α-galactosidase from Bacillus megaterium VHM1 and its application in removal of flatulence-causing factors from soymilk

摘要

A bacterial strain capable of producing extracellular α- galactosidase was isolated from a sample of sugarcane industrial waste. Microbiological, physiological, and biochemical studies revealed that the isolate belonged to Bacillus sp. Furthermore, based on a 16S rDNA sequence analysis, the new isolate was identified as Bacillus megaterium VHM1. The production of α-galactosidase was optimized based on various physical culture conditions. Guar gum and yeast extract acted as the best carbon and nitrogen sources, respectively. The optimum pH was 7.5 and the enzyme remained stable over a pH range of 5-9. The enzyme was optimally active at 55°C and thermostable with a half-life of 120 min, yet lost 90% of its residual activity within 120 min at 60°C. One mM concentrations of Ag`2, Cu~2, and Hg~(2+) strongly inhibited the α-galactosidase, whereas the metal ions Fe~2, Mn~(2+), and Mg~(2+) had no effect on the α-galactosidase activity, and Zn2+, Ni2+, and Ca2+ reduced the enzyme activity slightly. When treated with the B. megaterium VHM1 enzyme, the flatulence-causing sugars in soymilk were completely hydrolyzed within 1.5 h.