.29	28.85 ± 0.25	9.61
	2	11.70 ± 0.29	29.45 ± 0.20	11.89
Arginine	1	9.83 ± 0.22	27.22 ± 0.25	3.42
	2	9.77 ± 0.21	27.02 ± 0.21	2.66
Valine	1	9.69 ± 0.31	27.62 ± 0.25	4.94
	2	10.19 ± 0.23	27.52 ± 0.20	4.56

*Control group: B. subtilis Z15 is cultivated in the medium without amino acid addition.