High external pH enables more efficient secretion of alkaline α-amylase AmyK38 by Bacillus subtilis

Table 1 Effect of pH up-shift on the secretion stress response in B. subtilis

Strain	Genotype	Plasmid	Na₂CO₃^a	LacZ activity^b
R-1645	168 ΔamyE::P_htrB-lacZ	pHY300PLK	-	6.7 ± 0.3
R-1645	168 ΔamyE::P_htrB-lacZ	pHY300PLK	+	6.5 ± 0.5
R-1646	MGB874 ΔamyE::P_htrB-lacZ	pHY300PLK	-	9.5 ± 0.1
R-1646	MGB874 ΔamyE::P_htrB-lacZ	pHY300PLK	+	9.1 ± 0.3
R-1645	168 ΔamyE::P_htrB-lacZ	pHYK38	-	700 ± 86
R-1645	168 ΔamyE::P_htrB-lacZ	pHYK38	+	200 ± 48
R-1646	MGB874 ΔamyE::P_htrB-lacZ	pHYK38	-	1700 ± 36
R-1646	MGB874 ΔamyE::P_htrB-lacZ	pHYK38	+	590 ± 85

^aB. subtilis derivative strains were grown in 2xL-Mal medium at 30°C. At the transition phase (12 h), a Na₂CO₃ solution was added to the growth medium at a final concentration of 0.9% (w/v). -, No addition; +, Addition.
^bLacZ activity was determined after 48 h of cultivation. β-galactosidase-specific activities are reported in units (U) calculated using the following formula: 1000 x A420/reaction time (min) x OD₆₀₀ of culture.

ISSN: 1475-2859