Table 3. Mass Spectrometry Analysis and Bioactivity Determination of Nisin K12X Bank.

	Amino Acid		Molecular Mass		Bioactivity
	K12X		Predicted	Observed	Mean (S.D)
Hydrophilic: Charged	Lysine+ve	K	3353.06	3353.04	100 (N/A)
	Histidine+ve	H	3362.03	3361.40	75 (5)
	Arginine+ve	R	3381.08	3381.24	61 (6)
	Glutamic acid -ve	E	3354.01	3353.74	0 (N/A)
	Aspartic acid -ve	D	3339.98	ND	0 (N/A)
Hydrophilic: Neutral	Threonine	T	3326.00	3326.28
					129 (3)
			3307.98*	3307.63*
	Serine	S	3311.98	3311.14
					128 (1)
			3293.95*	3293.65*
	Asparagine	N	3339.00	3338.74	108 (9)
	Glutamine	Q	3353.03	3353.48	102 (9)
	Tyrosine	Y	3388.07	3388.43	73 (7)
Hydrophobic	Alanine	A	3295.98	3296.49	131 (2)
	Proline	P	3322.01	3321.71	118 (7)
	Valine	V	3324.03	3323.76	107 (9)
	Methionine	M	3356.08	3355.55	105 (9)
	Cysteine	C	3328.04	3328.89	103 (8)
	Leucine	L	3338.05	3339.02	89 (5)
	Isoleucine	I	3338.05	3337.88	89 (9)
	Glycine	G	3281.94	3281.90	68 (2)
	Tryptophan	W	3411.10	3410.83	63 (5)
	Phenylalanine	F	3372.07	3372.16	54 (5)

Observed molecular mass (+/−0.25 Da) from MALDI-TOF MS analysis of NZ9800 pDF05-K12X producers. ND: not detected. * represents dehydrated forms (hydrophobic modified residues), i.e. Dhb in the case of T and Dha in the case of S.

Bioactivity of NZ9800 pDF05-K12X producers against L. lactis HP. Values given are the mean of triplicate deferred antagonism assays and represent zone of inhibition (diameter of zone minus diameter of bacterial growth) expressed as a percentage compared to that of the wild-type nisin producer at 100%. S.D.: Standard Deviation; Relative Standard Deviation <10% for each given value. N/A: not applicable. All values in bold reached statistical significance compared to nisin control (K) (Student's t-test: P<0.05).