초록
<P><B>Background</B></P><P>Alkaline α-amylases have potential applications for hydrolyzing starch under high pH conditions in the starch and textile industries and as ingredients in detergents for automatic dishwashers and laundries. While the alkaline α-amylase gains increased industrial interest, the yield of alkaline α-amylases from wild-type microbes is low, and the combination of genetic engineering and process optimization is necessary to achieve the overproduction of alkaline α-amylase.</P><P><B>Results</B></P><P>The alkaline α-amylase gene from <I>Bacillus alcalophilus </I>JN21 (CCTCC NO. M 2011229) was cloned and expressed in <I>Bacillus subtilis </I>strain WB600 with vector pMA5. The recombinant alkaline α-amylase was stable at pH from 7.0 to 11.0 and temperature below 40°C. The optimum pH and temperature of alkaline α-amylase was 9.0 and 50°C, respectively. Using soluble starch as the substrate, the <I>K</I><SUB>m </SUB>and <I>V</I><SUB>max </SUB>of alkaline α-amylase were 9.64 g/L and 0.80 g/(L·min), respectively. The effects of medium compositions (starch, peptone, and soybean meal) and temperature on the recombinant production of alkaline α-amylase in <I>B. subtilis </I>were investigated. Under the optimal conditions (starch concentration 0.6% (w/v), peptone concentration 1.45% (w/v), soybean meal concentration 1.3% (w/v), and temperature 37°C), the highest yield of alkaline α-amylase reached 415 U/mL. The yield of alkaline α-amylase in a 3-L fermentor reached 441 U/mL, which was 79 times that of native alkaline α-amylase from <I>B. alcalophilus </I>JN21.</P><P><B>Conclusions</B></P><P>This is the first report concerning the heterologous expression of alkaline α-amylase in <I>B. subtilis</I>, and the obtained results make it feasible to achieve the industrial production of alkaline α-amylase with the recombinant <I>B. subtilis</I>.</P>