Cultivable bacterial diversity and amylase production in two typical light-flavor Daqus of Chinese spirits

Culture-dependent methods and molecular techniques were used to simultaneously investigate the cultivable bacterial diversity and amylase production in two typical light-flavor Daqus of Chinese spirits. Eight bacteria were identified from Niulanshan Daqu (Bacillus licheniformis, Bacillus subtilis, Bacillus cereus, Bacillus sonorensis, Streptomyces albus, Bacillus atrophaeus, Bacillus tequilensis and Bacillus megaterium) and eight from Hongxing Daqu (B. licheniformis, B. subtilis, B. cereus, Bacillus thuringiensis, Bacillus altitudinis, Bacillus pumilus, Geobacillus stearothermophilus and Bacillus amyloliquefaciens). All of the bacterial isolates from the Hongxing Daqu could produce extracellular α-amylase with a maximum yield of 25.3 U/ml by B. cereus H17, whereas B. licheniformis H55 could produce a maximum glucoamylase yield of 41.6 U/ml. Some of the bacterial isolates from the Niulanshan Daqu could also produce extracellular α-amylase and glucoamylase. The maximum yield of 27.6 U/ml α-amylase was achieved by B. subtilis N3, and the maximum yield of 58.1 U/ml glucoamylase was achieved by B. cereus N25. Bacillus licheniformis, B. subtilis and B. cereus were not only the dominant bacteria, but also possessed high α-amylase and glucoamylase activities, which may play very important roles during fermentation.