Table 2.

AmyK38 production indltBmutants with or without an up-shift of external pH

Strain	Plasmid	Na2CO3a	α-amylase activity(kU l-1)b
168	pHYK38	-	2.9 ± 0.3
168ΔdltB	pHYK38	-	7.0 ± 0.3
MGB874	pHYK38	-	0.10 ± 0.01
874ΔdltB	pHYK38	-	0.27 ± 0.02
168	pHYK38	+	14.3 ± 0.2
168ΔdltB	pHYK38	+	14.8 ± 0.4
MGB874	pHYK38	+	20.8 ± 0.8
874ΔdltB	pHYK38	+	20.1 ± 0.2

^aB. subtilis derivative strains were grown in 2xL-Mal medium at 30°C. At the transition phase (12 h), an Na₂CO₃ solution was added to the growth medium at a final concentration of 0.9% (w/v). -, No addition; +, Addition.

^bα-amylase activity was determined after 72 h of cultivation.